ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL Updated Draft June 2016
Alameda County Department of Environmental Health 1131 Harbor Bay Parkway Alameda, CA 94502
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MANUAL OVERVIEW
INTRODUCTION This Manual provides the procedural and technical details for implementation of the provisions of the Alameda County Onsite Wastewater Treatment Systems Ordinance, codified in Chapter 15.18 of the Alameda County General Ordinance. The provisions within this Manual are designed to protect public health, groundwater sources and surface water bodies from contamination, and provide safely operating Onsite Wastewater Treatment Systems (OWTS) through proper design, siting, installation, maintenance, and monitoring. This Manual is intended to provide technical guidance for Property Owners, Designers, Installers, Contractors, and Service Providers of OWTS. The Onsite Wastewater Treatment Systems Manual is divided into the following main chapters as follows:
Chapter 1: Chapter 2: Chapter 3: Chapter 4: Chapter 5: Chapter 6: Chapter 7: Chapter 8:
Chapter 9: Chapter 10: Chapter 11: Chapter 12: Chapter 13: Chapter 14: Chapter 15:
Administrative and Permitting Process Overview1 Professional, Contractor and Maintenance Provider Qualifications Site Evaluation Requirements General OWTS Design Criteria & Design Submittal Requirements Tanks – Design Requirements Supplemental Treatment Systems – Design Requirements Subsurface Dispersal Systems - Design Requirements Non-Discharging Toilet Units & Graywater Systems – Design Requirements Construction Materials & Installation Specifications Site Modifications and Stabilization Criteria OWTS Installation and Abandonment Inspection Requirements OWTS Operation, Maintenance, Monitoring and Reporting Requirements Existing OWTS Evaluation, Repair & Replacement Criteria OWTS Complaint Investigations Definition of Terms
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AMENDMENTS TO THE MANUAL The Alameda County Department of Environmental Health (the Department) is the agency responsible2 for the enforcement of the Alameda County Onsite Wastewater Treatment Systems Ordinance and provisions in this Manual. The California Regional Water Quality Control Boards (San Francisco Bay Region and Central Valley Region) are the state agencies responsible for the protection of ground and surface water quality in Alameda County. While the Department administers the local program, the Regional Boards retain the authority to issue permits for any discharge of Wastewater that may affect water quality, including discharges from Individual OWTS. Onsite Wastewater Treatment Systems treat and dispose of sanitary waste from structures with plumbing when public sewer is not available. Such OWTS must be located, designed, constructed, and operated in a manner to ensure that sewage effluent does not surface and that percolation of effluent will not adversely affect the public health, safety or welfare. Among other concerns, such OWTS shall not contaminate or otherwise be detrimental to the waters of the State of California. The regular review and update of this Manual is necessary to keep pace with new issues, policies, procedures, and technologies affecting the use and management of OWTS. Any substantive changes in requirements will require review and approval by the San Francisco Bay Regional Water Quality Control Board (Regional Water Board) and adoption by Resolution of the Alameda County Board of Supervisors. The amendments may include recommended changes originating from the Department, Regional Water Board, Zone 7 Water Agency, other departments or agencies, contractors and consultants working in the OWTS industry, or other affected groups or individuals. As changes are made to this manual, cross references throughout this Manual are also subject to change. Failure of a cross-reference to indicate the appropriate chapter of requirements due to these changes does not void the applicability of the requirements. The general process before final changes are made to this Manual will be as follows: 1. The Department will announce and provide copies of its proposed changes. 2. The Department will present the changes and allow opportunity for public comments at a meeting of the OWTS Commission or other public meeting. After further review and consideration of public comments the final changes will be presented to the Board of Supervisors and then will be forwarded to the Regional Water Board for review and approval.
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1
Administrative and Permitting Process Overview
[RESERVED]
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2.0 SECTION OVERVIEW This Chapter provides an overview of the professionals, contractors and other service providers that are qualified to perform site evaluations, OWTS design, and OWTS installation, repair, abandonment, and operations, maintenance and monitoring. The chapter is organized in the following sections:
Section 2.1:
Professional, Contractors, and Maintenance Providers Qualifications
Section 2.2:
OWTS Service Providers
Section 2.3:
Septage Pumper Truck Rentals
PROFESSIONAL, CONTRACTOR AND SERVICE PROVIDER QUALIFICATIONS A.
QUALIFIED PROFESSIONALS 1. A Qualified Professional is defined in the State Policy as an individual licensed or certified by a State of California Agency to design OWTS and practice as a professional for other associated reports, as allowed under their license or registration. 2. Information on the qualifications and licenses, registrations, and certifications on professionals that may be hired to work on an OWTS are provided in Table 2-1 and Table 2-2.
B.
OTHER PRACTITIONERS 1. Other practitioners that may be involved with the installation, operation and maintenance of an OWTS include contractors, service providers and septage pumpers. 2. Information on the qualifications and registrations, of other practitioners that may be hired to work on an OWTS are provided in Tables 2-1 and 2-2. 3. Contractors approved for OWTS installation or repair work are those possessing one of the following California contractor’s licenses: General Engineering (Class A), Plumbing (C-36), or Sanitation System (C-42). 4. The Department has a registration program for OWTS service providers as outlined in Section 2.2.
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5. The Department has a registration program for septage pumper businesses and vehicles as outlined in section 2.3 of this chapter. 6. More Information on professionals is located on the Departments website at http://www.acgov.org/aceh/landuse/owts_service_providers.htm.
2.2 OWTS SERVICE PROVIDERS A.
GENERAL
Advanced OWTS require periodic monitoring and inspections. Other OWTS can also benefit from periodic monitoring and inspections. When periodic monitoring and inspections must be conducted under Operating permits they must be conducted by a Qualified Professional or other practitioner registered by the Department as an OWTS Service Provider as required in section B below. Where manufacturers of a proprietary treatment system have certification or training requirements, verification of manufacturer approved training or certification must be provided to the Department as a condition of an Operating Permit. B.
REGISTRATION REQUIRED 1. Registration must occur every two years. 2. The requirements for registration include the following: a. Documentation of completion of an OWTS operation, maintenance, and monitoring training course provided by a third-party organization or entity such as California Onsite Wastewater Association (COWA), National Association of Waste Transporters (NAWT), or others approved by the Department, and b. Submittal of a complete application and a registration fee. 3. Registration is not required for Qualified Professionals.
SEPTAGE PUMPER BUSINESS REQUIREMENTS A.
GENERAL
Business that perform the service of pumping or cleaning septic tanks, chemical toilets, cesspools, seepage pits, or other sewage containments are regulated under the California Health and Safety Code, division 104, part 13, sections 117400 – 117450 and chapter 15.18 of the Alameda County General Ordinance requires an annual business registration (“Registration”). Each septage pumper truck that is used for this purpose in the County of Revised Draft 6-28-16 6
Alameda must be identified in the Registration and have its own registration from the Department. Vehicles must display valid Registration decal to operate in the County. B.
REGISTRATION REQUIRED 1. Registration annually is required for every business doing any of the following: a. A vehicle that pumps wastewater from septic tanks, cesspools, grease traps, grease interceptors, seepage pits, wastewater holding tanks, wastewater ponds, or other wastewater source; or b. A business that cleans portable toilets; or c. A vehicle that disposes of wastewater from these activities in Alameda County. 2. A pumper truck annual Registration is required for each septage pumper truck that performs liquid waste pumping and cleaning services as provided above. 3. Registration with Alameda County is required for all operators unless exempted by California Health and Safety Code, division 104, part 13, sections 117400 – 117450.
C.
APPLICATION 1. A Registration application shall include the name and address of the business, the names and addresses of all owners, (if a partnership, then all names and addresses of all partners shall be disclosed), vehicle license number(s), vehicle identification number(s), and the location(s) where wastes will be disposed. 2. The application shall be submitted to the Department with the required fee established by resolution of the Board of Supervisors.
D.
SEPTAGE PUMPER TRUCK OPERATOR KNOWLEDGE
The septage pumper truck owner, operator and all employees shall have knowledge of sanitary principles, and of the requirements and restrictions of septage pumper truck business operation and waste disposal. The Department may require demonstration of knowledge, such as employee training, pumping procedure, spill procedures, etc. E.
SEPTAGE PUMPER TRUCK BUSINESS COMPLIANCE
The septage pumper truck business shall observe sanitary laws, ordinances and other legal requirements. Failure of the Registered business to operate in compliance may result in Registration revocation.
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F.
SEPTAGE PUMPER TRUCK INSPECTION PROCEDURES 1. The applicant and operator(s) of the septage tank pumper truck shall schedule an annual inspection of each vehicle with the Department. During the inspection the applicant shall be required to demonstrate compliance with the following requirements for each vehicle being permitted: a. Vehicle Identification. The business name and phone number shall be permanently affixed on both sides of the vehicle in plain, legible letters and numbers at least four inches high, and shall be visible at all times. The certified capacity of the tank in gallons shall be permanently affixed on both sides of the tank in plain, legible numbers a minimum of four inches high and shall be visible at all times. The capacity as shown shall be that approved and certified by the sealer of weights and measures of the county, or other approved sealer of weights and measures. b. Vehicle in Good Repair. Vehicle and all hoses are leak proof and do not show signs of deterioration that could lead to leaking. c. Vehicle Equipment. A minimum of fifty (50) feet of pumping hose, a bucket and detergent shall be carried on each pumping vehicle. All pumping hoses must be cleaned out into the truck tank or into the septic tank, chemical toilet or other receptacle being pumped, and not on the surface of the ground. The customer's hose shall not be used. d. Vehicle Spill Kit. There shall be a spill kit carried on each vehicle at all times which shall include, but not be limited to a sufficient quantity of chloride of lime or other chlorine product for disinfection of hose, absorbent material such as kitty litter, garbage bags, gloves of an impervious material, shovel, and absorbent spill containment barrier.
G.
REPORTING REQUIREMENTS 1. On a quarterly basis, the owner of the permitted septage pumper truck shall report the following to Department. a. The name and address of the owner and tenant of each and every one of the premises where a wastewater septic tank, holding tank, vault toilet, cesspool, sewage pit, pond, chemical toilet has been pumped or cleaned out; b. The date of service; c. Gallons pumped;
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d. Incidents where sewage is surfacing or there are other signs of OWTS failure; and e. The locations where the pumped contents were disposed. 2. Immediate notification must be made to the Department if any of the following are observed at the time of septic tank pumping; a. Surfacing sewage that poses a clear threat to public health or the environment; b. Existence of a cesspool; or c. Other safety hazard associated with the OWTS 3. The Department recommends that the pumper document for the property owner the condition of the OWTS and recommendations for repairs if any.
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[RESERVED FOR TABLE 2-1]
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[RESERVED FOR TABLE 2-2]
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[RESERVED FOR TABLE 2-3]
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[RESERVED FOR TABLE 2-4]
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3.0 SECTION OVERVIEW AND PROCESS Site Evaluation is an assessment of the characteristics of a lot sufficient to determine its suitability for the installation, use, and sustainability of an OWTS meeting the requirements of this Manual and Ordinance. The site evaluation takes into consideration soil texture, soil percolation rate, depth to groundwater, distance from natural land features and structures, site topography, and usable space. A site evaluation is performed by a Qualified Professional in coordination with the Department so that Department personnel may be present for any facet of the process. Site Evaluation is the first step in evaluating an OWTS. The level of evaluation and assessment required will depend upon the type of project and property characteristics. The information presented in this Chapter is primarily for new construction and includes detailed procedures and requirements for the full range of potential studies and work that might have to be done to support the OWTS design. Some level of site evaluation will be required for the repair, upgrade and/or modification of existing OWTS, but the detail and level of work will vary depending on the specific project and site conditions. This chapter presents the site assessment, field investigation, and reporting requirements for site evaluations associated with the permitting of OWTS and is organized as follows:
Section 3.1:
Site Plan and Topographic Map
Section 3.2:
Soil Profile Study
Section 3.3:
Soil Percolation Testing
Section 3.4
Groundwater Monitoring
Section 3.5:
Cumulative Impact Assessment
Section 3.6:
Geotechnical Evaluation
3.1 SITE PLAN AND TOPOGRAPHIC MAP A.
GENERAL 1. An important step in the site evaluation process is review of the Site Plan and, when required, a topographic map to identify physical features of the lot and adjacent lots that may impact or limit: a. Siting and performance requirements of a new OWTS; b. Siting and performance requirements of an existing OWTS; Revised Draft 6-28-16 14
c. Proposed work associated with a local building agency permit for grading, demolition, or new site construction with respect to potential impact to existing OWTS and reserve/replacement dispersal field areas; d. Proposed land use projects including lot creation, lot line adjustments, subdivisions and conditional use permits with respect to new OWTS design or potential impact to existing OWTS and reserve/replacement dispersal field areas. 2. The Site Plan shall include data obtained by field inspection and survey, and review of information from the Department files, local building agency files, well permitting agency databases, Federal Emergency Management Act (FEMA) flood maps, United States Geological Survey (USGS) maps, and other available databases. 3. The Site Plan shall be used as the base map for OWTS evaluation and design. B.
SITE PLAN REQUIREMENTS
Site Plans must be prepared in accordance with the following general requirements. 1. Size. The plans shall be clearly and legibly drawn to scale on American National Standards Institute (ANSI) “D” sized sheets measuring twenty-two (22) inches by thirty-four (34) inches. 2. Scale. The scale of the plan shall not be smaller than one (1) inch equals twenty (20) feet. The plans shall include a statement of the nominal scale as a ratio or fraction and provide a bar scale to represent the nominal scale. 3. Title Block. The title block shall be include the following information: a. Assessor’s Parcel Number and address of the lot. b. Name, address, telephone number of the individual who prepared the Site Plan. c. Date of plans and subsequent revisions. d. Name, address, and telephone number of the property owner. 4. Vicinity Sketch. The plans shall include a vicinity sketch (not at map scale) indicating the location of the lot relative to the principal roadways, lakes, and watercourses in the area. 5. Assessor’s Parcel Map. The plans shall include a copy of the current Assessor’s parcel map. Revised Draft 6-28-16 15
6. North Arrow. The plans shall include a north arrow. 7. Lot Dimensions and Boundaries. The plans shall show property boundaries and lengths and compass bearings of property lines. 8. Property Line Location. Property lines in the vicinity of OWTS components shall be verified through pin location or boundary surveys (if required). 9. Contour Lines, Spot Elevations, and Slope Designations. The plans shall provide spot elevations, slope designations (percent and direction) and contours of the earth’s surface of existing terrain and proposed grading in the vicinity of existing and proposed OWTS to facilitate evaluation, siting and design. Contour intervals shall be adequate to verify code compliance during plan check. C.
SITE PLAN REQUISITE ELEMENTS
The following information obtained during the site evaluation shall be included on the Site Plan to facilitate OWTS evaluation, siting, and design and compliance with requisite horizontal setbacks from OWTS components. 1. Features on the Lot a. System Related Field Investigation Activities. The plans shall show the locations of soil profile test pits, percolation test holes, geotechnical evaluation test pits or borings, and groundwater observation and monitoring wells, and any other areas of the lot and adjacent lots investigated during site evaluation activities. b. Existing Onsite Wastewater Systems. The plans shall show the location of the components of all existing OWTS on the lot including: i. Prohibited wastewater OWTS (cesspools, seepage pits); ii. Non-discharging wastewater OWTS (holding tanks, vault toilets, portable toilets); iii. OWTS with subsurface dispersal fields; iv. Wastewater ponds; and v. Graywater Systems. c. Buildings and Structures. The map shall show the location and footprint of all existing and proposed buildings and detached structures on the lot. Revised Draft 6-28-16 16
2. Items that may have an impact on the OWTS siting and design must be included on the Site Plan, as applicable and where relevant to the OWTS. 3. The following may be relevant if they are within fifty (50) feet of existing and proposed OWTS: a. Property lines; b. Storm water and groundwater drainage structures (infiltration trenches, interceptor drains, roof run-off piping, sumps, swales, v-ditches, canals, culverts, energy dissipaters, outfalls, etc.); c. Vehicle traffic and storage areas (paved or unpaved); d. Subsurface Utility lines (existing and proposed electrical, sewer, water, gas, etc.); e. Landscaped/irrigated areas; f.
Easements, access agreements, and public right-of-ways (underground utility easements, above ground utility easements, public roadway right-of-ways, private potable water supply access agreements and easements, OWTS access agreements and easements, etc.);
g. Graded/fill areas (building pads, berms, etc.); h. Retaining walls; i.
French drains or groundwater interceptor drains;
j.
Hazardous materials storage areas including above ground and underground storage tanks;
k. General location and character of vegetation; l.
Any tree if judged to pose a construction or operational concern for the OWTS; and
m. Other site development related features and appurtenances including but not limited to patios, decks, gazebos, walkways, children’s play structures, fences, driveways, bridges, decorative ponds, hot tubs/spas, pools, pool houses, ground mounted solar installations, animal pens/corrals, animal wash pads, crush pads, garbage enclosures, etc.). Revised Draft 6-28-16 17
4. The following may be relevant if they are within fifty (50) to one hundred and fifty (150) feet of existing and proposed OWTS. a. Drainage ways, drainage swales, and ephemeral streams (measured from the edge of flow path); b. Steep slopes (measured from the break of slope); c. Cut or steep embankments (measured from the top of cut); d. Unstable land masses or any other areas subject to earth slides identified by a seismic hazard zone map or a registered Civil Engineer or other qualified professional; e. Private existing, abandoned, and proposed potable water supply sources (springs or wells) associated appurtenances including water storage and treatment facilities (storage tanks, pump houses, water softener ponds); f.
Watercourses defined as a body of running water flowing over the earth in a natural water course, where the movement of water is readily discernible or if water is not present it is apparent from review of the geology that when present it does flow (measured from the natural or levied top of bank);
g. Reservoirs, lakes, ponds, or other non-flowing surface water bodies (measured from the high water mark); h. Springs; i.
Floodplain boundaries (100-year); and
j.
Wetlands.
5. The following may be relevant if they are within one hundred and fifty (150) feet to four hundred and fifty (450) feet of existing and proposed OWTS: a. Public water wells; b. Surface water bodies (measured from high water mark of the reservoir, lake or flowing water body) located more than one-thousand two hundred (1,200) feet but less than two thousand five hundred (2,500 feet) from a public water system intake;
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c. Surface water bodies (measured from high water mark of the reservoir, lake or flowing water body) located within two thousand five hundred (2,500) feet from a public water system intake.
SOIL PROFILE STUDY A.
PURPOSE
The purpose of the soil profile study is to: 1. Determine the suitability of the soil for absorption of wastewater in the area of a dispersal system to: a. Ensure that proper soil conditions exist to allow appropriate effluent retention, treatment, and filtration; b. Prevent wastewater from discharging to the ground surface or contaminating groundwater or surface water resources; c. Inform the design of the OWTS. 2. Verify that there is adequate vertical separation between the bottom of the dispersal system and bedrock, groundwater, or impermeable soil strata. B.
DEPARTMENT OBSERVATION 1. A Qualified Professional must perform the soil profile in the presence of the Department representative. The Department may authorize the soil profile to proceed without a Department representative, however, such authorization must be in writing and, may require submittal of photo documentation. 2. Written notice must be given to the Department at least forty-eight (48) hours in advance of conducting the soil profile study. 3. Notification and the request must include Applicant’s name, Assessor’s parcel number, and street address. Failure to provide sufficient notice may result in delay or a requirement to repeat the test. 4. All soil test pits should be dug prior to the Department field observation appointment. 5. If more than one site visit is required to observe the sol profiles, a fee may be charged for reach visit.
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C.
SOIL PROFILE PITS – NUMBER, DEPTH, AND DISTRIBUTION 1. Test pits shall be sufficient in number and adequately spaced to encompass and represent the soil conditions of the entire area of the primary and secondary/ reserve dispersal system areas. 2. A minimum of two (2) soil profiles are required: a. One (1) profile in the primary dispersal system area. b. One (1) profile in the secondary/reserve dispersal system area. 3. Additional soil profiles may be required if the initial two soil profiles show conditions which are dissimilar to the extent that they do not provide sufficient information for design and/or determination of code compliance.
D.
SOIL PROFILE TEST PIT EXCAVATIONS 1. Soil profile test pits are preferred, excavated by a backhoe or excavator or by hand. 2. Auger test holes may be an acceptable alternative to backhoe or hand-dug test pits under the following conditions: a. The use of a backhoe or similar excavating machinery is impractical due to site access constraints or fragile soils; or b. It is necessary only to verify conditions based on prior soils investigations; or c. Soil profiles are required to be no greater than 3-feet deep; or d. It is done in connection with geologic investigation; or e. Where verification of groundwater separation requires additional deeper subsurface exploration; or f.
In connection with corrective actions or documentation of an existing OWTS;
3. When the auger method is used, for new or replacement fields, at least two test holes in the primary and two test holes in the secondary/reserve dispersal field are required. 4. Soil profiles must be excavated to the appropriate depth to verify that there is adequate vertical separation and effective soil beneath the bottom of the dispersal system.
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5. The measurement of effective soil depth is taken from natural grade and must not consider fill material or imported soil. 6. Soil profile test pit and percolation whole depth requirements for standard and alternative OWTS configurations approved for use in the County are shown on Table 3-1. OWTS configurations are further discussed in Chapter 4 of this Manual. E.
SOIL PROFILE OBSERVATIONS 1. For test pits, the excavated sidewall shall be picked away with a sharp instrument to expose the natural soil structure. 2. The Qualified Professional shall identify each soil horizon from ground surface to the bottom of the soil profile. 3. Soil profile observations shall be recorded on the Form 3-1 (Soil Profile Observations) using the abbreviations provided with the instructions. The Soil Profile form shall include a description of the following soil features: a. Soil texture, color, structure, consistency, plasticity, and porosity, for each soil horizon in the excavation utilizing the United States Department of Agriculture (USDA) soil classification system and Soil Textural Triangle (see Figure 3-3). b. Depth and type of limiting condition, including but not limited to bedrock, hardpan, impermeable soil layers, observed free water, saturated soils, or groundwater. c. Depth of soil mottling, gleying or other evidence of periodic soil saturation. d. Other prominent soil features including but not limited to percentage of rock or coarse fragments, root porosity, dampness, or depth and type of fill or imported soil in the profile.
F.
HYDROMETER TESTING 1. Hydrometer analysis is a laboratory test that measures the percentage of sand, silt, and clay in the soil. The data can be plotted on an USDA Soil Textural Triangle to confirm the field classification. 2. If the classification of the soil is in question, the Department may require the qualified professional to provide hydrometer test data to verify the actual classification of the soil.
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3. All samples shall be appropriately labeled and analyzed for soil structure by hydrometer testing in accordance with an approved American Society of Testing and Materials (ASTM) method or USDA method by a soils mechanics laboratory3. 4. The hydrometer analysis is for the purpose of verification of soil classification and cannot be used exclusively since the hydrometer test will not show presence of highly compacted soil or soil structures that limit infiltrative properties. G.
REFERENCES A. USDA, Natural Resources Conservation Service. “Field Book for Describing and Sampling Soils”. September 2002 B. USDA, Natural Resources Conservation Service. “Soil Survey Manual”. C. USEPA, “Design Manual – Onsite Wastewater Treatment and Disposal Systems”. 1980 (pages 28-38).
SOIL PERCOLATION TESTING A.
PURPOSE 1. Percolation testing shall normally be conducted at the time of or shortly following the soil profile investigation and is performed to provide supplemental information required to determine the potential absorption rate of soil in the primary and secondary/reserve areas of dispersal fields. 2. Percolation testing does not replace the need or requirement for soil profile study, soil textural determination, and determination of evidence of high seasonal groundwater.
B.
DEPARTMENT OBSERVATION 1. A Qualified Professional must perform the soil percolation test. The Department may elect to witness the installation of the percolation holes, verify presoaking, and be present during all or part of the testing. 2. Department may authorize the percolation tests to proceed without a Department representative, however, such authorization must be in writing. 3. Written notice must be given to the Department at least forty-eight (48) hours in advance of conducting the soil percolation test.
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4. Notification and the request must include Applicant’s name, Assessor’s parcel number, and street address. Failure to provide sufficient notice may result in delay or a requirement to repeat the test. . 5. All soil percolation test holes should be dug prior to the Department field observation appointment. 6. If more than one site visit is required to observe the soil percolation test, a fee may be charged for reach visit. C.
PERCOLATION TESTS – NUMBER, DEPTH AND DISTRIBUTION 1. Percolation tests shall be sufficient in number and adequately spaced to encompass and represent the soil conditions of the entire area of the primary and secondary/reserve dispersal system areas. 2. A minimum of six (6) percolation tests shall be conducted; three (3) in the primary dispersal area and three (3) in the secondary/reserve dispersal field area. 3. The location of the percolation test holes shall be evenly distributed horizontally and vertically in the dispersal field areas to provide a reasonable representation of conditions within the dispersal field bottom infiltration zone and the sidewall infiltration zone (if applicable). 4. Additional percolation tests may be required if the initial tests show conditions which are dissimilar to the extent that they do not provide sufficient information for design or to refine an exclusion area represented by failed percolation tests.
D.
PERCOLATION TEST HOLE CONSTRUCTION 1. Percolation test holes shall be hand augured or machine augered per the specifications provided below: a. Test holes shall be six inches (6) inches in diameter. b. Test hole sides shall be kept as straight as possible. c. Test holes shall be installed in accordance with the depth requirements in Table 3-1. d. The bottom and sides of the test holes shall be carefully scarified with a blunt edged instrument to remove smeared soil particles and remove all loose soil material.
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e. The native soil structure shall be visible on the bottom ten (10) to twelve (12) inches of the side wall. f.
Two (2) inches of pea-size gravel shall be placed in the bottom of the hole to protect the bottom from scouring and sediment.
g. The test hole shall be stabilized by placing a four (4) inch perforated pipe and a one (1) inch sidewall gravel pack (1/2 to ¾ inch clean washed drain rock) in the test hole to prevent silting of the bottom of the hole and sidewall cave-in. E.
PERCOLATION TEST HOLE PRESOAKING 1. The purpose of the presoaking is to bring the soil moisture to levels representative of wet season conditions. 2. Presoaking is required the day before the testing except under the following conditions: a. When the testing is during Wet Weather Conditions the presoak may occur on the same day. b. In sandy soils with little or no clay content, pre-soaking may occur on the same day of testing. If, after filling the hole twice with twelve (12) inches of water, the water seeps completely away in less than ten minutes, the test can proceed immediately the presoak may be reduced to a minimum period of two hours. 3. Presoaking shall consist of filling each percolation hole with clean water to a minimum depth of twelve (12) inches above the base of the hole for a four (4) hour period and refilling as necessary. 4. Wet Weather percolation testing is required when expansive or shrink/swell types of soil are encountered. Other methods to bring the soil moisture content to a level representative of Wet Weather conditions, such as application of irrigation water for an extended period of time (e.g. several days to a week or more) until appropriate conditions are achieved may be approved by the Department. 5. If more than six (6) inches of water remains above the bottom of the hole after presoaking and prior to the start of the test, this constitutes a failure without any further testing. 6. If less than six (6 inches of water remains) in the test hole after presoaking percolation testing of the hole may proceed.
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F.
CONDUCTING THE PERCOLATION TESTS 1. Conduct the test in accordance with the instructions on Form 3-2 by adding clean water to bring the depth of water in the test hole to approximately six (6) inches above gravel at the bottom of the hole. Maintain approximately six (6) inches of water in the hole, by refilling following each 30 minute interval throughout the test. Water should be added through the pipe rather than into the gravel. 2. Water level measurements shall be measured from the top of the pipe or other reference point and shall be recorded with a 1/8 inch accuracy. 3. Percolation tests results shall be recorded on Form 3-2 (Soil Percolation Test Recorded Measurements).
G.
