Appendix D
Technical Memorandum on Pump Station Condition Assessment
City of San Carlos Sewer Collection System Master Plan
Technical Memorandum San Carlos Sewer Collection System Master Plan Subject:
Sewer Pump Station Condition Assessment
Prepared for:
City of San Carlos
Prepared by:
Aaron Hope, P.E.
Reviewed by:
Tony Valdivia, P.E., Gisa Ju, P.E.
Date: Reference:
March 21, 2012 RMC Project No. 0464-001
This Technical Memorandum (TM) presents the observations and recommendations resulting from staff interviews and a visual inspection of the City of San Carlos’ wastewater pump stations. This work has been performed as part of the Condition Assessment and Rehabilitation/Replacement Program (Task 6) of the Sewer Collection System Master Plan project. This TM is organized as follows: 1. Introduction 2. Pump Station Reliability and Emergency Operations 3. Scope of Condition Assessment 4. Condition Assessment Findings 5. Useful Life and Summary of Recommendations
1 Introduction The City of San Carlos owns and operates a total of seven wastewater pump stations as a component of its wastewater collection system. Four of these pump stations are considered major facilities (they collect and pump sewage from a number of residential and/or commercial customers), two pump stations are minor (they serve only one customer), and one pump station is a wet-weather “booster” facility. The major pump stations are as follows: Upper Crestview Lower Crestview Tierra Linda Associated Pump Station (commonly referred to as “The Associate”) The two minor pump stations serve a single commercial user, the Kelly Moore manufacturing and commercial facility, on Old County Road near Commercial Street. Only one of these pump stations (referred to as the Kelly Moore I Pump Station) was visited as part of this project; the other minor station (Kelly Moore II) serves a single commercial bathroom and was not accessible at the time of the visit. The major and minor pump stations function to lift wastewater from low points in the collection system. Depending on the station, these flows are lifted to a higher elevation so that sewage can be conveyed via gravity or, as in the case of the Associated Pump Station, to the South Bayside System Authority (SBSA) San Carlos Pump Station.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
The wet weather pump station, called the “Industrial Booster Pump Station,” is located adjacent to the Pulgas Creek stormwater pump station on Industrial Road. The intended purpose of this pump station is to reduce the risk of sewer overflows during large rain events by lowering the hydraulic grade line in the sewers at the southern end of Industrial Road. A site visit to the four major pump stations, the wet-weather pump station, and the Kelly Moore I pump station was conducted by Aaron Hope and Tony Valdivia of RMC Water and Environment (RMC) on February 9, 2012. RMC staff were accompanied by Frank Amoroso, Public Works Supervisor for the City. The purpose of this site visit was to document existing conditions at each of the pump stations based upon visual inspection and interviews with the accompanying City staff. RMC also reviewed available pump station plans for comparison to field conditions.
2
Pump Station Reliability and Emergency Operations
Overall, the City does not experience any critical, ongoing issues with its pump stations, and pump station failure has not historically been a cause of sanitary sewer overflows. The City’s emergency response plan for pump station operation includes both internal City resources and a contract agreement with Rain4Rent to provide support in the event of a major issue. Typically, emergency planning scenarios include power failure (usually short term but not uncommon in this region) and sudden equipment failure. In the event of power failure, the City may mobilize a Cityowned “Vactor” vacuum truck to remove sewage from pump station wet wells. In addition, the City maintains a 4-inch trash pump, which can be used for bypassing a failed pump station. In the event that City resources are not available or are insufficient to handle a significant or prolonged emergency, the City can request emergency standby power and pumping equipment from Rain4Rent. Rain4Rent has specifications for each of the City’s pump stations and maintains up-to-date documentation so that it can deliver the correct equipment to the site. Rain4Rent staff is trained to install and operate equipment, as required. The City reports that this arrangement with Rain4Rent has worked well and that it will continue this arrangement in the future. Several other aspects of the City’s approach to pump station management help provide operational reliability:
There is redundancy in the alarm/controls systems. Each of the major pump stations has a highlevel float alarm in addition to ultrasonic level monitoring for SCADA. The City contracts with Peninsula Pump to exercise all of the pump station valves twice per year. Operators cannot clear critical alarms from SCADA central – crews must visit pumps and verify, in person, that the pump station is in working condition. All other types of alarms can be cleared from SCADA central. SCADA panels and control systems are new and identical at all pump stations; this consistency reduces system complexity and ultimately makes the pump stations easier to manage and maintain.
3 Scope of Condition Assessment Field inspection was limited to those conditions that could be directly observed from the ground surface, including a visual inspection and observation of noise, odor and vibration. The scope of this evaluation did not include in-depth structural, electrical, mechanical or civil evaluations, calculations or investigations. However, capacity analyses were conducted for two of the major pump stations (Tierra Linda and The Associate) and for the Industrial Booster station as part of the trunk system capacity evaluation conducted for the larger Master Plan effort.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
The sections below provide a general overview of the types of issues that have been identified at each station. Specific issues observed at each station, as well as recommended actions to correct observed deficiencies, are summarized in Section 4.
3.1
Pumping Equipment
With the exception of the Industrial Booster Pump Station, all of the City’s wastewater pump stations utilize submersible pumps in a concrete wet well. Submersible pumps (including close-coupled motors) are installed at the bottom of the wet wells, which vary in depth, while electrical equipment is housed in an enclosure adjacent to the wet well. When correctly designed and installed, submersible pumps often operate without significant issues, and this appears to be the case with all of the City’s pump stations. Where problems do occur, they are most often associated with noise and vibration during pump operation, pump “ragging,” capacity degradation due to pump wear, or inadequate pump access. The City has reported no such problems with their existing pumps, and none were observed during field visits. Noise Submersible pumps are rarely subject to noise complaints during normal operation because the motors are relatively small (all of the City’s wastewater pump motors are 10 Hp or less) and are often submerged and situated below grade. Abnormal noise or vibration is often a symptom of an operational problem that should be investigated further. Pump “Ragging” “Ragging” is a general term for pump clogging due to stringy or fibrous materials in the wastewater flow. Wastewater pump impellers are designed to accommodate solids in wastewater and pass these without issue. However, not all pumps are designed to combat ragging as effectively as do others. Ragging is typically a problem associated with larger stations, as smaller residential stations do not regularly encounter these types of materials. Pump impellers can sometimes be retrofit for improved ragging performance, but screening or grinding of influent flow may be required for ongoing problems. Persistent pump ragging may also be an indication of inadequate pumping energy at the eye of the impeller, which could suggest oversized pump or operation at too slow a speed. Pump Wear Over time, pump performance may diminish due to normal wear. Degradation in pump performance may be exacerbated if the wastewater contains unusually high levels of grit or solids, which will wear down the pump impeller and interior surfaces more quickly. As pump components wear, hydraulic efficiency will degrade, and the pump performance will drift away from its design performance curve. Eventually, pump performance may be inadequate to handle incoming flows, and pump inefficiencies will result in a higher pump operating cost. Pump wear can be assessed directly, through inspection, or indirectly, through monitoring and trending of pump performance (discharge flow and head). The most common solution for diminishing performance due to wear is replacement of the pump impeller, though electrical and other mechanical issues should be ruled out as the root cause, as well. Pump Access Submersible pumps are typically brought to the surface for maintenance and inspection. This is easiest for operators and also eliminates the need for confined space entry to the wet well. Guide rails and chains (usually stainless steel) are designed to raise the pumps through hatches as the top of the wet well. If these systems are designed and installed correctly, submersible pump access is rarely an issue. Issues do develop when larger pumps are retrofit into existing wet wells, and access can be compromised in these cases. At smaller stations (e.g., Kelly Moore I), the City has elected to forgo hatch access and instead utilizes manhole covers for access to these very small pumps.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
3.2
Discharge Piping
The term “discharge piping” is used to define piping between the pump discharge connection (in the wet well, in the case of a submersible pump station) and a point downstream of the discharge valves. Piping downstream of this point is considered to be the force main, and is beyond the scope of this assessment. Discharge piping is often ductile iron, but depending on age and pressure capacity may be cast iron, polyvinyl chloride (PVC), fiberglass or stainless steel. Ductile and cast iron are typically specified to be coated for external corrosion protection. All ferrous metal in the wet well, including pipe supports and bolts, is subject to corrosion over time, and new pump stations very often require high grade stainless steel for these accessories (galvanized steel may be acceptable in some circumstances). Surface corrosion does not always signal a significant problem so long as the pipe wall thickness is sufficient for the operating pressure, however the presence of pitting in the pipe wall or significant degradation of flange bolts may be a concern. This assessment did not investigate corrosion beyond a visual inspection.
