SITE CONSIDERATIONS OF A PHASE 2 ESA – Team Alpha

An Environmental Site Assessment (ESA) is done to examine a property for probable contamination with hazardous materials. Phase 1 ESAs detail the geography, topography, and history of the site, with notes on any hazardous materials found during the walk-through. Phase 2 ESAs are more complex, including sampling of all materials present on the property (soil, groundwater, plants) to determine how the site will respond to or could have responded to a hazardous material contamination in the past.

There are some vital factors that must be considered during a Phase 2 ESA (list taken from Pg 134-135 of Pichtel textbook):

- Depth to groundwater and bedrock
- Soil temperature
- Moisture content
- Bulk density
- Particle size distribution and texture
- Soil structure
- Saturated hydraulic conductivity
- Unsaturated hydraulic conductivity
- Organic matter content
- Soil microbial activity

These factors are explained and expanded on below.

1.) DEPTH TO GROUNDWATER AND BEDROCK – Kyle Gilbert

Image / Table 1 – Potential for Groundwater contamination based upon depth to groundwater, can be seen at http://www.omafra.gov.on.ca/english/engineer/facts/07-035.htm (not able to print tables here)

The depth to groundwater or bedrock is crucial because it determines how far down the contaminant must travel before reaching an aquifer (Pichtel 2007). The depth will also affect the amount of time the contaminant is in contact with the soil. Where the depth is shallow, the contaminant becomes much more likely to reach groundwater (Waldron 1992). When the water and contaminants make their way to the bedrock, the time until it reaches groundwater is very short. The treatment of contaminated water primarily takes place in soil in the unsaturated zone. Shallow depth results in a short travel time for water and contaminants to move through this unsaturated zone before reaching the ground water, therefore, there is little opportunity for the treatment of water to occur.

2.) SOIL TEMPERATURE – Grinnell Duncan

Soil Temperature Regimes of the United States, retrieved from http://soils.usda.gov/use/thematic/temp_regimes.html

Soil Temperature is considered to be the mean monthly soil temperature at a specific depth, or the average of the daily high and daily low temperature for the month (NRCS 2008). Despite changing outdoor air temperatures and the effects of soil layering, ground temperatures are generally able to stay consistent at depths below 30 meters (Esen et al., 2009). In conjunction with other soil temperature sampling methods, borehole drilling can be used to measure soil temperature by lowering a thermometer down the borehole, allowing for sampling at multiple depths (Fitts 2002). It is possible for chemical reactions to change the normal breakdown process of pesticides or other chemical residues, especially in colder soil temperatures. This happens because the chemical reactions create a “thermal pan” inside the soil matrix. (NRCS 2008)

3.) MOISTURE CONTENT – Rebekah Fox-Laverty

Moisture content is important to know on a corn farm because one would have a better idea of when to plant their corn for better production. Measuring for soil moisture is difficult on a farm due to not having consistent measurement devises or scales available. Dry measuring samples and sending them to a laboratory would give the corn-farmer a better measurement of their moisture content on their farm of their soil.

Thermal conductivity is higher as the moisture content increases. Water’s thermal conductivity is high which means that the more the moisture content of soil conductivity increases, the more like water’s conductivity it will be. If the soil moisture content is high, it will take longer for the soil to heat up in the sun than dry soil and the same to become cooler once the sun has gone down. The reason it takes longer to warm and cool if the moisture content is higher is because water evaporation removes the energy from the sun before the soil has a chance to use the energy to get hot or to cool down. However, soils like clay tend to not have as high moisture content and therefore do not take as long to heat and cool.

Moisture content can affect many things from wood and cotton to corn or nutrient concentration and proteins. Moisture content can also affect composting and land treatments. Moisture content is very important in agriculture and other various industries. Detection of soil moisture can help in flood control areas, forest and farming areas, and landscape and construction sites. Detection of moisture content can help farmers monitor their crops and know when it would be a good time to plant and harvest. It can also help in the monitoring of humidity. Moisture content also affects groundwater and soil by releasing contaminants. What type of contaminants released varies on conditions and area.

These are three types of techniques that are electronic for measuring the moisture content. These measuring techniques are time domain reflectometry, capacitive sensing, and resistance sensing. Capacitive sensing relies on the humidity of the air in the area. The resistance sensing type is the most common techniques. Resistance sensing relies on the relative humidity and measures the resistance; these sensors include polymeric, metallic, or electrolytic. The most common of the sensory types is electrolytic. Sensor probes are used in time domain reflectometry technique. The probes are inserted into the soil to measure the moisture of the soil.