CALCULATING PERCOLATION RATES 1. Individual Test Hole Percolation Rates a. An Average Stabilized Percolation Rate shall be determined for each test hole by averaging the last three successive stabilized readings varying by no more than 10 percent or 1/8-inch of each other. b. An Adjusted Percolation Rate shall be calculated using the equation below to adjust for the displacement of water by the gravel pack:
Adjusted Percolation Rate (mpi) = Average Percolation Rate (mpi) x Correction Factor Correction Factor = 1.6 for a six (6) inch diameter hole with a four (4) inch perforated pipe and one (1) inch thick gravel pack. 2. Average Adjusted Stabilized Percolation Rate a. An Average Adjusted Stabilized Percolation Rate shall be calculated as the sum of the Adjusted Stabilized Percolation Rates for each individual percolation test hole divided by the total number of percolation test holes completed. b. The Average Percolation Rate is used as the basis for Dispersal Field design. 3. Outliers. Where there is a substantial variation in individual test results (e.g., an order of magnitude difference between high and low outlier values) the wastewater application rate for dispersal field design may be determined by averaging the individual wastewater application rates corresponding to each percolation test result rather than using the wastewater application rate corresponding to the average adjusted stabilized percolation rate. Revised Draft 6-28-16 25
4. Failing Test Results. If there are one or two failing test results, three options are available: a. Include the failing result(s) in the calculated average and design the dispersal system accordingly; b. Exclude the area represented by the failing test hole(s), and design the dispersal system according to the average of the other test holes. Split the difference between the failing and nearby passing test holes to determine the area to be excluded. c. Conduct additional testing in an alternate area or to refine the exclusion area represented by the failed test result(s). If there are more than two failing test results, additional testing will be required to define the limits of acceptable soil areas for the dispersal system. H.
ALTERNATIVE PERCOLATION TEST PROCEDURES
Alternate methods of measuring the percolation rate may be approved by the Department if the proposed procedures can be shown to produce a stabilized rate as described in 1(a) above.
GROUNDWATER MONITORING A.
GROUNDWATER LEVEL DETERMINATION 1. Some locations in Alameda County are subject to high groundwater levels which can have an adverse impact on the performance of the OWTS by eliminating or minimizing the zone of aeration in soils that is critical for optimal wastewater treatment. 2. Installing an OWTS on a site that appears to have adequate separation to groundwater in the dry season but experiences shallow groundwater during the rainy season may result in a OWTS which functions properly only part of the year. 3. Failure to provide the required separation to seasonal high groundwater may potentially result in OWTS failure resulting in: a. Introducing untreated wastewater to the groundwater which could affect area water wells, water quality and public health. b. Effluent surfacing on the ground. c. Sewage backing up into the house fixtures. Revised Draft 6-28-16 26
4. If there are site characteristics or historical documentation indicating that a shallow groundwater table is likely to occur during the rainy season, a wet weather groundwater investigation shall be required. An exception to this may be allowed for sloping sites greater than 5% where a curtain drain may feasibly be installed to intercept and remove lateral ground water flow in the proposed dispersal area in accordance with the design criteria in Chapter 10. B.
DEPTH TO GROUNDWATER DETERMINATION 1. The anticipated highest level of groundwater in the vicinity of OWTS is estimated by: a. The highest extent of soil mottling and/or gleying to natural grade observed in a soil profiles study; b. Data from nearby soil evaluations or groundwater observations; or c. Direct observation of groundwater levels during the time of year when the highest groundwater conditions are expected or known to occur (i.e., during the wet weather period defined in this manual). 2. Where there is a discrepancy between soil profile indications (mottling or gleying) and direct observations, the direct observations shall govern.
C.
FILED OBSERVATIONS THAT MAY INDICATE NEED FOR WET WEATHER TESTING
Field observations that may indicate seasonal groundwater issues include: 1. Visual indication of seasonal groundwater, such as mottling or gleying in soil profiles. Sandy soil lacking the necessary iron compounds may not exhibit mottling or gleying. 2. Landscape position, such as dispersal field location at the base of a hill, near a creek or otherwise located where water is likely to accumulate. 3. Springs or other indications, such as swampy/marshy appearance or presence of riparian or water-loving vegetation such as sedges, rushes, dockweed, willows, or perennial grasses indicating prolonged soil moisture. D.
WET WEATHER TESTING REQUIREMENTS 1. P Piezometers sufficient in number and adequately spaced to encompass and represent the entire primary and secondary/reserve dispersal field areas shall be constructed. 2. At least one piezometer shall be constructed in each dispersal field area (primary and secondary/reserve). Revised Draft 6-28-16 27
3. Piezometer depth shall be equal or greater than the required depth from the bottom of the dispersal fields to groundwater for OWTS approval (see Table 3-1). 4. A permit to install piezometers may be needed from the applicable well permitting agency (Zone 7 water Agency, Alameda County Water District, or Alameda County Public Works). E.
WET WEATHER TESTING WINDOW & FREQUENCY 1. Seasonal wet weather groundwater level determination shall be conducted when sufficient rainfall has occurred in the area to establish the normal seasonal groundwater table. 2. Wet Weather testing period is from October through April and after at least fifty (50) percent of the average annual rainfall (as measured from October 1st through September 30th) has fallen and within a 10-day period following rainfall of at least 0.5 inch in a 48 hour period. The Wet Weather testing period may be extended or shortened by the Department depending on rainfall patterns in a given year. a. There must be three readings spread equally over a minimum two month period during the Wet Weather Period. b. During the testing period there must also be at least one additional reading within two days of a significant rainfall event, which is one (1) or more inches of rainfall within a twenty-four (24) hour period. c. More frequent observations may be necessary during elevated groundwater periods to identify maximum groundwater levels. d. A request may be made to the Department for an alternative testing frequency. 3. Data from local rainfall-monitoring stations shall be used to determine when sufficient rainfall has occurred (e.g., California Irrigation Management Information system (CIMIS) at: http://www.cimis.waterca.gov/).The qualified professional may propose a different source of historical data. 4. Monitoring ports must be staked and flagged so that they can be readily located for periodic confirmatory observations.
Revised Draft 6-28-16 28
F.
WET WEATHER TESTING ALTERNATIVES 1. During years of low rainfall, such as drought conditions, or when Wet Weather testing is not practical for other reasons alternative approaches for the determination of seasonal high ground water levels may approved. Approved alternatives are: a. Conservative Assumption. Adopt a highly conservative (worst case assumption) of ground water vertical separation for the dispersal field design by extrapolating data from adjacent sites with consistent site conditions; or b. Hydrogeological Report. A complete groundwater report prepared by a California Registered Civil Engineer, Registered Geologist, or Registered Hydrogeologist may be submitted to the Department for review and approval. The report must contain supporting data for groundwater elevation conclusions and include an analysis of expected maximum groundwater elevations for dispersal field area. Element for the report shall include:
G.
Topographical and geographical characteristics of the site including slope of the land that could affect surface and subsurface drainage characteristics.
Soil classification and hydraulic conductivity of the soil.
Restrictive layers in the soil profile.
Indicators of seasonal groundwater (e.g., soil mottling).
Depth of observed groundwater in relationship to minimum soil depth requirements and depth of Dispersal Field.
APPLICATION PROCESS FOR WET WEATHER TESTING 1. Single Family Residence OWTS. a. Submit a completed application and fee. b. Submit a preliminary site map showing the proposed locations of piezometers with pertinent topography and features. c. Submit piezometer construction details, including depth. 2. Other larger flow OWTS. a. Submit a completed application and fee. Revised Draft 6-28-16 29
b. Submit a Wet Weather Groundwater Study Plan prepared by a Qualified Professional. c. For larger flow OWTS, deeper groundwater monitoring wells may be required to assess groundwater mounding. H.
GROUND WATER MONITORING 1. Installation of groundwater monitoring wells to assess the current groundwater levels and water quality conditions beneath the site may be required as part of the OWTS design and installation approval. 2. Application Process: a. Submit a completed application and fee. b. Submit a Groundwater Quality Monitoring Work Plan prepared by a Qualified Professional to the Department. Zone 7 Water Agency or Regional Water Board review and approval may also be required. 3. Applications for permits for monitoring wells must be submitted for approval to the applicable well permitting agency (Zone 7 Water Agency, Alameda County Water District, or Alameda County Public Works).
CUMULATIVE IMPACT ASSESSMENT A.
PURPOSE 1. Certain projects require the completion of additional technical studies, termed “Cumulative Impact Assessment” in situations where cumulative impacts on groundwater and/or watershed conditions from OWTS are of potential concern. 2. Cumulative impact issues (mainly groundwater mounding and nitrogen loading) from OWTS may occur due to the following factors: a. the constituent levels in wastewater (e.g., nitrogen content); b. the volume of wastewater flow; c. the density of OWTS discharges in a given area; and/or d. the sensitivity and beneficial uses of water resources in a particular location.
Revised Draft 6-28-16 30
3. These issues are not necessarily addressed by conformance with standard siting and design criteria. B.
CUMULATIVE IMPACT ISSUES 1. The primary issues to be addressed in cumulative impact assessments include: a. Groundwater Mounding - A rise in the water table, referred to as "groundwater mounding", that may occur beneath or down-gradient of OWTS or OWTS as a result of the concentrated or high volume of hydraulic loading from one or more OWTS in a limited area. b. Groundwater Nitrogen Loading: Discharges from OWTS contain high concentrations of nitrogen that may contribute to rises in the nitrate level of local and regional aquifers. 2. Analysis of cumulative impact issues, other than those listed above which could pose potential water quality, public health, or safety risks may also be required.
C.
PROJECTS REQUIRING CUMULATIVE IMPACT ASSESSMENT 1. Projects where cumulative impact assessments shall be required are listed in Table 3- 2. 2. Criteria for assessing hydrological impacts for groundwater mounding or nitrogen loading will be considered on a case-by-case basis. The Department may rely upon Regional Water Board staff or a third-party consultant to assist in the review. Costs for retaining a third-party consultant would be the responsibility of the project applicant.
D.
GROUNDWATER MOUNDING ANALYSIS METHODOLOGY 1. Analysis of groundwater mounding effects shall be conducted using accepted principles of groundwater hydraulics. The cumulative impact assessment submitted to the Department shall include a description of the specific methodology and supported with accompanying literature references, as appropriate. 2. Assumptions and data used for the groundwater mounding analysis shall be stated along with supporting information. 3. A map of the project site showing the location and dimensions of the proposed OWTS and the location of other nearby OWTS, wells and relevant hydrogeological features (e.g., site topography, streams, drainage channels, subsurface drains, etc.) shall be provided. 4. The wastewater flow used for groundwater mounding analyses shall be the design daily sewage flow, unless supported adequately by other documentation or rationale. Revised Draft 6-28-16 31
5. Groundwater mounding analyses shall be used to predict the highest rise of the water table and shall account for background groundwater conditions during the wet weather season. 6. All relevant calculations necessary for reviewing the groundwater mounding analysis shall accompany the submittal. 7. Any measures proposed to mitigate or reduce the groundwater mounding effects shall be presented and described as to their documented effectiveness elsewhere, special maintenance or monitoring requirements or other relevant factors. 8. The maximum acceptable rise of the water table for short periods of time [e.g., one (1) to two (2) weeks] during the wet weather season, as estimated from groundwater mounding analyses, shall be such that the minimum two (2) feet separation to the groundwater is maintained for all OWTS. E.
NITROGEN LOADING ANALYSIS 1. Analysis of nitrate loading effects shall, at a minimum, be based upon construction of an annual chemical-water mass balance. The specific methodology shall be described and supported with accompanied literature references as appropriate. 2. Assumptions and data for the mass balance analysis shall be stated, along with supporting information. Such supporting information should include, at a minimum: a. Climatic data (e.g., precipitation, evapotranspiration rates); b. Groundwater occurrence, depth and flow direction(s); c. Background groundwater quality data, if available; d. Soils conditions and runoff factors; e. Wastewater characteristics (i.e., flow and nitrogen content); and, f.
Other significant nitrogen sources in the impact area (e.g., livestock, other waste discharges, etc.).
3. A map of the project siting showing the location and dimensions of the proposed OWTS and the location of other nearby OWTS, wells and relevant hydrogeological features (e.g., site topography, streams, drainage channels, subsurface drains, etc.) shall be provided. 4. The wastewater flow (average) used for nitrogen loading analyses shall be submitted with adequate backup documentation to support estimated average flows. An Revised Draft 6-28-16 32
average flow of 50 gallons per person per day is an acceptable value for residential OWTS when used in conjunction with an average wastewater nitrogen concentration of 70 milligrams per liter. 5. Minimum values used for the total nitrogen concentration of septic tank effluent shall be as follows, unless supported adequately by other documentation or rationale: a. Residential wastewater: 70 milligrams per liter (mg/L). b. Non-residential wastewater: as determined from sampling of comparable OWTS or from literature values. The use of nitrogen reducing treatment processes may justify reduction in the minimum values as if documented as provided in section 8 below.
6. The Department may require the use of more conservative values than cited above if the values are not likely to be representative of the proposed OWTS. 7. All relevant calculations necessary for reviewing the nitrogen loading analysis shall accompany the submittal. 8. Any measures proposed to mitigate or reduce the nitrogen loading effects shall be presented and described as to their documented effectiveness elsewhere, special maintenance or monitoring requirements or other relevant factors. 9. The minimum criteria for evaluating the cumulative nitrogen loading from the proposed OWTS for areas served by individual water wells shall be as follows: a. Existing lots of record: New OWTS on existing lots of record shall not cause the groundwater nitrate-nitrogen concentration to exceed 7.5 mg-N/L at the nearest existing or potential point of groundwater withdrawal (e.g., water well location); and b. New subdivisions: The total loading of nitrate from new subdivisions shall not result in an average groundwater nitrate-nitrogen concentration over the geographical extent of the subdivision that exceeds 7.5 mg-N/L. 10. The minimum criteria for evaluating the cumulative nitrogen loading from the proposed OWTS for areas not served by individual water wells shall be as follows: a. Existing lots of record: New OWTS on existing lots of record shall not cause the groundwater nitrate-nitrogen concentration to exceed 10 milligrams of Nitrate per liter (mg-N/L) at the nearest existing or potential point of groundwater withdrawal (e.g., water well location); and Revised Draft 6-28-16 33
b. New Subdivisions: The total loading of nitrate from new subdivisions shall not result in an average groundwater nitrate-nitrogen concentration over the geographical extent of the subdivision that exceeds 10 mg-N/L. 11. The Department reserves the right to require, in any individual case, more stringent nitrate-nitrogen compliance criteria where deemed necessary for protection of public health, or based upon specific requirements or recommendations of the Zone 7 Water Agency or San Francisco Regional Water Board.
GEOTECHNICAL EVALUATION A.
PURPOSE 1. Geotechnical/geological investigations shall be required in accordance with the provision of chapter 15.36 of the Alameda County General Ordinance and in any of the following circumstances: a. When dispersal systems are proposed on sites with natural ground slopes greater than thirty (30) percent; b. When a proposed OWTS is located within an earthquake fault zone or a seismic hazard zone, as delineated on the official maps published for that purpose by the California Geologic Survey, or when such hazards are otherwise known or suspected in the location of the OWTS; c. For proposed reductions in horizontal setbacks from cuts, embankments, steep slopes or an unstable land mass; or 2. The geotechnical evaluation shall assess slope stability, drainage, and other factors and demonstrate through a geotechnical report and engineering installation plan that the use of the subsurface dispersal field will not permit wastewater to surface, degrade water quality, create a nuisance, affect soil stability, or present a threat to the public health or safety.
B.
GEOTECHNICAL REPORT REQUIREMENTS 1. The geotechnical report shall include, but not be limited to, soil percolation rates, contours, soil depth, seasonal groundwater elevation(s), location of all existing or proposed ground cuts, rock formations, soil stability, drainage, and other data as determined by the Geotechnical Engineer. 2. The report must specially reference the OWTS plan. 3. If at some future date, the OWTS is appreciably modified an amended report must be submitted that references the modified plan. Revised Draft 6-28-16 34
4. The geotechnical report must discuss the following: a. b. c. d. e. f. g. h. i. j.
Geology Slope stability and seismic hazards Soil Groundwater Drainage Percolation Rate Topography Cuts Vegetation Other pertinent site features
5. The report shall include any recommendations deemed appropriate or necessary to mitigate potential slope stability, drainage or seepage concerns associated with the OWTS Installation and operation including as applicable recommended horizontal setback(s) from any cut banks, embankments, steep slopes or unstable land masses. 6. The report shall state specifically in the conclusion that the proposed OWTS will not (or other wording such as not likely to, risk is very low, etc.): a. b. c. d. e.
Permit sewage effluent to surface Degrade water quality Affect soil stability Present a threat to public health or safety Create a public nuisance
7. The report shall be wet-stamped and signed by the qualified professional.
Revised Draft 6-28-16 35
[RESERVED FOR TABLE 3-1]
Revised Draft 6-28-16 36
This chapter presents general design criteria used for designing all OWTS and for selecting OWTS components in the treatment train including tanks, supplemental treatment systems, and subsurface dispersal systems. This Chapter is organized in the following sections:
Section 4.1:
OWTS Types and Treatment Train Overview
Section 4.2:
Wastewater Design Flow Criteria
Section 4.3:
Wastewater Strength
Section 4.4:
Wastewater Application
Section 4.5:
OWTS Siting Criteria
Section 4.6:
OWTS Design Submittal Requirements
OWTS TYPES AND TREATMENT TRAIN OVERVIEW A.
TYPES OF SYSTEMS 1. OWTS may be individual systems or community systems. 2. Standard Systems. A Standard System is a type of onsite wastewater treatment system consisting of a septic tank for primary treatment of sewage followed by a system of drainfield trenches for subsurface dispersal of wastewater effluent into the soil. A standard system may utilize gravity flow or a pump system to convey effluent from the septic tank to the drainfield. 3. Advanced Systems: An Advanced System is a type of onsite wastewater treatment system that utilizes either a method of wastewater treatment or supplemental treatment other than a septic tank and/or a method of wastewater dispersal other than a standard drainfield trench. Advanced systems are designed to produce a higher quality wastewater effluent and improved performance of and siting option for effluent dispersal where a standard system is not suitable. 4. Other Systems. a. Holding Tanks. A holding tank is a self-contained, watertight container designed to hold Wastewater until it is pumped and/or cleaned and are only allowed in limited circumstances. Revised Draft 6-28-16 37
b. Non-Discharging Toilets. A Non-Discharging Toiletal Unit is a self-contained, watertight container designed to hold Wastewater until it is pumped and/or cleaned and includes vault privies, portable toilets, and waterless toilets and are only allowed in limited circumstances. c. Graywater Systems. A Graywater System is a type of system designed to collect graywater and transport it out of the structure for distribution in an irrigation field. A Graywater System may include tanks, valves, filter, pumps, or other appurtenances along with piping and receiving landscape and is governed by the California Plumbing Code and not the County OWTS. Ordinance. A Graywater System does not replace the requirement for an Onsite Wastewater Treatment System. B.
SYSTEM SELECTION OVERVIEW 1. Selection of the appropriate system type, size, and location at the site is based on the wastewater flow and composition, site evaluation, performance requirements, and evaluation of the available technology options approved for use in the County. A general overview is provided in Figure 4-1 and Figure 4-2. 2. The main criteria used in selection of the treatment train components includes the level of wastewater treatment required prior to discharging to the dispersal system, wastewater application and loading rates to infiltrative surfaces, wastewater dispersal mechanisms (gravity fed or pressure dosed), and siting constraints (including horizontal setbacks requirements, vertical separation to groundwater requirements, effective soil depth, soil classification and percolation rate, site topography, and available area on a parcel for a dispersal system).
C.
MAJOR SYSTEM COMPONENTS (TREATMENT TRAIN) 1. The major components commonly utilized in the treatment trains for sanitary waste include tanks, supplemental treatment systems, and dispersal systems. A schematic of the treatment train or sequence of the treatment components shall be shall be included on the design plans. 2. The types of tanks approved for use in the County are listed below. Design requirements for tanks are provided in Chapter 5 of this Manual. a. Septic Tanks b. Holding Tanks c. Pump Tanks d. Dosing Tanks Revised Draft 6-28-16 38
e. Flow Equalization Tanks f.
Grease Interceptor Tanks
3. The types of Supplemental Treatment Systems approved for use in the County are listed below. Design requirements for Supplemental Treatment systems are provided in Chapter 6 of this Manual. a. Proprietary Treatment Units (manufactured or “package” units) b. Intermittent Sand Filters c. Recirculating Sand Filters d. Other Supplemental Treatment systems approved by the Department and the Regional Water Quality Control Board. 4. The types of subsurface dispersal Systems approved for use in the County are listed below. Design requirements for dispersal Systems are provided in Chapter 7 of this Manual. a. Standard Gravity Trench Dispersal Systems b. Pressure Distribution Trench Dispersal Systems c. Pressure-dosed Sand Trench Systems d. Drip Dispersal systems e. At-Grade Systems f.
Mound Systems
g. Raised Sand Filter Bed Systems (repair or replacement Systems only) h. Engineered Fill with Subsurface Drip Systems (repair or replacement Systems only) i.
Other alternative dispersal systems approved by the Department and Regional Water Quality Control Board
Revised Draft 6-28-16 39
5. The types of non-discharging toilets approved for use in the County are listed below. Design requirements for non-discharging units are provided in Chapter 8 of this Manual. a. Vault toilet or privies b. Portable toilets c. Waterless toilets
WASTEWATER DESIGN FLOW CRITERIA A.
SINGLE FAMILY RESIDENCES AND SECONDARY UNITS 1. System sizing for residential dwellings shall be based on the maximum daily flow rate. 2. Wastewater flows used for design of Systems for single family residences and secondary units shall be based on a factor of one hundred and fifty (150) gallons per day (gal/day) per bedroom for the first three (3) bedrooms, plus seventy-five (75) gal/day for each additional bedroom, as indicated in Table 4-1. 3. For residential buildings the Department may grant design flow reductions of up to 20% where certain water saving devices such as 1.6 gallon low flush toilets, flow restrictors and aerators for faucets, and low flow showerheads are incorporated permanently into the buildings being used. 4. The design flows for a primary residence and secondary dwelling unit shall be determined independently, regardless of whether the flows are treated separately or combined in a single System.
B.
MULTIUNIT RESIDENCES AND NON-RESIDENTIAL FACILITIES 1. System sizing shall be based on the maximum daily flow rate. 2. Wastewater flows used for the design of Systems for multiunit residences and nonresidential projects shall be developed based on full consideration of projected activities, occupancy, and facilities. 3. Table 4-2 provides guidelines for use in estimating design wastewater flows. 4. For facilities not listed in Table 4-2 the wastewater design flow are to be estimated based on either: (a) appropriate literature references (e.g., US EPA) for the type of facility proposed; or (b) documented wastewater flow monitoring data for a comparable facility. Revised Draft 6-28-16 40
5. The Department may consider adjustment to the criteria listed in Table 4-2 for specific facilities based upon documented wastewater flow monitoring data. 6. In all cases, the design proposal shall include sufficient technical information to support the proposed design flow estimate. C.
WINE PROCESSING FACILITIES [RESERVED]
WASTEWATER STRENGTH DESIGN CRITERIA A.
GENERAL 1. The System Designer is responsible for ensuring that wastewater in each project is properly characterized. 2. For nonresidential facilities wastewater strength criteria can be obtained from literature or actual sample results from similar facilities.
B.
WASTEWATER TYPES 1. Blackwater a. Blackwater is defined as wastewater contaminated with human or kitchen wastes, generally originating from toilets and kitchen sinks. b. Blackwater includes, but is not limited to, wastewater discharges from kitchen sinks, garbage grinders, water closets, toilets, urinals or similar fixtures alone or in combination with other wastewater. 2. Graywater a. Graywater is defined as untreated wastewater that has not been contaminated by any toilet discharge, and has not been affected by infectious, contaminated, or unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes (Health and Safety Code section 17922.12). b. Graywater includes but is not limited to Wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs. Revised Draft 6-28-16 41
c. Graywater does not include wastewater from kitchen sinks or dishwashers. 3. Process Wastewater. Process wastewater is generated from any manufacturing, processing institution, commercial, or agricultural operation, or any operation that discharges other than sanitary wastewater. All waste water treatment and disposal systems for process wastewater are regulated by the Regional Water Board. C.
PRIMARY PARAMETER USED TO EVALUATE THE QUALITY OF WASTEWATER 1. Biochemical Oxygen Demand (BOD). BOD measures oxygen required for biochemical degradation of organic and inorganic material. High BOD causes an increased biological demand on downstream System components and may shorten the life of the System. 2. Total Suspended Solids (TSS). TSS are a constituent of total solids. TSS is residue retained on a filter after drying the sample and is a measure of the level of treatment being achieved. TSS can be inorganic particles, which are difficult for biological processes to break down, resulting in mechanical clogging. In wastewater with high TSS, inorganics are less easily broken down and can accelerate mechanical clogging of the infiltrative surface of the dispersal system. 3. Fats, Oil and Grease (FOG). FOG is a measure of biological lipids and mineral hydrocarbons. The analytical test for FOG does not measure an absolute quantity, but is useful in making comparisons of wastewater. High FOG results in increased biological demand on downstream System components and may shorten the life of the System. 4. Nitrogen. Nitrogen is of concern due to its impact on groundwater and surface water. Nitrogen can change form as it moves through a treatment system and into the receiving environment. Nitrogen is a nutrient that can impact surface water and poses a potential health risk in groundwater. The principal forms of nitrogen found in sewage wastewater are organic nitrogen (Organic-N), ammonia nitrogen (NH3-N), ammonium nitrogen (NH4-N), nitrite-nitrogen (NO2-N), and nitrate-nitrogen (NO3-N). Measurement of total nitrogen is determined from the combination of two anaylitical tests: (1) Total Kjeldahl Nitrogen (TKN which is the sum of (Organic-N) + (NH3-N) and (2) Nitrate–nitrogen.)
D.
WASTEWATER STRENGTH 1. Domestic Strength Wastewater a. Domestic strength wastewater is defined as wastewater with a measured strength less than high-strength wastewater (see Table 4-3) and is defined as Revised Draft 6-28-16 42
having a thirty (30) day average concentration of the following constituents prior to a septic tank or supplemental treatment component: i. BOD less than or equal to 300 milligrams per liter (mg/L); or ii. TSS less than or equal to 330 mg/L; or iii. FOG less than or equal to 100 mg/L. b. Domestic wastewater is normally discharged from, or similar to, that discharged from plumbing fixtures, appliances and other household devices including, but not limited to toilets, bathtubs, showers, laundry facilities, dishwashing facilities, and garbage disposals. c. Domestic wastewater may include wastewater from commercial buildings such as office buildings, retail stores, and some restaurants or from industrial facilities where the domestic wastewater is segregated from the industrial wastewater. d. Domestic wastewater may include incidental recreational vehicle (RV) holding tank dumping but does not include wastewater consisting of a significant portion of RV holding tank wastewater such as at RV dump stations. e. Domestic wastewater does not include wastewater from industrial processes. 2. High Strength Wastewater a. High strength wastewater is defined as wastewater with a measure strength greater than domestic wastewater (see Table 4-3) and is defined as having a thirty (30) day average concentration of the following constituents prior to the septic tank or a supplemental treatment component: i. BOD5 greater than 300 milligrams per liter (mg/L); or ii. TSS greater than 330 mg/L; or iii. FOG greater than 100 mg/L. 3. High Strength Facility Wastewater. Guidelines for high strength wastewater facilities are provided in Table 4-4 and are based on the type of business or facility, waste streams and usage characteristics.
Revised Draft 6-28-16 43
WASTEWATER APPLICATION RATES A.
GENERAL 1. Subsurface Dispersal Systems are sized based on wastewater application rates that are representative of the soil classification and percolation rates for the soil zone corresponding to the sidewall and bottom of the dispersal system.
B.
