Fort Hood Investigates Beneficial Re-use
of Pesticide Contaminated Soil
The management of pesticide-contaminated soil on military installations is becoming an important issue.Fort Hood found itself having to deal with this issue, excavating 3000 cubic yards of chlordane contaminated soil. What can be done with this soil has prompted Fort Hood to begin a multi-phase investigation into the beneficial re-use of chlordane-contaminated soil. Fort Hood had been investigating many methods for the remediation and treatment of pesticide contaminated soil, which lead us to the encapsulation method. Phase 1 of this investigation involves proving that encapsulated pesticide contaminated soil will not leach and securing Texas Commission on Environmental Quality approval to use this encapsulated soil as daily cover on the Fort Hood municipal solid waste landfill. Phase 1 is the focus of this paper.
During a field investigation in 2003 approximately 3,000 cubic yards of chlordane contaminated soil was excavated on Fort Hood. This soil is currently being stored in a lined, closed loop area.When tested these samples contained chlordane levels ranging from 15.4 ppm to 82.9 ppm. Initial investigation revealed that disposal of this soil will cost approximately $135 per ton or over $550,000, while placing this soil in Fort Hood’s special waste trench will cost approximately $29 per ton or approximately $117,000. Searching for a more efficient option, Fort Hood investigated encapsulation of chlordane-contaminated soil for beneficial re-use in lieu of disposal or placing in a landfill. Initial study also showed that encapsulation of chlordane-contaminated soil will cost approximately $8.64 per ton or around $35,000. Fort Hood desires to use this soil as a test for re-use methods in lieu of disposal.
The primary purpose of this project is the beneficial re-use of 3,000 cubic yards of chlordane contaminated soil by using it as daily cover on a pre-selected, isolated area of the Fort Hood municipal solid waste landfill. In the execution of this project, many other objectives will be accomplished that will significantly aid Fort Hood and the US Army.The execution of this project will include the investigation into encapsulation methods, the testing of leaching characteristic of encapsulated chlordane, the validation of a lined MSW cell and leachate monitoring as an acceptable location, and the final disposition of a household hazardous waste. To accomplish this Fort Hood must first secure TCEQ’s approval to conduct this test. The objective of the testing was to show that chlordane contaminated soil treated with Soil Sement® polymer emulsion would not leach the pesticide.
Chemical Structure of Chlordane (C10H6Cl8)
Chlordane is a man made pesticide approved for use by the EPA from 1948 until its ban in the United States in 1988. Before 1978 chlordane was used as a pesticide in agricultural crops, lawns and gardens as a fumigating agent. Concerned over cancer risks and evidence of human exposure, persistence in the environment and danger to wildlife the EPA phase out above ground use of chlordane. From 1983 until 1988 chlordane was approved for use to control termites in homes and was only applied underground to foundations. Today chlordane is not used in the United States; however, because of the chemical’s persistence it remains in the environment and a human health concern. Chemically, chlordane is a chlorinated cyclodiene with chemical formula C10H6Cl8.Technical chlordane is not a single chemical, but a mixture of over 140 chemicals.Major components are trans-chlordane (also know as gamma-chlordane or beta chlordane), cis-chlordane (also know as alpha-chlordane), beta-chlordane, heptachlor and trans-nonachlor. Because technical chlordane contains so many chemicals it is difficult to specify some chemical and physical properties. Technical chlordane is clear to amber colored viscous liquid.The volatility changes over time as the more volatile components are removed. Chlordane is not soluble in water; however is miscible in aliphatic and aromatic hydrocarbon solvents. Chlordane looses it chlorine in alkaline solvents.When applied in the environment, specifically soil, about half of the chlordane evaporates in two to three days. The remaining chlordane is very persistent and may remain in the soil for as long as 20 years.Chlordane attaches strongly to soil particles and is unlikely to leach into ground water. One study by the California Department of Food and Agriculture classified chlordane as a “nonleacher” based on records of groundwater contamination after normal agricultural use. Persistence is greater in heavy, clayey or organic soils than in sandy soils due to increased evaporation in sandy soils. Studies indicate that technical chlordane degrades very slowly in water and does not degrade in anaerobic conditions.C hlordane breaks down in the atmosphere by reacting with light and other chemicals. Chemical persistence of chlordane in soil causes human health concerns, particularly for children that play around homes that were treated with the pesticide. Everyone in the United States has been exposed to chlordane, either due to prior agricultural use and subsequent absorption by current food crops or primarily through contact with soils around homes. Exposure occurs through skin contact, inhalation or ingestion, where it remains in body fat until it is released to other parts of the body. The nervous system, digestive system and liver can be affected by chlordane exposure in humans.