3.3
Valves
In most cases, the City’s pump discharge valves are located in a valve vault adjacent to the wet well. Some stations have valves in the vertical discharge piping within the wet well, but this is less desirable due to access issues. Valves typically consist of an isolation valve and a check valve, one for each pump discharge. Exposed valves are ideal for access; however, the City has buried valves at The Associated Pump Station. Common issues with valves include valve freezing (the valve becomes stuck in one position), failure to seal (usually due to internal wear or obstructions), and leaks within the valve body (usually at the valve stem bushing). Regularly operating the valve (as the City does) can prevent freezing and maintain valve operation. Most valves can be “rebuilt” when required, as opposed to replacement, and valves can operate for decades if maintained regularly.
3.4
Electrical Equipment
Electrical equipment at the City’s submersible pump stations is housed within an electrical panel adjacent to the wet well. Thorough evaluation of the electrical gear is beyond the scope of this assessment, however the City may wish to investigate these items in the future. Electrical codes change over time, particularly with respect to operator safety, and it is common for older stations to not meet current codes for new construction. Only one of the City’s pump stations, Tierra Linda, has a standby diesel generator. The other stations have electrical connections for a portable generator. The City exercises the Tierra Linda generator monthly to confirm proper operation, which is the recommended practice for such equipment.
3.5
Controls and Communication
The City has standardized supervisory controls and data acquisition (SCADA) across all of its pump stations. Instrumentation required for operation of submersible pump stations is minimal, and the City utilizes ultrasonic level sensors with float backups for redundant monitoring and alarming of wet well levels. The City has the ability to monitor station and alarm status remotely, and has implemented a policy that requires operator visits to clear critical alarms such as pump failure. Radio communication is used to transmit control and status signals to and from the remote pump station sites, and City staff indicates that communication is reliable.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
3.6
Wet Well
All of the City’s submersible pump station wet wells are cylindrical concrete structures. Condition and operational issues at submersible wet wells vary depending on the design of the wet well and the characteristics of the incoming flow. Properly designed, many wet wells serving residential areas will operate with very minimal maintenance. Issues that may develop at submersible pump stations include buildup of grease, grit and sludge, odor, and corrosion of the wet well structure. Grease, Grit and Sludge Grease in a wet well may originate from either domestic or commercial sources. Generally, a pump station serving primarily residential areas will exhibit only minor grease build-up. Pump stations serving commercial land uses, and in particular restaurants or food processing facilities, may exhibit more significant grease build up, particularly if grease traps are not installed or maintained upstream of the collection system. Because grease is less dense than water, it tends to accumulate at the water surface and coat the walls and surfaces of a submersible pump station, making it difficult to remove using just the pumps. High pressure spraying or scraping is often required to remove grease, and enzyme-based solutions may be added upstream of the pump station to control significant grease issues. The City utilizes an enzyme-based system at its Tierra Linda Pump Station. Grit and sludge issues may occur in a submersible wet well if the design of the wet well does not allow for scouring velocities to develop during pump operation. Areas within the wet well where velocities are not sufficient to stir up accumulated solids are sometimes referred to as “dead zones,” and may require extra maintenance in order to maintain proper pump station operation. To combat this issue, wet wells are typically designed to slope toward the submersible pump intake, and existing wet wells may be retrofit in some cases to improve wet well hydraulics. Alternatively, submersible pump manufacturers may offer mechanical solutions to promote scouring of the wet well. Many Flygt pumps, for example, can be fitted with mixing valves (wet well space permitting) that automatically divert an initial amount of pump flow back into the wet well each time the pump actuates. Odor Odor issues typically develop as wastewater ages, but may be less of an issue in the absence of sensitive receptors like homes and public spaces. Typically, wastewater residence time in a small submersible pump station will not be sufficient to generate odors unless the station is relatively far downstream in the collection system (and further from the source of the oldest wastewater). Odor issues can be combated operationally by limiting residence time in a station wet well (adjusting level controls or changing pumping equipment), through chemical addition in the upstream system, or by scrubbing vented air. Most submersible stations have passive air venting through a small vent pipe, but some of the City’s older stations do not. Wet Well Corrosion Unlined concrete wet wells may be subject to degradation through reaction with hydrogen sulfide produced during anaerobic digestion of raw wastewater. Hydrogen sulfide is always present in wastewater facilities, but the amount that is present depends of the age and nature of the wastewater, wet well hydraulics and other site-specific considerations. Symptoms of minor, often not structurally significant, corrosion may include concrete discoloration and exposed aggregate. Advanced, structurally significant, symptoms include exposed or disintegrated rebar, and softening of concrete to significant depth. Testing and structural evaluation of existing concrete are beyond the scope of this assessment, but the City should continue to monitor for signs of corrosion at all unprotected concrete structures – RMC did observe signs of minor hydrogen sulfide corrosion at the City’s oldest stations, which also lack air venting. Protective coating above the low water level may be required in the future if signs of corrosion increase or structural inspection reveals a more serious issue.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
3.7
Site Access, Drainage and Security
Site access by maintenance vehicles appears to be adequate at all stations. Generally, station access and roadway turning radii should allow the largest anticipated maintenance vehicle to enter and exit the site without complex maneuvering and with minimal impacts to traffic of adjacent roadways. For small submersible stations, a standard flatbed truck with a small crane is often sufficient to pull the pumps from the wet well, and larger crane vehicles may not be required. Site drainage should generally convey runoff away from electrical and mechanical equipment and towards stormwater infrastructure (e.g. catch basin). Areas of the facility that may be subject to incidental wastewater spills during routine maintenance should generally be drained back to the wet well or to the sewer system. Basic site security is recommended to prevent unauthorized persons from accessing electrical or mechanical equipment or gaining access to dangerous areas like the wet wells. Not all of the City’s pump station facilities are fenced, but all electrical cabinets, hatches and covered protecting vital equipment should be locked at all times. The City reports no problems with vandalism at its pump station sites.