WASTEWATER4 APPLICATION RATES BASED ON PERCOLATION RATE 1. The maximum wastewater application rate for conventional gravity trench dispersal fields in Standard Systems shall be in accordance with the criteria in Table 4-5. 2. The maximum wastewater application rate for At-Grade Dispersal Systems shall be in accordance with the criteria in Table 4-6. Soil with average percolation rates greater than sixty (60) mpi shall utilize supplemental treatment. 3. Increased maximum wastewater application rates may be utilized for Advanced Systems with supplemental treatment due to the reduction in Biochemical Oxygen Demand (BOD) in the treated effluent. a. Wastewater application rates for Pressure-dosed Sand Trench Systems, Mound Systems, and Raised Sand Filter Beds are provided in Table 4-7. b. Wastewater application rates for Drip Dispersal Systems are provided in Table 4-8.
C.
SOIL PERCOLATION AND SOIL CLASSIFICATION COMPARISON 1. Table 4-9 provides a general relationship between soil type and expected percolation rate. Percolation may also be influenced by other factors such as structures, roots, coarse fragments, and shrink-swell conditions. 2. Where percolation test results, vary significantly from Table 4-9 guidelines, the System Designer shall evaluate and provide an explanation for the deviations.
OWTS SITING CRITERIA A.
MINIMUM HORIZONTAL SETBACK DISTANCES FROM SITE FEAUTURES TO SYSTEM COMPONENTS 1. The System design and installation shall meet the minimum horizontal setback distances provided in Table 4-10 and depicted on Figure 4-3.
Revised Draft 6-28-16 44
2. INSERT NARRATIVE FOR TABLE 4-10 3. Incorporated cities may also have their own requirements for setbacks that are not included in the Ordinance and this manual. Applicants are encouraged to check with the local jurisdiction Planning and Building Departments. B.
DUAL DISPERSAL SYSTEM REQUIREMENT 1. Standard OWTS. A primary and a secondary dispersal system shall each be designed to accept one hundred (100) percent of the peak daily design flow. Both primary and secondary systems shall be installed, and shall be equipped with an approved (manual) diversion device to allow alternating use of the two systems, typically switching between systems every 6 to 12 months. 2. Advanced OWTS. A replacement area with suitable site conditions for a new OWTS installation shall be identified and preserved for future use. The replacement area must be: a. For residential, a replacement area equal to one hundred (100) percent of the size required for the primary (installed) system; b. Non-residential OWTS. In lieu of a replacement area, must have a primary and secondary system installed, and shall be equipped with an approved (manual) diversion device to allow alternating use of the two systems, typically switching between systems every 6 to 12 months; c. Totally separate from the primary system area; d. Able to meet all current design requirements for the type of replacement system proposed; and e. Fully protected to prevent damage to Soil and any adverse impact on the immediate surrounding that may affect the installation of the replacement system and its function.
C.
MINIMUM VERTICAL SEPARATION DISTANCES & EFFECTIVE SOIL DEPTH FOR DISPERSAL AREA 1. Dispersal systems shall be designed to meet the minimum effective soil depth and vertical separation distances from high seasonal groundwater or limiting layer such as impermeable soil or bedrock. 2. The vertical separation and effective soil depth requirements depend on the soil characteristics and groundwater observations as discussed in Chapter 3.
Revised Draft 6-28-16 45
3. Where Advanced OWTS are utilized, the minimum effective soil depth and the vertical separation to groundwater distance may be reduced from the requirements that apply to Standard OWTS. 4. Minimum vertical separation distances to groundwater and minimum effective soil depth requirements for Standard and Advanced OWTS configurations approved for use in the County are provided in Table 3-1. D.
DISPERSAL AREA SLOPE REQUIREMENTS 1. Dispersal systems shall be designed to comply with the maximum slope requirements allowable for the specific type of system. 2. Maximum ground slope for Standard and Advanced OWTS configurations approved for use in the County are provided in Table 4-11.
Geotechnical/geological report is required (in accordance with the requirements of chapter 3 of this manual and chapter 15.36 of the Alameda County General Ordinance) for OWTS on sites with slopes greater than thirty (30) percent. 3. If the OWTS is located within earthquake fault zone and seismic hazard zone s delineated on the official maps published for that purpose by the California Geologic Survey (“Fault Zone”), the plans must show the zones. a. For any project that requires a geotechnical report due to its location with a Fault Zone within the map fault zone, the scope of geotechnical work shall include an evaluation and recommendations for the OWTS. A copy of the report shall be included with the OWTS design documents. b.
For corrective actions or repair of an existing OWTS a geotechnical evaluation with recommendations for the OWTS by a California- Licensed Civil Engineer or Certified Engineering Geologist may be required.
c. If any benching or fill is proposed in the dispersal field area, with the exception of that required for an At-Grade or Mound system, a geotechnical evaluation with recommendation for the OWTS by a California-Licensed Civil Engineer or Certified Engineering Geologist may be required. E.
FLOODPLAINS AND FLOODWAYS 1. Setbacks from floodplains and floodways as designated on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) shall be in accordance with the provisions of Chapter 13.12 and Chapter 15.40 of the Alameda County General Ordinance Code in order to prevent damage to OWTS components by associated flood events. Revised Draft 6-28-16 46
2. All new and replacement OWTS located within such floodplains, shall include design features to prevent infiltration of flood waters into the OWTS or discharge from the OWTS into flood waters. The analysis and design features must include: a. Protecting OWTS components from flood damage using structural tie-downs and/or elevating critical components above the one hundred (100) year flood level; b. Preventing discharge of wastewater into flooded dispersal areas from pump systems (e.g., using flood-activated float switches to override/disable pump operation during high water conditions); and c. Providing additional emergency storage capacity for flood periods. F.
UPPER ALAMEDA CREEK WATERSHED ABOVE NILES 1. Additional requirements related to development density and nitrogen loading must be met in the Upper Alameda Creek Watershed above Niles in accordance with Zone 7 Water Agency’s 2015 Nutrient Management Plan for the Livermore Valley Groundwater Basin, issued by Zone 7 in February 2015 and adopted by the San Francisco Bay Regional Water Board in March 2016. The additional requirements apply to new, upgraded, and replacement OWTS. Different requirements apply depending on where the parcel is located within the Watershed and are depicted on Figure 4-4. 2. The Nutrient Management Plan identifies designated areas of concern within the Upper Alameda Creek Watershed above Niles. For these areas Zone 7 requires nitrogen reduction treatment, which are contained on Figure 4-5. These areas, shown in Figure 4-6, are: a. b. c. d. e.
Happy Valley, Pleasanton Buena Vista, Livermore Mines Road, Livermore May School, Livermore Greenville, Livermore
3. The Department may be contacted to confirm what requirements apply to a parcel. 4. The additional requirements do not apply to existing, properly-working and properlysized OWTS. 5. The additional requirements are dependent on the total size of the parcel and whether the Lot is located inside or outside of the limits of five designated Areas of Concern (see Figure 4-4) and include: Revised Draft 6-28-16 47
a. Outside Areas of Concern. Minimization of nitrogen loading from new OWTS by applying one rural residential equivalence of wastewater (RRE) per five (5) acre maximum provisions. b. Inside Areas of Concern. i. Minimization of nitrogen loading from new systems by applying one (1) RRE per ten (10) acre maximum provisions and requiring Advanced OWTS with nitrogen- reducing treatment for new, upgraded, or replacement OWTS; or ii. Preparation of a hydrogeological study that assesses existing groundwater nitrate conditions beneath the site and demonstrates that nitrate concentration of total OWTS recharge does not exceed 36 mg/L (80 percent of the maximum contaminant concentration for drinking water) or the maximum concentration at the site, whichever is lower. c. High Strength and High Flow OWTS. Installation of groundwater monitoring wells to monitor nutrient loading from onsite operations.
OWTS DESIGN SUBMITTAL REQUIREMENTS A.
OWTS DESIGN PLANS 1. The OWTS plans must include sheets with legible and scaled plan views, cross sections, and details sufficient to allow: a. Review by Department staff for compliance with the requirements of the Ordinance and this manual. b. OWTS installation. 2. The OWTS plans must l include the signature and wet stamp of the OWTS designer and provide the name of the qualified professional who prepared the topographic base map and the date of the survey. 3. The OWTS plans must show the layout of all OWTS components including reserve areas on the Site Map prepared in accordance with the requirements of Chapter 3 of this Manual. The Site map shall include all information obtained from the Site Evaluation and sufficient spot elevation data to confirm the siting and hydraulic design of the OWTS. Revised Draft 6-28-16 48
4. The OWTS plans must be dimensioned to show at a minimum all requisite setback designations to OWTS components, slope designations in the vicinity of OWTS components (percent and arrows for direction), and surface water flow direction (arrows). 5. The OWTS plans shall include plan view sheets, cross sections and details showing as applicable: a. Elevations of building sewers as they exit buildings or structures connected to the OWTS to demonstrate adequate fall to the septic tank or other appurtenance; b. Tank depths and slope of original grade and proposed grading (if applicable) to prevent storm water infiltration; c. Effluent piping from the tank to the dispersal system; d. Cross section through the dispersal field that show dispersal line depths and details, and any benching that will be necessary to install the system and vertical separation to groundwater and effective soil depths relative to the bottom of the dispersal system; e. Effluent pipe crossings with site utilities to verify minimum vertical setback requirements; f.
Surface drainage facilities and diversion structures;
g. Curtain drains; and h. Other pertinent features that could affect OWTS installation and performance. 6. The OWTS plans must include an erosion control plan, incorporating measures consistent with guidelines and requirements contained in chapter 15.36 (grading, erosion and sediment control) of the Alameda County General Ordinance. 7. The OWTS plans shall incorporate applicable recommendation contained in the geotechnical report regarding the avoidance or mitigation of slope stability concerns, including, as applicable, recommended horizontal setback distance(s) from cut banks, embankments, steep slopes, or any identified unstable land mass within one hundred (100) feet of the OWTS. 8. The design plans shall include: a. All relevant elevation data and hydraulic calculations; Revised Draft 6-28-16 49
b. Make and model of all components; c. Pump system components, float settings, and dosing calculations; d. Control panel programming; e. Specific step-by-step construction guidelines and notes for use by the installation Contractor; and f.
An inspection schedule listing critical control points.
9. The plans submitted with the OWTS design documents must be identical or incorporated into the plans submitted to the authority issuing a building permit. B.
OWTS BASIS OF DESIGN REPORT 1. The OWTS plans shall be accompanied by a bound design report documenting the basis of the OWTS design. The design report shall include but not be limited to the following: a. Legible field data sheets documenting the results of the soil profile and percolation tests; b. Manufacturer spec sheets for all OWTS components; c. Hydraulic calculation sheets; d. Design flow and other wastewater characteristics; and e. Other pertinent data required to support the OWTS design. 2. Reports documenting geotechnical evaluations, cumulative impact assessments, hydrogeological studies, or other evaluations must be appended to the Basis of Design Report.
C.
OPERATIONS, MAINTENANCE AND MONITORING PLAN 1. Operations, Maintenance & Monitoring Plan (OM&M Plan) shall be submitted with the OWTS design plans and the Basis of Design Report for all OWTS. The content of the OM&M Plan will differ depe The OM&M Plan shall include requisite maintenance, monitoring and reporting activities for the OWTS, including the following elements as applicable: a. Diagrams of the OWTS and list of components; Revised Draft 6-28-16 50
b. Manufacturer name and model number for key equipment and proprietary system components; c. Explanation of general the OWTS function, operational expectations, Owner responsibility, etc.; d. Half sized copy (11”X17”) of the design plans, updated with “as built” information as applicable at the conclusion of OWTS installation (any changes must be approved by the Department); e. Routine maintenance schedule; f.
Information on troubleshooting common operational problems that might occur with the specific OWTS; and
2. The OM&M Manual will be supplemented or updated by as appropriate, including after repairs, or modifications to the OWTS. The guidelines presented in this chapter provide general design guidelines for the different types of tanks that may be utilized as part of the treatment train prior to effluent dispersal into a Supplemental Treatment System or the Dispersal System. OWTS employ various buried and/or above ground tanks such as septic, flow equalization, grease interceptor, holding, pump and dosing tanks.
Revised Draft 6-28-16 51
The chapter is organized in the following sections:
Section 5.1:
General Performance Requirements
Section 5.2:
Septic Tank Design Criteria
Section 5.3:
Flow Equalization Tank Design Criteria
Section 5.4:
Grease Interceptor Tank Design Criteria
Section 5.5:
Holding Tank Design Criteria
Section 5.6:
Pump and Dosing Tank Design Criteria
Section 5.7:
Tank Installation and Destruction/Removal Requirements
GENERAL PERFORMANCE REQUIREMENTS A. The following requirements apply to all new and replacement tanks (including septic, flow equalization, grease interceptors, holding, pump and dosing): 1. APPROVED TANKS a. All tanks in the treatment train (e.g., septic, flow equalization, pump, dosing, grease interceptor, treatment tanks) must have a current International Association of Plumbing and Mechanical Officials (IAPMO) or an American National Standards Institute (ANSI) accredited testing organization approval listing. b. An exception to IAPMO or ANSI approval listing may be granted where structural design calculations for the septic tank are provided by a California Registered Civil Engineer. c. Each tank shall be permanently marked on the uppermost surface with the manufacturer’s name and/or trademark, and the nominal working volume. d. Permanent markings shall be adequately protected from corrosion so as to remain permanent and readable over the life of the tank. The product shall also bear the Uniform Plumbing Code certification mark (UPC®).
Revised Draft 6-28-16 52
e. Heavy5 cement-based sealants are approved for sealing concrete tanks and may be required. 2. MATERIALS a. Tanks shall be constructed of reinforced concrete, heavyweight reinforced concrete blocks, fiberglass or other durable, non-corrodible materials as approved by the Department. b. Wood and metal tanks are prohibited. c. Tanks shall be monolithic or if not, tank seams shall be located above the effluent level. 3. STRUCTURALLY SOUND a. Tanks shall be designed to be structurally sound to withstand the live and dead loads experienced at the site to prevent cracking or collapse. b. The potential impacts due to structurally unsound tanks include safety of people in the area of the tank, the operation of the OWTS and the formation of cracks or other openings that cause leaks. c. Tanks shall be designed and certified by a Professional Engineer, licensed and qualified to perform structural design. d. Tank selection shall be based on all reasonably expected loading conditions, including burial depth, hydrostatic forces when tank is full or empty, and any other reasonable expected loading conditions. 4. TANK ACCESS a. Access to tanks shall be designed to allow maintenance and prevent injury or death caused to a human or animal due to unintended entry into the OWTS. b. Access at ground level or above shall be provided for all tanks and/or components contained therein. c. Access to each compartment of a tank for maintenance shall be provided by a minimum twenty (20) inch diameter opening or equivalent.
Revised Draft 6-28-16 53
d. Tanks shall be installed so that manhole covers are within twenty-four (24) inches of the ground surface. e. The riser lid must be capable of preventing accidental or unauthorized entry. Access shall be secured by bolting or locking lids or by virtue of the lids own weight. . Covers, risers and lids shall be capable of bearing the expected live and dead loads. Potential loads could include people, lawn equipment, or vehicles. f.
Access openings shall be located to provide visual inspection, maintenance and/or repair of sanitary tees, effluent filters, baffles, and pump assemblies.
g. Tanks with influent compartments twelve (12) feet in length or greater shall have an additional access opening located over the baffle. 5. TANK RISERS a. All access openings on tanks shall have risers extended a minimum of two (2) inches above the finished grade except in area of traffic, where they should be flush mounted. b. Except for concrete grade rings, risers shall be installed in one continuous piece without seams. c. All risers shall be securely attached by means of a watertight collar and/or other sealant material applied according to the manufacturer’s instructions. d. All risers shall be fitted with gastight, watertight, vermin proof, securely fastened covers that are removable with standard hand tools. e. All covers shall be of durable construction, manufactured specifically for their intended use. 6. TANK CONNECTIONS a. All connections from buildings and structures to tanks shall conform to construction standards as required by State and local building codes. b. A cleanout at finished grade shall be provided between each structure and/or building directly connected to a tank.
Revised Draft 6-28-16 54
7. HORIZONTAL SETBACKS All tanks shall meet the horizontal setbacks for septic tanks provided in Table 4-10. B.
WATERTIGHT 1. Prevention of Infiltration and Exfiltration. Tanks shall be watertight while installed and operating to prevent infiltration (or inflow) of groundwater and storm water and exfiltration (or outflow) of wastewater. a. Inflow of Groundwater or Storm Water. OWTS are designed to return a predetermined volume and quality of wastewater to the environment. A tank allowing inflow of groundwater or surface water into the OWTS can overwhelm the capacity of the downstream OWTS components and lead to hydraulic overload of the OWTS and/or inadequate wastewater treatment. Surges of inflow can also displace solids from the tank adversely affecting the operation and operating life expectancy of downstream OWTS components. b. Outflow of Wastewater. Leaking tanks can create a public health hazard and contaminate surface water and groundwater due to bypassing the downstream components of the Treatment Train. 2. New Tank Test Procedures. Watertight testing for new tanks shall be done in accordance with the following procedures: a. Tanks, inlet and outlet connections, risers and riser covers shall be completely watertight. b. Watertight tests shall be conducted under the oversight of the OWTS Designer. A watertight test certification form shall be submitted by the OWTS Designer prior to the Department granting final approval of the OWTS. c. The watertight test shall be performed after tank installation is complete including connecting inlet and outlet piping (with caps) and installing risers (if applicable). d. Whenever possible, risers shall be installed as one continuous piece. e. Backfill may or may not be in place depending on whether the backfill is integral to the structural design of the tank. f.
The tank shall be filled with water to two (2) inches above the highest connecting inlet or outlet piping or the tank and riser connection (if installed). If multiple riser connections or concrete grade rings are used, water shall be added to two (2) inches above the highest riser connection. The level of the Revised Draft 6-28-16 55
water in the tank or riser shall be marked and after a predetermined “test time” applicable to the material or assembly, the water level in the tank (or riser) shall be checked and a visual inspection shall be made on the outside of the tank for leakage (if possible). If no visual evidence of leaking is observed and water is at mark the tank shall be considered watertight. i. Fiberglass or Plastic Tanks. If there is no measurable loss of water for one (1) hour and no visual signs of leakage, the tank is considered watertight. ii. Concrete Tanks. Concrete tanks shall be left for twenty-four (24) hours after filling the tank to allow for a period of time for natural absorption into the material prior to beginning the watertight test. After twenty-four (24) hours the tank(s) shall be refilled to two (2) inches above the piping or riser connection). If there is no measurable loss after one (1) hour and no visual signs of leakage, the tank is considered watertight. 3. Existing Tank Test Procedures. In watertight testing for existing tanks undergoing modifications or repairs, the tank shall be pumped by a licensed septic pumper to remove its contents prior to conducting the test (as described in item 2 above). 4. Repairs. Repairs can be made to tanks failing the watertight test provided the structural integrity has not been compromised. C.
TANK SPECIFIC.
Tanks must also meet the requirements as applicable and contained in Sections 5.3 through 5.8.
SEPTIC TANK DESIGN CRITERIA SEPTIC TANK DESIGN CRITERIA A.
GENERAL 1. The primary purpose of the septic tank is to clarify the wastewater (i.e., separate constituents that float and sink from the other wastewater constituents). 2. A second benefit of the septic tank is that decomposition of organic material begins in the septic tank. Raw waste is reduced to sludge, scum, gases, and effluent with the aid of beneficial microbes that reduce the organic material without outside energy sources.
Revised Draft 6-28-16 56
3. The operating environment of most septic tanks is: buried below ground, in or above ground water, empty or full of sewage. 4. The septic tank system consists of the tank, riser(s) and inlet/outlet ports (see Figure 5- 1). 5. This section discussed the requirements and guidelines for new and replacement septic tanks, unless specifically stated otherwise. B.
MINIMUM CAPACITY 1. Adequate septic tankage will anaerobically digest organic material, remove settleable and floatable solids, help modulate flow, and consistently discharge effluent that meets the primary treatment standards. 2. The minimum capacity of septic tanks for residential OWTS shall be determined by the number of bedrooms in the dwelling as follows: No. of Bedrooms
Minimum Septic Tank Capacity (gallons)
1 to 2 3 to 4 5 to 6 7 to 8 9 to 10
1,000 1,200 1,500 2,000 2,500
3. The minimum capacity of septic tanks for non-residential OWTS with Type 1 residential quality waste (see Chapter 4 for discussion of waste Types) shall be one thousand two hundred (1,200) gallons or two times the peak daily wastewater flow for the facility served, whichever is greater. Larger tankage is recommended for Type 2 through Type 5 waste for optimal OWTS performance and may be required for certain proprietary treatment systems. Guidelines for minimum and preferred tank sizing for certain facility types and certain proprietary units is provided in Table 5-1. C.
SEPTIC TANK COMPARTMENTS 1. Septic tanks shall have a minimum of two (2) compartments. 2. The inlet compartment shall be a minimum of two-thirds (2/3) of the total liquid capacity of the tank. 3. Septic tank compartments shall be separated by a baffle that is permanently affixed, constructed of a solid durable material, and extends a minimum of four (4) inches above the working liquid level. Revised Draft 6-28-16 57
4. The septic tank baffle shall provide an air vent that connects the two compartments above the working liquid level. 5. A baffle fitting specified by the septic tank manufacturer to prevent the transfer of solids from the first compartment to the second, shall be in place. 6. Single compartment septic tanks may be used in series for high flow OWTS that incorporate multiple tanks. D.
INLETS, OUTLETS AND SANITARY TEES 1. The invert of the inlet of all septic tanks shall be a minimum of three (3) inches higher than the invert of the outlet. 2. In no case shall the inlet and outlet openings be less in diameter than the connecting influent and effluent lines. 3. All inlets of septic tanks shall be fitted with sanitary tees which have an internal diameter equivalent to the inlet piping. 4. The upper end of inlet sanitary tees shall extend a minimum of four (4) inches above the working liquid level and a minimum of two (2) inches below the soffit of the tank top. 5. The lower end of all sanitary tees shall extend a minimum of twelve (12) inches below the working liquid level. 6. For multiple septic tanks in series, outlet sanitary tees may be used in lieu of an effluent filter except for the last septic tank where an effluent filter is required.
E.
EFFLUENT FILTERS 1. Effluent discharged from a new septic tank(s) directly to a dispersal area or dosing tank must pass through an effluent filter sized based upon the type of facility (residential or commercial) and the estimated peak daily flow. 2. The outlet of the septic tank shall be fitted with an effluent filter capable of screening solids in excess of three-sixteenths (3/16) of an inch in diameter and conforming to NSF/ANSI Standard 46 or as otherwise approved by the Department. 3. All effluent filters shall be located in the outlet compartment of the septic tank, and shall be easily inspected, cleaned and maintained. 4. For multiple tank configurations, only the last septic tank shall be required to be equipped with an effluent filter. Revised Draft 6-28-16 58
5. All effluent filters shall be appropriately sized, manufactured for their specific use.
FLOW EQUALIZATION TANK DESIGN CRITERIA A.
GENERAL 1. Flow Equalization is the process of controlling the rate of Wastewater flow through an OWTS by providing surge capacity storage and timed-dosing of the incoming flow. 2. Flow Equalization may be used for non-residential and mixed use facilities that experience significant, regular and predictable fluctuations in Wastewater flows and allow for flexibility and efficiency in OWTS design. 3. Examples of applicable facilities include, but are not limited to churches, schools, and special-event venues. 4. Flow Equalization Tanks are installed following the Septic Tank to aid in better OWTS performance by allowing peak surges in Wastewater flow (e.g., from a weekend event) to be temporarily stored and metered into the Supplemental Treatment System and/or Dispersal Field at a relatively even (“average”) rate over an extended number of days (e.g., during the subsequent week).
B.
FLOW EQUALIZATION REQUIREMENTS 1. Where Flow Equalization is proposed to be incorporated in a OWTS, the following shall apply: a. The Septic Tank capacity shall be sized based on the peak daily flow for the facility; b. The Design Flow used for sizing Supplemental Treatment unit(s) and/or the Dispersal Field may be based on the equalized (“average”) flow rate rather than the peak daily flow rate for the facility; and c. Design calculations and specifications must be submitted to substantiate the proposed design and operation of the Flow Equalization System. 2. Depending on the size and complexity of the OWTS, an Operating Permit may be required.
Revised Draft 6-28-16 59
GREASE INTERCEPTOR TANK DESIGN CRITERIA A.
GENERAL 1. Grease interceptors are required at all facilities connected to an OWTS that generate more than two hundred (200) gallons per day of wastewater and provide foodservice and/or food preparation producing wastewater containing floatable oil, wax, fats, or grease.
B.
EXEMPTIONS 1. A food facility or other commercial operation that demonstrates that the discharge of grease, floatable oil, wax or fats is less than one hundred (100) milligrams per liter (mg/L) may be exempt from the minimum grease interceptor sizing, installation or maintenance requirements of this Chapter. 2. Sampling and testing, if required by the Department, shall be performed at the owner’s expense and by and independent certified testing organization using accepted testing methods. 3. An under counter type grease trap may be used in lieu of a grease interceptor if justifiable based on the proposed food facility menu.
C.
PLUMBING FIXTURE CONNECTIONS 1. Wastewater from plumbing fixtures where floatable oil, wax, fats or a grease may be introduced shall be plumbed separately from other plumbing fixtures into the grease trap/interceptor first and then into the septic tank. 2. The following plumbing fixtures shall be connected to a grease interceptor: a. Dishwashers (kitchen dishwashing appliances should be high-temperature disinfection models only; low temperature chemical disinfection dishwashers are not recommended); b. Three-compartment sinks; c. Floor sinks; d. Mop sinks; and e. Other fixtures as determined by the Department. 3. Garbage disposals are prohibited for commercial establishments. Revised Draft 6-28-16 60
4. Plans and specifications for the plumbing system shall be submitted to the Department. D.
MINIMUM CAPACITY 1. Grease interceptors for nonresidential use shall be sized according to the following formula:
Required Grease Interceptor Capacity (gallons) = P * WF * RT * SF
Where, P = Peak number of meals per hour6 WF = Design wastewater flow rate (from Table 4-2) RT = Retention Time RT = 1.5 (for single-service/disposable utensils) RT = 2.5 (for multi-service utensils) SF = Storage Factor (minimum capacity of 750 gallons) SF = 1 (for hours of operation ≤ 8 hours) SF = 2 (for hours of operation between 9 and 16 hours) SF = 3 (for hours of operation between 17 and 24 hours) 2. The minimum capacity of the grease interceptor shall be eight hundred and ten (810) gallons. Larger tankage is required for optimal OWTS performance. Recommended guidelines for minimum and preferred tank sizing for certain facility types is provided in Table 5-1. 3. An interior Grease Recovery Devices (RGD) meeting the requirements of Chapter 15.20 of the Alameda County General Ordinance may be approved at the discretion of the Department. E.
MAINTENANCE 1. Grease interceptors shall be located, installed and constructed so that the temperature of wastewater will be reduced to allow separation of grease and to allow easy access for cleaning. 2. Grease interceptors shall be cleaned regularly by licensed liquid waste haulers (septate and/or grease- pumping) Registered by the Department.
Revised Draft 6-28-16 61
3. Written receipts of all grease interceptor and Grease Recovery Devices pumping and maintenance events shall be included in annual Operating Permit reports submitted to the Department. The receipts shall indicate the following: a. Name and address of the company performing the work; b. Date the work was performed; and c. Volume of grease removed
HOLDING TANK DESIGN CRITERIA A.
GENERAL 1. A holding tank is a watertight container designed to receive and store wastewater for removal, hauling and disposal at an approved septate receiving facility. The use of holding tanks is limited.
B.
RESIDENTIAL DWELLINGS 1. Holding tanks for lots for existing residential dwellings are only allowed as a temporary measure while corrective action on a failed OWTS is being completed. 2. Holding tanks for lots for existing residential dwellings on a non-temporary basis are only allowed as a last resort when a OWTS has failed and may be permitted under the following conditions: a. The site cannot be approved for the installation of a replacement OWTS due to severe site constraints; and b. No public sewer system is available.
C.
NON-RESIDENTIAL FACILITIES
Holding tanks may be permitted for industrial, commercial, or recreational facilities where installation of an OWTS for sanitary or process wastewater is not feasible or allowed. D.