4.) BULK DENSITY – Rebekah Fox-Laverty

Bulk density affects contaminants and erosion rates. Soils can be measured in weight by unit volume called bulk density. Volume is considered to be the pores and solids. The bulk density of soils like minerals has a bulk density of 1.0 to 2.0. Bulk density can help compare two different soils. To get bulk density, divide the total weight by the volume (see formulas below).

There are different methods in acquiring bulk density; core method, clod method, excavation method, and radiation method. These methods are different in how the samples of soils are taken and how the volumes are established. The excavation method is used when sampling of soil is not as easily available due to lose soils. The radiation method uses the joined density of gas, liquid, and soil to determine the soil mass. The core method involves weighing the dried soil. Each of these methods helps determine the bulk density of soils.
Bulk density is important when trying to figure out the movements of moisture in soil. As the bulk density increases, the growth of roots are decreased, less exposure of air, and infiltration of water is reduced. Increased bulk density can assist in building roads and structure foundations because it reflects tight compaction of the soils beneath. Bulk density affects the movement of contaminants in both soils and tocks. Knowing the moisture content, porosity, and permeability will assist in figuring out the bulk density of soil.

5.) PARTICLE SIZE DISTRIBUTION AND TEXTURE – Josh Beutler

Particle size distribution and texture determines the mobility of contaminants within the soil structure and the type of remediation technique that may be successfully utilized. As we have seen from Dr. Edwards’ lectures, the particle size effects fluid permeability and can range from unfractured metamorphic and igneous rock (10^-16 cm^2) to gravel (10^-3 cm^2). When particle size distribution and texture is relatively constant, the primary route of flow of a contaminant is downward. When the texture is not consistent, for example when sandy soils have intermittent clay layers, the layers tend to route contaminant flow in a horizontal direction due to their relative impermeability.Permeability is a term often referred to in the Environmental Protection Agency’s evaluations for remediation technique effectiveness and intrinsic permeability directly correlates with particle size and distribution. For example, the effectiveness for soil vapor extraction remediation, also known as soil venting or vacuum extraction, has a permeability factor of greater than or equal to 10^-8 cm^2, as defined by the EPA. This indicates that soil substructure and the particle size and distribution must at least be in the range of silty sand and/or larger for soil vapor extraction to be effective. Procedures for measuring particle size and distribution are usually done through collection of soil core samples and laboratory evaluations. Assessment criteria and categorization strategies are available from the EPA or through standardized tests available from the American Society for Testing and Materials (ASTM).

6.) SOIL STRUCTURE – Ali Forouhar

The soil structure is a mix of inorganic materials, organic materials, and void spaces. Examples of inorganic materials include silt, clay, gravel, and other sediments. The void spaces can be occupied by either water or air. The texture/structure of the soil is dependent on what materials it consists of, which are an important factor in which remediation technique should be used.

Soils with high gravel/sand soil content should also have high permeability or high hydraulic conductivity, in which case aeration or flushing technologies can be used for remediation. Clayey soils have very low hydraulic conductivity (low permeability) and do not allow vertical movement of the contaminants, which means that they may require different remediation technologies. Clay can be used as a landfill liner due to its estimated hydraulic conductivity of 10-7 centimeter/second.

Structure of Soil http://www.gf.uns.ac.rs/~wus/wus07/web6/2/soil%20structure.jpg
Void spaces and porosity help determine how water is able to move through soil particles. Higher porosity indicates higher velocity of water movement, as well as increased microbial activities. Soils with low porosity may allow for runoffs and pond formations. Organic materials contribute 1% to 50% of the total composition of soil – these are also called humus, where the organic materials are decomposed by living organisms in the soil. Decaying organic materials hold the soil particles together. Soils with low organic materials content are found mostly in arid lands. Living beings such as earthworms, fungi, nematodes, protozoa and bacteria are also major contributors to soil structures. Soil pH is also an important aspect of soil structure.

7.) SATURATED HYDRAULIC CONDUCTIVITY – Tedla Gebre

USGS defines saturated hydraulic conductivity as (see class notes session 2): “The capacity of a rock to transmit water. It is expressed as the volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow’’ (http://Capp.water.usgs.gov/GF). Saturation is fraction of pore space filled by a particular fluid multiple porous media (Class lecture session 2).

Saturated hydraulic conductivity is used in predicting or calculating flow to wells, lakes, rivers or storages from groundwater. It also predicts if deformation or subsidence is going to happen due to discharge or recharge.
The conductivity is used to calculate the volumetric flow, using Darcy’s Law.

K= -Q/(AI)Q is flow rate

A is the area perpendicular to the flow

I is gradient

dh/dx- Is due to higher to lower flow

K is flow constant in one or more media like clay, sand, and so on.K can be calculated from density, viscosity and gravity.

