Inventory and Analysis Flashcards
Perennial Stream
Year round flow, fed by shallow groundwater moving through soil
Intermittent Stream
Flows part of the year
Ephemeral Stream
Flows or during or after rainfall events
Depth of groundwater analysis
- How deep wells must be drilled for water supply, impacts cost
- Determining feasibility of stormwater infiltration/retention
- Determining feasibility of siting septic system leaching fields
- Groundwater quality and contamination impacts it usefulness for water supply purposes
Stormwater Controls
- Filtration through planted medium to remove sediments and pollutants before going into municipal stormwater systems
- Reduce downstream flashiness to protect streams
- Groundwater recharge
Stormwater Mitigation
- Grassy filtration strip along drainage edge
- Vegetated swale with broad bottom to slow water
- Biofiltration basin with fast-draining soil and planted with species that can tolerate flooding, pipe at the bottom might collect clean water
Stream Protection
Slow It, Spread It, Sink It:
• To hold back water, to slow it down with check dams
• To get runoff into the ground by enhancing infiltration and percolation.
• To provide storage capacity to allow more time for runoff to infiltrate or be released to the storm drainage system at a slower rate through the use of basins.
Technological Stormwater Management Methods
- Direct surface runoff to recharge areas (to improve groundwater recharge)
- Detention measures (to reduce peak flows)
- Retention measures (to reduce runoff volume and peak flows)
- Biotechnical Stream Restoration (repair natural channels using “natural” technology in lieu of hard armoring)
- Habitat Restoration or Enhancement (Riparian systems, wetlands)
Vegetation Analysis
Depends on scale of project • Plant Communities • Species Lists • Edge Profiles • Rare and Endangered Species • Fire History • Physionomic Profiles
Remote Sensing for Vegetation Inventory
- Aerial Photographs or Satellite Imagery (vegetation associations, species identification, wetlands, patch/corridor mapping)
- Stereoscopic 9” x 9” (available from: U.S. Soil Conservation Service, U.S. Forest Service, and U.S. Bureau of Land Management) for topographic maps
- Non-photographic Sensors (electromagnetic)
- Infrared Radiation: meteorology and climatology, foliage health
- Light Detection and Ranging (LIDAR): Tree canopy heights, forest biomass
- Thermal Imaging: Heat stress in vegetation, surface water temperature, city energy audits, wildlife distribution and density.
Sampling Vegetation - Quadrat Sampling
Site is subdivided into plots of a standard size, can be random, regularly distributed, or subjectively selected. Quadrats can be square, rectangular, or round. Contents of selected plots are inventoried.
Sampling Vegetation - Transect Sampling
Samples are taken along a baseline. Points can be selected with a grid, randomly chosen coordinate pairs, or regular or random points along the line.
Sampling Vegetation - Relevé Sampling
“Sample stand” community types are defined by a specialist. Several representative sample stands for each community are inventoried.
Sampling Vegetation - Aerial Photography
Using large scale color or infrared photography can provide a basis for acceptable estimates of plant cover and soil surface conditions, though understory plants may be obscured in a forest setting.
Sampling Vegetation - Windshield Survey
Commonly used in land-use surveys; enables rapid but not verifiable assessment of site. Note: Roadside planting is often not a good indicator of interior planting
Vegetation Information/Classification Types
- Species Richness: How many species occupy the sample area.
- Frequency: How often a species occurs in a sample, or a proportion of the samples in which it occurs.
- Density: How many plants (of a species) per unit area.
- Cover: How much ground within the sample area is covered or shaded by a species.
- Total Biomass: The dry weight of plant material per sample unit.
Physiognomy
The spatial/vertical structure of a plant community. It can include an inventory of the number of canopy layers, with the plant that dominates each layer.