DESIGN REQUIREMENTS 1. The holding tank and piping shall be designed by a Qualified Professional. 2. The holding tank and piping shall be structurally sound and water tight. 3. The holding tank shall have a minimum liquid capacity of fifteen hundred (1,500) gallons and shall be sized to accommodate two hundred (200) percent of the estimated flow between anticipated pumping events: Revised Draft 6-28-16 62
Holding Tank Capacity (gallons) = 2 * (Daily Peak Design Wastewater Flow, GPD) * (#Days between Pumping Events)
4. The tank shall be located and designed to facilitate visual inspection and removal of contents by pumping. 5. The tank shall be equipped with both an audible and visual alarm, placed in a location acceptable to Department to indicate when the tank is seventy-five (75) percent full. Only the audible alarm may be user cancelable. 6. The tank shall have no overflow vent at an elevation lower than the overflow level of the lowest fixture served. E.
PERMIT REQUIREMENTS 1. Issuance of a Installation Permit is conditioned on the acceptance of the conditions that will be contained in the Operating Permit. An operating permit is required prior to issuance of the final installation approval. 2. The Installation and Operating Permits shall be conditioned on the owner of the property connecting to a public sewer system when it becomes available and prior to the renewal date of the Operating Permit. An Operating Permit for a Holding Tank will not be renewed if a public sewer system is available. 3.
The Owner shall provide the Department with: a. A copy of a contract with a licensed septage pumper (with a current County operating permit) that shows the tank shall be pumped at regular intervals or as needed to prevent use of greater than seventy-five (75) percent of the tank's capacity. b. A record of pumping dates and amounts pumped that shall be maintained by the property owner and included in the annual operating report and made available to the Department upon request.
PUMPING & DOSING TANK DESIGN CRITERIA A.
WASTEWATER PUMPING SYSTEMS
Revised Draft 6-28-16 63
1. Wastewater pumping systems may be considered when they offer a better alternative for the protection of public health and safety or are required for parcel development. 2. Wastewater pumping systems may be utilized to enable: a. Installation of a dispersal system hydraulically upgradient of the structure to be served; b. Pressure dosing of effluent to the dispersal system; c. Flow equalization; d. Transporting of wastewater or solids from a sump tank serving non-dwelling units to a septic tank; and/or e. Supplemental treatment. 3. All wastewater pumping systems shall be separate from the septic tank when there is discharge directly to a dispersal field. An exception to this requirement is when the discharge unit. Any effluent pumping system transporting wastewater or solids to a septic tank shall have its own penetration into the septic tank with a three (3) inch minimum diameter sanitary ee. An exception to this requirement may be granted where a Y connection to is provided to the gravity line. At least three (3) feet should be provided between the connection and the septic tank to minimize turbulence in the septic tank. The pumping flow rate, in either case, should be minimized. B.
DOSING TANK SIZING REQUIREMENTS 1. The minimum dosing tank size shall have sufficient capacity to hold the following volumes: a. Dosing volume and the displacement volume of the pump required to deliver the design dose. b. Emergency reserve storage volume in case of a power outage equal to one (1) day’s peak wastewater design flow between the high level alarm and the invert of the tank inlet. c. Multiple interconnected tanks may be used to meet these requirements. 2. An exception to providing reserve storage capacity equal to one day’s peak flow, may be granted where the following are provided (1) reserve storage capacity equal Revised Draft 6-28-16 64
to 50% of the daily peak wastewater design flow, (2) duplex pump system, and (3) emergency backup power capability. C.
SUMP TANK SIZING REQUIREMENTS
The minimum capacity of sump tank installed to serve non-dwelling units (e.g., bathrooms in barns or garages) shall have a minimum capacity of seventy (70) gallons7. D.
EFFLUENT PUMPS REQUIREMENTS 1. The pump system shall be designed by a Qualified Professional. 2. The pump shall be rated for wastewater applications. 3. Motors shall be continuous-duty with overload protection. 4. Pumps shall have durable impellers of bronze, cast iron, or other materials approved by the Department. 5. Pumps8 used to pump sewage to a septic tank shall be rated as a solids handling pump and shall be able to pass two (2) inch solids. Grinder pumps are not allowed. 6. The pump shall be sized to meet the hydraulic design requirements of the OWTS and shall be able to provide the required gallons per minute (gpm) at the design head. 7. Pumps shall be automatically controlled with mechanical switches (or floats) that are compatible with the specified pump and control panel. 8. All pumps shall be equipped with a high level alarm float, set to trigger at a liquid level approximately 2 inches above the “on” float. d. The required emergency storage volume is measured from the high level alarm to the invert of the inlet pipe. 9. Float switches shall be installed such that the float switches or wires do not become entangled. Clamps shall be of non-corrosive material. 10. Pumps shall be provided with an easy, readily accessible means of electrical and plumbing disconnect, and a noncorrosive lifting device as a means of removal for servicing. 11. A check valve shall be required at the pump.
Revised Draft 6-28-16 65
12. The pump shall be seated on a level and stable platform of poured concrete or cement block or placed in suspended pump assemblies. 13. The pump or suspended pump assembly shall be installed in accordance with the manufacturer’s requirements. 14. There shall be sufficient distance from the tank bottom to the pump inlet to allow space for any solids to settle without interfering with the pump operation. 15. The pump intake port shall be placed in the clear liquid zone. E.
DOSING SIPHONS
F.
CONTROLS AND ALARMS 1. All pumps shall be connected to, and operated from, control panel assemblies manufactured specifically for their intended use. 2. Electrical components used in OWTSs shall comply with all applicable State and local Building codes. Prior to doing any electrical work a permit must be obtained from the local building department and all permit and inspection requirements met. 3. Pump controls and alarms shall be contained in an exterior rated, water proof, non- corrosive, tamper proof control panel box that can be opened with standard hand tools. Control panels in areas accessible to the public shall be locked to prevent unauthorized access. 4. Control panels shall be equipped with a visible and audible alarm and located in accordance with the following provisions: a. The control panel shall be easily accessible for service and inspection. b. The control panel shall not be located in an environment that may damage the components. c. The control panel shall be mounted no more than fifty (50) feet away from the residence served by the OWTS or the common area of a commercial building. d. In cases where there are multiple buildings, the alarm shall be located at the building that is most often occupied.
Revised Draft 6-28-16 66
e. A remote visible and audible alarm shall be required if the primary alarm is not located as required above. 5. Pumps shall have automatically resetting audible and visual high water level alarms with a manual silence switch. Only the audible alarm may be user cancelable. 6. Each pump shall have a non-resettable dose counter and/or elapsed time meter included in the control panel. 7. The pump control and alarm float shall be connected to separate electrical circuits. 8. There shall be a manual override switch in the electrical box to facilitate dosing control during inspections. G.
DESIGN SPECIFICATIONS AND CALCULATIONS 1. The following minimum information shall be provided on the OWTS design plans and on the Pump Tank Diagram (Form 5-1) and Pump System Worksheet (Form 5-2) to be included in the Design Report submittal: a. Specification sheets for the pump tank, tank risers, and pump, including the pump performance curve. b. Float switch specification sheets and placement indicating the storage capacity, audio/visual alarms. c. The elevation of the pump and drain field pipe at the highest elevation. d. Calculations for total dynamic head including friction losses through the effluent piping and valves. The OWTS Designer shall provide friction loss tables to support the total dynamic head calculations. Friction loss values for PVC pipe and fittings are provided in Table 5-2 and Table 5-3 and can be used where applicable. e. Dosing volume and emergency storage volume calculations supported by manufacturer volume-depth rating information.
TANK INSTALLATION & DESTRUCTION/REMOVAL REQUIREMENTS Revised Draft 6-28-16 67
A.
INSTALLATION REQUIREMENTS 1. Excavations and installation of tanks must be in accordance with manufacturer’s requirements, including depth, backfilling and compaction. The manufacturer’s specification sheet and installation instructions must be submitted with the OWTS design documents. 2. Excavations shall provide a level, uniform load-bearing surface free of imbedded rock formations or large boulders. 3.
If the bedding under the tank is uneven or has rocks protruding, the tank may crack causing failure of the water tightness test.
4. The separation between any two septic tanks shall be a minimum of two (2) feet unless a closer distance is approved by the tank manufacturer. 5. In areas where the Site Evaluation has determined that the high seasonal groundwater level is within six (6) feet or less from original grade, tanks shall be analyzed for and properly designed to resist buoyant forces. B.
TANK DECOMISSIONING 1. Abandoned tanks that have not been properly decommissioned can pose hazards and create undesirable situations. a. Tanks that have collapsed pose safety hazards for people, pets and other animals. b. Tanks that are not properly decommissioned may fill with water over time and cause an entrapment or drowning hazard. 2. Improperly decommissioned tanks may not be able to support the weight of vehicular traffic, building foundations, or other structures built on the property. 3. A Special Permit for decommissioning is required prior to destruction or removal of a tank. An inspection by the Department must be requested within thirty (30) days from the date of one of the following circumstances: a. When the OWTS is permanently disconnected from the structure served and has not been approved for subsequent use by another structure. b. When the building sewer has been connected to a sanitary sewer that is part of a municipal treatment works. c. When the tank has been determined to be failing and cannot be repaired. Revised Draft 6-28-16 68
4. The procedures for decommissioning of tanks shall be as follows: a. The tank shall be pumped by a Septic Tank Pumper with a valid Registration from the Department and all contents removed and disposed of at a permitted facility. b. All equipment shall be removed. c. Electrical connections shall be disconnected. d. For tank abandonments, the tank lid shall be completely broken and several holes shall be made in the tank bottom. e. For tank removals, the tank lid and tank shall be completely removed from the excavation. f.
All contaminated soil and debris shall be removed, transported and property disposed. Concrete rubble may be left in place, but all other materials must be removed and properly disposed. Hydrated lime or chorine may be spread over the tank and the void or excavation area to reduce odors.
g. After inspection by the Department, the tank or void shall be completely filled with soil, sand, gravel, concrete or other suitable inert material and then completely covered with soil or material similar to that at the surface in the immediate surrounding area. h. When the tank is to be decommissioned and subsequently covered with a foundation or other structure, a structural engineer should determine the method of backfill and compaction. i.
Future construction in the area of the abandoned tank may require special construction considerations.
j.
A brief tank decommissioning report, using the form provided by the Department.
k. The building or structure wastewater plumbing system shall be permanently capped unless the building or structure is connected to an approved OWTS or a public sewer system. If the building or structure is not connected to a wastewater disposal system the building shall be recorded as a non-habitable structure. If the building or structure is to continue to be used as a nonhabitable structure all plumbing fixtures and all water inlets shall be removed.
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l.
Connection of a building or structure to a new tank or public sewer system shall be inspected by the local building authority having jurisdiction.
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SECTION OVERVIEW The guidelines presented in this chapter provide general design guidelines for Supplemental Treatment Units approved for use in the County. Supplemental Treatment Units may be proprietary Treatment units and/or engineered filter systems that provide a specified level of Treatment prior to effluent dispersal into the Dispersal Field. Guidelines are provided for the following Supplemental Treatment Systems:
Intermittent Sand Filters
Recirculating Sand Filters; and
Proprietary Treatment Units.
Other Supplemental Treatment Systems may be utilized provided they are approved by the Department and the Regional Water Board. The chapter is organized in the following sections:
Section 6.1:
General Performance Requirements for Supplemental Treatment Units
Section 6.2: Systems
Guidelines for Intermittent Sand Filters & Recirculating Sand Filter
Section 6.3:
Proprietary Treatment Units
GENERAL PERFORMANCE REQUIREMENTS FOR SUPPLEMENTAL TREATMENT UNITS A.
PERFORMANCE REQUIREMENTS
Supplemental Treatment Units must be designed to meet the following Biological Oxygen Demand (BOD) and Total Suspended Solids (TSS) concentrations and, where nitrogen is identified as a water quality concern, the following nitrogen reducing performance: 1. Thirty (30) day average BOD concentration shall not exceed thirty (30) milligrams per liter (mg/L), or alternately, a carbonaceous BOD (CBOD) in excess of twenty-five (25) mg/L. 2. Thirty (30) day average TSS concentration will not exceed 30 mg/L.
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B.
DISINFECTION9 1. Disinfection may be required when: a. The soil texture indicates a coarse sand or the percolation rate is 5 minutes per inch (5 mpi) or faster, and seasonal high groundwater is within eight (8) feet of the bottom of the dispersal field; or b. Replacement OWTS located within the minimum horizontal setback distances from a surface water body or a well and requiring maximum extent practicable technology. 2. Add-on components performing disinfection must be designed to achieve an Effluent total coliform bacteria concentration, at the 95th percentile, not greater than the following: a. Ten (10) Most Probably Number (MPN) per 100 ml prior to discharge into the Dispersal Field where the Soils exhibit percolation rates of 1 to 10 mpi or where the Soil Texture is sand; or b. One thousand (1,000) MPN per one hundred (100) ml prior to discharge into the Dispersal Field where the Soils exhibit percolation rates greater than 10 mpi or consist of a Soil Texture other than sand.
C.
REMOTE NOTIFICATION
Where feasible, Supplemental Treatment components shall be equipped with a remote notification mechanism that notifies the Owner and Service Provider in the event of OWTS malfunction. D.
OWTS PERFORMANCE
OWTS performance shall be demonstrated through the Operation, Maintenance and Monitoring (OM & M) Program as described in Chapter 12 of this Manual.
GUIDELINES FOR INTERMITTENT SAND FILTERS & RECIRCULATING SAND FILTER SYSTEMS A.
DESCRIPTION 1. Intermittent Sand Filters (ISF) and Recirculating Sand Filters (RSF) are used to provide Supplemental Treatment of Septic Tank Effluent prior to discharge to the Dispersal OWTS. They are used to improve or restore the capacity of the Dispersal
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Field, reduce pathogenic bacteria loading and can provide additional nitrogen removal. 2. An ISF consists of a packed-bed filter of medium-grained sand, designed for single pass- through Treatment of Septic Tank Effluent; it is sometimes referred to as a “single pass filter”. 3. An RSF utilizes coarse-grained sand and a recirculation system, usually controlled by a timer that causes the effluent to pass through the sand media several times prior to final dispersal. RSFs have the ability to produce Effluent quality similar to ISFs, except that they are less effective in bacteria removal. However, RSFs typically provide greater nitrogen removal than ISFs, on the order of 50-percent reduction as compared with Standard Tank Effluent. 4. Effluent from sand filters may be discharged to Standard Dispersal Fields and to any type of alternative Dispersal System identified in this Manual. Effluent from an ISF or RSF designed and operated in accordance with these guidelines will be considered to meet the criteria for Supplemental Treatment. 5. Schematic and cross-section diagrams are provided in Figure 6-1, Figure 6-2 and Figure 6-3 to illustrate the key design features of Intermittent Sand Filters Systems and Recirculating Sand Filters. B.
SITING REQUIREMENTS 1. Sand Filter Treatment Unit. All siting criteria for Septic Tanks, as specified in Chapter 4, shall also apply to intermittent and recirculating sand filters and associated tanks and pumping units. 2. Dispersal Systems Receiving Sand Filter Effluent. Dispersal Systems receiving sand filter effluent are subject to the siting criteria in Chapter 7 for the specific type of alternative dispersal system proposed, including any allowances for the incorporation of Supplemental Treatment. Allowances for Supplemental Treatment may include reduced Vertical Separation distances or increased Wastewater Application Rates.
C.
TREATMENT REQUIREMENTS 1. Sand Filter Systems are designed for treating residential strength Wastewater. The wastewater applied to the sand filter (influent) shall not be higher in strength than Domestic Wastewater (for numerical values see Chapter 4.4). Lower Wastewater strengths, without increased flow rates are preferable for assuring long term operation of Sand Filter Systems.
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2. The following treatment requirements shall apply in connection with the use of sand filter systems: a. Primary (septic tank) treatment shall be the minimum level of treatment. b. Pre-treatment, using an approved alternative treatment system identified in this Manual, shall be required for High Strength Wastewater in order to reduce its strength prior to introduction into the sand filter. D.
PRESSURE DOSING 1. Septic Tank Effluent shall be applied to the Sand Filter Treatment unit by Pressure Dosing, utilizing either an automatic dosing siphon (intermittent filter only) or pump. 2. The Pressure Distribution System shall be designed in accordance with accepted industry practices to achieve, at a minimum: a. Uniform dosing of Effluent over the surface application area of the sand filter distribution bed; b. Adequate flow rate, screening of Effluent and suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices; c. Suitable access provisions for inspection, testing and adjustment of the Pressure Distribution System; d. Dosing volume as follows: i. Intermittent Sand Filters: Dosing may be either on demand or time dosing. For on demand the dosing volume should be designed to achieve a minimum of 3 to 5 doses per day at design flow conditions. For time dosing the volume should be sufficient to ensure complete filling of the distribution piping and even dispersal throughout the sand filter bed with each dose; ii. Recirculating Sand Filters: Timed dosing to achieve a recirculation rate of approximately five to 1 (5:1) at design flow conditions. e. At least one distribution lateral for every thirty-six (36) inches of bed width. 3. Pump or siphon system designed in accordance with the pump system requirements provided in Chapter 5 of this Manual. 4. Additional requirements for the design and construction of Pressure Distribution Systems contained in Chapter 7 shall also apply. Revised Draft 6-28-16 74
5. Where a sand filter is used in conjunction with a gravity-fed Dispersal System, the dosing pump system for the sand filter shall provide emergency storage capacity equal to at least one (1) times the daily wastewater flow, consistent with requirements for pump systems provided in Chapter 5 of this Manual. E.
SAND FILTER BED CONTAINMENT STRUCTURE 1. Containment Liner. The sand filter shall be provided with an impermeable containment liner along all sides of the filter bed to prevent lateral leakage out of or into the filter. a. The lilner shall consist of either: i. 30 mil plastic; ii. reinforced poured-in-placed concrete; or iii. an equivalent impermeable structure or barrier. 2. Finished Grade and Structural Support. The finished grade of the sand filter shall be above the surrounding ground elevation and shall be structurally supported with retaining wall(s), as required. 3. Bed Dimensions. The sand filter shall not be restricted as to its shape in plan view. 4. Multiple Units. The raised sand filter bed may be divided into compartments or multiple units.
F.
SAND FILTER MEDIA 1. Sand Specifications. The sand media shall be a medium to coarse sand which meets the gradation specifications for ISFs or RSFs in Table 9-1. Documentation of laboratory sieve analysis results for the proposed sand filter media material shall be supplied to the Department to verify conformance with the above specifications. 2. Additional Sand Specifications for RSF. The following additional sand specifications apply for RSF: a. Effective size of sand/gravel, D10: 1.5 to 2.0 millimeters (mm) b. Uniformity coefficient, Uc < 2.5 3. Sand Depth. The minimum depth of sand fill, below the gravel distribution bed, shall be twenty-four (24) inches. Revised Draft 6-28-16 75
G.
SAND FILTER SURFACE AREA SIZING
The surface area of the sand filter shall be sized as follows: 1. Wastewater Flow. The wastewater flow used for sizing the surface area of the sand filter shall be the design wastewater flow for the OWTS. 2. Wastewater Application Rate. Wastewater application rates used for sizing the surface area of the sand filter shall be as follows:
Sand Filter Type ISF RSF
Individual Residential OWTS 2 1.2 gpd/ft 2 Maximum 5.0 gpd/ft
Commercial, Industrial, Institutional, and MultiResidential OWTS 2 1.0 gpd/ft 2 Maximum 4.0 gpd/ft
Reduction in the above wastewater loading rates or other provisions to insure the long- term integrity and performance of the sand filter may be required for High Strength Wastewater flows. 3. Minimum Sizing. The minimum size (square feet) of the basal area of the raised sand filter bed shall be determined by dividing the design wastewater flow (in gpd) by the applicable wastewater application rate.
Design Wastewater Flow Rate (gpd)
Sand Filter Surface Area (ft2) =
H.
Wastewater Application Rate (gpd/ft2)
GRAVEL DISTRIBUTION BED 1. Material. The distribution bed shall consist of three-eighth (3/8) inch double-washed pea gravel, substantially free of fines. 2. Depth. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches above the top of the distribution piping. If the distribution piping is installed with chambers, the pea gravel depth below the distribution pipe may be reduced from six (6) inches to four (4) inches, and the two (2) inch pea gravel cover may be eliminated. 2. Silt Barrier. a. Intermittent Sand Filters. The gravel distribution bed shall be covered in its entirety with a geotextile ("filter fabric") silt barrier. Filter fabric shall either be polyester, nylon or polypropylene, or any combination thereof, and shall be Revised Draft 6-28-16 76
suitable for underdrain applications. Filter fabric shall be non-woven, shall not act as a wicking agent and shall be permeable. b. Recirculating Sand Filters. RSFs do not require a silt barrier. I.
UNDERDRAIN 1. Material. The underdrain beneath the sand media shall consist of three-eighths (3/8) inch washed pea gravel with four (4) inch diameter perforated drain pipe, installed with perforations oriented down. 2. Depth. The pea gravel underdrain shall have a minimum depth of nine (9) inches. 3. Grade. The underdrain shall be constructed and the drain pipe set with a minimum grade of one (1) percent toward the outlet point. 4. Watertight Outlet "Boot". The sand filter underdrain shall be equipped with a watertight outlet "boot" for connection of piping to the dosing tank. An exception to this is for intermittent sand filters that are equipped with an internal pump system for direct dosing to the disposal field (see below). 5. Clean-out Riser. For clean-out and inspection purposes the upslope end of the perforated drain pipe in the underdrain shall be equipped with a vertical riser constructed of non-perforated pipe of equal diameter. The riser shall extend to finished grade of the sand filter.
J.
AIR MANIFOLD 1. An air manifold shall be installed within the pea gravel underdrain for the purpose of introducing forced air into the sand filter media, as needed, for maintenance or drainage rehabilitation. 2. The air manifold shall consist of small diameter PVC piping, with drilled perforations (pointed down), and positioned above the perforated underdrain pipe, or an equivalent piping system, for example drip line tubing. 3. The manifold shall be connected to a vertical leader pipe that extends to the surface of the sand filter, fitted with a threaded pipe cap or plug at the top where a portable air-line can be connected.
K.
INTERNAL PUMP SYSTEM (ISF ONLY) 1. In lieu of gravity flow from the sand filter to the dispersal field (or dispersal field dosing system), an internal pump system may be installed within the intermittent sand filter for dosing directly to the dispersal field. Revised Draft 6-28-16 77
2. In such applications: a. The pump chamber shall be seated at or below the bottom of the underdrain; b. The pump operating depth shall be entirely within the depth of the underdrain; and, c. The storage volume equal to at least 50 percent of the disposal field dose volume shall be provided in the network of perforated drain pipes within the underdrain. L.
COVER 1. Intermittent Sand Filters a. Material. A continuous soil cover consisting of a medium, loamy-textured soil shall be placed over the entire distribution bed. b. Depth. Soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen (18) inches over the top of the distribution bed. Soil cover shall be crowned or sloped to promote rainfall runoff. 2. Recirculating Sand Filters a. Material. A granular media cover shall be placed over the distribution bed, consisting of clean gravel that may range in size from three-eighths (3/8) inch pea gravel to two and one half (2 ½) inch rounded rock. b. Depth. Cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen (18) inches over the top of the distribution bed.
M.
INSPECTION PORTS
A minimum of one (1) inspection port shall be installed within the gravel distribution bed of each sand filter compartment in accordance with the requirements in Table 6-1 for the purpose of checking water quality sampling. N.
REFERENCE GUIDELINES
In addition to the requirements set forth herein, design and construction of sand filter systems should utilize applicable guidelines contained in the following references: a. "Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February 2002 and as amended. b. “Design Manual – Onsite Wastewater Treatment and Disposal Systems”, U.S. Environmental Protection Agency, October 1980. Revised Draft 6-28-16 78
6.3 A.
PROPRIETARY TREATMENT UNITS DESCRIPTION 1. Propriety treatment units cover a category of manufactured or “package” Supplemental Treatment Units specifically developed for residential and other smallscale Wastewater Treatment applications. Most proprietary treatment units currently available fall into the following two general categories: a. Aerobic Treatment Units (ATUs). ATUs utilize forced air to oxidize the Wastewater, promoting aerobic decomposition of the Wastewater solids. These systems provide Supplemental Treatment of Wastewater for improvement in dispersal field performance; they also provide varying degrees of nitrogen removal. In general, ATUs can be relied on to produce secondary quality effluent, better than 30 mg/L BOD and TSS. ATUs are generally not as effective in reducing pathogen levels as are systems that incorporate media filtration. However, some ATUs provide reduction in nitrogen levels equal to or greater than that provided by sand filters and other media filters. b. Media Filters. Media Filters include proprietary designs that function similar to sand filters. In these systems the sand is replaced with an alternate media including but not limited to peat, gravel or textile. Textile and other media filters have been found to produce effluent quality reasonably similar to recirculating sand filters, and provide similar capabilities in overcoming various soil and site constraints. 2. Effluent from proprietary treatment units may be discharged to Standard Dispersal Fields and to any type of Alternative Dispersal System identified in Chapter 7 of this Manual. Effluent from proprietary treatment units designed and operated in accordance with these guidelines will be considered to meet the criteria for Supplemental Treatment.
B.
SITING CRITERIA 1. Treatment Unit. All siting criteria for septic tanks, as specified in Chapter 4 of this Manual shall also apply to proprietary treatment units and associated tanks and pumping units. 2. Dispersal Systems Receiving Proprietary Treatment Effluent. Dispersal systems receiving effluent from a proprietary treatment unit are subject to the siting criteria for the specific type of alternative dispersal system proposed, including any allowances for the incorporation of supplemental treatment. Allowances for supplemental treatment may include reduced vertical separation distances, increased wastewater application rates or modified slope restrictions. Refer to Chapter 4 of this Manual for Revised Draft 6-28-16 79
the adopted guidelines for the specific type of dispersal system for applicable requirements and supplemental treatment allowances. C.
DESIGN AND CONSTRUCTION REQUIREMENTS 1. NSF Standard 40. a. Proprietary treatment units must be listed by the National Sanitation Foundation (NSF)/ANSI (American National Standards Institute), b. Meeting the NSF/ANSI Standard 40, Class 1 performance evaluation and have a training/certification program for installers. c. Proprietary treatment units must be manufactured and installed in accordance with the design specifications used to determine compliance to NSF/ANSI Standard 40. The NSF/ANSI Standard 40 listing is applicable to treatment units for wastewater flows of up to 1,500 gpd and is based on compliance with United States Environmental Protection Agency (USEPA) standards for secondary treatment of municipal wastewater, including 30-day average effluent limits of twenty-five (25) mg/L for CBOD5 and thirty (30) mg/L for TSS. d. Treatment units for flows in excess of 1,500 gpd will require certification by a third- party listing agency as complying with NSF/ANSI Standard 40 performance requirements. 2. Design Sewage Flow. Sizing and design of proprietary treatment units shall be based on the projected wastewater flow for the structure(s) or facility(ies) being served, determined in accordance with wastewater flow estimation guidelines in Chapter 4 of this Manual. 3. Tanks. All tanks housing a proprietary treatment unit shall be structurally sound, water-tight and should be capable of withstanding one-thousand (1,000) pounds of weight. 4. Controls. Control panels shall be designed and configured in such a manner that, in the event of a treatment unit malfunction, an alarm system will be triggered and discharge from the treatment system to the dispersal field will be interrupted until the treatment unit malfunction is rectified. At a minimum, the alarm system shall include an audible and visual alarm located within the building served by the OWTS. 5. Emergency Storage Provisions. Where a proprietary treatment unit is used in conjunction with a gravity-fed dispersal system, the system shall provide emergency storage capacity equal to at least one (1) times the daily wastewater flow, consistent with requirements for pump systems provided in Chapter 5 of this Manual. Revised Draft 6-28-16 80
6. Compliance with Manufacturer Requirements. The OWTS designer and installer shall follow the proprietary manufacturer’s design, installation, construction, and operations procedures. 7. OWTS Plans. OWTS plan submittals for proprietary treatment units shall provide documentation of compliance with manufacturer requirements and sufficient design analysis to verify the appropriateness of the treatment unit for the proposed application. OWTS plans shall contain specific step-by step construction guidelines and notes for use by the installer, including any manufacturer instructions. 8. Installer Requirements. Anyone installing a proprietary treatment unit shall be trained and certified by the system manufacturer. Documentation verifying the training/certification shall be provided to the Department prior to system installation. 9. Maintenance Contract. The OWTS owner provide proof of a written maintenance agreement with a qualified service provider for the proposed proprietary treatment unit to ensure satisfactory post-construction operation and maintenance. Proof of a written maintenance agreement is required as a condition of the Operating Permit.