K=kρf g/μk is permeability

ρf is density

g is gravitational constant

μ is viscosity

Therefore, K is inversely proportional to viscosity μ. In most cases, saturated flow assumes homogeneity and isotropicity so that Darcy’s law applies with less complexity. To understand saturated underground flow, data of porosity and values of K tables are given.

The tables below are from Groundwater Science by Charles Fitts (2001).

Table 2.2 Typical Values of Porosity
Material n (%)
Narrowly graded silt, sand, gravel 30-50
Widely graded silt, sand, gravel 20-35
Clay, clay silt 35-60
Sand stone 5-30
Lime stone, dolomite 0-40
shale 0-10
Crystalline rock 0-10

**Will correlate the above value to hydraulic conductivity.

Table 3.1 Typical Values of Hydraulic Conductivity
Material K (cm/sec)
Gravel 10-1 to 100
Clean sand 10-4 to 1
Silt sand 10-5 to 10-1
Silt 10-7 to 10-3
Glacial till 10-10 to 10-6
Clay 10-10 to 10-6
Shale 10-14 to 10-8
From the above data, the conductivity and pore sizes determine the flow including the media and the content of liquid in the pores. Unlike unsaturated hydraulic conductivity, saturated conductivity is constant because the water content stays the same. The pore water pressure does not vary with volumetric water content θ (Fitts 2001).

For more reading I found this site: http://soils.usda.gov/technical/technotes/note6.html

8.) UNSATURATED HYDRAULIC CONDUCTIVITY – Sachie Dale

Unsaturated hydraulic conductivity is used to measure or predict water movement through pore spaces and fractured rock when the soil and fractured rocks are unsaturated with water. The knowledge of unsaturated hydraulic conductivity helps to understand the movement and travel times of pesticides, hazards, and radioactive substances through the unsaturated zone when contamination occur. It also helps to understand the flow of nutrients through the zone.

These are many techniques and methods to measure unsaturated hydraulic conductivity.Here are some examples:

· Steady-State Centrifuge Method
· Capillary Bundle Model
· Infiltration Tests
· Constant Flux and Crust Methods

9.) ORGANIC MATTER CONTENT – Jamie Ekholm

Organic matter plays an important role in the ability of a contaminant to move through the vadose zone and eventually into the phreatic zone. A large portion of what is considered soil organic matter is made up of mainly plant and animal material that has broken down over time. This material is called humus. There are other organic components of the soil (such as polysaccharides); however, these constituents are rather short-lived due to microbial breakdown.

There is a huge variety of different organic molecules that make up what is considered humus. Overall, these chemicals are found to have a considerable cation exchange capacity (CEC). CEC gives organic matter the ability to both absorb and exchange cations.

Organic matter also possesses anion exchange capacity, though to a lesser degree than CEC. Having both positive and negative charges is quite advantageous from a contaminant capture standpoint. This is especially true with many negatively-charged metal complexes as well as positively charged metal ions. The organic molecules that make up humus are also non-polar to some degree like most organic molecules. This means that humus has the ability to capture many different organic contaminants such as pesticides, organic solvents, and fuels.

10.) SOIL MICROBIAL ACTIVITY – Morgan Bliss

The microbial activity present in soil can assist in decreasing the contaminant load of soil. For instance, a highly active (aerobic or anaerobic) group of microorganisms present in the soil may allow for faster degradation of contaminants like hydrocarbons, metals, and petrochemical residues (Pichtel 2007). Microbial activity can consist of both bacteria and fungi that are able to break down contaminants and use them as a food/metabolic source.

You can estimate existing soil microbial activity by measuring the soil gas oxygen and/or carbon dioxide composition. Oxygen concentrations are generally a better indicator of microbial activity; because carbon dioxide levels can be affected by other aspects of the soil (precipitation or dissolution of carbonate rock can cause increased levels of carbon dioxide in the soil). In a soil gas survey, if you find elevated carbon dioxide and lowered oxygen levels as compared to background soil levels, it can indicate that biological activity is present in the soil. If you find that there are decreased oxygen or carbon dioxide levels in the soil of concern as compared to background soil levels, it may indicate that microbiological activity has been limited or inhibited by the site. This limitation or inhibition can be due to increased toxicity of the soil as well as insufficient water content or elevated temperatures (Hyman and Dupont 2001).