Factors Influencing Physiognomic Plant Distribution
- Duration of Growing Season (climatic zone)
- Point of Succession
- Ground Temperature
- Continuous Wind
- Soil Moisture
- Shallow Soils on Fractured Rocks
- Shallow Soil Without Subsoil Moisture Reserves
- Disturbance
- Wildlife populations and browse patterns
Vegetation Physiognomic Types
• Forest • Woodland • Savanna • Scrub • Grassland • Tundra • Swamp* • Marsh* • Bog* * indicates wetland types
Ecological Land Classification:
A process of delineating and classifying ecologically distinctive areas of the earth’s surface.
Ecoregions
Geographical areas within which climate, hydrology, plant communities, and wildlife populations are characteristic of the area. To a lesser extent, topography, geology and soils also help distinguish ecoregions.
Ecosystem
An interactive system including physical habitat as well as living organisms.
Land Use is also a factor in ecological classification as human activities impact both physical habitats as well as plant and animal populations.
Biodiversity
A contraction of biological diversity. It is the variety within and between all species of plants, animals and micro-organisms and the ecosystems within which they live and interact.
Ecological Mapping Systems of the United States
- Bailey Ecoregions Map (1976) (developed through USDA/US Forest Service)
- Omernik Ecoregions Maps (1982) (developed through the US Department of Interior, USGS and the Environmental Protection Agency)
Agents of Environmental Change
- Climate Change
- Wildfire
- Invasive Species
- Development
Vegetation Dynamics
- Seasonal (1 yr, i.e., spring to fall)
- Cyclical (20 yrs, i.e., fire cycle)
- Succession (1000 yrs, i.e., sand dune to forest)
- Geologic (20,000 yrs, i.e., ice age)
- Genetic (1,000,000 yrs, i.e., development of a new species)
Succession
The observed process of change in the species structure of an ecological community over time. Typically a relatively bare site will begin with a few pioneer species of plants and over a long period of time develop into a climax community of plants and animals. A mature redwood forest would be a California Coast Range example of a climax community.
Vegetation Analysis Factors
- More biodiverse habitats are generally considered to be healthier ecosystems within habitat types (forests, meadows, grasslands, tundra, etc.)
- Presence and predominance of invasive species is an indicator of less healthy or less mature habitat types.
- Development can destroy or fragment habitats. Smaller fragments are generally able to support lesser populations of wildlife or less diverse populations of wildlife.
- Removal of vegetation through logging, mining, or clearing for agricultural or other human uses can severely alter habitat suitability for both terrestrial and aquatic habitats.
- Wildfire and other catastrophic events can drastically alter ecosystems and return areas to pioneering stages in vegetation succession.
- Soil erosion severity can be impacted by removal of vegetation, winds, storm runoff, and slope steepness or slope instability.
- Pollution due to human uses can negatively impact soil health, surface and groundwater, and vegetation, wildlife, and human health.
- Rare and endangered species of plants and animals usually occupy fairly narrow ecological niches which is why they are rare and very sensitive to change in their environments.
Landscape ecology
a broad, well established field of study that looks at regional ecosystem patterns and tries to set standards for maintaining ecological integrity. As human development fragments and degrades natural areas, they reach a point where they can no longer sustain a healthy, interdependent ecological web.
Landscape
a heterogenous land area composed of interacting stable ecosystems
Patch
an intact area of consistent ecological character that differs from its surroundings
Matrix
the background ecological system of a landscape
Connectivity
a measure of how easily plants, animals etc can access the resources they need, moving through patches, networks and corridors
Fragmentation
is the breaking up of an ecosystem into isolated patches
Classification of Wetlands
two approaches to classification:
• Geographically based systems (broad-based mapping similar to USDA soils maps)
• Site inventory/environmental characteristics as found on the ground (watershed position, existing habitats, vegetation based approaches, etc)
Geographical Wetland Classification Schemes
US Fish and Wildlife maintains the National Wetlands Inventory (NWI) system, a collection of maps showing many wetlands identified using aerial photography.