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The guidelines presented in this chapter provide the design criteria for subsurface dispersal systems approved for use in the County. The criteria apply to new OWTSs and modifications or repairs to existing OWTSs. The dispersal system types presented in Sections 7.9 through 7.12 shall be used only for repair or replacement of existing OWTSs on severely constrained sites. This chapter is organized in the following sections:
Section 7.1:
Standard (Gravity) Trench Dispersal Systems
Section 7.2:
Pressure Distribution Trench Dispersal Systems
Section 7.3:
Pressure Dosed Sand Trench Dispersal Systems
Section 7.4:
Subsurface Drip Dispersal System Design
Section 7.5:
Cover Fill Dispersal Systems
Section 7.6:
At-Grade Systems
Section 7.7:
Mound Dispersal Systems
Section 7.8:
Raised Sand Filter Bed Systems
STANDARD (GRAVITY) TRENCH DISPERSAL SYSTEMS A.
DESCRIPTION 1. Standard trench dispersal systems consist of a series of gravity-fed drainfield trenches for subsurface dispersal of effluent into the soil. Typically they consist of rock and perforated pipe but may also include chambers or other approved gravelless alternatives and may be constructed with or without coverfill. Schematic and cross-section diagrams are provided in Figure 7-1, Figure 7-2, Figure 7-3 and Figure 7-4 to illustrate the key design features of standard trench dispersal systems.
B.
DUAL SYSTEM REQUIREMENT 1. Primary and Secondary Dispersal Area. Two dispersal fields (primary and secondary), each with one hundred (100) percent of the total size required for the design wastewater flow shall be installed. Trenches for primary and reserve areas may be interfingered as long as trench spacing between the primary and reserve trenches is in compliance with the manual requirements.
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2. Diversion Valve. The dispersal system shall be equipped with an approved manual diversion device to allow alternating use of the two fields, typically switching between fields every six (6) to twelve (12) months. C.
SITING REQUIREMENTS
Siting requirements for standard gravity trench dispersal systems are provided in Table 3-1, Table 4-10 and Table 4-11, respectively. 1. Vertical Separation Requirements. a. Depth to Groundwater. Minimum depth to seasonal high groundwater for standard gravity trench dispersal systems, as measured from the trench bottom, shall vary according to soil percolation rate as shown in Table 3-1. b. Effective Soil Depth. Minimum depth of effective soil, as measured from the trench bottom to impermeable soil or rock, for standard trench dispersal systems shall be five (5) feet as shown in Table 3-1. 2. Maximum Ground Slope. a. The maximum ground slope in areas used for conventional trench dispersal systems shall be thirty (30) percent (see Table 4-11). b. The maximum ground slope in areas used for trench dispersal systems with cover fill shall be twenty (20) percent (see Table 4-11). D.
WASTEWATER APPLICATION RATES
Wastewater application rate(s) used for determining the required infiltrative surface area and overall trench length of Standard Trench Dispersal Systems are provided in Table 4-5. E.
EFFECTIVE INFILTRATIVE AREA AND TRENCH SIZING a. Effective Infiltrative Area Requirement. The Effective Infiltrative Area for trench dispersal systems shall be limited to four (4) square feet per lineal foot of trench length, which may include any combination of trench bottom area and trench sidewall area below the invert of the perforated distribution pipe. b. Effective Infiltrative Area Requirement Exception. The Effective Infiltrative Area may be increased up to eight (8) square feet per lineal foot of trench length, under the following circumstances:
The ground slope of the dispersal area is less than 20 percent. The soil percolation rate is between 5 and 60 mpi. The depth to groundwater is greater than or equal to five feet. Revised Draft 6-28-16 83
All other OWTS dispersal field siting requirements are met.
c. Trench Infiltrative Surface Calculation. The required square footage of trench infiltrative surface shall be calculated based on the design flow and the applicable wastewater application rate as provided in Table 7-1. d. Trench Length Calculation. The required trench length for one hundred (100) percent capacity dispersal field shall be calculated as provided in Table 7-1. F.
TRENCH SPECIFICATIONS
Standard Dispersal Trench Systems shall be constructed with drainrock and perforated pipe and shall meet the specifications in Table 7-2 (Standard Trenches) and Chapter 9. 1. Trench Depths. a. Minimum trench depths for rock and pipe design shall be sufficient to provide twelve inches of drainrock below the pipe and two inches of drainrock above the pipe and twelve inches soil backfill. For cover fill systems the soil backfill may extend above ground. b. Trench depths for chambers and other gravelless alternatives will depend on the dimensions of the product, however, in any case must be installed entirely below original grade with a minimum of twelve inches of soil backfill or cover fill. c. In general, trenches should be kept as shallow as possible to take advantage of those soil horizons that best provide oxygen and promote microbiological activity; and within the root zone of plants to take advantage of nitrogen uptake in plants. 2. Drainrock Alternatives. Other material may be substituted for drainrock in the dispersal trenches if they have been approved by the Department. All substitute material shall serve the same function as drainrock as follows: a. Support the trench sidewalls and maintain the integrity of the infiltrative surface; b. Provide adequate storage for septic tank effluent surges; c. Provide equivalent effective infiltrative surface consistent with the trench sizing requirement for trenches with drainrock;
Revised Draft 6-28-16 84
d. Plastic dispersal chamber systems shall be accepted for use in sewage dispersal systems and shall be certified by IAPMO, UPC, NSF or other nationally recognized certification organization; e. Reduction in trench sizing requirement up to thirty (30) percent may be approved by the Department for IAPMO-certified dispersal systems. 3. Trench Spacing. Trench spacing shall be in accordance with the requirements in Table 7-3. G.
INSPECTION WELLS 1. A minimum of one (1) inspection well shall be installed within each trench for the purpose of checking ponded water levels periodically. 2. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending from the ground surface to depth of twelve (12) inches, minimum (see Figure 6-4).
H.
DISPERSAL TRENCH GENERAL DESIGN CONSTRUCTION CRITERIA 1. Trenches shall be placed in undisturbed earth, in an accessible area, and shall not be covered by paving or other impermeable or compacted surface. Natural topography shall not be graded to modify slope. Trenches shall be installed on contour (i.e., aligned parallel to the ground surface contours) to the greatest extent practicable. 2. The bottom of a trench shall be level, with a variation of no more than two (2) inches per one hundred (100) lineal feet of trench; trenches shall be aligned parallel to the ground surface contours to the greatest extent practicable. 3. Adjacent trenches on slopes shall be connected with a watertight overflow line (“relief line”) in a manner that allows each trench to be filled with wastewater effluent to the depth of the rock before the wastewater flows to the next lower trench (see Figure 74). Alternatively, a distribution box (D-box) may be used to equally divide the flow amongst the trenches. 4. Trenches shall not be excavated when the soil is so wet that smearing or compaction occurs. Revised Draft 6-28-16 85
5. In clay soils when glazing occurs, the trench surfaces shall be scarified to the depth of the glazing and the loose material removed. 6. Rock material in the trench shall be washed and free of fines. 7. Drain pipe shall be perforated pipe for standard Dispersal Systems must conform to the 8. California Plumbing Code and must be three (3) or four (4) inches in diameter installed with perforations down. 9. A minimum of two (2) inches of rock shall be placed over the drain pipe. 10. Prior to backfilling the trench, the drain rock shall be covered with geotextile filter fabric. 11. Backfill shall be carefully placed to prevent damage to the system and mounded over the trench to compensate for expected settlement. 12. Backfill shall be native soil. Backfill shall be free of large stones, frozen clumps of earth, masonry, stumps, waste construction materials, or other materials that could damage the OWTS. 13. The slope shall not exceed percent in the dispersal areas (primary and secondary). 14. For purposes of determining effective soil depth and vertical separation, the depth of limiting layer shall be measured from the upslope side of the dispersal trench bottom. 15. Erosion control measures must be implemented following installation. 16. Additional requirements for the design and placement of cover fill are provided in Section 7.6 of this Chapter. I.
REFERENCE GUIDELINES
In addition to the requirements set forth herein, design and construction of Standard Trench Dispersal Systems should utilize applicable guidelines contained in the following references: 1. "Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February 2002 and as amended. 2. “Design Manual – Onsite Wastewater Treatment and Disposal Systems”, U.S. Environmental Protection Agency, October 1980. Revised Draft 6-28-16 86
PRESSURE DISTRIBUTION TRENCH DISPERSAL SYSTEMS A.
DESCRIPTION
Pressure Distribution Trench Dispersal Systems are an alternative to a Standard Trench Dispersal System that use a pump or dosing siphon and small-diameter pressure piping to achieve broad and uniform distribution of Wastewater for improved Soil absorption and better Treatment of percolating Effluent. Schematic and cross-section diagrams are provided in Figure 7-5 and Figure 7-6 to illustrate the key design features of Pressure Distribution Trench Dispersal Systems. B.
PRIMARY AND RESERVE AREA REQUIRED 1. Vertical Separation Requirements a. Depth to Groundwater. Minimum depth to seasonal high groundwater for Pressure Distribution systems, as measured from trench bottom, shall vary according to soil percolation rate as shown in Table 3-1. b. Effective Soil Depth. Minimum depth of soil, as measured from trench bottom to impermeable soil or rock, for Pressure Distribution systems shall vary according to soil percolation rate and the level of treatment provided as shown in Table 3-1. 2. Maximum Ground Slope a. The maximum ground slope in areas used for trench pressure distribution systems shall be forty (40) percent (see Table 4-11). The maximum ground slope in areas used for deep trench pressure distribution systems shall be twenty (20) percent (see Table 4-11). b. Any pressure distribution system located on slopes greater than thirty (30) percent shall require the completion of a geotechnical report and slope stability analysis as specified in Chapter 3 of this Manual.
D.
TREATMENT REQUIREMENTS
The following treatment requirements shall apply in connection with the use of pressure distribution systems: 1. Primary (septic tank) treatment shall be the minimum level of treatment, and shall be acceptable where the applicable vertical separation distances are met per Tables 3-1.
Revised Draft 6-28-16 87
2. Supplemental treatment, using an approved alternative treatment system identified in this Manual, may be used to allow compliance with reduced vertical separation distances as provided in Tables 3-1. E.
WASTEWATER APPLICATION RATES
Wastewater application rate(s) used for determining the required infiltrative surface area and overall trench length of Pressure Distribution Trench Dispersal Systems are provided in the following tables: 1. Table 4-5 (Standard Wastewater Application Rates). Standard Wastewater Application rates shall be used in Pressure Distribution Systems receiving wastewater effluent from Primary Treatment (Septic Tank) where the minimum Vertical Separation to Groundwater and/or Effective Soil Depth for Standard Trench Dispersal Systems provided in Table 3-1 are met. 2. Table 4-7 (Wastewater Application Rates). Wastewater Application Rates may be used in Pressure Distribution Systems receiving wastewater effluent from Supplemental Treatment where the minimum Vertical Separation to Groundwater and/or Effective Soil Depth for Standard Trench Dispersal Systems provided in Table 3-1 are met. 3. A reduction in the wastewater application rates may be required for high strength wastewater flows or other site constraints. F.
TRENCH DESIGN 1. Pressure distribution trenches shall conform to the same design and construction requirements as Standard Trench Dispersal Systems, per Section 7.2 of this Chapter and Table 7-1 and Table 7-2 with the exception that the piping system shall consist of pressure piping rather than gravity piping. 2. Cover fill may also be used in conjunction with pressure distribution trenches.
G.
PRESSUE DISTRIBUTION PIPING
Pressure distribution piping shall comply with the material specifications provided in Chapter 9 and the following criteria: 1. Pipe Sizing. All pressure distribution pipes and fittings, including transport lines, manifolds, laterals and valves, must be adequately sized for the design flow, and shall be designed to minimize frictional losses to the maximum extent practicable. 2. Pipe Support. All Pressure Distribution transport piping must be uniformly supported along the trench bottom and bedded in native soil, except in rocky soil
Revised Draft 6-28-16 88
conditions in which case sand or other material approved by the Department are to be used 3. Thrust Blocks. Concrete thrust blocks, or equivalent restraint, shall be provided at sharp changes in piping directions. 4. Shut-off Valves. The distribution lateral for each trench shall be fitted with a shut-off valve to adjust or terminate the flow to individual trenches. Shut-off valves may be ball or gate valves, and shall be located in a utility/valve box. 5. Dosing Tank Valves. A gate valve or ball valve must be placed on the pressure transport pipe inside or outside of the pump riser of the dosing tank. 6. Pump Check Valve: A check valve shall be placed between the pump and the gate valve when required. All check valves and gate valves shall be in an accessible and protected location for maintenance and repair. 7. Lateral End Riser. The end of each lateral shall be fitted with a ninety (90) degree long sweep to facilitate line cleaning and hydraulic testing. The end riser pipe shall also be fitted with a ball valve and/or threaded end cap or plug, housed in a valve box. 8. Anti-siphon Device. An anti-siphon device must be placed on the discharge line within the pump basin when the Dispersal Field is located at a lower elevation than the pump. 9. Valve Boxes. All valves must be placed in boxes accessible for maintenance from the surface. H.
PRESSURE DOSING 1. The pressure distribution system shall be hydraulically designed in accordance with accepted industry practices to provide an adequate flow rate, screening of effluent, and a suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices and to achieve uniform dosing of septic tank effluent throughout the pressure distribution trenches. 2. Orifices shall have a minimum diameter of one-eighth (1/8) inch and shall be evenly spaced at a distance between two (2) and three (3) feet. Greater hole spacing may be allowed on a case by case basis subject to evaluation of design and siting factors such as those related to dose volume, Effluent quality, dispersal field size, and soil conditions.
Revised Draft 6-28-16 89
3. A minimum head of three feet where holes are oriented up and two feet where holes are oriented down at the orifice farthest from the manifold and no more than 10 percent head variation within a Dispersal Trench. 4. Effluent shall be applied to the Pressure Distribution system by pressure dosing, utilzing either an automatic dosing siphon or pump system. 5. The pressure distribution system laterals piping shall be designed to drain following a dose. 6. The dose volume shall be sufficient to refill any part of the pressure distribution system including supply line and lateral lines plus deliver sufficient additional volume to disperse the daily Design flow in an appropriate number of doses per day at design flow conditions. 7. Dispersal Field performance is enhanced when the daily flow is dispersed in smaller, more frequent doses throughout the day. 8. Pumps shall comply with the material specifications and designed and constructed in accordance with pump system requirements provided in Chapter 5 of this Manual. I.
INSPECTION WELLS 1. Groundwater Observation Wells. For OWTS utilizing Pressure Distribution for the purpose of reduced groundwater separation or where a groundwater mounding analysis has been required, a minimum of three (3) groundwater observation wells shall be installed within and around the Pressure Distribution Dispersal System in accordance with the requirements in Table 7-4 for the purpose of checking groundwater levels periodically and water quality sampling, if needed. Groundwater observation wells may also be required by the Department, for example where recommended by geotech report, in connection with a setback variance or there have been complaints about OWTS performance. 2. Trench Inspection Wells. A minimum of one (1) inspection well shall be installed within each trench for the purpose of checking ponded water levels periodically (see Figure 7-5 and Figure 7-6). Any trench length greater than 100 feet shall have a minimum of two (2) inspection wells. a. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commerciallyslotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending Revised Draft 6-28-16 90
from the ground surface to depth of twelve (12) inches, minimum (see Figure 6-4). J.
REFERENCE GUIDELINES
In addition to the requirements set forth herein, design and construction of Pressure Distribution systems should utilize applicable guidelines contained in the following references: 1. "Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February 2002 and as amended. 2. “Design Manual – Onsite Wastewater Treatment and Disposal Systems”, U.S. Environmental Protection Agency, October 1980.
PRESSURE DOSED SAND TRENCH DISPERSAL SYSTEMS A.
DESCRIPTION
Pressure Dosed Sand Trench (PDST) Dispersal Systems are a variation of a pressure distribution system that utilizes a medium-grade sand in place of a portion of the gravel backfill in the dispersal trench, to improve treatment of effluent and normalize the flow of effluent before it reaches the trench bottom. Treatment occurring in the sand fill can enhance the acceptance rate of native soils beneath the trench. This type of design can also be used with supplemental treatment, and is well suited for conditions where underlying soils are highly permeable and/or groundwater beneath a system is especially vulnerable to wastewater contaminants. Schematic and cross-section diagrams are provided in Figure 7-7 to illustrate the key design features of Pressure Dosed Sand Trench Dispersal Systems. B.
SITING REQUIREMENTS
Siting requirements for Pressure Dosed Sand Trench Dispersal Systems are provided in Table 3-1, Table 4-10 and Table 4-11. 1. Vertical Separation Requirements. a. Depth to Groundwater. The minimum depth to seasonal high groundwater for PDST systems, as measured from trench bottom, shall vary according to soil percolation rate, level of treatment provided, and sand fill thickness as shown in Table 3-1. b. Effective Soil Depth. The minimum depth of soil, as measured from trench bottom to impermeable soil or rock, for PDST systems shall be two (2) feet as shown in Table 3-1.
Revised Draft 6-28-16 91
2. Maximum Ground Slope. a. Maximum ground slope in areas used for PDST systems shall be forty (40) percent. b. Any PDST system located on slopes greater than thirty (30) percent shall require the completion of a geotechnical report and slope stability analysis as specified in Chapter 3 of this Manual. C.
PRIMARY AND RESERVE AREA REQUIRED 1. Primary Dispersal Area. A Primary PDST Dispersal System designed to treat one hundred percent of the design wastewater flow shall be installed. 2. Reserve Dispersal Area. A reserve area having suitable site conditions and sufficient area for full, one-hundred (100) percent replacement of the primary PDST Dispersal System shall be identified during the Site Evaluation and reserved for future use.
D.
TREATMENT REQUIREMENTS
The following treatment requirements shall apply in connection with the use of PDST systems: 1. Primary (septic tank) treatment shall be the minimum level of treatment, and shall be acceptable where the applicable vertical separation distances are met per Table 3-1. 2. Supplemental treatment, using an approved alternative treatment system identified in this Manual, may be used to allow compliance with reduced vertical separation distance provided in Table 3-1. E.
PRESSURE DOSING
Septic tank effluent shall be applied to the PDST system by pressure dosing, utilizing either an automatic dosing siphon or pump system. The pressure distribution system shall be designed in accordance with accepted engineering practices to achieve, at a minimum: 1. Uniform dosing of septic tank effluent throughout the PDST Dispersal System trenches; 2. Adequate flow rate, screening of effluent and suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices; 3. Suitable access provisions for inspection, testing and adjustment of the pressure distribution system; 4. The dose volume shall be sufficient to refill any part of the pressure distribution system including supply line and lateral lines plus deliver sufficient additional volume Revised Draft 6-28-16 92
to disperse the daily Design flow in an appropriate number of doses per day at design flow conditions; 5. Dispersal Field performance is enhanced when the daily flow is dispersed in smaller, more frequent doses throughout the day; 6. Pump system designed in accordance with the pump system requirements provided in Chapter 5 of this Manual; and 7. Additional requirements for design and construction of pressure distribution piping systems contained in the guidelines for Pressure Distribution Systems in Section 7.3 of this Manual, as applicable. F.
WASTEWATER APPLICATION RATES
Wastewater application rates used for system sizing shall include consideration of both the pea gravel-sand interface and the sand-soil interface using the bottom area of the trench only. The more restrictive criterion shall govern system sizing. 1. Pea Gravel-Sand Interface. The wastewater application rate used for sizing the pea gravel-sand interface shall be: Facility Type Individual Residential Systems
Wastewater Application Rate 1.2 gpd/ft2
Commercial, Industrial, Institutional and Multi-Residential Systems
1.0 gpd/ft
2. Sand-Soil Interface. The Wastewater Application Rate for sizing the sand-soil interface (considering bottom area only) shall be based upon representative percolation test results for the soil zone corresponding with the trench bottom depth. Wastewater Application Rates shall be used as provided in Table 4-5 and Table 4-7, respectively. Reduction in the above Wastewater Application Rates or other provisions to insure the long- term integrity and performance of the PDST trenches may be required for high strength waste flows. G.
DRAINFIELD TRENCH DESIGN
PDST Dispersal Systems shall conform to the same general design and construction requirements as Pressure Distribution Dispersal Systems per Section 7.3 of this Chapter, with the following exceptions as specified in Table 7-5 and Table 7-6. 1. Cover Fill. Cover fill may also be used in conjunction with pressure-dosed sand trenches. Revised Draft 6-28-16 93
2. Trench Filter Material. The trench filter material (below the distribution pipe) shall consist of a minimum of six (6) inches of double-washed pea gravel underlain by six (6) to twenty- four (24) inches of medium sand fill. a. The sand media shall be a medium to coarse sand that meets the gradation specifications provided in Table 9-1. Documentation of laboratory sieve analysis results for the proposed sand fill material shall be supplied to the Department to verify conformance with the above specifications. b. The minimum depth of sand below the pea gravel shall be dependent on the level of wastewater effluent treatment (Primary or Supplemental) and the soil percolation rate as specified in Table 7-7. 3. Trench Sizing. a. Effective Infiltration Area. The required square footage of trench infiltrative surface shall be calculated based on the design flow and the applicable wastewater application rates as provided in Table 7-6. b. Trench Length. The required length of trench shall be calculated based on the bottom area only, up to a maximum of three (3) square feet of effective infiltrative surface per lineal foot of trench per the requirements of Table 7-6. 4. Trench Spacing. PDST trench spacing shall comply with the requirements of Table 7-3. H.
INSPECTION WELLS 1. Groundwater Observation Wells. For OWTS utilizing Pressure Distribution for the purpose of reduced groundwater separation or where a groundwater mounding analysis has been required, a minimum of three (3) groundwater observation wells shall be installed within and around the Pressure Distribution Dispersal System in accordance with the requirements in Table 7-4 for the purpose of checking groundwater levels periodically and water quality sampling, if needed. Groundwater observation wells may also be required by the Department, for example where recommended by geotech report, in connection with a setback variance or there have been complaints about OWTS performance. 2. Trench Inspection Wells. A minimum of one (1) inspection well shall be installed within each trench for the purpose of checking ponded water levels periodically (see Figure 7-5 and Figure 7-6). Any trench length greater than 100 feet shall have a minimum of two (2) inspection wells. a. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All Revised Draft 6-28-16 94
wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commerciallyslotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending from the ground surface to depth of twelve (12) inches, minimum (see Figure 6-4). I.
REFERENCE GUIDELINES
In addition to the requirements set forth herein, design and construction of PD systems should utilize applicable guidelines contained in the following references: 1. "Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February 2002 and as amended. 2. “Design Manual – Onsite Wastewater Treatment and Disposal Systems”, U.S. Environmental Protection Agency, October 1980.
SUBSURFACE DRIP DISPERSAL SYSTEM DESIGN A.
DESCRIPTION
Subsurface drip dispersal is a method for disposal of treated wastewater that uses special drip tubing designed for use with wastewater. The dripline is placed normally eight (8) to twelve (12) inches below ground surface and makes use of the most biologically active soil zone for distribution, nutrient uptake and evapotranspiration of the wastewater. A drip dispersal system is comprised of small-diameter (½” to 1”) laterals (“driplines”), usually spaced about 24 inches apart, with small-diameter emitters (1/8”) located at twelve (12) to twenty-four (24) inches oncenter along the dripline. Effluent is conveyed under pressure to the laterals, normally with timed doses. Prior to dispersal the effluent requires supplemental treatment. Schematic and cross-section diagrams are provided in Figure 7-8 and Figure 7-9 to illustrate the key design features of Drip Dispersal Systems. 1. Primary Dispersal Area. A Primary Drip Dispersal System designed to treat one hundred percent of the design wastewater flow shall be installed. The dripfield area shall be marked and protective measures installed around the perimeter, for example use of railroad ties, landscape border or similar measures to clearly delineate the extent of the drip field. 2. Reserve Dispersal Area. A reserve area having suitable site conditions and sufficient area for full, one-hundred (100) percent replacement of the primary Drip Dispersal System shall be identified during the Site Evaluation and reserved for future use.
Revised Draft 6-28-16 95
C.
SITING REQUIREMENTS
Siting requirements for Drip Dispersal Systems are provided in Table 3-1, Table 4-10 and Table 4-11. 1. Advantages. Drip dispersal has several advantages, including: a. It can be effective in very shallow soil conditions since it distributes the wastewater very uniformly to substantially all of the available soil in the field; b. It can be installed in multiple small discontinuous “zones”, allowing the hydraulic load to be spread widely rather than concentrated in one main area; c. It can be installed on steeper slopes, causes less soil disturbance and erosion or slope stability hazards; and d. Water movement away from the drip emitters is substantially by unsaturated/capillary flow, which maximizes contact with and treatment by the soil. 2. Disadvantages. Drip dispersal also has several disadvantages including: a. Susceptibility to damage due to its shallow depth from surface activities, rodents and animals; b. Higher maintenance requirements. 3. Vertical Separation Requirements. a. Depth to Groundwater. The minimum depth to seasonal high groundwater, as measured from the bottom of the dripline, shall vary according to soil percolation rate as specified in Table 3-1. b. Effective Soil Depth. The minimum depth of soil, as measured from the bottom of the dripline to impermeable soil or rock, shall be two (2) feet. 4. Maximum Ground Slope. a. Maximum ground slope in areas used for Drip Dispersal Systems shall be fifty (50) percent; b. Any Drip Dispersal System located on slopes greater than thirty (30) percent shall require the completion of a geotechnical report and slope stability analysis as specified in Chapter 3 of this Manual. Revised Draft 6-28-16 96
D.
TREATMENT REQUIREMENTS
The following treatment requirements shall apply in connection with the use of Drip Dispersal Systems: 1. Wastewater effluent discharged to a Drip Dispersal System shall be treated to at least a secondary level through an approved supplemental treatment system; 2. All drip dispersal systems shall include a filtering device capable of filtering particles larger than one-hundred (100) microns; this device shall be located downstream of the supplemental treatment system. E.
WASTEWATER APPLICATION RATES
Wastewater application rates used for sizing Drip Dispersal Systems shall be based on soil percolation rate in accordance with the criteria in Table 4-8. In applying these criteria, the wastewater application area refers to the ground surface area encompassed by the drip dispersal field. F.
DRIPFIELD SIZING AND DESIGN 1. Minimum sizing of the dripfield area shall be equal to the design wastewater flow divided by the applicable wastewater application rate. 2.
For sizing purposes, the effective ground surface area used for drip field sizing calculations shall be limited no more than four (4) square feet per drip emitter. For example, two hundred (200) lineal feet of dripline with emitters at two (2) foot spacing would provide a total of one-hundred (100) emitters (200/2) and could be used for dispersal to an effective area of up to four-hundred (400) square feet (100 emitters x 4 ft2/emitter). Conversely, if wastewater flow and percolation design information indicate the need for an effective area of one-thousand (1,000) square feet, the dripline design and layout would have to be configured to provide a minimum of two hundred and fifty (250) emitters spaced over the required one-thousand (1,000) square foot dispersal area.
3. Dripfields may be divided into multiple zones which may be located in different areas of a site, as desired or needed to provide the required dripfield size. A single continuous dripfield area is not required. However, any areas proposed for drip dispersal shall be supported by field observations/measurements to verify conformance with soil suitability and other site requirements. Differences in soil conditions and percolation characteristics from one zone to another may require the use of correspondingly different wastewater application rates and dripfield sizing for each zone.