4 Condition Assessment Findings The condition assessment findings for each pump station are summarized in the sections that follow. Findings are based on visual inspections of these pump station facilities and interviews with City staff. In this section, the terms “Good”, “Fair”, and “Poor” are sometimes used to describe asset conditions. The table below describes the intended meaning of these terms:
Good Asset has had no operational problems, requires only typical preventive maintenance, and/or shows no signs of deterioration
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Fair Asset has had only minor problems, has had minor repairs in addition to typical preventive maintenance, and/or shows little sign of deterioration
Poor Asset has had major operational problems, has had major repairs or has been repaired several times, and/or shows visible signs of deterioration.
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
4.1
Lower Crestview Pump Station
The Lower Crestview Pump Station consists of a concrete wet well and valve box, as well as an above grade electrical/SCADA panel. Lower and Upper Crestview Pump Stations operate in conjunction with one another, with Lower Crestview pumping to Upper Crestview. The lower pump station will stop pumping if the upper pump station fails. Operators report that these pump stations cycle about every 40 minutes during normal, dry-weather conditions. Two pumps are installed in the wet well, and operators report that only one is required for wet weather operation. The table, below, summarizes general pump station information: Lower Crestview Pump Station Information City Designation Code
PS07
Year Constructed/Improved
10/1/1975
Last Serviced
3/31/2011
Pump Type
Submersible
Number of Pumps
2 (1 duty, 1 standby)
Pump Manufacturer &Model
Flygt 3126
Motor Horsepower
9.4 HP
Discharge Size
4-inch
Drive type
Constant Speed
Valve Location
Valve box
Overall, this pump station is in good condition, despite being one of the City’s oldest. More detail and specific observations are noted in the table that follows. The primary concern is corrosion of valves and enclosures, potentially due to site drainage conditions.
Lower Crestview Pump Station
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Lower Crestview Pump Station Condition Assessment
Aspect
Comments
Lower Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Electrical Enclosure
Overall, the electrical enclosure looks to be in fair condition. The bottom of the enclosure is at-grade.
Corrosion (rust) is evident at the bottom of the enclosure. This may be indicative of water entering the enclosure and/or poor site drainage conditions. There appears to be evidence of standing water around the site and at the bottom of the enclosure. Recommend evaluation of water-tight enclosure to determine if infiltration is occurring. If so, take measures to prevent water from entering the enclosure or replace the enclosure.. Evidence of corrosion and moisture intrusion in the electrical cabinet
Standby Power
Pump station has an electrical connection for a standby generator.
No immediate concerns; City’s contractor maintains compatible standby power generation equipment.
Portable emergency generator connection
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Lower Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Controls and Communication (SCADA) SCADA Panel/Screen Primary Level Instrumentation Secondary Level Control/Level Alarm Communications
Flow monitoring
Panel is new and in good condition Ultrasonic sensor High level float as a backup to SCADA Radio telemetry
Flow monitoring is not performed at this site.
No immediate concerns No immediate concerns No immediate concerns No immediate concerns; line of sight communication is reported to be acceptable for reliable communication. Flow monitoring can be useful in tracking impeller wear and troubleshooting other pump station issues. The City may wish to consider adding a flow meter (typically, electromagnetic-type) as part of future pump station upgrades.
The SCADA Panel/Screen
The controls and communication equipment is relatively new and includes battery backup
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Lower Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Wet Well Grease
This pump station experiences minor grease buildup
No immediate concerns; the residential service area does not contribute significant grease to the collection system. City staff report that minor grease build-up is easily combated with quarterly cleaning at this station.
Odor
No odor issues reported
No immediate concerns; the relatively short wastewater residence time in the wet well and upstream system result in no significant issues.
Structural Condition
Wet well is unlined concrete but appears to be in good condition.
Protective coating above the low water level may be required in the future if signs of corrosion increase.
The wet well cover exhibits signs of ongoing corrosion.
Venting
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This pump station does not have an air vent.
Renewal of protective coatings will prolong the life of metallic components by insulating the metal from the elements. Corrosion is not structurally significant at this time and protective coating can prevent further deterioration. If the hatch is replaced in the future, aluminum, galvanized steel or stainless steel hatches may be used to eliminate the need to provide protective coating.
The pump station hatch exhibits signs of corrosion (inside of cover)
Wet well cover (top side)
Venting of air helps prevent the accumulation of hazardous gases. The City’s newer station (Tierra Linda) has a simple 4” air-vent. Venting is recommended to be installed at this location (minimum of 4” to 6”).
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Lower Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Valves Valve vault
Valves are partially buried
Recommend improving drainage of this box. If possible, valves should be fully exposed, with a layer of drain rock below to minimize standing water. Alternatively, the existing utility box can be replaced with a concrete box with bottom that is drained back to the wet well.
Valves
Valves show indications of corrosion
The valves are operated regularly and City reports that valve operation is acceptable. Surface corrosion appears cosmetic; however, a renewed protective coating is recommended to prevent continued degradation in this moist environment.
Valve Vault Cover
Corrosion of the existing, half-buried valves is apparent
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Lower Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Discharge Piping Piping
Discharge piping is ductile or cast iron (material has not been confirmed).
RMC recommends renewing the protective coating on the discharge piping and replacing corroded bolts with stainless steel bolts. Non-stainless piping in wet wells is typically provided with an epoxy coating.
No protective coating is evident; pipe surface shows corrosion but no significant pitting. Bolts appear to be corroding to a greater extent than the piping.
Existing pump discharge piping Pumping Equipment Pumps
Pump Operation
Pump Access
Two submersible 9.4 HP Flygt pumps, Model No. 3126. No issues reported by staff. No vibration or excessive noise was observed or reported. Pumps are accessed via new steel chains and rails
Pump performance was not confirmed.
No immediate concerns; pumps appear to be operating well (flow performance was not confirmed). No immediate concerns
New chains and guide rails
Site Conditions Site Access
March 2012
Site is easily accessible
No immediate concerns
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect Drainage
Comments The site gently slopes toward a catch basin at the north end of the site. However, there are depressions in the asphalt which contribute to ponding near the valve box and electrical enclosure
Security
This pump station does not have a fence, but security has not been an issue. The electrical panel is locked to prevent tempering, and pump station access is padlocked to prevent unauthorized entry.
Lower Crestview Pump Station Concerns/ Recommendations Site drainage may contribute to corrosion of the control panel and sediment buildup in the valve box. Regrading and paving to direct water away toward the catch basin more efficiently is advisable, but not urgent if the impacts of ponding can be mitigated through other improvements listed above.
Photo Documentation
The valve box is lid is not secured, and the City may wish to secure this to prevent unauthorized operation of the discharge valves (which may render the pump station inoperable and damage the pumping equipment).
The existing valve vault (foreground) is not secured, and there is evidence of water ponding on the site.
No signs of vandalism or graffiti.