Cowardin Wetland Classification System (US Fish and Wildlife Service)
- Marine (open water and assoc. coastline)
- Tidal (influenced by tides, brackish or saline)
- Estuarine (tidal waters of coastal rivers and embayments, salty tidal marshes, mangrove swamps, and tidal flats)
- Riverine (rivers and streams)
- Lacustrine (lakes, reservoirs, and large ponds)
- Palustrine (marshes, wet meadow, fens (non-acidic bogs), playas, potholes, pocosins, bogs, swamps, and small shallow ponds)
The Nature Conservancy Wetland Classification system
Based on vegetation associations; has been adopted as the Federal standard for habitat-based classification.
Clean Water Act Wetland Classification System
The US Army Corps of Engineers and EPA generally define a wetland as a place where wetland vegetation occurs.
Wetlands must have the following three attributes:
1) at least periodically, the land supports predominately hydrophytes
2) the substrate is predominantly a hydric soil
3) the substrate is saturated with water or covered by shallow water at some time during the growing season of each year.)
Hydrogeomorphic Wetland Classification (HGM) used by Army Corps of Engineers (7 classes)
Based on site’s geomorphic setting (topographical position and shape), dominant water source, and dominant hydrodynamics.
Seven classes: • Riverine (rivers and streams) • Depressional (ie. vernal pools, pocosins, etc.) • Slope (Artesian wells, seeps, other places where groundwater discharges to the surface but does not accumulate) • Mineral Soil Flats (dry lakes, etc) • Organic Soil Flats (peat bogs) • Tidal Fringe (ocean edges) • Lacustrine Fringe (lake edges)
Topographical Analysis
- Temperature: vertical lapse rate (typically -3.5 degree F per 1000 ft. elevation gain)
- Orographic effects on precipitation: moist air pushed up a ridge will condense and turn to rain which results in different moisture regimes and vegetation types on either side of a ridge.
Aspect
Orientation of the face of a slope
• North side and south side of hills have different daily temperatures, night time temperatures are similar.
• Evaporative stress is greater on south-facing and west-facing slopes. It is less on east and north-facing slopes. This has implications for the types of vegetation that can grow there, soil moisture levels, organic matter levels in the soils, and wildlife habitats.
Terms for Mapping and Measurement of Slopes (surveying)
• Degrees vs. Percent Slope: tanA=rise/run=S
• Typical angle of repose for different materials, by percent:
drained sand 33%, boulders 45%, loam 45%, well-compacted clay 65%
• Influence of vegetation
• Slope ordinances:
Cities or counties may restrict development on steep slopes for public safety
Soil Horizons
Soil horizons are the layers in a typical soil profile which have distinctly different physical, chemical and biological qualities.
• O = Organic Matter in a recognizable form, including leaves and partially decomposed matter.
• A = Heavy non-recognizable organic matter mixed with minerals
• B = Nutrients left by rain water leaching, hardpans & clay pans develop here.
• C = Partially weathered rock fragments
• D = Bedrock
• Subordinate designations are too specific for the exam. They can be found in Time Saver Standards.
Soil Test Reports
Test soil and tailor planting plan to be adapted to soils. Typical Information in Soil Test Reports • USDA Soil Classification • pH • Organic matter content • Macro and Micronutrient content
Geotechnical Reports
A geotechnical report is a summary report of the exploration of the subsurface soils and how they are to be used as construction materials.
• Boring Locations shown on a plan of the site:
• Summary of all subsurface exploration data, including subsurface soil profile, exploration logs, laboratory or in situ test results, and ground water information;
• Interpretation and analysis of the subsurface data;
• Specific engineering recommendations for design, especially thicknesses and reinforcing for pavements and footings;
• Discussion of conditions for solution of anticipated problems; and
• Recommended geotechnical special provisions.
• Permeability (for septic systems, stormwater filtration, etc – test for the percolation rate, or how many minutes per inch (MPI). Metric equivalents may be minutes per 25mm or minutes per liter. You can request permeability tests for undisturbed site soils or for fill soils.
Soil Bearing Capacity
the maximum average contact pressure between a structure and the soil surface on which it rests that the soil can support without failure.