Revised Draft 6-28-16 97
4. Dripline shall be manufactured and intended for use with secondary quality wastewater, with minimum forty-five (45) mil tubing wall thickness, bacterial growth inhibitor(s), and means of protection against root intrusion. 5. The bottom of each dripline row shall be level and parallel to the slope contour. 6. The dripline depth shall be installed at a depth between eight (8) and twelve (12) inches below original grade. Deeper placement of driplines may be considered by the Department on a case-by-case basis. 7. The maximum dripline length shall be designed in accordance with accepted industry practices and in accordance with the manufacturer’s criteria and recommendations. 8. Line and emitter spacing shall be designed as appropriate for soil conditions, slope, and contour. Emitters shall be located at no less than twelve (12) inches from the supply and return manifolds. G.
PRESSURE DOSING
Effluent treated by a Supplemental Treatment System/Unit shall be delivered to the dripfield by pressure, employing a pump system and timed dosing. The pressure distribution system shall be designed in accordance with accepted industry practices and manufacturer recommendations for drip dispersal systems to achieve, at a minimum: 1. Uniform dosing of treated effluent; 2. An adequate dosing volume and pressure per manufacturer’s guidelines; 3. Adequate flow rate, final filtering of effluent and suitable piping network to preclude solids accumulation in the pipes and driplines or clogging of discharge emitters; 4. A means of automatically flushing the filter and driplines at regular intervals; 5. Suitable access provisions for inspection, testing and adjustment of the dripfield and components; 6. Pump system designed in accordance with the pump system requirements provided in Chapter 5 of this Manual; 7. Additional requirements for design and construction of pressure distribution piping systems contained in the guidelines for Pressure Distribution Systems in Chapter 10 of this Manual, as applicable. H.
COVER FILL
Cover fill may also be used in conjunction with subsurface drip dispersal systems. Revised Draft 6-28-16 98
I.
GROUNDWATER OBSERVATION WELLS 1. A minimum of three (3) Ground Water Observation wells shall be installed within and around the Drip Dispersal System area for the purpose of checking groundwater levels periodically and water quality sampling, if needed. 2. Groundwater Observation wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending from the ground surface to depth of twelve (12) inches, minimum.
J.
REFERENCE GUIDELINES
Installation of subsurface drip dispersal systems shall be in accordance with applicable manufacturer guidelines and recommendations.
COVER FILL DISPERSAL SYSTEMS A.
DESCRIPTION 1. The term “cover fill” refers to a dispersal trench or drip dispersal system where the trenches or dripline are excavated entirely below grade, but up to twelve (12) inches of soil fill is placed on top of original grade to provide the required backfill cover over the pipe and drain rock. 2. The wastewater is dispersed into the native soils, not into the fill soil. The purpose is to allow for shallower trench depths where necessary or desirable to meet soil depth and groundwater separation requirements. 3. It provides for improved use of the absorption capacity of the near surface soils, which tend to be most permeable and most effective for absorption and treatment of wastewater effluent. 4. Cover fill can be used in conjunction with Standard Trench Dispersal Systems, Pressure Distribution Systems, Pressure-Dosed Sand Trench Dispersal Systems, and Drip Dispersal Systems presented in this Chapter. 5. Schematic and cross-section diagrams of cover fill trench systems are provided in Figure 7-2 to illustrate the key design features of Cover Fill Dispersal Systems.
Revised Draft 6-28-16 99
B.
SITING REQUIREMENTS 1. Horizontal Setback Requirements. The minimum horizontal setback distances specified in Table 4-10 apply to Cover Fill Systems. The setback is measured from the edge of the dispersal trench or dripline, as applicable, however, the runout of coverfill must be contained fully within the property boundaries. 2. Vertical Separation Requirements. Soil depth, groundwater separation and percolation rates shall conform to the requirements applicable to the type of the dispersal system (standard trench, pressure dosed trench, pressure-dosed sand trench, subsurface drip) as provided in Table 3-1. 3. Maximum Ground Slope. The maximum ground slope in areas used for Cover Fill Systems shall be twenty (20) percent. Where a geotech slope stability evaluation is provided slopes of up to 25% may be allowed.
C.
DESIGN CONSTRUCTION REQUIREMENTS 1. Dispersal Trenches. The drain rock and perforated pipe sections shall be installed entirely below original grade, and all other aspects of the dispersal trench design shall be in conformance with requirements for Standard Trench Dispersal Systems, or in the case of an Alternative Dispersal System, in accordance with requirements for the particular type of system (e.g., Pressure Distribution Trench, Drip Dispersal System, etc.) as specified in this Chapter. 2. Site Preparation. Prior to placement of fill material, all vegetation shall be removed and the ground surface ripped or ploughed to a depth approximately six (6) to ten (10) inches to permit good mixing of native soil and fill material. 3. Fill Material. The soil used for fill shall be similar in texture to the native surface soil in the dispersal field area. Sand, gravel or rock do not qualify as acceptable material for cover fill. Particle size analysis (hydrometer method) of the dispersal site soils and fill soil shall be required for the Department review and acceptance of the proposed fill soil, except in cases where the fill is obtained from similar soils at the project site. 4. Sequencing. The fill shall be placed prior to dispersal trench excavation and installation of dispersal piping and appurtenances. 5. Areal Coverage. The fill shall be continuous and constructed to provide a uniform soil cover. The fill, in combination with the trench backfill, shall achieve a total thickness of at least twelve (12) inches over the dispersal trenches. The fill shall extend a minimum distance of fifteen (15) feet from the edge of trench in the downslope direction and ten (10) feet in the upslope and side-slope directions. On a level site, the fill shall extend a minimum of 10 feet in all directions. The toe of the fill shall Revised Draft 6-28-16 100
be tapered at no less than a three horizontal to 1 vertical (3:1) grade, beginning at the above required fifteen (15) foot or ten (10) foot distance, as applicable. Where the primary and secondary dispersal fields are adjacent to one another, the cover fill should be continuous over both fields. 6. Fill Compaction. Fill shall be placed in layers (“lifts”) of not more than six (6) inches, and compacted to approximately the same dry density as the native soil. Normal compaction procedures to achieve this requirement shall consist of track-rolling each lift, two passes minimum. Alternative compaction procedures may be allowed by the Department in accordance with recommendations and supporting technical data supplied by a Qualified Professional.
AT-GRADE SYSTEM A.
DESCRIPTION
At-Grade Systems are similar to Mound Systems, except that they do not include the sand bed; the gravel distribution bed is placed directly on the scarified (i.e., plowed) soil surface. They are often used in conjunction with a supplemental treatment system. They can be used in the same types of situations as Mound Systems to overcome shallow soil depths and high groundwater. Schematic and cross-section diagrams are provided in Figure 7-10 and Figure 7-11 to illustrate the key design features of At-Grade Dispersal Systems. B.
PRIMARY AND RESERVE AREA REQUIRED 1. Primary Dispersal System. A Primary At-Grade Dispersal System designed to treat one hundred percent of the design wastewater flow shall be installed. 2. Reserve Dispersal System Area. A reserve area having suitable site conditions and sufficient area for full, one-hundred (100) percent replacement of the primary AtGrade Dispersal System shall be identified during the Site Evaluation and reserved for future use. 3. Dispersal System Overlap. In determining the necessary space for the primary and secondary (reserve) field, the required gravel distribution bed area of the primary and secondary At-Grade shall not overlap. The surplus soil fill run-out shall also not overlap unless the primary and secondary At-Grades are both installed (i.e., as a dual system). 4. Dual At-Grade Dispersal System. Dual At-Grade Dispersal Systems (primary and secondary installed) shall be required for any system where, due to space constraints, the soil cover run-out of the primary At-Grade overlaps the soil cover run-out area of the secondary At-Grade.
Revised Draft 6-28-16 101
D.
SITING REQUIREMENTS 1. Horizontal Setback Requirements. The minimum horizontal setback distances specified in Table 4-10 apply to the At-Grade System (as measured from the edge of cover soil) except where modified below for buildings, structures, property and underground utility easements: a. Upgradient and laterally: Ten (10) feet b. Downgradient: Twenty five (25) feet 2. Vertical Separation Requirements. Vertical separation and slope requirements for At- Grade Systems are provided in Table 3-1. a. Depth to Groundwater. Minimum depth to seasonal high groundwater for At- Grade systems, as measured from ground surface, shall vary according to soil percolation rate and the level of treatment. b. Effective Soil Depth. Minimum depth of soil, as measured from ground surface to impermeable soil or rock, for At-Grade systems shall vary according to soil percolation rate and the level of treatment. These soil depth requirements shall apply within the dispersal field and in the adjacent area extending a distance of twenty-five (25) feet down-slope of the At-Grade system on sloping sites, and a distance of fifteen (15) feet on all sides on level sites. 3. Maximum Ground Slope. The maximum ground slope in areas used for At-Grade Systems shall be twenty (20) percent. Where a geotech slope stability evaluation is provided slopes of up to 25% may be allowed. 4. Percolation Rates. At-Grade systems may be installed where soil has an average soil percolation rates between five (5) and one hundred and twenty (120) mpi. For percolation rates greater than 60 mpi supplemental treatment is required.
E.
TREATMENT REQUIREMENTS
The following treatment requirements shall apply in connection with the use of At-Grade Systems: 1. Primary (septic tank) treatment shall be the minimum level of treatment, and shall be acceptable where the applicable vertical separation distances are met per Table 3-1. 2. Supplemental treatment, using an approved alternative treatment system identified in this Manual, may be used to allow compliance with reduced vertical separation distance provided in Table 3-1. Revised Draft 6-28-16 102
F.
PRESSURE DOSING
Wastewater Effluent, from the Septic Tank or Supplemental Treatment System, shall be applied to the At-Grade Dispersal System by pressure dosing, utilizing a pump system. The pressure distribution system shall be designed in accordance with accepted industry practices to achieve, at a minimum: 1. Uniform dosing of treated effluent over the surface application area of the At-Grade distribution bed; 2. Adequate flow rate, screening of effluent and suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices; 3. Suitable access provisions for inspection, testing and adjustment of the pressure distribution system; 4. At least one distribution lateral for every thirty-six (36) inches of distribution bed width; 5.
Pump system designed in accordance with the pump system requirements provided in Chapter 5 of this Manual; and
6. Additional requirements for design and construction of pressure distribution piping systems contained in the guidelines for Pressure Distribution Systems in Section 7.3 of this Chapter, as applicable. G.
AT-GRADE SYSTEM CONFIGURATION 1. On sloping sites (greater than 2 percent), the At-Grade System shall be aligned with its longest dimension parallel to the site contours so as not to concentrate the effluent into a small area as it moves laterally down slope. 2. The At-Grade System shall not be aligned perpendicular to the contours. 3. The At-Grade System shall not be placed in a concave landscape position. 4. The gravel distribution bed shall be as long and narrow as possible to limit the linear loading rate of effluent to assure that all the effluent infiltrates into the natural soil before it reaches the toe of the At-Grade System. 5. Site drainage shall be provided so that rainfall and runoff is directed away from or around the At-Grade System. On sloped sites curtain drains may be required to divert runoff away from the At-Grade System.
H.
GRAVEL DISTRIBUTION BED DESIGN Revised Draft 6-28-16 103
1. Material. The distribution bed shall consist of 3/8-inch double-washed pea gravel, substantially free of fines (defined as less than one (1) percent fines, dust, sand and/or silts passing the #200 seive). 2. Depth. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches above the top of the distribution piping. 3. Slope Contour. The toe of the gravel distribution bed shall follow contour and not deviate more than three (3) inches vertically per one-hundred (100) feet horizontally. 4. Gravel Bed Sizing. The minimum gravel distribution bed area shall be sized to meet the maximum wastewater application rates and linear loading requirements in accordance with the criteria provided in Table 7-8. 5. Distribution Bed Placement. Where multiple distribution beds are used for the primary system, beds may be placed end-to-end or upslope/down-slope of one another, subject to meeting minimum sizing requirements determined from basal area and linear loading criteria in Table 7-8. Where any portion of the gravel distribution beds overlap in an upslope/downslope configuration and are within twenty-five feet the linear loading analysis must account for the combined flow from the overlapping portions. I.
SOIL COVER 1. Material. A continuous soil cover shall be placed over the entire distribution bed. The soil cover shall consist of a medium, loamy-textured soil. 2. Silt Barrier. The gravel distribution bed shall be covered in its entirety with a geotextile ("filter fabric") silt barrier. Filter fabric shall either be polyester, nylon or polypropylene, or any combination thereof, and shall be suitable for underdrain applications. Filter fabric shall be non-woven, shall not act as a wicking agent and shall be permeable. 3. Depth. Soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen (18) inches over the top of the distribution bed. Soil cover over the distribution bed shall be crowned to promote rainfall runoff, and compacted by trackrolling, minimum two passes. 4. Lateral Extension. The soil cover shall extend a minimum of four (4) feet beyond the perimeter edge of the gravel bed in all directions on level sites. On sloping sites (greater than 2 percent), the soil cover extension beyond the down-slope edge of the gravel bed shall increase according to slope length correction factors for Mound Systems in Table 7-
Revised Draft 6-28-16 104
J.
DUAL AT-GRADE DISPERSAL SYSTEMS 1. Distribution Bed Placement. Dual At-grade systems shall have at least two (2) distinctly separate distribution beds. The beds may be placed with one continuous soil cover fill or with independent soil cover fill. The distribution beds may be placed end-to-end or upslope/down-slope of one another, subject to meeting minimum sizing requirements determined from basal area and linear loading criteria above. 2. Distribution Bed Separation. The minimum lateral (i.e., end-to-end) separation between distribution beds for dual At-grade systems shall be six feet. 3. Alternate Dosing. The distribution beds for At-grade systems shall be designed and operated to provide alternate dosing and resting of the beds.
K.
GROUNDWATER OBSERVATION WELLS 1. A minimum of five (5) groundwater monitoring wells shall be installed within and around the At-Grade System area in accordance with the requirements in Table 7-4 for the purpose of checking groundwater levels periodically and water quality sampling, if needed. 2. Groundwater monitoring wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending from the ground surface to depth of twelve (12) inches, minimum.
REFERENCE GUIDELINES Additional guidelines for At-grade Dispersal Systems should be in accordance with guidelines contained in the following references: 1. "Wisconsin At-grade Soil Absorption System Siting, Design and Construction Manual”, Small Scale Waste Management Project, University of Wisconsin-Madison, 1990. 2. "Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February 2002. 3. “At-grade Component Using Pressure Distribution Manual for Private Onsite Wastewater Treatment Systems”, State of Wisconsin, Department of Commerce, 1999. Revised Draft 6-28-16 105
MOUND DISPERSAL SYSTEMS A.
DESCRIPTION
A Mound Dispersal System consists of an elevated sand bed with a gravel distribution bed covered by soil fill. Mound systems are intended to raise the soil absorption system above grade and provide further treatment (sand filtration) of effluent before it reaches native soils. It utilizes the shallow surface soils for broad distribution of effluent, and is used to mitigate high water table and shallow soil conditions on flat or gently sloping terrain. Schematic and cross-section diagrams are provided in Figure 7-12 through Figure 7-18 to illustrate the key design features of Mound Dispersal Systems. B.
PRIMARY AND RESERVE AREA REQUIRED 1. Primary Mound System. A Primary Mound Dispersal System designed to treat one hundred percent of the design wastewater flow shall be installed. 2. Reserve Mound System Area. A reserve area having suitable site conditions and sufficient area for full, one-hundred (100) percent replacement of the primary Mound Dispersal System shall be identified during the Site Evaluation and reserved for future use. 3. Overlap of Dispersal Areas. In determining the necessary space for the primary and secondary (reserve) field, the required sand fill basal area of the primary and secondary Mound shall not overlap. The surplus sand run-out and soil fill shall also not overlap.
C.
SITING REQUIREMENTS 1. Horizontal Setback Requirements. The minimum horizontal setback distances specified in Table 4-10 apply to the Mound system (as measured from the edge of cover soil) except where modified below for buildings, structures, property and underground utility easements: a. Upgradient and laterally: Ten (10) feet b. Downgradient: Twenty five (25) feet 2. Vertical Separation and Slope Requirements. Vertical separation and slope requirements for Mound Dispersal Systems are provided in Table 3-1. a. Depth to Groundwater. Minimum depth to seasonal high groundwater for Mound Systems, as measured from ground surface, shall vary according to soil percolation rate. Revised Draft 6-28-16 106
b. Effective Soil Depth. Minimum depth of soil, as measured from ground surface to impermeable soil or rock, for mound systems shall be two (2) feet. This soil depth requirement shall apply within the mound fill area and in the adjacent area extending a distance of twenty-five (25) feet down-slope of the Mound system. c. Maximum Ground Slope. d. Soil Percolation Rates between one (1) and sixty (60) mpi: The maximum ground slope in areas used for Mound Systems with average soil percolation rates between one (1) and sixty (60) mpi shall be twenty (20) percent. e. Soil Percolation Rates greater than 60 mpi: The maximum ground slope in areas used for Mound Systems with average soil percolation rates greater than sixty (60) mpi shall be fifteen (15) percent. D.
TREATMENT REQUIREMENTS 1. Mound Systems are designed for treating residential strength wastewater. The wastewater applied to the Mound System shall meet the definition of residentialstrength wastewater (or less) per the criteria provided in Chapter 4. 2. The Mound Dispersal System shall be preceded by a septic tank sized for the design wastewater flow. 3. High strength wastewater shall require Supplemental Treatment in order to reduce its strength to residential waste strength or less prior to introduction into the Mound System.
E.
PRESSUE DOSING
Septic Tank Effluent shall be applied to the Mound Dispersal System by pressure dosing, utilizing a pump system. The pressure distribution system shall be designed in accordance with accepted industry practices to achieve, at a minimum: 1. Uniform dosing of treated effluent over the surface application area of the Mound distribution bed; 2. Adequate flow rate, screening of effluent and suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices; 3. Suitable access provisions for inspection, testing and adjustment of the pressure distribution system;
Revised Draft 6-28-16 107
4. The dose volume shall be sufficient to refill any part of the pressure distribution system including supply line and lateral lines plus deliver sufficient additional volume to disperse the daily Design flow in an appropriate number of doses per day at design flow conditions; 5. Mound System performance is enhanced when the daily flow is dispersed in smaller, more frequent doses throughout the day; 6. At least one distribution lateral for every thirty-six (36) inches of distribution bed width; 7. Pump system designed in accordance with the pump system requirements provided in Chapter 5 of this Manual; and 8. Additional requirements for design and construction of pressure distribution piping systems contained in the guidelines for Pressure Distribution Systems in Section 7.3 of this Chapter, as applicable. F.
MOUND PLACEMENT 1. On sloping sites (greater than 2 percent), the mound shall be aligned with its longest dimension parallel to the site contours so as not to concentrate the effluent into a small area as it moves laterally down slope. 2. The mound shall not be aligned perpendicular to the contours. 3. The mound shall not be placed in a concave landscape position. 4. The infiltration bed shall be as long and narrow as possible to limit the linear loading rate of effluent to assure that all the effluent infiltrates into the natural soil before it reaches the toe of the filter media. 5. Site drainage shall be provided so that rainfall and runoff is directed away from or around the mound system. On sloped sites curtain drains may be required to divert runoff away from the mound.
G.
GRAVEL DISTRIBUTION BED DESIGN 1. Material. The gravel distribution bed shall consist of three-eighth (3/8) inch doublewashed pea gravel, substantially free of fines (defined as less than one (1) percent fines, dust, sand and/or silts passing the #200 sieve). 2. Depth. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches above the top of the distribution piping. Revised Draft 6-28-16 108
3. Level. The bottom of the distribution bed shall be level. 4. Slope Contour. The down-slope side of the gravel distribution bed shall be parallel to the slope contour. The bed shall be installed within a tolerance of three (3) inches vertically per one-hundred (100) feet horizontally. 5. Gravel Bed Sizing. The minimum gravel distribution bed area shall be sized to meet the maximum wastewater application rates and linear loading requirements in accordance with the criteria provided in Table 7-9. 6. Distribution Bed Placement. Where multiple distribution beds are used for the primary system, beds may be placed end-to-end or upslope/down-slope of one another, subject to meeting minimum sizing requirements determined from basal area and linear loading criteria in Table 7-8. Where any portion of the gravel distribution beds overlap in an upslope/downslope configuration and are within twenty-five feet the linear loading analysis must account for the combined flow from the overlapping portions. H.
SAND FILL MEDIA 1. Sand Specifications. The sand media shall be a medium to coarse sand which meets the gradation specifications in Table 9-1. Documentation of laboratory sieve analysis results for the proposed sand fill material shall be supplied to the Department to verify conformance with the above specifications. 2. Sand Depth. a. The minimum depth of sand fill below the gravel distribution bed shall be twelve (12) inches. b. The minimum depth of sand fill shall be increased to twenty-four (24) inches for sites where the average percolation rate is between one (1) and five (5) mpi; such sites also require a three (3) foot separation to groundwater below sand-soil interface. 3. Slope Contour. The toe of the sand fill shall follow contour and not deviate more than three (3) inches vertically per one-hundred (100) feet horizontally. 4. Sand Fill Area Sizing. The minimum basal area of the sand fill (i.e., sand/soil interface area) shall be sized to meet the maximum basal wastewater application rates and linear loading requirements in accordance with the criteria provided in Table 7-10.
Revised Draft 6-28-16 109
5. Effective Sand Fill Basal Wastewater Application Area. The effective sand fill basal wastewater application area shall be determined based on the slope of the original ground surface as follows. Slope (%)
Effective Basal Wastewater Application Area
0 to 2
The entire sand fill basal area
>2
The sand basal area immediately below and directly down-slope (at right angles to the natural slope contours) of the gravel distribution bed.
6. Lateral Dimensions a. On level sites the top of the sand fill shall extend horizontally beyond the gravel distribution bed a minimum of twenty-four (24) inches in all directions, then slope uniformly as determined by the mound dimensions. b. On slopes greater than 2 percent, the twenty-four (24) inch sand fill dimension on the upslope side of the distribution bed may be reduced to 12 inches, then slope uniformly as determined by the mound dimensions. c. The maximum side slope of the top of the sand surface shall be three (3) horizontal to one (1) vertical. I.
SOIL COVER 1. Material. A continuous soil cover shall be placed over the entire distribution bed and sand fill. The soil cover shall consist of a medium, loamy-textured soil. 2. Silt Barrier. The gravel distribution bed shall be covered in its entirety with a geotextile ("filter fabric") silt barrier. Filter fabric shall either be polyester, nylon or polypropylene, or any combination thereof, and shall be suitable for underdrain applications. Filter fabric shall be non-woven, shall not act as a wicking agent and shall be permeable. 3. Depth. Soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen (18) inches over the top of the gravel distribution bed, and twelve (12) inches minimum over the sand fill portion of the mound. Soil cover over the distribution bed shall be crowned to promote rainfall runoff, and compacted by trackrolling, minimum two passes. 4. Lateral Extension. The soil cover shall extend a minimum of four (4) feet beyond the perimeter edge of the sand fill in all directions on level sites. On sloping sites (greater than 2 percent), the soil cover extension beyond the down-slope edge of the Revised Draft 6-28-16 110
sand fill shall increase according to slope length correction factors for Mound Systems in Table 7- 10. J.
DUAL AT-GRADE DISPERSAL SYSTEMS 1. Distribution Bed Placement. Dual At-grade systems shall have at least two (2) distinctly separate distribution beds. The beds may be placed with one continuous soil cover fill or with independent soil cover fill. The distribution beds may be placed end-to-end or upslope/down-slope of one another, subject to meeting minimum sizing requirements determined from basal area and linear loading criteria above. 2. Distribution Bed Separation. The minimum lateral (i.e., end-to-end) separation between distribution beds for dual At-grade systems shall be six feet. 3. Alternate Dosing. The distribution beds for At-grade systems shall be designed and operated to provide alternate dosing and resting of the beds.
K.
GROUNDWATER OBSERVATION WELLS 1. A minimum of five (5) groundwater monitoring wells shall be installed within and around the At-Grade System area in accordance with the requirements in Table 7-4 for the purpose of checking groundwater levels periodically and water quality sampling, if needed. 2. Groundwater monitoring wells shall be constructed of two (2) inch to four (4) inch diameter pipe, equipped with a wrench-tight cap or pipe plug and a bottom cap. All wells shall be perforated beginning at a depth of eighteen (18) inches below grade and extending to the bottom of the pipe. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a bentonite or concrete annular seal (or equivalent), extending from the ground surface to depth of twelve (12) inches, minimum.
L.
REFERENCE GUIDELINES
Additional guidelines for mound system design are contained in the following references: 1. “Design and Construction Manual for Wisconsin Mounds”, Small Scale Waste Management Project, University of Wisconsin, Madison, January 2000, including any amendments. 2.
“Onsite Wastewater Treatment Systems Manual”, U.S. Environmental Protection Agency, February 2002.
Revised Draft 6-28-16 111
RAISED SAND FILTER BED SYSTEMS A.
DESCRIPTION 1. Raised sand filter beds shall be used only for repair or other corrective action of Existing OWTS on severely constrained sites where site specific conditions limit treatment and dispersal options. 2. A raised sand filter bed, sometimes referred to as a bottomless sand filter, combines features of an intermittent sand filter and a mound system. It consists of a raised or terraced sand bed, commonly supported by a low retaining wall or bulkhead, where the bottom surface is even with or slightly below ground surface and forms the absorption surface. The raised sand filter bed provides additional polishing treatment of effluent and final dispersal of wastewater into native soil. 3. The OWTS may be designed for use with supplemental treatment ahead of the raised sand bed when required for very shallow soil or very highly permeable soils. 4. Schematic and cross-section diagrams are provided in Figure 7-19 to illustrate the key design features of Mound Dispersal Systems.
B.
SITING REQUIREMENTS
Siting requirements for Raised Sand Filter Beds are provided in Table 3-1, Table 4-10 and Table 4-11 and should be followed to the maximum extent practicable. The following are a summary of the table requirements to be followed to the maximum extent practicable. 1. Vertical Separation Requirements a. Depth to Groundwater. Minimum depth to seasonal high groundwater for Raised Sand Filter Bed Systems, as measured from ground surface, shall vary according to soil percolation rate. b. Effective Soil Depth. Minimum depth of soil, as measured from ground surface to impermeable soil or rock, for Raised Sand Filter Bed is 2 feet. This soil depth requirement applies within the dispersal field area beneath the Raised Sand Filter Bed and in the adjacent area extending a distance of twenty-five (25) feet down-slope of the Raised Sand Filter Bed. c. Soil Percolation Requirements. Raised Sand Filter Beds may be used in areas with soil percolation rates of one (1) to one hundred and twenty (120) mpi. 2. Maximum Ground Slope. Maximum ground slope in areas used for Raised Sand Filter Beds shall be thirty (30) percent. Revised Draft 6-28-16 112
C.
TREATMENT REQUIREMENTS
The following treatment requirements shall apply in connection with the use of raised sand filter bed systems: 1. Primary (septic tank) treatment shall be the minimum level of treatment, and shall be acceptable where the design includes sand fill depth of twenty-four (24) inches. 2. Supplemental treatment, using an approved Supplemental Treatment Unit may be used to allow reduction of the sand fill depth to twelve (12) inches. D.
PRESSURE DOSING
Septic Tank Effluent shall be applied to the Raised Sand Filter Bed by pressure dosing, utilizing a pump system. The pressure distribution system shall be designed in accordance with accepted industry practices to achieve, at a minimum: 1. Uniform dosing of treated effluent over the surface application area of the Raised Sand Filter Bed; 2. Adequate flow rate, screening of effluent and suitable piping network to preclude solids accumulation in the pipes or clogging of discharge orifices; 3. Suitable access provisions for inspection, testing and adjustment of the pressure distribution system; 4. The dose volume shall be sufficient to refill any part of the pressure distribution system including supply line and lateral lines plus deliver sufficient additional volume to disperse the daily Design flow in an appropriate number of doses per day at design flow conditions; 5. Raised Sand Filter Bed performance is enhanced when the daily flow is dispersed in smaller, more frequent doses throughout the day; 6. At least one distribution lateral for every thirty-six (36) inches of distribution bed width; 7. Pump system designed in accordance with the pump system requirements provided in Chapter 8 of this Manual; and 8. Additional requirements for design and construction of pressure distribution piping systems contained in the guidelines for Pressure Distribution Systems in Section 7.3 of this Chapter, as applicable.