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4.2
Upper Crestview Pump Station
The Upper Crestview Pump Station is nearly identical to the Lower Crestview Station in configuration; they were installed at the same time. The station consists of a concrete wet well and valve box, as well as an at-grade electrical/SCADA panel. This station receives pumped flow from Lower Crestview Pump Station, and the station controls between the two stations are coordinated as described in the previous section for the Lower Crestview Pump Station. General pump station information is summarized in the table below. Upper Crestview Pump Station Information Pump Designation Code
PS06
Year Constructed/Improved
10/1/1975
Last Serviced
3/31/2011
Pump Type
Submersible
Number of Pumps
2 (1 duty, 1 standby)
Pump Manufacturer &Model
Flygt 3126
Motor Horsepower
9.4 HP
Discharge Size
4-inch
Drive type
Constant Speed
Valve Location
Valve box
More detail and specific observations are noted in the table that follows. Overall, this pump station is in good condition; the primary concern is corrosion of valves and enclosures. Many of the issues observed at this station are similar to those observed at Lower Crestview.
UpperCrestview Crestview Pump Upper Pump Station Station
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Upper Crestview Pump Station Condition Assessment
Aspect
Comments
Upper Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Electrical Enclosure
The bottom of the enclosure is at-grade.
Enclosure shows signs of age, but is in no immediate need of replacement.
Enclosure is showing minor signs of corrosion on the side, but corrosion appears stable.
Rust at the bottom may be indicative of a nonwaterproof enclosure or a failed seal.
Corrosion noted on metal bracing and enclosure welds.
Recommend renewing protective coating on rusted areas of enclosure and verifying that water infiltration into cabinet is not an ongoing concern.
Exterior protective coating appears to be in good condition.
Minor corrosion in the electrical enclosure
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect Standby Power
Comments Pump station has an electrical connection for standby generator.
Upper Crestview Pump Station Concerns/ Recommendations No immediate concerns; City’s contractor maintains compatible standby power generation equipment.
Photo Documentation
Portable emergency generator connection
Controls and Communication (SCADA) SCADA Panel/Screen Primary Level Instrumentation
Panel is new and in good condition Ultrasonic sensor
No immediate concerns No immediate concerns
Secondary Level Control/Level Alarm
High level float as a backup to SCADA
No immediate concerns
Communications
Radio tower appears to have somewhat obstructed line of sight. Staff noted that communication is interrupted occasionally
Recommend trimming of trees as necessary to ensure consistent communications integrity.
There is no flow monitoring
This is not a concern, but flow monitoring can be useful in tracking impeller wear and troubleshooting other pump station issues
Flow monitoring
The controls and communication equipment is relatively new and includes battery backup
Trees must be kept trimmed to ensure reliable communication
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Upper Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Wet Well Grease Odor Structural Condition
No issue No issue Some concrete aggregate visible at higher wet well levels.
No immediate concerns No immediate concerns Protective coating above the low water level may be required in the future if signs of corrosion increase.
Venting
This pump station does not have an air vent.
Venting of air helps prevent the accumulation of hazardous gases. The City’s newer station (Tierra Linda) has a simple 4” air-vent. Venting is recommended to be installed at this location (minimum of 4” to 6”). View inside of the wet-well
Valves Valve Box
Valves
The lip of the vault appears to have little clearance above the surrounding grade.
Recommend improving drainage of this box. Raising the lip of the vault relative the ground surface would likely reduce water entering the vault.
Valves are partially submerge in standing water.
If possible, valves should be fully exposed, with a layer of drain rock below to minimize standing water. Alternatively, the existing utility box can be replaced with a concrete box with bottom that is drained back to the wet well.
Uniform rust noted on valves
Protective coating should be applied as necessary to prevent further corrosion. Reducing sediment buildup will also reduce corrosion. Valve box drainage is poor and corrosion is evident
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Upper Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Discharge Piping Piping
Discharge piping is ductile or cast iron (material has not been confirmed).
RMC recommends renewing the protective coating on the discharge piping and replacing corroded bolts with stainless steel bolts. Non-stainless piping in wet wells is typically provided with an epoxy coating.
No protective coating is evident; pipe surface shows corrosion but no significant pitting. Bolts appear to be corroding to a greater extent than the piping.
Discharge piping shows signs of corrosion, including flange bolts.
Pumping Equipment Pumps
Two submersible 9.4 HP Flygt pumps, Model No. 3126.
Pump performance was not confirmed.
No issues reported by staff. Pump Operation
No vibration or excessive noise was observed or reported.
No immediate concerns; pumps appear to be operating well (flow performance was not confirmed).
Pump Access
Pumps are accessed via new steel chains and rails
No immediate concerns
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Upper Crestview Pump Station Concerns/ Recommendations
Photo Documentation
Site Conditions Site Access
Site is easily accessible
No immediate concerns
Drainage
The site appears to have good drainage
No immediate concerns
Security
This pump station does not have a fence, but security has not been an issue.
The valve box is lid is not secured, and the City may wish to secure this to prevent unauthorized operation of the discharge valves (which may render the pump station inoperable and damage the pumping equipment).
The Electrical panel is locked to prevent tempering, and pump station access is padlocked to prevent unauthorized entry.
Paved access at the Upper Crestview Pump Station
No signs of vandalism or graffiti.
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4.3
Tierra Linda Pump Station
The Tierra Linda Pump Station is the City’s highest volume pump station, and its newest. The area tributary to this pump station used to flow into the Belmont sewer system until about 2002. The station was designed with two submersible pumps, each sized to handle a peak wet weather flow of 250 gallons per minute. A passive overflow diversion to the Belmont system still exists if flows exceed the capacity of the station. This is the only pump station with permanently installed standby power. This pump station is well-maintained and, overall, in good condition. Specific observations are given in the table, below. General pump station information is summarized below. Tierra Linda Pump Station Information City Designation Code
PS05
Year Constructed/Improved
9/1/2002
Last Serviced
3/15/2011
Pump Type
Submersible
Number of Pumps
2 (1 duty, 1 standby)
Pump Manufacturer & Model
Flygt 3127
Motor Horsepower
10 HP
Discharge Size
6-inch
Drive type
Constant Speed
Valve Location
Valve box
Emergency Generator
28 kW Olympian Diesel Generator Set
Tierra Linda Pump Station
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Tierra Linda Pump Station Condition Assessment
Aspect
Comments
Tierra Linda Pump Station Concerns/ Recommendations
Photo Documentation
Electrical Enclosure
Enclosure is in good condition
No immediate concerns
Standby Power
28 KW Diesel Standby Generator with testing panel.
Anchorage bolts may be undersized relative to current seismic standards (no evaluation has been performed to confirm) and corrosion of these bolts is apparent.
Generator is tested monthly Recommend replacing bolts with stainless steel bolts sized in accordance with current seismic code. A seismic evaluation would be required.
Existing generator bolts may be undersized and show signs of corrosion.
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Aspect
Comments
Tierra Linda Pump Station Concerns/ Recommendations
Photo Documentation
SCADA SCADA Panel/Screen
Panel is new and in good condition
No immediate concerns
Primary Level Instrumentation
Ultrasonic sensor
No immediate concerns
Secondary Level Control/Level Alarm
High level float as a backup to SCADA
No immediate concerns
Communications
No issues noted.
