WOSSA Training Nov. 2012 Advanced Soil Science Concepts Today’s Subjects: • Review of Soil Basics • Horizontal Groundwater Movement (Soil Physics) • Wicking in Sands and Soil Layering (Capillary Functions) • Hydric (wetland) Soils Development and Regional Indicators
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Presenter: Lisa Palazzi, CPSS, PWS J.W. Morrissette & Associates, Inc. www.jwmorrissette.com (previously with Pacific Rim Soil & Water, Inc. www.pacificrimsoilandwater.com) Olympia, WA
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FIVE SOIL FORMING FACTORS Parent Materials (geology) Climate (weather) Organisms (living and dead) Time Topography
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The forces of Weather and of Living Organisms, modified by Topography, acting over Time upon Parent Material (Dukochaev, 1883)
___________________________________ ___________________________________ ___________________________________ Basic Soil Profile Development Organic Profile Mineral Profile O horizon: Organic matter accumulation above mineral sediments
A horizon: Zone of organic matter accumulation and incorporation into the mineral soil surface, structured
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O??
A
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B
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O B horizon: Color change, Zone of leachate accumulation (clay and minerals) from above. Structured
B or C?
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C horizon: Unweathered, Massive (Structureless) Parent Material
C
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Soil Forming Processes
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Geology maps
Soil maps
Parent Materials Washington Geology and Soils Maps Terrain or Topography maps
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Geologic Time Scale and Terminology Eon: Half a billion years + (Biggest) Era: Several hundred million years (Even Bigger) Period: A few hundred million years (Bigger) Epoch: Tens of millions of years (Smallest -- Late and Early) Age: Reported in Millions of Years Ago or MYBP
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PARENT MATERIAL (prioritize your PM list based on local conditions) 1. CONTINENTAL OR ALPINE GLACIATION (NORTH HALF OF WA STATE) a. Till soils (ice-laid) b. Outwash soils (meltwater deposits) c. Glacio-lacustrine (glacial lakebed sediments) 2. VOLCANIC EVENTS a. Lava flows (HOW OLD?) b. Mudflows (lahars) (HOW OLD?) c. Ash effects 3. BASALT OR GRANITE (IGNEOUS) BEDROCK (HOW OLD?) 4. SEDIMENTARY / METAMORPHIC BEDROCK (HOW OLD?) 5. RECENT ALLUVIUM AND WIND-BLOWN SOILS a. Floodplains b. Loess
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Glacial Landscape effects • Huge vertical and horizontal weight compacting substrate • Glacial terminus with outwash flood deposits • Dammed glacial lakebeds (next slide)
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CONTINENTAL GLACIATION IN WASHINGTON, IDAHO AND MONTANA HTTP://HUGEFLOODS.COM/
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Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are dammed by the Cordilleran Ice Sheet during the Vashon Glaciation (ended about 10,000 ybp). The areas inundated in the Lake Columbia and Lake Missoula floods are shown in gray – the “Channeled Scablands” and extending along Columbia River and Willamette Valley.
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GLACIAL TILL SOILS (ICE LAID) A horizon: Surface organic accumulation B horizon: Color change, slight weathering below A
C horizon: Unweathered glacial till
GLACIAL OUTWASH SOILS (WATER LAID) A horizon: Surface organic accumulation B horizon: Color change, slight weathering below A
GLACIAL LAKEBED SEDIMENTS (WATER LAID)
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A horizon: Surface organic accumulation B horizon: Color change, slight weathering below A
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C horizon: Unweathered glacial flood deposit C horizon: Unweathered glacial lakebed
Shelton soil, Mason Co.
Everett soils, Pierce Co.
Giles soils, Thurston Co.
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Volcanic Impacts • PNW volcanoes • Basalt Plains • Granite Intrusions
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Volcanic Parent Material : Recent Mt. St. Helens Lahar and Ash Deposits
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___________________________________ VOLCANIC IMPACTS: ASH DEPOSITS
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VOLCANIC IMPACTS: OLDER MUD FLOWS (LAHARS)
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Lahar (mudflow) soil (Buckley: ~6000 yrs. old)
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RECENT (QUATERNARY TO PRESENT) ALLUVIUM AND WIND-BLOWN SOILS
Floodplains: Recent Alluvial Sediment Deposits
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RECENT (QUATERNARY TO PRESENT) ALLUVIUM AND WIND-BLOWN SOILS
Palouse Area: Wind-Blown (loess) Sediments
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CLIMATE Monthly Patterns
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ORGANISMS
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• PLANTS
Actinomycetes, Fungi, Algae Herbs, Grasses Woody plants (shrubs to trees) Crops
• ANIMALS
Microbes Earthworms Burrowing animals (moles, gophers, snakes...) Surface animals (deer, birds, cattle, horses…) Humans (farms, roads, home sites, cities…)
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SLOPE • Erosion, sediment movement, soil
depth • Hydrology (runoff vs. infiltration potential) ASPECT AND ELEVATION • Temperature (duration of direct sunlight) • Moisture (evaporation) • Vegetation (transpiration)
TOPOGRAPHY Bedrock mountains: steep, shallow soils
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Glacial moraine: rolling terrain, layered, gravelly soils
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Floodplain: flat, layered, fine-textured soils
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Two Basic Types of Soil Textures/ Profiles
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A horizon: Surface organic accumulation B horizon: Color change, slight weathering below A
In between these two extremes are soils with overthickened surface O-horizons overlying mineral soils below.