Revised Draft 6-28-16 113
E.
RAISED SAND FILTER BED CONTAINMENT STRUCTURE 1. Containment Liner. The raised sand filter bed shall be provided with an impermeable containment liner along all sides of the filter bed to prevent lateral leakage out of or into the filter. a. The liner shall extend a minimum of twelve (12) inches below original grade. b. The liner shall consist of either: i. 30 mil plastic; ii. reinforced poured-in-placed concrete; or iii. an equivalent impermeable structure. 2. Retaining Wall. The finished grade of the raised sand filter bed shall be above the surrounding ground elevation and shall be structurally supported with retaining wall(s), as required. 3. Bed Dimensions. The maximum width of the sand bed shall be ten (10) feet. The raised sand filter bed shall not be restricted as to its shape in plan view. 4. Multiple Units. The raised sand filter bed may be divided into compartments or multiple units.
F.
SAND FILTER MEDIA 1. Sand Specifications. The sand media shall be a medium to coarse sand which meets the gradation specifications for Raised Sand Filter Beds in Table 9-1. Documentation of laboratory sieve analysis results for the proposed sand filter media material shall be supplied to the Department to verify conformance with the above specifications. 2. Sand Depth. The minimum depth of sand fill, below the gravel distribution bed, shall be: a. Twenty-four (24) inches for septic tank effluent. b. Twelve (12) inches for supplement treatment.
Revised Draft 6-28-16 114
G.
SAND FILL BASAL AREA SIZING
The basal area of the sand filter bed (i.e., area of the sand-soil interface) shall be sized to meet the maximum basal wastewater application rates and linear loading requirements provided in Table 7-11. 1. Wastewater Flow. The wastewater flow used for sizing the basal area of the sand filter bed shall be the design wastewater flow for the system. 2. Wastewater Application Rate. Wastewater application rates used for sizing the basal area of the sand filter bed shall be based on soil percolation rates in the upper (12) to twenty- four (24) inches of soil depth in accordance with the criteria in Table 4-5 (Standard Wastewater Application Rates) if primary treatment only is utilized, or Table 4-7 (Wastewater Application Rates) if Supplemental Treatment is utilized. Reduction in the wastewater loading rates or other provisions to insure the long-term integrity and performance of the raised sand filter bed may be required for high strength waste flows. 3. Minimum Sizing. The minimum size (square feet) of the basal area of the raised sand filter bed shall be determined by dividing the design wastewater flow (in gpd) by the applicable wastewater application rate per Table 4-5 or 4-7.
Design Wastewater Flow Rate (gpd) Sand Fill Basal Area (ft2) =
Wastewater Application Rate (gpd/ft2)
4. Effective Length. The effective length (L) of the Raised Sand Filter Bed shall be the total length of the raised bed along the downslope edge.
Effective Length (ft) =
Design Wastewater Flow Rate (gpd) Linear Loading Rate (gpd/lineal foot)
a. Linear Loading Rate. Maximum linear loading rates for raised sand filter bed systems sizing shall vary according to soil depth, ground slope, and percolation rate as indicated in Table 7-11. If a change from these criteria is proposed, it must be supported by detailed groundwater mounding analysis carried out in accordance with accepted methodology and/or scientific references dealing with water movement in soils and utilizing site specific hydraulic conductivity data.
Revised Draft 6-28-16 115
b. Wastewater Flow (Q). The wastewater flow used for determining the linear loading rate shall be as follows: System Type
Q (gpd)
Residential Systems
100 gpd/bedroom1
Commercial, Institutional, Industrial and Multi-residential Systems
Design wastewater flow rate
Note: 1One hundred and fifty (150) gpd shall be used for System design H.
GRAVEL DISTRUBTION BED 1. Material. The distribution bed shall consist of three-eighth (3/8) inch double-washed pea gravel, substantially free of fines. 2. Depth. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches above the top of the distribution piping. If the distribution piping is installed with chambers, the pea gravel depth below the distribution pipe may be reduced from six (6) inches to four (4) inches, and the two (2) inch pea gravel cover may be eliminated. 3. Silt Barrier. The gravel distribution bed shall be covered in its entirety with a geotextile ("filter fabric") silt barrier. Filter fabric shall either be polyester, nylon or polypropylene, or any combination thereof, and shall be suitable for underdrain applications. Filter fabric shall be non-woven, shall not act as a wicking agent and shall be permeable.
I.
SOIL COVER 1. Material. A continuous soil cover consisting of a medium, loamy-textured soil shall be placed over the entire gravel distribution bed. 2. Depth. Soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen (18) inches over the top of the gravel distribution bed. Soil cover shall be crowned or sloped to promote rainfall runoff.
J.
INSPECTION PORTS
A minimum of four (4) inspection ports shall be installed within and around the Raised Sand Filter Bed in accordance with the requirements in Table 7-4 for the purpose of checking groundwater levels periodically and water quality sampling, if needed. Revised Draft 6-28-16 116
OVERVIEW The chapter presents specifications for non-discharging wastewater toilet units. A non-discharging wastewater toilet unit is a self-contained, watertight container designed to hold wastewater until it is pumped and/or cleaned. A non-discharging wastewater toilet unit includes but is not limited to a Vault Privy, Portable Toilet, and Waterless Toilet. These methods may be subject to the requirements of an Operating Permit. This chapter is organized in the following sections:
Section 8.1:
Vault Toilets
Section 8.2:
Portable Toilets
Section 8.3:
Waterless Toilets
VAULT TOILET REQUIREMENTS A.
DESCRIPTION 1. A Vault Toilet is a structure used for disposal of human waste without the aid of water and consists of a shelter built above a subsurface vault into which human waste falls. 2. The Vault Toilet may also collect drainage from hand washing facilities.
B.
SITING CRITERIA 1. The Vault Toilet shall only serve non-residential and non-commercial in and allowed in areas where it is the preferable method of wastewater disposal for the protection of public health and environmental resources due to such factors as remote location, limited water supply, and site constraints for an OWTS. Limited use applications examples are primitive type picnic grounds, campsites, camps and remote recreation areas. OWTS. 2. Vault Toilet shall not be used for seasonal dwellings, commercial facilities, or singlefamily dwellings.
C.
GENERAL REQUIREMENTS 1. The vault shall be watertight and tested for water tightness at the time of installation using the same methods as found in Section 5 for tank water tightness. 2. The vault shall meet the same setbacks requirements as a Septic Tank ( Chapter 4). Revised Draft 6-28-16 117
3. The capacity of the vaults shall be adequately sized to accommodate the proposed usage and frequency of pumping 4. Vaults must be vented to the outside atmosphere by a flue or vent stack having a minimum inside diameter of four (4) inches. D.
PERMIT REQUIREMENTS 1. An Operating Permit is required. 2. Vault Toilet shall be maintained to prevent health hazards and pollution of public waters. 3. The Vault Toilet shall not be allowed to become filled with waste to a point within two (2) feet of the ground surface. 4. The contents in the vault shall be regularly pumped by a Septage Pumper in Alameda County. 5. Each Vault Toilet shall display the name of the Owner, and the registered septate pumper that is responsible for servicing it.
PORTABLE TOILET REQUIREMENTS A.
DESCRIPTION 1. A Portable Toilet is any self-contained Chemical Toilet Facility that is housed within a Portable Toilet Shelter that collects toilet waste and any drainage from its hand washing sink.
B.
SITING CRITERIA 1. Portable Toilets may be allowed for temporary or limited use areas, such as construction Sites (for use by onsite employees), mobile or temporary agricultural uses, temporary campsites, and special events. 2.
Portable Toilets meet the same setbacks requirements as a Septic Tank (Chapter 4).
3. When associated with a Use Permit, a Plot Plan may be required which indicates the placement of the Portable Toilets relative to required setbacks. 4. When associated with a Use Permit, the minimum number of Portable Toilets shall be determined based on estimated attendees and duration of event and relevant published industry guidance, such as the Portable Sanitation Association International Special Event Extended Chart Breakdown. Revised Draft 6-28-16 118
5. Portable Toilets shall not be allowed for seasonal dwellings, commercial facilities or single- family dwellings. C.
GENERAL REQUIREMENTS 1. Portable Toilet Shelters shall display the business name and contact information of the Owner or licensed sewage disposal service that is responsible for servicing them. 2. No water-carried sewage may be piped to or placed in Portable Toilets. 3. Portable Toilets shall be maintained to prevent health hazards and pollution of protected waters. 4. Contents of Portable Toilets will not be discharged into storm sewers, on the surface of the ground or into protected waters. 5. Biocides and oxidants must be added to waste detention chambers at rates and intervals recommended by the manufacturer. 6. Wastes shall be removed from the chamber as necessary to prevent overflow. 7. All hand washing within a portable unit must be plumed to the tank.
D.
PERMIT REQUIREMENTS
An Operating Permit are not be required for temporary use (less than 7 days) of Portable Toilets and in agricultural field activities.
WATERLESS TOILET REQUIREMENTS A.
DESCRIPTION
A Waterless Toilet includes a composting toilet, an incinerating toilet or similar device for the holding and processing of Wastewater from a toilet. B.
LIMITATIONS 1. Waterless Toilets are only allowed in limited instances: a. Outbuildings not used as a residence or sleeping quarter. b. As part of a corrective action for repair or replacement of a failed OWTS on severely constrained sites.
Revised Draft 6-28-16 119
2. Waterless Toilets must meet each the following conditions: a. Five (5) acre minimum Lot size is five AND b. Setbacks from the unit and the disposal area must meet the minimum requirements for OWTS dispersals field setbacks, with the additional requirement that setback from the all property lines must be at least 100 feet. AND c. The property is not located in a designated Area of Concern. (Chapter 4). AND 3. The excrement from Waterless Toilets shall not create a public nuisance. C.
REQUIREMENTS 1. A Qualified Professional must: a. Conduct a Site Evaluation in the area of the proposed disposition of Waterless toilet wastes. The Site Evaluation shall verify at least five (5) feet of separation to groundwater or other limiting layer from the bottom of the disposal area. b. Submit an operating and management plan for the unit and, if applicable, the disposal area. 2. The property owner must have and maintain an annual operating permit and comply with all of the permit conditions. 3. The Waterless Toilet shall be installed, maintained, and replaced in accordance with the manufacture’s recommendations. 4. No material shall be placed in a Waterless Toilet other than the material for which it has been designed. 5. The Waterless Toilet shall be certified and currently listed by the National Sanitation Foundation (NSF) under NSF/ ANSI Standard 4110. 6. The model of the Waterless Toilet selected shall be appropriate for the number of users and intended demand. The manufacturer specification sheet shall be provided and shall demonstrate the toilet is appropriately sized for the planned use.
10
Check if correct standard
Revised Draft 6-28-16 120
7. The product of the Waterless Toilet shall only be handled and disposed of after the digestion process is complete as specified in the manufacturer’s instructions. The product of the Waterless Toilet digestion must be transported and/or disposed of in a manner that does not create a public nuisance and is in accordance with the requirements of the Operating Permit, Operation and Management Plan and the Owner’s operation and maintenance manual The Operation, Maintenance and Management Plan must include the following: i.
Manufacturer’s name and model number;
ii.
Manufacturer’s NSF listing and certification;
iii.
Manufacturer’s recommended operational capacity;
iv.
Manufacturer’s operation and maintenance guidance;
v.
Minimum burial depth; and
The location of the burial area; and vi.
Schedule and timing for burial; and
vii.
Method of handling and site for disposal of the waste product of the Waterless Toilet; and
viii.
Contact information in case of the need of repair or replacement
ix.
Other items as requested by the Department for the protection of public health and the environment.
a. Trouble-shooting information; D.
OPERATING PERMITS 1. Each Waterless Toilet must have an Operating Permit issued by the Department to the property owner. 2. A Person selling a parcel on which there is an approved Operating Permit for a Waterless Toilet must notify the Department of the transfer and disclose to the prospective purchaser of the presence of the Waterless Toilet and the requirements to obtain an Operating Permit. A Waterless Toilet permit is issued to the owner of the property and any change in ownership requires a new permit be filed with the Department. Revised Draft 6-28-16 121
3. No person shall install, maintain, or replace a composting toilet unless an Operating and Maintenance Manual is maintained and available for reference on the premises. The Operating and Maintenance Manual shall at a minimum contain all of the following information:
Revised Draft 6-28-16 122
CHAPTER OVERVIEW The chapter presents specifications for construction materials and installation. The criteria apply to new OWTSs and modifications or repairs to existing OWTSs. This chapter is organized in the following sections:
Section 9.1:
Pipes
Section 9.2:
Distribution Boxes and Diversion Valves
Section 9.3:
Drainrock, Sand & Filter Fabric
PIPES Unless otherwise specified, piping shall consist of materials and be constructed in conformance with the standards outlined below. All connection of pipes of different diameters shall be made with the proper fittings. 1. Labeling. All pipe throughout the OWTS shall be clearly labeled and installed so that the labeling can be readily identified by the Department inspectors. 2. Solid Pipe, Joints and Connections: Solid (non-perforated) pipe for OWTSs must conform to the standards of the most recent edition of the California Plumbing Code. 3. Tightlines under Traffic Areas: Tightline under traffic areas must be installed to prevent deformation, which may include use of appropriate piping materials, burial depth and sleeving. 4. Perforated Distribution Pipe: Perforated pipe for standard Dispersal Systems must conform to the California Plumbing Code and must be three (3) or four (4) inches in diameter. 5. Gravelless Alternatives: Gravelless chambers or other gravelless alternatives may be used provided the products IAPMO certified. 6. Building Sewer Requirements: The Building sewer pipe from the structure to the Septic Tank must meet California Building Code Requirements.
DISTRIBUITON BOXES & DIVERSION VALVES A.
DISTRIBUTION BOXES 1. Distribution boxes must be water tight and accessible. Revised Draft 6-28-16 123
2. Distribution boxes shall be designed to accommodate the necessary distribution laterals and expected flows and placed in a non-traffic area. 3. Distribution boxes may be installed for equal distribution to trenches on a level site or serial distribution on a sloping site. 4. The11 box design, materials and construction shall comply with all requirements of the Uniform Plumbing Code. 5. All distribution boxes must be installed level on bedding material. B.
DIVERSION VALVES 1. Diversion valves shall be corrosion resistant, watertight, and designed to accommodate the inlet and outlet pipes. 2. Each diversion valve shall have a positive stop. 3. The valve design, materials and construction shall comply with all requirements of the Uniform Plumbing Code.
A.
GRAVEL 1. Gravel used for drainrock shall be three quarter (¾) inch to two and one half (2½) inches in diameter. 2. Uniformly graded material is recommended to maximize pore space. 3. Drainrock shall be clean, washed, non-deteriorating gravel and free of fines. The drainrock must be accepted by the OWTS designer prior to placement.
B.
SAND 1. All filter materials used in single-pass sand filters, raised and intermittent sand filters, mound systems, pressure dosed sand trench systems and recirculating sand filters shall fall within the limits of the specifications shown in Table 9-1 for the amounts of material retained/passing (by weight). 2. The material shall also have a uniformity coefficient of four (4) or less. The uniformity coefficient is calculated by dividing D60 (the size of screen opening where sixty (60) percent of a sample passes and forty (40) percent is retained) by D10 (the size of screen opening where ten (10) percent of a sample passes and ninety (90) percent is
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retained). For sands with a D10 less than mm, the designer should consider a loading of no greater than 1.0 gallon/square foot-day, and specify frequent dosing. A sieve analysis, (done in accordance with ASTM D 136 for dry product, or ASTM C-117 for wet product), of the material is required prior to transport to the construction site. 3. A report of the sieve analysis and on-site analysis results must be available for the Department prior to system approval and for inclusion in the system's permanent file. C.
FILTER FABRIC 1. Filter fabric shall meet or exceed the specifications described in the following table12: Property
Requirement
Test Method
Grab Strength
80 lbs.
ASTM D4632
Puncture Strength
25 lbs.
ASTM D4833
Trapezoid Tear
25 lbs.
ASTM D4533
Apparent Opening Size Permeability
AOS < 0.297 mm, or > #50 US Standard Sieve
ASTM D4751
> #50 US Standard Sieve 0.4 cm/sec for Soil Types 1,2 0.004 cm/sec for Soil Types >2
ASTM D4491
2. Examples of filter fabrics meeting this specification include: Mirafi 140 NSL.
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10.0 OVERVIEW The chapter presents site modifications and stabilization measures used to control surface water and shallow perched groundwater and stabilize the site to protect the integrity and performance of OWTS components in certain situations. This chapter is organized in the following sections:
Section 10.1: Curtain Drains
Section 10.2: Stormwater Diversion Structures and Erosion Control Measures
10.1 CURTAIN DRAINS A.
BACKGROUND
In areas where rainfall readily percolates through very permeable surface soils and perches along the contact with the less permeable substrata a curtain drain may be required. Dispersal trenches can act as a collection area for this transient subsurface water flow, and in the worst case may be flooded during heavy rain events or throughout the rainy season. This reduces the dispersal capacity during the wet season; and it can also contribute to a long-term decline in the dispersal system effectiveness and potential surface failures. One of the most effective drainage measures is a “curtain drain” (also called “subdrain” or “french drain”), which consists of a gravelfilled trench installed uphill of a drainfield system, designed to intercept shallow perched groundwater flow and divert it away from or around the dispersal field. The installation of curtain drains may be considered for new system installations as well as to rehabilitate a failing system affected by high groundwater. B.
SITING CRITERIA AND INVESTIGATION REQUIREMENTS 1. Ground Slope. Curtain drains are only to be used on sites with a slope of greater than five (5) percent. The use of curtain drains to de-water a flat site will not be allowed. 2. Setbacks. Curtain drains may be positioned upslope or to the side of a dispersal field to intercept and drain subsurface water away from dispersal trenches in accordance with the horizontal setback requirements in Chapter 4. Curtain drains are not to be used as underdrains located downslope from the dispersal field in an attempt to lower the groundwater table.
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3. Site Investigation and Engineering Plan. a. Prior to approval of a curtain drain, a site investigation shall be conducted and an engineering plan for the installation shall be developed by a Qualified Professional. b. The engineering plan for the curtain drain shall include drawings, supporting data and calculations, as applicable, and a plan for groundwater monitoring, as applicable. c. The site investigation shall be conducted to: i. prepare a suitable map of the site, including slope contours, drainage and other pertinent site features; ii. document soil, geologic and groundwater conditions on the site; iii. assess the subsurface conditions to determine the feasibility and means of controlling groundwater levels with a curtain drain including whether or not the groundwater of concern is a perched condition above a clearly definable restrictive/impermeable soil layer; iv. determine the appropriate depth and location for the proposed curtain drain and outlet point, based on soil, groundwater, and other site conditions. 4. Approval Process. The process for approval of the curtain drain will depend on the site conditions and the supporting information supplied with the engineering plan, as follows: a. No Field Demonstration Required. For cases where the site investigation shows the groundwater condition to be mitigated is perched water above a clearly definable restrictive/impermeable layer (e.g., stiff, plastic, clayey subsoil), the curtain drain plan may be approved without the need for field demonstration of its effectiveness. b. Pilot Demonstration Required. For cases where the site investigation shows the groundwater condition to be mitigated is most probably perched water but there is some level of uncertainty about the extent or degree of impermeability of the identified restrictive layer, then the Department may require a pilot test of a portion of the proposed curtain drain prior to approval. The pilot test, conducted by the applicant, would involve the installation of a section of curtain in accordance with the proposed design, along with installation of monitoring wells in appropriate locations (upslope and downslope of the drain) Revised Draft 6-28-16 127
as needed to provide evidence of the effectiveness in lowering the water table during the wet season. The Qualified Professional is responsible for presenting the details of the pilot demonstration, overseeing the installation, monitoring the performance, and reporting the results to the Department. c. Full-scale Demonstration Required. For cases where the site investigation shows limited or questionable evidence that the groundwater condition to be mitigated is perched water above a defined restrictive/impermeable layer, then the Department may require a full-scale installation and monitoring of the proposed curtain drain prior to approval. The full-scale test, conducted by the applicant, would involve the installation of the entire curtain in accordance with the proposed design, along with installation of monitoring wells in appropriate locations (upslope and downslope of the drain) as needed to provide evidence of the effectiveness in lowering the water table during an entire wet weather season. The Qualified Professional is responsible for presenting the details of the monitoring plan, overseeing the installation, monitoring the performance, and reporting the results to the Department. C.
DESIGN AND CONSTRUCTION REQUIREMENTS
A curtain drain shall consist of a gravel-filled trench constructed as shown in Figure 10-1 and designed in accordance with the following specifications: 1. Trench Width: Twelve (12) inches minimum. 2. Trench Depth: Shall extend to a depth of at least six (6) inches into the underlying impermeable layer. 3. Filter/Backfill Material: Filter material shall be clean, durable 3/4 to 1½-inch drain rock, extending from trench bottom to within six (6) to twelve (12) inches of grade; backfill to grade with native soil. Caltrans Class 2 permeable filter material may substituted for drain rock. 4. Filter Fabric: A geotextile “filter fabric” envelope shall surround the drain rock. The Department may waive the requirements of a filter fabric where Caltrans Class 2 permeable filter material is used. 5. Perforated Collection Pipe: Collection pipe shall consist of four (4) inch diameter perforated drain pipe, oriented with holes down and installed on top of the drain rock, approximately two (2) to four (4) inches above trench bottom. 6. Outlet Pipe: The outlet pipe shall consist of minimum four (4) inch diameter solid (non- perforated) drain pipe.
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7. Cleanouts. Cleanouts shall be provided to grade: (a) at the upslope end of the drain; (b) at bends of forty-five (45) degrees or greater; and (c) at least every four hundred (400) feet along the length of the drain. 8. Slope: The trench and pipe shall be sloped for gravity flow at a minimum one (1) percent gradient throughout the trench and extending to the outlet point. The curtain drain must drain by gravity only. 9. Outlet. The outlet must be on the property being developed, and located so the flow does not adversely affect the drainage or any existing or proposed OWTS on the subject parcel or neighboring parcels. The downslope outlet shall be protected against blockage or damage through the use of screening, rock cover, junction box or other suitable means. 10. Erosion Control. Provide erosion protection at drain outlet point.
A.
____ 1. Any concentrated flow of surface water drainage that may affect the OWTS treatment or dispersal field shall be intercepted and diverted from the OWTS. 2. For new OWTS site drainage for the site development shall be planned and dispersed in a way that does not adversely affect the OWTS and is in accordance with setback requirements in table 4-10. 3. Where surface water diversion measures are proposed as part of the OWTS design it must be designed by a Qualified Professional and incorporated into the drainage and grading plan The design must, at minimum, meet the following: a. Be properly sized for the expected flow, including supporting run off and hydraulic calculations; b. Provide appropriate outlet protection; c. Located so the flow does not adversely affect the drainage or any existing or proposed OWTS on the subject parcel or neighboring parcels; and d. Meet setback requirement in table 10-4. The plan must meet all other requirements, including local ordinances, and be approved by the local building authority. Revised Draft 6-28-16 129
B.
EROSION CONRTROL MEASURES 1. The site must be protected against erosion during construction and stabilized at the conclusion of work. 2. Design of the OWTS must consider erosion control measures. Erosion control measures must be implemented and shown on the plans in the following OWTS: a. Any OWTS that includes above ground dispersal systems ( e.g. at grades or mound systems) or with cover fill; or b. Any OWTS on slopes greater than 20%; or c. Large flow OWTS; or d. OWTS located in environmentally sensitive areas, as determined during planning or building review. 3. The plan must meet all other requirements, including local ordinances, and be approved by the local building authority, as applicable.
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11.0 OVERVIEW The chapter presents the requirements for Department inspections of OWTS installation, modifications, and abandonment and final approval requirements. This chapter is organized in the following sections:
Section 11.1: Installation and Abandonment Inspection Requirements
Section 11.2: Issuance of Final Installation Approval
11.1 SYSTEM INSTALLATION & ABANDONMENT INSPECTION REQUIREMENTS A.
GENERAL PERFORMANCE CRITERIA 1. To ensure installation of a safe, effective OWTS and conformance with the standards in this Manual, inspections of the OWTS are required. The OWTS must be ready for the type of inspection requested. 2. If extra inspections are needed, an additional inspection fee will be charged. 3. No portion of the OWTS shall be covered without prior inspection and approval by the Department, unless specific written authorization has been provided. 4. Written notice must be given to the Department and an inspection requested least forty-eight (48) hours prior to beginning construction of a OWTS, and at least fortyeight (48) hours advance notice prior to reaching required construction inspections points (see below). 5. Notification and the request must include Applicant’s name, Assessor’s parcel number, street address, and Permit number. Failure to provide sufficient notice may result in delay of construction or duplication of work.
B.
REQUIRED CONSTRUCTION INSPECTIONS 1. The inspection steps required for the installation of an OWTS will vary with the type and complexity of the OWTS installed. 2. The Department may combine one or more required inspections into a single field visit if possible. 3. The following inspections are required to be performed by the OWTS Designer. The Department may be at each inspection, or may respond to an inspection request that Revised Draft 6-28-16 131
the Designer may proceed with the inspection and notify the Department of the results. The inspection cannot occur until the Department has confirmed that it will attending or that it may proceed. The Department may require specific documentation, such as photos be provide by the Designer if the Department allows an independent inspection. The minimum required inspection are: a. Preconstruction Meeting. Unless waived, at the preconstruction meeting the Contractor shall have the ground marked with the layout of the OWTS, including but not limited to tanks, dispersal fields, pipes and transport line. If not already existing, include the footprints of all proposed buildings, pools, or other structures which could affect the OWTS and Replacement Area. Minimum horizontal setbacks must be confirmed during the preconstruction meeting. b. Open13 Trench Inspection. Open trench inspection shall confirm all the following are completed: i. All excavations necessary for the OWTS at designed depth, width, and length. ii. All smeared or compacted surfaces shall be corrected. iii. Bottom of the trenches are level. c. Rock and Pipe Inspection. The connection of the Septic Tank, all distribution piping and the quality of the rock will be inspected. i. For Advanced OWTS, this inspection will also include inspection of the dosing tank, pump and filter assembly, and hydraulic squirt test for Pressure Distribution System by the OWTS Designer. d. Final Inspection. At the time of final inspection by the Department, all the following shall be completed: i. The trenches filled with rock to the specified level with the filter material in place or the gravel-less chambers installed. ii. Approved Distribution Boxes, with covers, installed level on undisturbed Soil and at the proper elevation. iii. Approved tank risers and inspection ports.
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iv. All pipe, other than in trenches, must be installed on grade (1/8 in./ft. minimum) and grouted to Septic Tank or Distribution Boxes. v. All pipe in trenches installed level (maximum drop of three (3) inches in one-hundred (100) feet) in the full length of trenches with ends capped. Sealing around pipe is also to be completed at the Distribution Boxes. vi. The Septic Tank set level in place on undisturbed soil. vii. All trenches must be uncovered to the filter material and visible for inspection and pipes ends exposed. e. Tank Water Tightness Tests. Tanks or other primary components may be required to be filled with water to the flow line prior to requesting inspection. All seams or joints shall be left exposed (except the bottom) and the tank shall remain watertight. f.
Flow Test. A flow test may be required to be performed through the OWTS to the point of Effluent disposal. All lines and components shall be watertight and distribution shall be according to the approved OWTS Design.
g. Other Inspections. Other inspections may be required as a Permit condition by the Department depending upon the type of OWTS proposed. Ownerinstalled OWTSs may require additional inspections to verify workmanship during the construction. The costs of additional inspections and related services beyond services normally covered by the Permit fee may be charged to the Applicant. h. Backfill. OWTS must be backfilled within ten (10) days of written approval for backfill from the Department and Qualified Professional (if required), or as specified by the approved OWTS Design. C.