No immediate concerns
Flow monitoring
There is no flow monitoring
This is not a concern, but flow monitoring can be useful in tracking impeller wear and troubleshooting other pump station issues. The existing SCADA and controls are new and function well for the City
Fuses on the Electrical Panel
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Tierra Linda Pump Station Concerns/ Recommendations
Photo Documentation
Wet Well Grease is an issue at this pump station. Grease buildup is mitigated with an automated enzyme injection system consisting of a peristaltic pump and a 7 gallon enzyme tank. This system is located in a manhole directly upstream of the pump station.
No immediate concerns
Odor
There are odor issues, but no complaints because of the station’s somewhat isolated location
No immediate concerns
Structural Condition
Wet well has been epoxy lined and appears to be in good condition. A wet well overflow connection is present, which is unique to this station
No immediate concerns
Venting
The pump station wet well is vented which is recommended.
No immediate concerns
Grease
An enzyme-based grease control system is used at this station.
The wet well is vented, which is recommended for all submersible stations.
March 2012
23
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Tierra Linda Pump Station Concerns/ Recommendations
Photo Documentation
Valves Valve vault
Vault is new and in good condition.
A hatch would allow for easier access to the valve vault and could be locked for additional security.
Access to the valve vault requires moving two large pieces of metal plating; there is no hatch. Valves
Valves are accessible and in good condition.
No immediate concerns. City reports that ball checks have performed reliably.
The station uses ball checks, which is unique to the City’s stations. The existing valve vault is in good conditions and is well drained. Ball check valves (on left) are used at this station.
March 2012
24
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Tierra Linda Pump Station Concerns/ Recommendations
Photo Documentation
Discharge Piping Piping
Discharge piping has a protective coating.
No immediate concerns
Bolts appear to be stainless steel.
6” Force Main Pumping Equipment Pumps
Two submersible 10 HP Flygt pumps, Model No.3127 Staff noted that it is undesirable to run both pumps at the same time because downstream PVC components may break if subjected to high flow and pressure.
Pump Operation
March 2012
No vibration or excessive noise was observed or reported.
Although running both pumps at the same time is not typically necessary, City reports that this capability must be maintained. In light of this, RMC recommends replacing the downstream components with adequate pressure capacity to eliminate this concern.
Pump access rails and chains No immediate concerns; pumps appear to be operating well (flow performance was not confirmed).
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect Pump Access
Comments Pumps are accessed via new steel chains and rails
Tierra Linda Pump Station Concerns/ Recommendations No immediate concerns
Photo Documentation
Site Conditions Site Access
Site is easily accessible
No immediate concerns
Drainage
The site appears to have good drainage Pump Station is surrounded by screened fence and locked gate.
No immediate concerns
Security
Valve vault is not lockable.
No immediate concerns. The existing level of protection is appropriate given that there are no reported security issues. The City may wish to consider a lockable valve vault cover (also see comments under “Valves”, above)
Security fence around the Tierra Linda Pump Station
March 2012
26
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
4.4
Associated Pump Station
The Associated Pump Station (often referred to as simply “The Associate”) is the City’s oldest pump station. This pump station receives flow from local industry on the east side of Highway 101, including a solid waste collection operation. Sewage consists mostly of industrial wash down water. The station pumps directly to the SBSA San Carlos Pump Station via a force main that crosses Holly Street to the south. This pump station recently underwent improvements including a new driveway, new buried valves, and fencing. Additional planned improvements include modification of the existing bypass pumping discharge connection to allow for easy connection of the City’s existing trash pump and removal of the large crane arm at this site, which is not used. Overall, this pump station is in good condition, with the exception of corrosion on the discharge piping flange bolts. More detail and other specific observations are noted in the table, below. General pump station information is summarized below. Associated Pump Station Information City Designation Code
PS02
Year Constructed/Improved
10/1/1970
Last Serviced
3/31/2011
Pump Type
Submersible
Number of Pumps
2 (1 duty, 1 standby)
Pump Manufacturer &Model
Flygt 3127
Motor Horsepower
9.4 HP
Discharge Size
4-inch
Drive type
Constant Speed
Valve Location
Valve box
TheAssociated Associated Pump The PumpStation Station (“The Associate”)
March 2012
27
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
The Associated Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
Electrical Enclosure
Enclosure recently received a protective coating and the outside appears to be in fair condition. However, there is minor corrosion inside the enclosure. This enclosure is elevated above the concrete slab and, because of this, it is protected from stormwater ponding.
Enclosure shows signs of age, but is in no immediate need of replacement. Rust at the bottom of the enclosure may be indicative of a non-waterproof enclosure or a failed seal. RMC recommends the City continue to refresh the protective coating at regular intervals. This pump station is closer to the Bay than other stations; because of this, moisture intrusion is a concern.
Evidence of corrosion and moisture intrusion in the electrical cabinet
Standby Power
Pump station has an electrical connection for standby generator.
No immediate concerns; City’s contractor maintains compatible standby power generation equipment.
Portable emergency generator connection
March 2012
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
SCADA SCADA Panel/Screen
Panel is new and in good condition
No immediate concerns
Primary Level Instrumentation Secondary Level Control/Level Alarm Communications
Ultrasonic sensor
No immediate concerns
High level float as a backup to SCADA Radio telemetry
No immediate concerns
Flow monitoring
Flow monitoring is not performed at this site.
No immediate concerns; line of sight communication is reported to be acceptable for reliable communication. Flow monitoring can be useful in tracking impeller wear and troubleshooting other pump station issues. The City may wish to consider additional of a flow meter (typically, electromagnetic-type) as part of future pump station upgrades. The controls and communication equipment is relatively new and includes battery backup
SCADA Interface mounted on the outside of the control panel
March 2012
29
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
Wet Well Grease
No grease issues were reported
Odor
Industrial sewage present at this station can have foul odor, but there are no complaints due to the isolated location.
Structural Condition
Wet well appears to be in good condition. Interior is protected by a bituminous coating that is aging but intact
No immediate concerns
This pump station does not have an air vent.
Venting of air helps prevent the accumulation of hazardous gases. The City’s newer station (Tierra Linda) has a simple 4” air-vent. Venting is recommended to be installed at this location (minimum of 4” to 6”).
Venting
March 2012
No immediate concerns; the industrial service area that drains to this pump station does not contain much grease and so this is not likely to be a problem in the future. No immediate concerns
Bituminous coating on the inside of the Wet Well
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
Valves Valve vault
Valves
There is no single valve vault at this pump station (as is the case with the other major pump station). Instead, the isolation valves are buried while the check valves are located in the wet well.
Buried valves may be a concern because they cannot be easily replaced if, for example, the valves become stuck in the closed position.
Isolation valves are buried and their condition could not be determined.
RMC recommends renewing the protective coating on the check valves to maximize their useful life.
The underground valving may be bypassed with the force main bypass connection (which is unique to this pump station). This configuration provides redundancy to the buried valves. However, this bypass connection is not accessible because of the direction the pipe faces (north, toward the creek). The City has plans to reorient the piping so that the connection faces south (toward Holly). RMC encourages the City to implement this improvement.
Buried valves in front of the pump station
Bypass pumping discharge connection
The protective coating of the check valves in the wet well appear to be in poor condition.