Clay 1-2 tons/ sq. ft.
Silt 1.5-3 tons/sq. ft.
Sand (loose) 2-3 tons/ sq. ft.
Gravel (loose) 4 tons/ sq. ft.
Sand-gravel(compact) 6 tons/ sq. ft.
Well graded, well compacted 10 tons/ sq. ft.
clayey sand and gravel
Sedimentary rock 15 tons/ sq. ft.
Foliated rocks (layered metamorphic) 40 tons/ sq. ft.
Massive bedrock 100 tons/sq. ft.
Soil Texture
affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it. The technical term for this is leaching
Sandy Soils (over 45% sand)
- Drains quickly
- Light weight
- Non-expansive
- Erodable
Silty Soils (over 40% silt)
- Small grain size
- Moderate permeability
- Highly erodable
Clayey Soil (over 35% clay)
- Low permeability or impermeable
- Heavy weight
- Expansive: heaves, shrinks (Swells when wet, shrinks when dry)
- Low water availability at low moisture content
- Colloidal content describes presence of clay particles in sample (Colloid: A suspension of finely divided particles in a dispersing medium; particles do not rapidly settle out of suspension and are not readily filtered.
- Erodable to highly erodable
Loam (usually less than 40% clay with good particle size distribution)
- Blend of soil types. Also variations such as sandy loam, sandy clay loam, etc.
- Rated as highly valuable agricultural soil
- Very good drainage, moderately permeable, high water holding capability
- Slight erosion potential, 0-3% slope, no rocks
- Highly fertile
- Easily worked
Soil Structure
Soil structure describes the arrangement of the solid parts of the soil and of the pore space located between them.
Soil structure is generally classified as one of the following:
Platy -flat and platelike, usually found in subsurface soils that have been subject to leaching or compaction
Blocky - structural units are blocklike or polyhedral
Prismatic - units are bounded by flat to rounded vertical faces
Granular - structural units are approximately spherical or polyhedral and are bounded by curved or very irregular faces that are not casts of adjoining peds. In other words, they look like cookie crumbs
Columnar - similar to prisms and are bounded by flat or slightly rounded vertical faces
Structureless - no units are observable in place or after the soil has been gently disturbed
Gypsum (calcium sulfate dihydrate)
is used as a soil amendment to improve soil structure. It also helps reduce salt toxicity in soils that are heavily irrigated. It also provides sulfur and calcium to the soil and often improves permeability. It does not significantly affect soil pH.
Soil Acidity (Ph) Acidic
Acidic
• Low pH 0-7
• Usually have a high percentage of organic matter
• Often associated with areas of higher rainfall
four major reasons for soils to become acidic: rainfall and leaching, acidic parent material, organic matter decay, and harvest of high-yielding crops.
Macronutrients tend to be less available in soils with low pH.
Aluminum sulfate or Sulfur can be added to increase soil acidity.
Soil Acidity (pH) akaline/basic
Alkaline/Basic
• High pH 7-14
• Heavy in salts and other solutes
• Usually associated with areas of lower rainfall
two primary ways that soils become basic.
- the soil is derived from a basic parent material such as limestone
- located in a climate where the alkaline elements are not leached out by rain.
Micronutrients tend to be less available in soils with high pH.
Lime can be added to the soil to make it less acidic and also supplies calcium and magnesium for plants to use.
Hydric Soils
formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part of the soil. This lack of oxygen in the soil can lead to the formation of a thick layer of non-decomposed organic matter in the upper horizon. While hydric soils usually have low pH (acidic), this is not always the case.
Soil Macronutrients
- Nitrogen
- Phosphorus
- Potassium
- Calcium
- Magnesium
- Sulfur
availability of macronutrients is largely determined by three variables: the abundance of parent minerals present, the chemical conditions in the soil, particularly the pH, and the rate of movement of the nutrients that are in compounds available to plants within the soil media. Many micronutrients are almost immobile in soil, or react with organic matter and clays to form immobile compounds. This protects the micronutrients from being lost due to leaching.