OWTS MODIFICATIONS
Any changes during installation from the plans approved by the Department requires review and approval by the Department.
11.2 FINAL SYSTEM INSTALLATION APPROVAL 1. General. Final Approval is a letter issued by the Department that indicates the OWTS was installed in compliance with this Manual and relevant County Codes, and all Installation Permit conditions of approval have been fulfilled, including issuance of any required Operating Permit. Prior to the issuance of the Final Approval the following must occur: Revised Draft 6-28-16 133
a. The OWTS has received final installation approval by the Department. b. The Designer and the Installer shall submit written certification that the OWTS has been installed in accordance with the approved OWTS Design and Permit conditions. c. For Advanced OWTSs, verification of the contracted services of a Service Provider. d. The Designer shall provide the Owner with an operations and maintenance manual that outlines the operation of the OWTS, including the Owner’s responsibilities for maintaining the OWTS. A copy of the maintenance manual shall be provided to the Department for archiving. 2. Requirements of submitting As-Built Drawings. If changes have been made to the approved OWTS design, at completion of construction and prior to receiving acceptance Final Approval by the Department, the Contractor and/or Qualified Professional shall provide to the Department and OWTS Owner, a set of “As- Built” drawings of the completed OWTS installation.
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12.0 OVERVIEW The chapter presents an overview of the Operations, Maintenance & Monitoring Program (OM&M) and OWTS performance and monitoring requirements for Standard and Advanced OWTSs. This chapter is organized in the following sections:
Section 12.1: Applicability and Administration
Section 12.2: General System Performance Requirements
Section 12.3: Operating Permit Requirements
Section 12.4: Corrective Action
12.1 APPLICABILITY AND ADMINISTRATION A.
APPLICABILITY 1. The14 Operating, Monitoring, and Maintenance (OM&M) requirements are mandatory for all OWTS required by the Ordinance to have an Operating Permit. 2. Owners of Standard OWTSs, which are exempt under the Ordinance, are encouraged to voluntarily opt into the OM&M program. 3. Prior to issuance of a Final Approval the property Owner shall obtain an Operating Permit from the Department. a. The Operating Permit shall be renewed annually and any required fees shall be paid. The Owner of the property shall keep the Operating Permit valid for the life of the OWTS. b. The Department may suspend or revoke an Operating Permit for failure to comply with any operational, monitoring, or maintenance requirements. Upon revocation or suspension of an Operating Permit further operation of the OWTS shall cease until the suspension is lifted or a new permit is issued.
B.
ADMINISTRATION 1. The OM & M program will be administered county-wide by the Department.
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2. Any required OM&M inspections will be performed by or under the supervision of an approved Service Provider.
12.2 GENERAL SYSTEM PERFORMANCE REQUIREMENTS A.
ALL OWTS 1. All OWTS shall be operated in compliance with applicable performance requirements particular to the type of OWTS, the facility served, and the site conditions. 2. All OWTS shall function in such a manner as to: a. Be sanitary and not create a health hazard or nuisance; b. Prevent backup or release of wastewater or wastewater effluent into the structure(s) being served by the onsite wastewater system; and c. Not discharge wastewater or wastewater effluent onto the ground surface or into surface water, or in such a manner that groundwater may be adversely impacted. 3. All OWTS and the individual components shall meet the performance requirements for the specific site conditions and application for which they are approved.
B.
STANDARD OWTS 1. All components of the OWTS shall be functional and in proper working order. 2. All septic tanks shall be: a. structurally sound; b. watertight; c. provide clarified effluent; d. have adequate space available for sludge and scum storage; e. operate in such a manner as to not create odors or vector attraction; f.
be properly vented; and
g. have a functional baffle(s).
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3. Dispersal systems shall: a. have adequate dispersal capacity for the structures and/or uses served; b. not result in seepage or saturated soil conditions within 12 inches of ground surface in or adjacent to the dispersal field; c. be free from soil erosion or instability; and d. not have effluent continuously pond at a level above the invert (bottom) of the perforated distribution pipe in the dispersal trench or serial distribution overflow line, as applicable. C.
ADVANCED DISPERSAL SYSTEMS
In addition to the requirements in A and B above, Advanced dispersal systems shall also comply with the following. 1. Pressure Distribution Systems. a. Pump tanks, risers and lids shall be structurally sound, watertight and store wastewater effluent in such a manner as to not create odors or vector attraction. b. Pumps, floats, alarms and associated controls shall be in good condition and operate in accordance with design specifications. c. Dispersal field and components shall: i. be operable and in good condition; ii. maintain uniform distribution of effluent throughout the dispersal field; iii. not result in continuously ponded effluent in the dispersal trench (or bed) to a level above the invert (bottom) of the distribution pipe; and iv. in the case of pressure-dosed sand trenches, not result in continuously ponded effluent above the sand interface. 2. Mound, At-Grade and Raised Sand Bed Systems. Mound, at-grade and raised sand bed systems shall: a. not result in seepage or saturated soil conditions within twelve (12) inches of ground surface anywhere along the perimeter toe or edge of the system; Revised Draft 6-28-16 137
b. be free from erosion, slumping or damage to the soil cover; c. not result in continuously ponded effluent within the gravel distribution bed or in the sand fill (for mounds and raised sand bed systems); and d. conform to applicable requirements for pressure distribution in C.1 above. 3. Subsurface Drip Dispersal Systems. Subsurface drip dispersal systems and components shall: a. not result in seepage or saturated soil conditions above the depth of the dripline within or anywhere along the perimeter of the dripfield; b. be free from erosion, slumping or other soil disturbance that threatens to expose or cause damage to drip dispersal tubing or appurtenances; c. conform to applicable requirements for pressure distribution in C.1 above; and d. be operated and maintained in accordance with manufacturer recommendations.
12.3 OPERATING PERMIT REQUIREMENTS A.
GENERAL REQUIREMENTS 1. All OWTS requiring an Operating Permit must submit an application and fees to the Department after the OWTS design has been approved by the Department. 2. All OWTS issued an Operating Permit shall be operated, maintained, and monitored pursuant to the requirements of the standards found in the Ordinance and Manual and the issued Operating Permit. 3. A monitoring program is required and will be included as a condition of the Operating Permit. The monitoring program may be amended at the time of a permit renewal. 4. The permit holder is responsible for contracting with a qualified Service Provider for monitoring to ensure that the OWTS is functioning satisfactorily to protect water quality and public health and safety. 5. Maintenance and performance monitoring shall be performed by , an approved Service Provider at a frequency of once per year or more often as required by the Operating Permit. Revised Draft 6-28-16 138
6. Operating Permits shall be renewed annually, or as otherwise required in the Operating Permit with payment of a renewal fee. 7. The property owner shall notify the Department, in writing, of any change in property ownership within 10 days of the change with the name and contact information for the owner. a. The Department will issue an updated Operating Permit to the new property owner. b. The new owner must complete an application and submit it to the Department for Operating Permit renewal on or before the permit renewal date. c. The Department strongly encourages the new property owner submit an application as soon as possible and not wait until the renewal date, in order for the Department to have all the information required in the application. 8. Inspection frequency shall be performed as outlined in Table 12-1. B.
MONITORING ELEMENTS 1. The monitoring requirements will vary depending on the specific OWTS, however, typically including the following: a. Recording of wastewater flow based on water meter readings, pump event counter, elapsed time meter, in-line flow meter, or other approved methods; b. Measurement and recording of water levels in inspection/monitoring wells in the dispersal field; c. Inspection and observation of pump operation and other mechanical equipment; d. Water quality of selected water samples taken from points in the treatment process, from groundwater monitoring wells, or from surface streams or drainages; typical water quality parameters include total and fecal coliform, nitrate, BOD, and suspended solids; e. General review and inspection of treatment and dispersal area for evidence of seepage, effluent surfacing, erosion or other indicators of system malfunction; and f.
Other monitoring as recommended by the OWTS designer or equipment manufacturer. Revised Draft 6-28-16 139
C.
MINIMUM INSPECTION AND MONITORING REQUIREMENTS
OWTS components shall be inspected and monitored in accordance with the criteria below and listed in Table 12-2 and Table 12-3. 1. Septic Tank a. Inspection frequency should be once every three (3) to seven (7) years. b. Scum and sludge measurements (pumped as needed). c. Integrity of tank, including observation for: cracks or indications of structural deterioration; condition of inlet and outlet tees; condition of lids and risers; indication of leaks in risers or other water intrusion. d. Presence and condition of Effluent filter. 2. Pump and Dosing Chamber a. Scum and sludge measurements, pumping as needed b. Integrity of tank, including observation for: cracks or indications of structural deterioration; condition of inlet and outlet T’s; condition of lids and risers; indication of leaks in risers or other indications of water intrusion c. Condition of and correct operation of all floats d. Orderly wrap of float cords e. Condition of pump intake screen f.
Verification of pump cycle
g. Siphon sitter functioning, if applicable 3. Control Panel a. Timer and digital counter readings recorded by the Service Provider during the inspection. For control panels that record pump activity electronically, manual recordings are not necessary. b. Pump cycle counter operation verified by the Service Provider in the field by manual operation of the pump. For control panels that record pump activity electronically, counter operation can be verified remotely. c. Audible and visual alarms functioning Revised Draft 6-28-16 140
d. Run time appropriate, if demand dose e. Electrical box free from moisture and secure connections 4. Supplemental Treatment Systems a. Supplemental treatment systems shall comply with the additional performance requirements listed below and shall be monitored at a minimum annually for performance in the following manner. b. Monitoring requirements will be contained in each Operating Permitting. The following guidelines will generally be followed: i. For individual residential OWTS, semiannual sampling and analysis for BOD, and TSS of wastewater Effluent for the first two years of operation. Thereafter sampling frequency may be reduced or eliminated based on satisfactory OWTS performance and reporting. The sampling is recognized to be a spot check of OWTS operation and not to be interpreted for purposes of compliance of 30 day average performance standards. ii. For nonresidential small (less than 1500 gallons per day) OWTS, semiannual sampling and analysis for BOD, and TSS of wastewater Effluent for the first two years of operation. Thereafter sampling frequency may be reduced to annual based on satisfactory OWTS performance and reporting. The sampling is recognized to be a spot check of OWTS operation and not to be interpreted for purposes of compliance of 30 day average performance standards. iii. For high strength and large OWTS, sampling parameters will include at least sampling and analysis for BOD, and TSS of wastewater Effluent and may also include nitrogen, FOG and other constituents as applicable. Sampling frequency may be increased and will be dependent on the size, location and features of the OWTS. Sampling may include both spot check analysis as well as those used for compliance with performance standards. iv. For OWTS within the setbacks for a public water supply intake or well, wastewater treated by Disinfection Units testing for total fecal coliform. 1. When compliance monitoring results exceed performance limits for b3 and b4 above, the following will typically be required. Revised Draft 6-28-16 141
2. Repeat sampling and analysis until compliance is demonstrated. 3. If needed, adjustments to the OWTS operations to bring wastewater quality into conformance with performance limits. 5. Effluent Quality. Effluent15 produced by OWTS requiring supplemental treatment systems shall comply with the following maximum constituent limitations: Where Supplemen tal Treatment
Constituent
Biochemical Oxygen Demand (BOD), mg/L
30
Total Suspended Solids (TSS), mg/L
30
Fecal Coliform, MPN/100 ml
w her e Pathogen Removal Required 30 30 200
6. Proprietary Treatment Units. Proprietary treatment units shall comply with the following: a. the unit and its components shall be structurally sound, free from defects, be watertight, and not create odor or vector attraction nuisance. b. The unit shall be operated in accordance with the approved manufacturer and certification/listing organization standards. 7. Sand Filters. Sand filters shall: a. be operated to maintain uniform effluent distribution throughout the sand filter bed; b. not result in continuously ponded effluent on the distribution bed infiltrative surface; c. be operated and maintained to prevent channeling of flow, erosion of the sand media or other conditions that allow short-circuiting of effluent through the OWTS;
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d. not result in leakage of effluent through the sand filter liner or supporting structure; and e. conform to applicable requirements for pressure distribution. 8. Gravity Drainfield (Standard or Gravelless) a. Depth of Effluent ponding within trench. b. Indication of Effluent breakout or discharge to surface of the ground. c. Upkeep and accessibility of observation port and inspection ports. d. Area verified as free from road, structures, vehicular traffic, surface water drainage with downspouts and landscape drainage properly diverted. e. Results of hydraulic loading test, if test is needed. 9. Pressure Distribution Systems. a. Pump tanks, risers and lids shall be structurally sound, watertight and store wastewater effluent in such a manner as to not create odors or vector attraction. b. Pumps, floats, alarms and associated controls shall be in good condition and operate in accordance with design specifications. c. Dispersal field and components shall: i. be operable and in good condition; ii. maintain uniform distribution of effluent throughout the dispersal field; iii. not result in continuously ponded effluent in the dispersal trench (or bed) to a level above the invert (bottom) of the distribution pipe; and iv. in the case of pressure-dosed sand trenches, not result in continuously ponded effluent above the sand interface. D.
INSPECTION FREQUENCY AND MAINTENANCE CHECKS 1. Inspection Frequency: OWTS requiring an Operating Permit, shall meet the inspection frequencies and maintenance checks as specified in Table 12- 1, or as otherwise required by the Operating Permit. Revised Draft 6-28-16 143
2. Nothing contained in this provision shall prevent the Department from requiring more frequent inspections and maintenance checks as deemed necessary to ensure proper OWTS performance. 3. Complexity and frequency of inspection will be related to the complexity and maintenance requirements of the OWTS components, recommendations of the manufacturer and industry standards. E.
REPORTING REQUIREMENTS
For OWTSs with Operating Permits, the property Owner must submit an annual report prepared by the Service Provider to the Department, or as otherwise required by the Operating Permit. Reports will typically include the following: 1. Actual wastewater flows for Operating Permit period, or estimated based on water usage. Inspection findings of the OWTS components as listed in table 12-2 and submitted on Form 12116, or similar documentation.
12.5 CORRECTIVE ACTION 1. Corrective Action for non-compliance with OWTS maintenance may result in administrative fines and penalties. 2. The Department may take any or all of the following Corrective Actions for noncompliant OWTS: a. Notification of non-compliance to the OWTS Owner, Qualified Professional, and Service Provider. b. Notice and request to participate in an informal meeting with the Department to review the lack of compliance and corrective actions. c. Additional testing, inspections, or other monitoring until the OWTS is compliant, . d. Restricted or prohibition of the use of the OWTS. A.
GROUNDWATER QUALITY MONITORING
Installation of groundwater monitoring wells to assess the current groundwater nitrate conditions beneath the site and/or monitor nutrient loading from the OWTS may be required as part of the OWTS design and installation approval. Applications for permits for monitoring wells must be
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submitted for approval to the applicable well permitting agency (Zone 7 Water Agency, Alameda County Water District, or Alameda County Public Works). Monitoring wells are required to be installed on High Strength and High Flow OWTS for the purpose of monitoring the groundwater quality in the vicinity of the OWTS. 1. For High Strength and High Flow OWTS, at least one monitoring well shall be constructed to a depth that will allow verification that the OWTS is functioning properly and not contaminating groundwater. 2. Monitoring wells shall extend to one foot below the anticipated lowest seasonal groundwater level. 3. Monitoring wells must meet applicable standards for monitoring wells and be constructed under permit from the Administrative Authority for Well Permits. 4. Monitoring wells must be sampled for nitrates at least annually or as frequently as determined by the Department. Sampling may be required for other contaminants at the discretion of the Department. 5. A OWTS is considered to be failing or having an adverse effect on groundwater quality when monitoring well nitrate levels are above 10 mg/l of nitrate as nitrogen.
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13.0 COMPLAINTS & INVESTIGATIONS The chapter will present criteria for existing OWTS performance evaluation, repair and replacement. The criteria in this chapter will be developed after conducting workshops with stakeholders.
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14.0 COMPLAINTS & INVESTIGATIONS A.
INVESTIGATIONS
Upon receipt of a complaint, the Department will conduct a complaint investigation. If the Department determines that public health and/or the environment may be at risk, or that a system has been installed or repaired illegally, the property Owner shall be responsible for all costs associated with the complaint. 1. Right to Investigate: No person(s) shall obstruct, impede or interfere with the investigation performed by the Department in the performance of code enforcement and nuisance abatement duties. 2. Collection of Evidence: The Department may take photographs and videos during the investigation as evidence of conditions found on the site. B.
ILLEGAL SYSTEM INSTALLATION OR REPAIR WORK
If the Department determines that an OWTS has been illegally installed or work is being conducted without necessary permits, or outside of issued permit conditions, the Department may issue a “Stop Work Order”. Once the order is issued, no further work shall be conducted until the Stop Work Order is released by the Department. If a licensed Contractor is found performing work without necessary Permits, they may be reported to the State Contractors License Board. Any Person conducting work without necessary Permits s in violation of the Alameda County Ordinance and, in addition to any other fine an penalty that may be imposed, subject to a fine of double the Permit fee. The fine is separate from required fees for Permits and services to bring the OWTS or condition into compliance.
14.1 FAILED SYSTEMS & ABATEMENT A. A property Owner must immediately abate conditions that pose a threat to human health and/or the environment, including conditions created due to a failing OWTS on all properties that have been impacted by surfacing Effluent. At a minimum the Owner must hire a Qualified Professional to assist to immediately implement the following interim abatement measures: 1. Stop all wastewater flows to the OWTS until a permanent solution has been permitted and installed or an interim solution has been implemented. Interim solutions may include but are not limited to hiring a Qualified Professional to install plugs in the outlet of the existing septic tank if it is watertight or install a holding tank and pump the tank at appropriate intervals to dispose of wastewater coming from site structures. 2. Collect surfacing or ponding wastewater with a Vactor Truck. Revised Draft 6-28-16 147
3. Contain surfacing wastewater as close as practical to the failed OWTS through the use of berms or other measures. 4. Isolate storm drain collection systems if wastewater has the potential to enter inlets. 5. Conduct general cleanup measures including removing all impacted debris. 6. Prevent public contact with wastewater by covering impacted areas with clean soil and/or installing fencing or hazard tape and warning signs around the impacted area. 7. Wash down impacted impervious surfaces and collect and dispose of wash water in a sanitary sewer. 8. Notify adjacent property owners that have the potential to be directly affected by the failed system and or cleanup activities. B.
Depending on the extent of the failing or failed OWTS impacts, the Owner may be required to implement additional measures including but not limited to: 1. Investigation and/or monitoring the source and or movement of wastewater. 2. Collection of water well, surface water, and/or soil samples for analysis of fecal indicator bacteria to determine the extent of the release and threat to public health and the environment. 3. Identification of appropriate cleanup action. Depending on the extent of impact of the wastewater release to the environment, oversight by other regulatory agencies may be required including but not limited to the Regional Water Board, State Water Board, California Department of Fish and Wildlife, or the U.S. Army Corp of Engineers. 4. Implementation of additional soil cleanup measures including but not limited to covering the impacted area with clean soil, excavation, aeration, or disinfection of the impacted soil.
ENFORCMENT A.
NOTICE OF VIOLATION
A Notice of Violation or citation may be issued to the property Owner, and any or all Persons (such as the Contractor or Occupant) that contribute to a violation of this Manual or the Ordinance. The Notice of Violation shall indicate the specific violation and corrective action to be taken.
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B.
FALSIFICATION
If false information is provided for the Site Evaluation, Permit Application or in any supporting documentation, including information about OWTS performance, in addition to any other remedies, the Permit(s) may be immediately suspended or revoked. C.
CONDEMNATION
A building, structure or facility that is causing, or failing that is likely to result in, the accumulation or disposal of wastewater in a manner that is be detrimental to the public health, safety, and welfare may be condemned. Vehicle illegally discharging wastewater may be impounded by authorities. D.
FINES AND PENALTIES
Any Person violating any provisions of the Ordinance and Manual is subject to fines or penalties.
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DEFINITIONS Definitions are provided for terms used in this Manual. Abandoned System: An OWTS that will no longer be used to receive Effluent because the Dwelling has been connected to an approved sewer system or the Department has issued a notice or order to destroy the OWTS under Permit. Abandoned Well: A well whose original purpose and use has been permanently discontinued or which is in such a state of disrepair that it cannot be used for its original purpose. If an Abandoned Well has been properly destroyed so that it will not produce water nor act as a conduit for the movement of water, it will not be subject to well setback requirements. Advanced System or Advanced OWTS: A type of Wastewater disposal or System component(s) that utilizes either a method of Wastewater Treatment other than a standard Septic Tank and/or a method of Wastewater dispersal other than a standard Dispersal Field. Applicant: A property Owner or the property Owner’s Authorized Representative. Artificial Drain: Any Artificial Drainage feature or structure that intercepts and concentrates Groundwater or surface water. For example: driveways, roads, road ditches, agricultural drain tile, Cut banks, and Curtain Drains. As-Built Drawing: A scaled drawing of features on the lot where the OWTS is installed; identifying the location of the installed OWTS and components in relation to structures on the property. The As-Built Drawing is completed after the OWTS is installed or repaired. Authorized Representative: Person or Persons authorized by the property Owner to act on the property Owner’s behalf on matters pertaining to application for Permits and services, or holder of an easement sufficient to authorize the work on the land on which the OWTS is to be installed, in order to represent the Owner’s or easement holder’s interests. Bedrock: Unweathered solid rock that is impermeable or has less than 15% porosity. If present, fractures are tight, dry, and cemented. Beneficial use: Those qualities of waters of the state that may be protected against quality degradation that include, but are not necessarily limited to, domestic, municipal, agricultural and industrial supply; power generation, recreation; esthetic enjoyment; navigation; and preservation and enhancement of fish, wildlife and other aquatic resources or preserves. Biological Oxygen Demand (BOD): The amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. Blackwater: See Wastewater Revised Draft 6-28-16 150
Building Permit: An official document or certificate issued by the authority having jurisdiction which authorizes performance of a specified activity. Building Division: A local building agency of a city or county which has the jurisdiction to issue Building Permit to construct, alter, Repair or destroy structure. Building Sewer: The part of the OWTS or drainage piping which conveys sewage from a building to the Septic Tank or public sewer. Cesspool: An excavation in the ground receiving Wastewater, designed to retain the organic matter and solids, while allowing the liquids to seep into the Soil. Cesspools differ from Seepage Pits because a Cesspool does not have a Septic Tank. Chemical Toilet Facility: See Portable Toilet Clay: See Soil Texture Cleanout: A fitting inserted into a piping system, with a removable plug whereby access to the pipe is obtained for the purpose of cleaning or unstopping. Cluster System: An Onsite Wastewater Treatment System serving at least two (2) but not more than four (4) Dwellings or other buildings that are sources of Wastewater discharge on the same Lot and under the same ownership. Color: See Soil Color. Commercial Facility: Any structure or building, (excluding single-family residential units), or any portion thereof, intended for commercial or industrial use. Community System: A System that accepts Wastewater discharges from two or more Lots or a System shared by Dwellings under separate ownership whether or not they are on the same Lot. A Community System is not a Public Sewer System. Composting Toilet: A type of dry toilet that uses a predominantly aerobic processing system to treat human excreta, by composting or managed aerobic decomposition. Conditions Associated with Saturation: The following are Conditions Associated with saturation: a) Reddish brown or brown oxidized Soil Horizons with dull gray zones of redox depletions (chromas of 2 or less), and red or yellowish red zones of redox concentrations; or b) Reduced, or iron-depleted Horizons of gray, blue, or olive colors (chromas of 2 or less) with dull red, yellowish red, or brown zones of redox concentrations; or c) Organic Soils and dark-colored Soils very high in organic matter. 1 Consistence: See Soil Consistence. Revised Draft 6-28-16 151
Contamination: Impairment to the quality of the waters of the State from Wastewater to a degree which creates a hazard to public health through toxicity or through the spread of disease. Contamination shall include any equivalent effect resulting from the disposal of Wastewater, whether or not waters of the state are affected. Contractor: A Person who possesses an active license as a General Engineering Contractor (Class A), a General Building Contractor (Class B), a Sanitation System Contractor (Class C-42) or a Class C-36 Plumbing Contractor (Class C-36) license in accordance with the provisions of the California Business and Professions Code. Contractors shall be approved by the Department and shall possess knowledge, and skills of Systems siting, design using given design parameters, and installation. Cumulative Impacts: The persistent and/or increasing effect resulting from the density of System(s) discharges in relation to the assimilative capacity of the local environment. Examples include, but not limited to: a.
Nitrate, salt additions, or other indicator of human excreta to ground water or surface water; or
b.
Rise in Groundwater levels that interfere with the performance of the OWTS, causing drainage problems or results in other adverse hydrological or Soil conditions affecting public health, water quality or public safety; or
c.
Coliform Contamination from animal and human waste in surface water, Groundwater, and drinking water wells.
Cut or Embankment: Any altered area of land surface having distinctly greater Slope than the adjacent natural ground surface, over 24 inches in vertical height, and any part of which is lower in elevation than the ground surface at the nearest point of the OWTS. Cuts supported by retaining walls or similar structures shall be included in this definition as shall steep natural ground surfaces where a sharp break in the ground Slope is discernible. Curtain Drain: An Artificial Drain installed up Slope from a disposal field to intercept and divert ground water. Deep Trench System: A system with disposal trenches greater than thirty (36) inches deep. Department: See Department of Environmental Health. Design Daily Sewage Flow: The quantity of daily sewage flow assigned to a building or structure. It may be referred as Design Flow. Design Flow: See Design Daily Sewage Flow. Director of Environmental Health: The Director of the Alameda County Department of Environmental Health and his/her designated employee(s). Dispersal Field: The area occupied by the Dispersal System. It may also be referred to as leach field. Revised Draft 6-28-16 152
Dispersal System: A subsurface Wastewater distribution System and its components which conveys Wastewater from the Septic Tank, Pump Tank and or Supplemental Treatment Unit to the Soil for subsurface discharge and final Wastewater treatment. Dispersal Trench: A ditch or trench with vertical sides and substantially flat bottom designed to receive Wastewater Effluent. Distribution Box: A structure which receives Effluent and distributes it to the Dispersal Field.
Distribution Pipe or Lateral Pipe: A perforated pipe used in the dispersion of Effluent into disposal trenches. Distribution Unit: A Distribution Box, crossover unit, Dosing Tank, Diversion Valve or box, Header Pipe, Effluent lift pump or other means of transmitting Effluent from the Effluent Sewer to the Distribution Pipes. Diversion Valve: A device that receives Wastewater through one inlet and distribute it to two (2) or more outlets, only one of which is used at a given time. Department of Environmental Health: The Alameda County Department of Environmental Health, the Director of Environmental Health, and designated employees. Also called the Department in this Manual. Domestic Wastewater: Wastewater with a measured strength less than high-strength Wastewater and is the type of Wastewater normally discharged from, or similar to, that discharged from plumbing fixtures, appliances and other household devices including, but not limited to toilets, bathtubs, showers, laundry facilities, dishwashing facilities, and garbage disposals. Domestic Wastewater may include Wastewater from commercial buildings such as office buildings, retail stores, and some restaurants or from industrial facilities where the Domestic Wastewater is segregated from the Industrial Wastewater. Domestic Wastewater may include incidental RV Holding Tank dumping but does not include Wastewater consisting of a significant portion of RV Holding Tank Wastewater such as at RV dump stations. Domestic Wastewater does not include Wastewater from industrial processes. For numerical values see Chapter 4.4. Dosing Tank: A watertight receptacle constructed of approved materials designed to receive and store clarified Effluent and convey it to a secondary Treatment device or a Dispersal field under positive pressure. The Dosing Tank is equipped with a pump(s), Effluent screen, and level control and alarm floats. Drain Rock: Clean, sound gravel or crushed rock ranging in size from 3/4 to I 1/2inch diameter, with