March 2012
31
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
Discharge Piping Piping
The discharge piping is ductile or cast iron (material has not been confirmed). Part of the discharge piping appears to have a protective coating, while other parts do not.
Where there is no protective coating, the discharge piping shows uniform corrosion. RMC recommends renewing the protective coating on the discharge piping and valves to maximize their useful life. Nonstainless piping in wet wells is typically provided with an epoxy coating. Some of the bolts appear to have been replaced with stainless steel while others show advanced stages of corrosion. RMC recommends replacing all corroded bolts with stainless steel.
Existing pump discharge piping Mechanical Pumps
Two submersible 9.4 HP Flygt pumps, Model No. 3127.
Pump performance was not confirmed.
No issues reported by staff. Pump Operation
No vibration or excessive noise was observed or reported.
No concerns; pumps appear to be operating well (flow performance was not confirmed).
Pump Access
Pumps are accessed via new steel chains and rails
No immediate concerns
March 2012
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Associated Pump Station Concerns/ Recommendations
Photo Documentation
Site Conditions Site Access Drainage
Security
March 2012
Site is easily accessible from Holly Street. The site appears to have good drainage. No evidence of ponding was observed. The site has recently been repaved and the asphalt is in good condition. Pump Station is surrounded by screened fence and locked gate. Level of protection is appropriate given that there are no ongoing security issues.
No immediate concerns No immediate concerns
No immediate concerns
Security Fence at the Associated Pump Station
33
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
4.5
Kelly Moore I Pump Station
Kelly Moore I is one of the City’s two minor pump stations. The pump station serves a single commercial customer, the Kelly Moore manufacturing and commercial facility. The facility originally discharged by gravity to the sewer system, but in 2000, the City constructed sewer improvements in the area that prevented gravity discharge from the Kelly Moore facility; hence, the City constructed the two small stations to correct this situation. General pump station information is summarized below. Kelly Moore I Pump Station Information City Designation Code
PS03
Year Constructed/Improved
8/1/2000
Last Serviced
4/1/2011
Pump Type
Submersible
Number of Pumps
2 (1 duty, 1 standby)
Pump Manufacturer &Model
Barnes SE411
Motor Horsepower
0.4 HP
Discharge Size
2-inch
Drive type
Constant Speed
Valve Location
Valve box
Kelly Moore I Pump Station
March 2012
34
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Kelly Moore I Pump Station Condition Assessment
Aspect
Comments
Kelly Moore I Pump Station Concerns/ Recommendations
Photo Documentation
Electrical Enclosure
Enclosure is in good condition
No immediate concerns
Standby Power
Pump station does not have standby power generation or a standby power electrical hookup.
The lack of standby power capabilities is likely not an issue due to the small size of flows into this pump station. In the event of a power loss, a vactor truck would be capable of transporting flows and the City could coordinate with Kelly Moore to reduce wastewater until the situation was resolved.
Electrical and SCADA Enclosure SCADA SCADA Panel/Screen
Panel is new and in good condition. The pump station has an alarm indicator (red light) which is visible from the street
No immediate concerns
Primary Level Instrumentation
Ultrasonic level sensor
No immediate concerns
Secondary Level Control/Level Alarm
There is a high level float as a backup to SCADA.
No immediate concerns
Communications
Radio telemetry
No immediate concerns; line of sight communication is reported to be acceptable for reliable communication.
March 2012
Control and SCADA Enclosure with Alarm Indicator
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect Flow monitoring
Comments Flow monitoring is not performed at this site.
Kelly Moore I Pump Station Concerns/ Recommendations Flow monitoring can be useful in tracking impeller wear and troubleshooting other pump station issues. However, the small size of this pump station does not warrant flow monitoring. The cost of the meter and installation may not be justified given the relatively inexpensive replacement cost of the pumps.
Photo Documentation
Wet Well Grease
Grease did not appear to be an issue at this pump station nor did the operator report grease problems.
No immediate concerns
Odor
No odor issues reported
No immediate concerns; the relatively short wastewater residence time in the wet well and upstream system result in no significant issues.
Structural Condition
Wet well appears to be in very good condition.
No immediate concerns
Venting
The wet well is semi-vented through small perforations in the manhole cover.
No immediate concerns
No valve vault – valves are located within the wet well. Valves are small, 3” PVC, and appear to be in good condition.
No immediate concerns
Kelly Moore I Wet Well
Valves Valve vault Valves
March 2012
No immediate concerns
36
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Kelly Moore I Pump Station Concerns/ Recommendations
Photo Documentation
Force Main Piping
Discharge piping is PVC and appears to be in good condition..
No immediate concerns
PVC discharge piping is in good condition Mechanical Pumps
Vibration
Pump Access
March 2012
Two submersible pumps, 9.4 HP, Flygt 3127 No issues reported by staff No vibration or excessive noise was reported Steel chains and rails are not present at this pump station as they are at the other pump stations.
Pump performance was not confirmed
No concerns; pumps appear to be operating well (flow performance was not confirmed) Although no chains are present, the pumps and the discharge manifold are lightweight and may be lifted directly from the wet well by a small transportable crane or winch. Overall, because of their small size, this is not expected to be an issue. However, the City would have to lower an operator into the wet well to undo the union in order to decouple the discharge piping assembly.
37
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Kelly Moore I Pump Station Concerns/ Recommendations
Photo Documentation
Site Conditions Site Access
Site is easily accessible
No immediate concerns
Drainage
The site appears to have good drainage Pump station is not fenced. There have been no reports of vandalism or theft.
No immediate concerns
Security
March 2012
No immediate concerns
38
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
4.6
Industrial Wet Weather Pump Station
The Industrial Wet Weather Pump Station (often referred to as the “Industrial Booster Pump Station” or the “Pulgas Booster Pump Station”) only operates during wet weather. The intended purpose of the booster pump station is to prevent overflows in the trunk sewers in Industrial Road upstream of Brittan Avenue by “boosting” flow to the downstream sewers. The pump station is controlled by water level in an upstream, shallow manhole. When the water level reaches a predetermined “pump on” level, the pump begins to draw flow directly from the surcharged pipeline. Flow is returned to the same pipeline 60 feet downstream. The effectiveness of this station in reducing upstream surcharging has not been confirmed. RMC notes that the close proximity of the suction and discharge connections and apparent lack of backflow prevention toward the upstream connection may limit the effectiveness of operation. It should be noted that based on the results of the capacity assessment, RMC has recommended that this pump station be replaced and a new force main be installed which extends all the way to the San Carlos Pump Station. These upgrades will significantly reduce the hydraulic grade line in the trunk sewers along Industrial Road during wet weather flows. Currently, the Industrial Wet Weather Pump Station consists of a single horizontal pump in a dry-pit configuration. Because the station is not considered a critical component of the collection system, there is no redundancy. The pump station is new (completed in 2009) and all pump components that could be visually inspected are in good condition. General pump station information is summarized below. Industrial Wet Weather Pump Station Information City Designation Code
PS08
Year Constructed/Improved
8/14/09
Last Serviced
3/31/2011
Pump Type
Submersible, Dry Pit, Horizontally Mounted
Number of Pumps
1 duty
Pump Manufacturer &Model
Flygt 3127
Motor Horsepower
7.4 HP
Discharge Size
6-inch
Drive type
Constant Speed
Valve Location
Dry-Pit Vault
Industrial Booster Pump Station March 2012
39
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Industrial Wet Weather Pump Station Condition Assessment Aspect
Comments
Concerns/ Recommendations
Documentation
Electrical Enclosure
Electrical equipment is housed in the Pulgas Creek Wet Weather Pump Station building.