Soil Micronutrients
- Iron
- Manganese
- Zinc
- Copper
- Boron
- Molybdenum
Nitrogen
Responsible for the vegetative growth of plants above ground. With good supply, plants grow sturdily and mature rapidly, with rich, dark green foliage. Nitrogen helps seed and fruit production and improves the quality of leaf and forage crops. Plants deficient in nitrogen tend to have a pale yellowish green color (chlorosis), have a stunted appearance, and develop thin, spindly stems. Lower leaves are more affected than upper ones. Natural sources include blood meal, alfalfa meal, feather meal, fish emulsion, and manure.
Phosphorus
Healthy growth, strong roots, fruit and flower development, and greater resistance to disease. Enhances photosynthesis, nitrogen fixation, flowering, fruiting (including seed production), and maturation. Root growth, particularly development of lateral roots and fibrous rootlets, is encouraged by phosphorous. A phosphorous-deficient plant is usually stunted, thin-stemmed, and spindly. Its foliage (particularly lower leaves) is often red or purple. Natural sources include rock phosphate, guano, and bone meal.
Potassium
Helps plants to resist diseases, protects them from the cold and protects during dry weather by preventing excessive water loss. Potassium is known to activate 80 different enzymes in plants. Potassium plays a critical role in reducing the loss of water from leaves and increases the ability of the roots to take up water from the soil. It also helps plants adapt to environmental stresses. Potassium deficiency causes the tips and edges of the oldest leaves begin to yellow (chlorosis) and die, so that the leaves appear to have been burned on the edges. Natural sources include potassium sulfate, granite dust, wood ash and kelp meal.
Calcium
an essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant. Deficiency symptoms: Deformed tips of leaves and little root growth.
Magnesium
is essential for photosynthesis. It also activates many plant enzymes needed for growth. Deficiency symptoms: Yellowing of leaves, purple leaf margins.
Sulfur
reduces soil pH. is essential for production of protein. Helps in chlorophyll formation.
Improves root growth and seed production. Helps with vigorous plant growth and resistance to cold. Deficiency symptoms: yellow and brown leaves.
Iron
deficiency symptoms include chlorosis, death of leaf edges, and stunted growth.
Chemical Fertilizers
classified by the three major nutrients (N-P-K) which are expressed as a total percentage of weight as packaged. High concentrations of nitrogen in fertilizers can chemically burn the delicate feeder roots of plants. Chemical fertilizers are water soluble, and are often over applied to force plant growth. Excess nutrients washing off of over fertilized lawns and gardens build up in natural drainage systems can throw off the balance between species in downstream aquatic habitats.
Natural fertilizers
forest litter, compost and manure have much lower concentrations of nutrients, but add organic matter and other beneficial organisms to soil.
New soil fertility model
Plants are one part of an intricate web of living things that are interrelated, and require dozens of other nutrients and elements that are essential to plant growth such as sulfur, hydrogen, oxygen, carbon, magnesium, and beneficial soil organisms. It is better to use plants adapted to local conditions of soil, drainage, and micro climate than to make extraordinary efforts to compensate for local conditions.
Cation Exchange Capacity (CEC)
the cation exchange capacity (CEC) of a soil is an indicator of soil fertility. A higher CEC is generally an indicator that the soil is more “fertile” in that exchangeable ionic nutrients are more available to plants
In general, soils with higher clay content or good amounts of organic matter have high CEC. Soil CEC also generally increases as pH increases. Sandy soils typically have low CEC due to nutrient leaching.
The exchangeable cations of most importance in soil are • Calcium (Ca2+), • Magnesium (Mg2+), • Sodium (Na+), • Potassium (K+), • Ammonia (NH4+)
Soil Amendments and Treatments
- Acid Soils: Add lime to neutralize, or calcium nitrate (a nitrogen fertilizer)
- Alkaline Soils: Add sulfur, or Calcium Sulfate to release alkaline compounds from soil so that they may leach out. Areas irrigated with reclaimed water have a tendency to become more alkaline.