C horizon: Unweathered Parent material
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Mineral Soil: (mostly sand, silt and clay)
Organic Soil: (composed of rotting leaves, moss, roots…)
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• BREAK??? ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________
Soil Water Movement (Soil Physics)
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Hydraulic Conductivity: The BIG Picture and the little picture
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How water moves through the soil and why you should care. • Saturated flow (gravity driven - down)
• Unsaturated flow (matric potential – i.e. capillary driven – any direction)
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Water Molecule • Dipolar • Cohesion vs. Adhesion • Surface Tension • Capillary Rise Mechanism
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___________________________________ ___________________________________ Biggest pores
Solid 50%
Empty Macropores Fill to Sat. Saturated Micropores 25% Water at F.C.
Smallest pores
Soil at Field Capacity
___________________________________ Macropores drain with Gravity Micropores hold water against pull of Gravity (only roots can drain this zone)
Solid 50%
All Soil Pores Full = 100% Saturation
Soil at Saturation
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Soil Aggregates: The living system = texture + structure + biota + time Impacts on soil drainage 26
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Granular
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Platy Sub-angular Blocky
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Water perches at textural and structural changes. Coarse over fine: macro to micropore
Fine over coarse: micro to macropore
Water is “sucked” into fine layer below.
More water is held in finer layer against pull of gravity.
Coarse layer above allows more water through and at a faster rate, until it is slowed at the top of fine layer.
loamy sand
100 % Sat.
sandy loam
Fine layer allows less water through, and at a slower rate; weight of water column will push through at some point.
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Old Soil Physics video http://www.youtube.com/watch?v=jWwtDKT6NAw&feature=related Watch 2:58-14:10
Surface Tension and Capillarity (fast!) http://www.youtube.com/watch?v=wOOY1szbcX4&feature=related http://www.youtube.com/watch?v=Z0gNOB-v1iI&feature=related http://www.youtube.com/watch?v=HZgeanXiChg Soil texture by hydrometer method (better) http://www.youtube.com/watch?v=XpLIwwX9oyE&feature=related
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• BREAK??? ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________
ADVANCED SOILS SUBJECT AREA: WETLAND (HYDRIC) SOILS Why should a wastewater system designer care about understanding wetlands and/or studying hydric soils – i.e., why don’t we just look for wetland hydrology (or wetland plants)? 1. Because siting a septic system requires awareness of wetland and other water-related setbacks; 2. Because hydric soil morphology indicators help to prove the depth and duration of the water table (even if below 12 inches); 3. Because hydrology is the most ephemeral of the 3 wetland parameters (soils, plants and hydrology); 4. Because Facultative plants, in particular, are highly adaptable; 5. Because liability associated with making the wrong call (wetland or not?) in EITHER direction (too wet or not wet enough) is enormous.
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WHEN SHOULD YOU ASSESS WETLAND CONDITIONS FOR A SEPTIC PROJECT? Answer: Before anything else…. You can avoid many problems by first defining or delineating (flagging) wetlands or related shallow groundwater conditions.
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Ducks!!
Mound septic system
___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ How we picture wetlands
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___________________________________ How we DON”T picture wetlands
___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Two Basic Types of Soil Textures/ Profiles
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A horizon: Surface organic accumulation B horizon: Color change, slight weathering below A
In between these two extremes are soils with overthickened surface O-horizons overlying mineral soils below.
C horizon: Unweathered Parent material
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Mineral Soil: (mostly sand, silt and clay)
Organic Soil: (composed of rotting leaves, moss, roots…)
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Organic Soil Texture Classes •
Based on degree of decomposition of leaves, roots, moss…
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A result of chemical and physical weathering of organics
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3 textural classes – Peat (fibric – can see what the living plants once were) – Mucky Peat (hemic – halfway decomposed) – Muck (sapric – highly decomposed)
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Determining organic soil texture – Visual observation in the field – Send to a lab for OC content test
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NOTE: Peat soils can change from fibric to sapric (i.e. muck) within a week or so of being exposed to oxygen
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Mineral Soil Texture Classes •
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Based on particle size distribution (percent sand, silt, clay)
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A result of chemical and physical weathering of rock Physical weathering reduces rock to sand and silt Chemical weathering creates secondary clay minerals 12 soil textural classes (see textural triangle)
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Determining texture Hand Texturing (field) Hydrometer methods (lab)
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Hydric soils can be: • Dominantly organic material (~20-100% OM [by wt.] – i.e., peat, muck or mucky peat), • Partly OM (from ~8-20% -i.e., mucky mineral) or • Dominantly mineral material (16 in. of the upper 32 in. is organic* soil • Indicator A2. Histic Epipedon (Taxonomy**) Surface layer of organic* soil >8 in.
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* i.e., Peat, mucky peat, or muck
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Indicator A3. Black Histic • Diagnostic layer*: A layer of peat, mucky peat, or muck >8 inches thick;
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• Starting at: 6 inches * Starting at: 60% chroma of 2 inches thickness allowed layer is entirely within the upper 6 in. of the soil ____________________________________
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If depleted matrix colors have – values/chromas of 4/1, 4/2, and 5/2, then > 2% redox concentrations (Fe/Mn soft masses and/or pore linings) are required; – other values/chromas (5/1, 6/1, 6/2, 7/1, 7/2, 8/1, 8/2), then no redox concentrations are required.
The low chroma matrix must be caused by wetness and not be a relict or parent material feature – i.e., think – do you have evidence of hydrology and hydrophytic plants?
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Definition • Depleted matrix (describes a process): For loamy and clayey material, a depleted matrix refers to the portion of a the diagnostic soil layer where reduction and translocation have removed or transferred iron, thereby creating colors of low chroma (4). NOTE: A, E, and calcic horizons may have low chromas and high values and may be mistaken for a depleted matrix; however, they are excluded from the concept of depleted matrix unless the soil has “common” or “many”, “distinct” or “prominent” redox concentrations occurring as soft masses or pore linings.
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Indicator F6. Redox Dark Surface Diagnostic layer: >4 inches thick Located: Entirely