The existing building appears to be in sound condition, but is older construction that is likely not designed to current seismic codes. The City may wish to perform a full seismic analysis of this structure to determine if it is subject to failure during a large earthquake.
Pulgas Creek Pump Station Building Standby Power
There is no standby power for this pump station (and no electrical hookup)
This is a non-critical pump station, for wet-weather only. If a power failure were to occur during a significant storm event, the City could call on help from Rain4Rent to provide emergency power.
SCADA Panel
Panel is new and in good condition
No immediate concerns
Level Instrumentation
An ultrasonic level transducer monitors level of the upstream sewer and controls the pump on/off. No instrumentation issues were reported for this pump station.
No immediate concerns
SCADA
The existing SCADA panel is new and in good condition.
March 2012
40
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect Communications
Flow monitoring
Comments Radio tower. There are no reported communication issues. There is no flow monitoring
Concerns/ Recommendations No immediate concerns
Documentation
Dedicated flow monitoring would not be necessary for this pump station because of its infrequent use.
Dry-Pit Vault Structural Condition
A single concrete dry pit houses the pump and valves. Pit is in good condition. The pit is in good condition.
No immediate concerns
The pump dry pit is new and in good condition. Suction and Discharge Piping Piping
Discharge piping is coated, ductile iron with stainless steel bolts.
No immediate concerns
The piping system is in very good condition. Pumping Equipment Pumps
Pump Station consists of a single submersible, dry pit, horizontally mounted pump, 7.4 HP, Flygt 3127
No immediate concerns; operation was not witnessed during field visit (station can only operate in wet weather)
Pump Operation
No vibration or excessive noise was or reported. Stainless steel guide rail system is new
No concerns. Performance could not be confirmed.
Pump Access
No concerns Horizontally mounted Flygt Pump
March 2012
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San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Aspect
Comments
Concerns/ Recommendations
Documentation
Site Conditions Site Access Drainage Security
Site is easily accessible Site appears to have no drainage issues All pipe, pump, electrical components are secured in the dry pit or in the electrical building. Both the dry-pit access and building enclosure are locked and secure.
March 2012
No immediate concerns No immediate concerns No immediate concerns
Access the Pump Dry-Pit via steel cover
42
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
5 Useful Life and Summary of Recommendations This section summarizes the important recommendations identified in Section 4. It also lists the typical useful life of major wastewater pump station components in comparison to the current age of the City’s pump station assets. The expected life of an asset is the typical duration that equipment is predicted to operate when properly maintained. Expected life is a general value that is used to trigger a condition assessment of equipment to determine if the asset should be replaced or if extended service is possible. This condition assessment found that many of the City’s pump station assets are beyond or nearing their typical useful life. However, this does not necessarily mean that replacement is the immediate course of action. In fact, with diligent maintenance, wastewater equipment often exceeds typical useful life values. Where RMC has identified that an asset is at or beyond its useful life and where our inspection revealed that an asset is indeed deteriorating, we have recommended actions which will inhibit further deterioration so that the useful life may be extended. However, as older equipment continues to operate beyond its typical useful life, even if properly maintained, the City should conduct condition assessments more frequently so as not to compromise reliability. The tables presented in this section provide a summary of recommendations and useful life information. More detailed about specific recommendations along with supporting documentation is given in Section 4. Note that because all of the SCADA systems at the City’s pump stations are new, recommendations related to electrical equipment do not apply to the SCADA system (e.g. new panel, new screen, new wiring, new level transducers, etc.). Source of Useful Life Data The expected useful life values given in this section are based on RMC’s experience with wastewater assets, equipment life expectancy provided by equipment suppliers, and on published values by the Environmental Protection Agency (EPA). The EPA publication “Asset Management: A Handbook for Small Water Systems” provides expected life data for assets typically found at wastewater facilities. This document is referenced by presentations and publications related to asset management for a wide range of equipment including pump station equipment. RMC’s wastewater life expectancy data and the EPA published data were compared in determining the range of useful life values for this project. Capital Improvement Costs based on Recommendations Overall, the City’s pump stations are in acceptable condition and this condition assessment evaluation has found that no major capital improvements are necessary. The recommendations presented in this section are considered operational and maintenance related and so cost estimates are not provided. In general, these recommendations are not expected to cost more than $20K each. Industrial Booster Pump Station The Industrial Booster pump station is currently in good condition and there are no immediate improvement needs. However, based on the results of the capacity assessment, RMC has recommended that the Industrial Booster Pump Station be replaced and a new force main be installed to reduce wet weather surcharging in the trunk sewer along Industrial Road. Therefore, an individual table showing recommendations for this pump station is not shown in this section.
March 2012
43
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Table 1: Lower Crestview – Useful Life and Recommendations Summary Current Age
Typical Useful Life
Electric Conduit, Wiring, and Fixtures (Does not include SCADA system)
37
20-25
Electrical Enclosure
37
Major Components
Recommendations Based on Visual Inspection The original equipment is beyond typical useful life for similar equipment in wastewater facilities. A detailed inspection of the conduit and wiring was not conducted as part of this work and so the actual condition could not be assessed; however, the City operators did not indicate any equipment problems. Because of the age of this pump station, the City should have an electrical engineer conduct a thorough condition assessment of the electrical components.
15-25
The original equipment is beyond typical useful life for similar equipment in wastewater facilities. RMC recommends an evaluation of the enclosure to determine if infiltration is occurring. If so, the City should take measures to prevent water from entering or replace the enclosure.
Valves
37
25-40
The valves are nearing the end of their typical useful life for wastewater valves; however, the City operators did not indicate any equipment problems. RMC recommends renewing the protective coating to prevent further surface corrosion.
Discharge Piping (DIP, or similar)
37
30-40
The discharge piping is nearing the end of typical useful life for wastewater valves; however, the City operators did not indicate any issues with the piping. RMC recommends renewing the protective (epoxy) coating on the discharge piping and replacing corroded bolts with stainless steel bolts. The pump station would need to be shutdown for as long as two days to complete this work. Another option is to replace the discharge piping with new epoxy coated DIP. Although the material cost for replacement would be more expensive, the pump station could be brought back into service faster (with 4 to 8 hours) and the useful life would be reset.
Concrete Wet Well
Wastewater Pump
Other
March 2012
37
30-50
The wet well appears to be in good condition. RMC recommends installing a 4-inch or 6-inch vent on the wet well to vent hazardous gasses.
The useful life of submersible wastewater pumps are extremely variable and depend on wastewater constituents, environmental conditions, and maintenance. The City staff did not report any excessive vibration or operational issues that would be indicative of a shortened useful life. Therefore, RMC recommends that the City continue routine maintenance and monitor any changes in performance.