There is a great need to minimize human exposure to chlordane and use of contaminated soil as a daily cover in a control landfill will fulfill that need. Chlordane is not water-soluble and is not expected to leach into groundwater. However, should the chemical leach it will be collected, monitored, detected and remediated as needed in the landfill. There is no possibility of this sort of control in a home setting. Waste regulations dictate that only non-hazardous material may be put or used in a municipal waste landfill. The purpose of this experiment is to prove that the chlordane contaminated soil on the base at Fort Hood can be used, with encapsulation treatment by Soil Sement®, as a daily cover on the Fort Hood municipal solid waste landfill.
Waste regulation historically utilizes EPA 1311, TCLP (Toxicity Characteristic Leaching Procedure) testing as measure for acceptability for disposal in non-hazardous landfills.TCLP is an agitated extraction test that was designed to reach steady state, acidic conditions as quickly as possible. It is a snapshot of conditions that prompt leaching of hazardous compounds of concern in landfill conditions. The pH of the extraction fluid is slightly acidic in an attempt to simulate landfill conditions.
The Texas Department of Environmental Quality (TDEQ) offered their experience and guidance for method determination. The proposed use for the chlordane-contaminated soil is outside the scope of disposal; it will be used as daily cover on an isolated cell on Fort Hood’s municipal solid waste landfill. For this reason more stringent testing and evaluation was required to prove that chlordane will not leach into groundwater. TCLP would not demonstrate the desired degree of technical assurance that chlordane would not leach from the Soil Sement® encapsulated soil into the groundwater. EPA Hazardous Regulatory Levels for chlordane are 0.6 mg/kg for total chlordane and 0.03 mg/L for TCLP chlordane. Most recent testing for total chlordane shows 4.39 mg/kg in the soil at Fort Hood, making it a hazardous waste. Testing needed to demonstrate that although the total chlordane was above regulatory levels it would not leach and that best control technologies utilizing Soil Sement® for encapsulation would render the soil non-hazardous by EPA TCLP regulatory standards.
Testing should show Soil Sement® would encapsulate the chlordane in the soil for a long period of time in landfill conditions. This necessitated a test method that would repeatedly “attack” the integrity of encapsulation under long term landfill conditions. EPA 1320, Multiple Extraction Procedure (MEP), was recommended by TCEQ. MEP was designed to simulate the leaching that a waste will undergo from repetitive precipitation of acid rain on an improperly designed or constructed sanitary landfill. Repetitive insults of the waste to “acid rain” reagent show the highest concentration of the test constituents (chlordane in our test) that could potentially leach in a natural environment.
MEP is a serial batch extraction test that subjects the waste to successive batches of fresh acidic buffer (pH 3.0 + 0.2). A sample of waste is first subject to extraction with deionized water and separated from the leachate (extract). Extraction consists of placing a know weight of waste in a tumbling vessel with a specified volume of acid rain buffered water. The pH is recorded and the sample is tumbled at room temperature for 18 hours. The pH is once again recorded at the conclusion of the extraction procedure. Standard laboratory separation procedures are used to isolate the extract from the waste. The leachate is analyzed for the desired constituent (s). The waste sample remains in the extraction vessel where it is subjected to nine (9) turns of synthetic acid rain extraction.At the conclusion of each turn the waste is separated from the leachate and the leachate tested for desired constituent(s).
Because Fort Hood samples showed only two instances where chlordane was detected in the leachate, TCEQ requested that at the conclusion of the tenth turn of the MEP, TCLP utilizing the slightly higher pH buffer be run on the waste sample. The procedure of TCLP is the same as a single turn of MEP except for the change in extraction fluid.
