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Final B-20 Soil Stabilization/Solidification Treatability Study Report
Section 3 - Treatability Study Methods
This section summarizes activities performed by Parsons ES and Eagle Construction and Environmental Services, Inc. during the treatability study. A detailed description of methods and techniques used for the study is presented in the WAP provided in Appendix A.
Solidification is used to describe treatment systems that improve waste handling, decrease the surface area across which transfer, or loss, of contained pollutants can occur, or limit the solubility or toxicity of hazardous waste constituents (EPA, 1985). Solidification typically implies encapsulation of the contaminant in a rigid or structurally sound matrix. Stabilization involves the use of materials that limit the solubility or mobility of waste constituents. Solidification and stabilization are closely related techniques for disposal of hazardous waste and are typically considered as one method.
Solidification and stabilization of hazardous materials using a portland cement mixture is a well established method of treating hazardous debris prior to land disposal. The EPA considers S/S an established treatment technology (EPA, 1995). For remediation (cleanup) sites, 29 percent of source control Records of Decision (RODs) signed from 1982 through 1994 in EPA�s Superfund program included S/S as part of the selected remedy (EPA, 1995). This makes S/S the most frequently selected technology for treating the source of contamination. In the treatment of industrial hazardous wastes, the EPA has identified S/S as BDAT for 57 RCRA listed wastes (EPA, 1993). Portland cement is proven to significantly reduce the leachability of metals, in particular lead. A study prepared for the EPA compared different techniques for the S/S of contaminated soils. The study concluded that when the appropriate immobilization agent is used, �S/S can reduce the leachability of many metals to near the normal detection limits�as determined by the TCLP.� Additionally, The S/S comparative study found that there are no definitive contaminant restrictions for portland cement.
Portland cement alone accomplishes treatment objectives to a high degree in many instances. However, some situations (because of the waste characteristics, disposal scenario, and/or regulatory requirements) require the use of additives or physical/chemical techniques to provide improved properties in the waste form or to counter problems in solidification caused by the waste itself. Methods implemented for the S/S effort were in compliance with the WAP provided in Appendix A and in Volume 4-1 of the CSSA Environmental Encyclopedia in the RL33 Addendum section to the Field Sampling Plan.
During April and May 1999, soils treatability study efforts were accomplished at SWMUs B-20, B-32, B-33 prior to disposal. The purpose of this study is to determine the effectiveness of S/S and its applicability to other sites at CSSA.
In order to gauge the effectiveness of stabilization of B-20, B-32, and B-33, and soils, TCLP lead and total explosives analysis was performed on both untreated and stabilized soils. Untreated B-32 and B-33 soil samples were collected on April 14, 1999. These samples were sent to an independent laboratory (Emax Laboratories, Torrance, CA) for analysis. Analytical results obtained from previous investigations were used as a basis of comparison for B-20 soils.
SWMUs B-32 and B-33 Soil Stabilization
On April 27, Parsons ES stabilized small samples of contaminated B-32 and B-33 soil samples. Soils were stabilized in 8 oz. glass jars using a mixture of 86 percent by weight soil, 14 percent by weight portland cement, and 80 ml of water. Samples were analyzed by Emax Laboratories.
Following stabilization of the 80 oz. samples, large batch stabilization efforts began. For each stabilization batch, Eagle placed 10 cubic yards of contaminated soil in roll-off boxes, then mixed in approximately 37 bags of portland cement and 650 gallons of water with a trackhoe. Stabilized soils then either remained in roll-off boxes or placed on a plastic liner and covered with a plastic liner to allow to cure. In order to profile the stabilized waste from B-32 and B-33 soils, four additional samples from B‑33 and two additional samples from B-32 were analyzed for TCLP lead on May 3, 1999. Additional samples were collected from this stabilization effort on May 23, 1999 in order to test any variations in analytical data resulting from increased sample cure times.
SWMU B-20 Soil Stabilization
On April 14, 1999, 8 ounce B‑20 soil samples were collected by Parsons ES and sent to Eagle for stabilization. Due to sample integrity and shipment errors, an additional 8 ounce sample was stabilized and analyzed for TCLP lead on April 27, 1999. The soil was stabilized in the same manner as discussed for the B-32 and B-33 stabilization effort in 8 oz. jars. Batch stabilization of B-20 soils did not occur. Cure times for both B-20 S/S efforts are estimated to be less than 3 days.
3.4 - Treatability Study Analysis
All samples were analyzed using EPA SW-846 methods for lead (SW7421) and explosives (SW8330) and TCLP extraction method (SW1311) by Emax Laboratories. All analytical techniques followed procedures described in Test Methods for Evaluating Solid Waste, U.S. Environmental Protection Agency, SW-846.
Samples were collected at SWMUs B-32 and B-33 before and after stabilization. Due to TNRCC�s scheduled requirements Parsons ES was unable to subcontract a laboratory capable of meeting project CSSA and AFCEE Quality Assurance Project Plan (QAPP) requirements in a timely manner. Therefore the data packages were validated using Contract Laboratory Procedures (CLP) guidelines. The data validation report is in Appendix C of this document.