REFERENCES:
Pichtel, John. (2007) Fundamentals of Site Remediation, 2nd Edition. Toronto: Government Institutes.
Fitts, Charles R. (2002) Groundwater Science. London: Academic Press, an imprint of Elsevier.
Depth to Groundwater and Bedrock
Waldron, Acie C. Ohio Cooperative Extension Service – Ohio State University. (1992) Bulletin 820: Pesticides and Groundwater Contamination. Retrieved October 2, 2009. http://ohioline.osu.edu/b820/b820_8.html

Soil Temperature
Esen, H., Inalli, M., & Esen, Y. (2009). Temperature distributions in boreholes of a vertical ground-coupled heat pump system. Renewable Energy, 34(12), 2672-2679.
“Part 618: Soil Properties and Qualities.” United States Department of Agriculture – National Resources Conservation Service (NRCS) Website. National Soil Survey Handbook (NSSH) Online. Accessed October 6, 2009. http://soils.usda.gov/technical/handbook/contents/part618.html

Moisture Content and Bulk Density
Peters, John. On-Farm Moisture Testing of Corn Soilage, Retrieved October 1, 2009. http://www.uwex.edu/ces/crops/uwforage/CSMoistTest.htm.
Cook, David R. Ask a Scientist; Soil Moisture Content. Retrieved October 2, 2009. http://www.newton.dep.anl.gov/askasci/wea00/wea00105.htm.
Table D-4: Operating Parameters: Measurement Procedures and Potential Effects on Treatment Cost or Performance. Retrieved October 4, 2009. http://www.frtr.gov/matrix2/appd_d/appd_d_tab4_fr.html.
Moisture Meter, Humidity Sensor. January 2007. Retrieved October 4, 2009 http://www.electronics-manufacturers.com/info/sensors-and-detectors/moisture-meter-humidity-sensor.html.
Bulk Density Determination. Retrieved October 4, 2009. http://www.geology.iupui.edu/research/SoilsLab/procedures/bulk/Index.htm.
EcoSystem Restoration; Analytical Methods. Physical Propertied: Bulk Density. Montana State University Bozeman; September 2004. Retrieved September 29, 2009. http://ecorestoration.montana.edu/mineland/guide/analytical/physical/bulk.htm.

Particle Size Distribution and Texture
Environmental Protection Agency. (2004). How to Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites: A Guide For Corrective Action Plan Reviewers. EPA 510-R-04-002. Washington, D.C.

Soil structure
Environmental Protection Agency (EPA). (1995) Decision Maker’s Guide to Solid Waste Management, Volume 2. EPA 530-R-95-023. Glossary and Chapters accessed October 6, 2009 from http://www.epa.gov/waste/nonhaz/municipal/dmg2/glossary.pdf
Saturated hydraulic conductivity
ETM 523 Lecture Materials Fall 09 by Dr. David Edwards.
Natural Resources Conservation Service (NRCS) United States Department of Agriculture Website. “Saturated Hydraulic Conductivity: Water Movement Concepts and Class History.” Retrieved October 4, 2009 from http://soils.usda.gov/technical/technotes/note6.html
Unsaturated hydraulic conductivity
AGVISE Laboratory. Unsaturated Hydraulic Conductivity. Retrieved October 4, 2009, from AGVISE Laboratory. Website: http://www.agvise.com/tech_art/unsathy.php
Australian Government Connected Water. Hydraulic Conductivity Measurement. Retrieved October 4, 2009, from Australian Government Website: http://www.connectedwater.gov.au/framework/hydrometric_k.php
Daniel, D.E. & Trautwein, S.J. (1994). Hydraulic Conductivity and Waste Contaminant Transport in Soil. Philadelphia, PA.
Perkins, K.S., & Winfield, K.A. (2007). Property-Transfer Modeling to Estimate Unsaturated Hydraulic Conductivity of Deep Sediments at the Idaho National Laboratory, Idaho. Retrieved October 4, 2009, from U.S. Geological Survey. Website: http://pubs.usgs.gov/sir/2007/5093/pdf/sir20075093.pdf
U.S. Geological Survey. (2001). Steady-State Centrifuge Method. Retrieved October 4, 2009, from USGS Science for a changing world. Website: http://www.rcamnl.wr.usgs.gov/uzf/ssc.html
U.S. Geological Survey. (2001). Unsaturated-Zone Flow Project. Retrieved October 4, 2009, from USGS Science for a changing world. Website: http://www.rcamnl.wr.usgs.gov/uzf/
Organic Matter Content
Washington State University. Tree Fruit Research & Extension Center. (2004). Cation-Exchange Capacity (CEC). Retrieved September 28, 2009 from: http://soils.tfrec.wsu.edu/webnutritiongood/soilprops/04CEC.htm

Soil Microbial Activity
Hyman, M. & Dupont, R.R. (2001) Groundwater and Soil Remediation: Process Design and Cost Estimating of Proven Technologies. Reston, VA: American Society of Civil Engineers (ASCE Press).