Lock valve box
44
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Table 2: Upper Crestview – Useful Life and Recommendations Summary Current Age
Typical Useful Life
Electric Conduit, Wiring, and Fixtures (Does not include SCADA system)
37
20-25
Electrical Enclosure
37
Major Components
Recommendations Based on Visual Inspection The original equipment is beyond typical useful life for similar equipment in wastewater facilities. A detailed inspection of the conduit and wiring was not conducted as part of this work and so the actual condition could not be assessed; however, the City operators did not indicate any equipment problems. Because of the age of this pump station, the City should have an electrical engineer conduct a thorough condition assessment of the electrical components.
15-25
The original equipment is beyond typical useful life for similar equipment in wastewater facilities. RMC recommends an evaluation of the enclosure to determine if infiltration is occurring. If so, the City should take measures to prevent water from entering or replace the enclosure.
Valves
37
25-40
The valves are nearing the end of typical useful life for wastewater valves; however, the City operators did not indicate any equipment problems. RMC recommends a renewed protective coating to prevent further surface corrosion. In addition, the valves should be fully exposed, with a layer of drain rock below to minimize standing water. Alternatively, the existing utility box can be replaced with a concrete box with bottom that is drained back to the wet well.
Discharge Piping (DIP, or similar)
37
30-40
The discharge piping is nearing the end of typical useful life for wastewater valves; however, the City operators did not indicate any issues with the piping. RMC recommends renewing the protective (epoxy) coating on the discharge piping and replacing corroded bolts with stainless steel bolts. The pump station would need to be shutdown for as long as two days to complete this work. Another option is to replace the discharge piping with new epoxy coated DIP. Although the material cost for replacement would be more expensive, the pump station could be brought back into service faster (with 4 to 8 hours) and the useful life would be reset.
Concrete Wet Well
Wastewater Pump
Other
March 2012
37
30-50
The wet well appears to be in good condition. RMC recommends installing a 4-inch or 6-inch vent on the wet well to vent hazardous gasses. This action will help maximize the useful life of the wet well.
The useful life of submersible wastewater pumps are extremely variable and depend on wastewater constituents, environmental conditions, and maintenance. The City staff did not report any excessive vibration or operational issues that would be indicative of a shortened useful life. Therefore, RMC recommends that the City continue routine maintenance and monitor any changes in performance.
Lock valve Box Frequent tree-trimming to ensure consistent communications integrity 45
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Table 3: Tierra Linda – Useful Life and Recommendations Summary
Current Age
Typical Useful Life
Electric Conduit, Wiring, and Fixtures (Does not include SCADA system)
10
20-25
Electrical Enclosure
10
Major Components
Recommendations Based on Visual Inspection The original equipment is within typical useful life for similar equipment in wastewater facilities and City staff did not report any electrical issues. No recommendations
15-25
The original enclosure is within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
10
Valves
25-40
The original valves are within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
10
Discharge Piping (DIP, or similar)
30-40
The original discharge piping is within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
10
Concrete Wet Well
30-50
The wet well is within typical useful life for similar equipment in wastewater facilities and appeared to be in good condition. No recommendations
Wastewater Pump
Other
The useful life of submersible wastewater pumps are extremely variable and depend on wastewater constituents, environmental conditions, and maintenance. The City staff did not report any excessive vibration or operational issues that would be indicative of a shortened useful life. Therefore, RMC recommends that the City continue routine maintenance and monitor any changes in performance.
March 2012
A valve vault hatch would allow for easier access to the valves and could be locked for additional security. Recommend replacing standby generator anchorage bolts with stainless steel bolts sized in accordance with current seismic code Staff noted that it is undesirable to run both pumps at the same time because downstream PVC valves may break if subjected to high flow and pressure. RMC recommends replacing the components downstream of the pump station with adequate pressure capacity to eliminate this concern.
46
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Table 4: Associated Pump Station – Useful Life and Recommendations Summary Current Age
Typical Useful Life
Electric Conduit, Wiring, and Fixtures (Does not include SCADA system)
42
20-25
Electrical Enclosure
42
Major Components
Recommendations Based on Visual Inspection The original equipment is beyond typical useful life for similar equipment in wastewater facilities. A detailed inspection of the conduit and wiring was not conducted as part of this work and so the actual condition could not be assessed; however, the City operators did not indicate any equipment problems. Because of the age of this pump station, the City should have an electrical engineer conduct a thorough condition assessment of the electrical components.
15-25
The original equipment is beyond typical useful life for similar equipment in wastewater facilities. RMC recommends the City continue to refresh the protective coating at regular intervals. This pump station is closer to the Bay than other stations; because of this, moisture intrusion is a concern.
Valves
Force Main (DIP, or similar)
42 (check valves)
42
25-40
30-40
The check valves are beyond their end of typical useful life for wastewater valves; however, the City operators did not indicate any equipment problems. Because the isolation valves are buried, RMC could not confirm their condition. RMC recommends renewing the protective coating on the check valves to maximize their useful life. The original discharge piping is beyond typical useful life for similar equipment at wastewater facilities; however, the City operators did not indicate any issues with the piping. RMC recommends renewing the protective (epoxy) coating on the discharge piping and replacing corroded bolts with stainless steel bolts. The pump station would need to be shutdown for as long as two days to complete this work. Another option is to replace the discharge piping with new epoxy coated DIP. Although the material cost for replacement would be more expensive, the pump station could be brought back into service faster (with 4 to 8 hours) and the useful life would be reset.
Concrete Wet Well
Wastewater Pump
Other
March 2012
42
30-50
The wet well appears to be in good condition. RMC recommends installing a 4-inch or 6-inch vent on the wet well to vent hazardous gasses. This action will help maximize the useful life of the wet well.
The useful life of submersible wastewater pumps are extremely variable and depend on wastewater constituents, environmental conditions, and maintenance. The City staff did not report any excessive vibration or operational issues that would be indicative of a shortened useful life. Therefore, RMC recommends that the City continue routine maintenance and monitor any changes in performance.
No other recommendations
47
San Carlos Sewer Collection System Master Plan Pump Station Condition Assessment
Table 5: Kelly Moore I Pump Station – Useful Life and Recommendations Summary
(years)
Typical Useful Life (years)
Electric Conduit, Wiring, and Fixtures (Does not include SCADA system)
11
20-25
Electrical Enclosure
11
Major Components
Current Age
Recommendations Based on Visual Inspection The original equipment is within typical useful life for similar equipment in wastewater facilities and City staff did not report any electrical issues. No recommendations
15-25
The original enclosure is within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
Valves (PVC)
11
25-40
The original valves are within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
Force Main (PVC)
11
15-30
The original discharge piping is within typical useful life for similar equipment in wastewater facilities and City staff did not report any issues. No recommendations
Concrete Wet Well
11
30-50
The wet well is within typical useful life for similar equipment in wastewater facilities and appeared to be in good condition. No recommendations
Wastewater Pump
Other
March 2012
The useful life of submersible wastewater pumps are extremely variable and depend on wastewater constituents, environmental conditions, and maintenance. The City staff did not report any excessive vibration or operational issues that would be indicative of a shortened useful life. Therefore, RMC recommends that the City continue routine maintenance and monitor any changes in performance.
No other recommendations
48