- Nutrient Deficiency: Add commercial/organic fertilizer, manure, compost or leaf mold
- Humus Deficiency: Add organic fertilizer, manure, compost, leaf mold
- Heavy Soils: Add manure, compost, gypsum (for clay) or add a thick layer of deciduous tree and shrub chips.
- Gypsum: Gypsum can improve heavy clay soil structure and remove sodium from saline soils. Gypsum has no effect on soil fertility, structure, or pH of other soil types.
- Compaction: Loosen soil or aerate.
- Slow Drainage: Install drain lines, bore through hardpans. Poorly drained subsoils tend to be blue to gray in color which indicates low oxygen in the soil. Well drained soils are more oxidized and are red, to tan in color.
Six principles to manage healthy soil.
- Enhance organic matter.
- Avoid excessive tillage.
- Manage pests and nutrients efficiently.
- Prevent soil compaction.
- Keep the ground covered with vegetation or mulch.:
- Increase plant species diversity or rotate crops.
Types of Erosion Caused by Water
- Splash erosion (usually by rainfall)
- Sheet erosion
- Rill and gully erosion
- Stream and channel erosion
Factors Influencing Erosion
- Soil Characteristics
- Slope Length and Gradient
- Erosive Forces Present (rainfall, wind, solar)
- Vegetative Cover
Soil Erodibility
affected by:
• Average particle size
• Gradation
• Percentage organic content
• Textural classifications (see page on soil texture)
• Soil infiltration rates and permeability (i.e. a sand allows greater infiltration and therefore produces less runoff than a clay soil)
• Vegetative cover: holds soil, protects surface, slows runoff, maintains the soils capacity to absorb water
• Topography: slope length, gradient influence runoff velocity and volume
• Climate: frequency, duration and intensity of rainfall; wind effects; solar effects
Universal Soil Loss Equation
used to predict long-term annual rates of erosion based on rainfall, soil type, topography, crop system, and management practices.
A = R x K x LS x C x P A = estimated average soil loss in tons per acre per year R = rainfall-runoff erosivity factor K = soil erodibility factor L = slope length factor S = slope steepness factor C = cover-management factor P = support practice factor
Landslide Prevention and Correction -Excavation
- Removal of unstable material
- Flattening of slopes
- Benching of slopes
- Lightweight fill
Landslide Prevention and Correction -Drainage
- Slope treatment for faster runoff
- Surface ditches
- Sealing joints, planes, and fissures
- Subdrainage to relieve hydrostatic pressure
Landslide Prevention and Correction -Restraining structures
- retaining walls
- buttresses
- rock fill
- reinforced earth
- shotcrete (gunite)
Landslide Prevention and Correction -Flexible reinforcements
- using geotextiles and geogrids
- using soil nailing - This is a modern variation on dead men in retaining walls. Holes are bored into an unstable slope and filled with steel and concrete
- Pilings
- rock bolts: similar to soil nails, but embedded into fractured rock faces.
Landslide Prevention and Correction -Vegetation
- hydroseeding
* forestation
Igneous Rocks
classified based on their mineral composition and grain-size, which is a result of the cooling rate of the parent magma. Igneous rocks fall into two sub-categories:
• Extrusive rocks cooled quickly when brought to the surface by volcanic eruption. The grains in the rocks tend to be fine. Common examples include Basalt and Gabbro.
• Intrusive rocks cooled more slowly within the earth. The rocks grains are coarse, easily seem with the naked eye. Common examples include Granite and Rhyolite.
Sedimentary Rocks
classified based on their depositional mode.
• Mechanically eroded and precipitated rocks include Conglomerate, which has some particles that are gravel sized, Sandstone which has sand size particles, and Shale and Siltstone in which the particles are in the silt to clay size range.
• Chemically precipitated rocks include Limestone, which is primarily calcium carbonate, and Chert which contains quartz crystals and is harder than limestone.