A composite sample of the chlordane contaminated soil stockpiled on the property of Fort Hood in Texas was tested for total chlordane, treated with various levels of Soil Sement® and extraction procedures were used to determine the leaching characteristics of the chlordane. Samples of untreated and treated Fort Hood soil had to be prepared prior to extraction testing.A composite sample of soil was retrieved from the chlordane contaminated soil pile by Fort Hood personnel and shipped to Midwest Industrial Supply, Inc. The unaltered soil was sent to Tri-State Laboratories for total chlordane testing. Results showed total chlordane at 4.39 mg/kg. Once an above regulatory level of chlordane was established for the soil, test samples were prepared in the Midwest lab.
Three Soil Sement® application rates were used for testing:
- Sample A prepared at 7.2 gal. Soil Sement® per yd3
- Sample B prepared at 4.0 gal Soil Sement® per yd3
- Sample C prepared at 27.0 gal Soil Sement® per yd3
Sample A rate represents the rate proposed for use at the Fort Hood Site.Sample B rate was used to bracket a possible low end point and Sample C rate was the application rate used in the initial leachate testing performed by Fort Hood personnel to establish the viability of this project.
Fort Hood soil was blended with the appropriate amount of Soil Sement® concentrate and water, this method simulates the proposed application method of “mix and blend” proposed for the Fort Hood application. Samples were compacted and allowed to dry in laboratory conditions (approximately 680F) for 4 days before taking to Tri-State Laboratories for leachate testing. Samples were not crushed, but left intact for leachate testing. It should be noted that the vigorous tumbling broke the samples into small particles during the first rotation. Vacuum filtration was required indicating very small silt / clay size particles were produced.
Seven samples were tested corresponding to the following TSL ID #:
- 25030821Untreated control
- 25030822Sample rate A
- 25030823Sample rate A, spike
- 25030824Sample rate B
- 25030825Sample rate B, spike
- 25030826Sample rate C
- 25030827 Sample rate C, spike
A total of 11 extraction rotations were preformed on all of the samples.The first 10 extractions were preformed per EPA method 1320, Multiple Extraction Procedure. The final extraction was performed per EPA 1311, (TCLP) Toxicity Characteristic Leaching Procedure. The basic mechanics of all of the extractions was the same; the pH of the extraction fluid (buffer) was the relevant difference between the first extraction, the next 9 extractions and the final TCLP extraction. Method 1320 specifies that the first extraction be performed using deionized water and that the initial pH of the sample is recorded and the final pH of the sample be recorded before the addition of the acid rain buffer. The pH is reflective of the test sample pH, not reflective of the buffering solution conditions. The purpose of the extraction is to simulate acid rain on an “improperly constructed landfill”, irrelevant of the pH of the system. The Fort Hood sample pH indicates a slightly basic soil pH.Method 1311, TCLP, specifies that the extraction be forced to an acidic environment. The Fort Hood sample required the use of extraction Fluid II with the sample being forced to a pH of 5. This is reflected in the initial and final pH of the extraction fluid.
Chlordane was detected only in the untreated control sample and the sample treated at Rate B “spiked” with chlordane. These results indicate chlordane is available in the soil samples, for low levels of leaching. The use of a control sample as well as multiple “spiked” samples demonstrates the validity of the method for the leaching and detection of chlordane. Chlordane was not detected in any of the un-spiked treated samples, further indicating the efficacy of Soil Sement® encapsulation of pesticide contaminated soil.
Soil Sement® effectively encapsulates chlordane in the soil obtained from Fort Hood. Acrylic and polyvinyl acetate polymers are used in the formulation of Soil Sement®. These plastics have a long history of persistence in landfill conditions; in fact the lack of degradation of plastics in landfills has prompted EPA plastics recycling programs. Biodegradation of the polymers in Soil Sement® require oxygen and ultraviolet exposure, neither of which will be available in this application as a daily cover in the landfill.Landfills are in essence a “tomb” for materials, preserving or “mummifying” wastes for decades. Excavation of decades old landfills has uncovered intact newspapers from 35 years ago as well as 10-year-old carrots and 15-year-old corn! Degradation in landfills is anaerobic and the polymers in Soil Sement® do not degrade anaerobically. Plastics such as those in Soil Sement® have to be made to degrade in landfill environments by the addition of natural starch materials.
