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Final B-20 Soil Stabilization/Solidification Treatability Study Report
Section 5 - Analysis and Evaluation
Nine criteria are typically used in evaluating remediation technologies, such S/S. These evaluation criteria are as follows:
Attainment of Cleanup Standards. The ability to attain media cleanup standards set by state or federal regulations.
Protection of Human Health And Environment. Protection of human health and environment is assessed based on the overall effectiveness of the alternative to block pathways for human exposure to the contamination.
Control the Sources of Releases. The ability to stop further environmental degradation by controlling or eliminating further releases that may pose a threat to human health and/or the environment is used to define the ability to control the source of release.
Short-Term Effectiveness. Risk of short-term pollution exposure, physical injury and damage to site workers, community residents, community structures, and the greater environment during implementation is considered for the remediation technology.
Long-Term Effectiveness. The ability to protect human health and the environment over the long term. Assessment of long-term effectiveness and permanence includes the durability of actions to block pollutant pathways and the minimization of monitoring requirements.
Implementability. Site conditions, project time requirements, and service availability that effect remedial design. The complexity of land use restrictions, administrative responsibilities, regulatory approval, and long-term monitoring obligations are also considered.
Reduction of Toxicity, Mobility, and Volume. The evaluation of toxicity, mobility, and volume was based on the degree to which the metals and explosive contaminants were contained, treated, or removed from the site.
Cost. Cost estimations are based upon published cost estimation guides and engineering experience.
Compliance with Waste Management Standards. A discussion of specific waste management activities required for the remedial technology is included.
The conclusions drawn from the S/S treatability study are discussed in detail in this section. The treatability study results support the following conclusions for physical treatment techniques for CSSA soils.
Resulting S/S efforts for SWMU B-32 and B-33 were successful in treating lead contaminated soils to maximum containment level (MCL) requirements. TCLP lead results for the S/S for B-32 and B-33 were non-detects.
The soils from SWMU B-20 small arms disposal areas were not sucessfully treated to action levels. TCLP results from the S/S effort ranged from 236 mg/l to 376 mg/l.
Appropriate curing times are required to achieve MCL requirements for off-site disposal of soils within a municipal landfill.
5.2.1 Attainment of Cleanup Standards.
Cure times are critical in reducing the leaching of contaminants in solidified/stabilized samples. While the initial effort of S/S at B-32 and B-33 resulted in higher TCLP lead concentrations than the untreated soils, samples taken from the additional S/S effort with an extended cure time were below the method detection limit (MDL) and considered non-detects. The cure time was approximately 3 days for the first S/S effort and 20 days for the second effort. The pattern of insufficient cure time adversely affecting the TCLP lead results is also noticed in the B-20 stabilization samples. Both stabilization efforts of B-20 soils had a cure time of less than 3 days. As with the B-32 and B-33 samples, the TCLP lead for these samples was higher than for the untreated sample. While analyses for B-20 samples with longer cure times are not available, it may be concluded that additional cure times will reduce lead contaminant leaching. Thus, given that sufficient cure times are provided for samples, S/S is an effective method for treating soils.
Soil composition also affects the ability of S/S to reduce contaminant leaching. SWMU B-20 soils used for this stabilization study contained a high level of total lead available in the soil matrix. Analytical results received from Brice Environmental Services Corporation (Brice) while performing a treatability study on another remediation technology reveal that the small arms ammunition disposal areas contained 364,989 mg/kg of total lead, of which 258,885 mg/kg was particulate lead. These higher lead concentrations may adversely affect the S/S of the portland cement, thus reducing the effectiveness of S/S to reduce lead leaching. Another factor is the organic matter of the soil. SWMU B-32 soils contained more organic matter resulting in a more favorable condition for solidification. Therefore, while the B-20 and B-32 soils contained similar TCLP lead concentrations (21.7 mg/l and 14.4 mg/l respectively), different cure times, lead availability, and the percentage of organic matter affected the effectiveness of S/S.
While the focus of this treatability study is on the immobilization of lead contaminants, S/S is also suitable for immobilizing other metals. As stated by the EPA, �Cement solidification is most suitable for immobilizing metals because at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. [However] portland cement alone is not effective in immobilizing organics.� Implementation of S/S for the purpose of immobilizing metal contaminants other than lead will require a small treatability study.
5.2.2 Protection of Human Health and the Environment
The leaching of contaminants may be successfully reduced below detection limits using S/S. Following successful S/S, soils will be removed from the site and disposed of in a municipal landfill. Therefore, this option is protective of human health and the environment.
5.2.3 Control the Sources of Releases
Further degradation of environmental conditions following S/S is not anticipated. Excavated areas will be backfilled with clean fill.
5.2.4 Short-Term Effectiveness
S/S is a one-time operation with the stabilized soils being disposed of as non-hazardous waste within an off-site municipal landfill.
Aside from restoration activities, site conditions are not expected to change following the completion of S/S. Therefore, long-term effectiveness is equivalent to short-term effectiveness.
Implementability of S/S is considered excellent. The technology is proven and for lead-contaminated soils is considered BDAT. Successfully stabilized soils may be disposed of as non-hazardous waste at a municipal landfill following characterization.
This ex situ process does not require monitoring during treatment activities. Transportation and disposal of contaminants will require administrative support. Other administrative requirements are considered minimal.
5.2.7 Reduction of Toxicity, Mobility, and Volume
S/S reduces the toxicity and mobility of contaminated soil at the site. With the removal of contaminants from the site, the overall toxicity and volume of particulate lead will be reduced.
S/S of soils is estimated to cost $130 per cubic yard. The basis of this cost estimation as well as a cost breakdown is provided in Appendix B.
5.2.9 Compliance with Waste Management Standards
Treated waste can be disposed of in a municipal landfill if it is determined, after treatment, to have been successfully treated to below TNRCC non-hazardous levels. All waste transportation and disposal will be performed in compliance with Department of Transportation (DOT) guidelines.