Metamorphic Rocks
classified based on composition and texture.
• Foliated metamorphic rocks exhibit a distinctive layering. Examples include Gneiss, Schist, and Slate.
• Non-foliated metamorphic rocks include Quartzite, which results from the deformation of sandstone and Marble, which results from the deformation of limestone.
Geomorphic Processes
Processes that make or alter landforms.
• Tectonic
• Fluvial: erosion, transportation, and sedimentation from rivers and streams.
• Aeolian: erosion , transportation, and deposition by wind.
• Mass Wasting: movement by gravitational forces - landslide.
• Glacial
• Weathering
Mechanical: wind, frost
Chemical: oxidation, carbonation. hydrolysis, hydration
• Volcanic
• Biological: root penetration, litter deposition and biochemical action
• Wave Action
Littoral Drift (movement of sand along a coastline due to wave and tidal action)
Aquifer
an underground reservoir that can be accessed with drilled wells
Artesian Well
underground pressure forces water up to the surface of the ground through manmade well or a naturally occurring channel
Karst
barren rocky ground with many sinkholes and underground streams
Moraine
glacial landform created when ice retreats, leaving the soil it was pushing as a mound. Also called glacial till
Strata
layers of soil and rock
Vadose Zone
a layer under the surface where the soil pores contain a mixture of air and water.
Littoral Zone
the area between the high and low tide lines along coasts, estuaries and bays. Generally subject to wave action and periodic inundation.
Expansive Soils
soils that swell in volume when they are wetted and shrink when they dry out. Such soils may cause sidewalks to crack, foundations to crack or fail, basement walls to fail, and retaining walls to fail.
Plasticity Index
widely used for assessing the shrink-swell potential of soil. Soils with a PI greater than 20 are considered expansive. Greater than 40 is considered highly expansive. The Plasticity Index is the difference between the Plastic Limit and the Liquid Limit of a soil. The plastic limit is the point where the soil is moist enough to deform under pressure without returning to its shape (like modeling clay). The liquid limit is where the soil behavior changes from plastic to liquid (like quicksand).
Liquefaction
Soil liquefaction occurs when a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid.
Soil Color
A blue or gray color in soil is usually due to poor drainage (lack of air in soil).
Yellows and reds indicate good drainage (plenty of air). These are usually caused by iron oxides.
Dark colors in surface layers are usually caused by the presence of organic matter.
Light colors in the upper soil layers are often due to nutrient and iron leaching due to high percolation rates. High levels of calcium carbonates also create light colors.
Environmental Site Assessments
evaluations of risk for conditions of possible environmental contamination. Under federal law, a landowner is liable for environmental conditions on his property whether they had any knowledge of the contamination or not, or was involved in the contamination. Liability can include cost of cleanup and damages to third parties. Buyers or lending agents minimize this risk by engaging environmental professionals to conduct these ESAs in advance of purchasing property.
Transaction Screen (or environmental screening)
- Has the site been filled in the past?
- Knowledge of hazardous materials or petroleum products in fill?
- In area currently or historically used for industrial or commercial activities?
- Zoned for commercial or industrial uses?
- Adjacent properties zoned for commercial or industrial uses?
- Evidence of present or past use or storage of hazardous materials?
- Adjacent properties drain on to the site?
- Reasons to suspect the quality of runoff from adjacent sites?
- Presence of electrical transformers?
- Is an on-site well used for the sites water supply?
Phase 1 Environmental Assessment
more intensive level of assessment of contamination hazard and should be conducted by a qualified environmental professional.
- Site condition
- Applicable zoning regulations
- Land development regulations
- Utility access
- Traffic
- Topography
- Soils/geology
- Hydrology
- Vegetation/Wildlife
- Historic or cultural features
- Existing public space
- Environmental hazard concerns
- Review of existing records
- Sources used to determine the history of the site
- On site walkthrough
- Interviews
- Conclusions and recommendations