Further testimony to the environmental stability of Soil Sement® is our application history. Midwest Industrial Supply, Inc. has an over 30 year history of treating open areas for dust control and erosion as well as a reputation for effectively sealing coal piles for the minimization of moisture penetration. All of these applications require that Soil Sement® maintain integrity in extreme environmental conditions including UV exposure for up to 3 years. Granted, these applications do not require 30 years of persistence as in a landfill, but a landfill is void of the two necessary components for degradation; oxygen and ultraviolet exposure.
How do you determine biodegradation of polymers? If a chemical has any tendency to degrade it will degrade in soil. Ideal degradation testing of polymers is non-existent.The matrix interference in soil as well as monitoring complications makes testing difficult and inconclusive at best. There are four established methods for measuring polymer degradation in soil:carbon dioxide evolution, weight loss measurement, viscosity measurement and loss of tensile strength.All are difficult and severely limited in accuracy. Carbon dioxide evolution is best done with 14C labeling, but is expensive and at times unobtainable and the interpretation of carbon dioxide evolution results is complicated and ambiguous.
Results show that after 11 rotations of extractions, chlordane does not leach from the treated soil. Table A contains a summary of results.
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TABLE A: FORT HOOD SOIL ANALYSIS RESULTS | |||||||||
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Total Chlordane of Soil Sample (EPA 8081) = 4.39 mg/kg |
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Control |
Rate A |
Rate A spike |
Rate B |
Rate B spike |
Rate C |
Rate C spike | |||
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Lab ID # |
25030821 |
25030822 |
25030823 |
25030824 |
25030825 |
25030826 |
25030827 | ||
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Soil Sement Application Rate (gal/cu yd) |
Untreated |
7.2 |
7.2 |
4.0 |
4.0 |
27.0 |
27.0 | ||
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EPA 1320 Multiple Extraction Procedure; Chlordane Levels Detected (mg/L) |
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Note Detection Limit = 0.0025mg/L |
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Rotation 1 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 2 |
0.0054 |
BDL |
BDL |
BDL |
0.0026 |
BDL |
BDL | ||
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Rotation 3 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 4 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 5 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 6 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 7 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 8 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 9 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Rotation 10 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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EPA 1311 Toxicity Characteristic Leaching Procedure; Chlordane Detected (mg/L) |
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Note Detection Limit = 0.0025mg/L |
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Rotation 11 |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL |
BDL | ||
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Chlordane was detected only in the untreated control sample and the sample treated at Rate B “spiked” with chlordane. These results indicate chlordane is available in the soil samples, for low levels of leaching. The use of a control sample as well as multiple “spiked” samples demonstrates the validity of the method for the leaching and detection of chlordane. Chlordane was not detected in any of the un-spiked treated samples, further indicating the efficacy of Soil Sement® encapsulation of pesticide contaminated soil.
Based on the leaching test results, the fact that the environmental conditions are not conducive to polymer degradation, historical data from Soil Sement® applications in more severe environments, the consuming problem of persistence of plastics in landfills, the lack of a reliable test method for polymer degradation and finally a test design that eliminates potential ground or surface water exposure to leachate further evaluation of the integrity of the polymers in Soil Sement® is not warranted. Soil Sement® is an effective means for the encapsulation of chlordane in contaminated soil for use as a daily cover in a municipal waste landfill under the controlled conditions.
Once we have proven the chlordane will not leach from the encapsulated soil, our next task is to prove that Fort Hood’s municipal solid waste landfill is the ideal place for this project.Area 3 of Fort Hood’s landfill is a lined cell with a leachate collection system. If the chlordane were to leach from the soil it will be collected on the liner in the leachate sump. The leachate can then be collected and treated in accordance with proper established methods. At the time of this article publication, TCEQ and Fort Hood are discussing the application of Soil Sement® on the chlordane contaminated soil for use a daily cover on the municipal solid waste landfill.
Federal Facilities Environmental Journal / Autumn 2005, page 63-70.