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Investigations at several low, medium, and high priority SWMUs at CSSA are currently taking place as described in Sections 1 through 4 of this work plan. This addendum is added as Section 5 to the work plan. The units in the original work plan (Sections 1 through 4) are listed in Table 5.1.

This addendum (Section 5 only) describes investigations and closure activities to be carried out at four additional high priority SWMUs (B-20, B-24, B-28, and the demolition dud (DD) area), investigations/closure activities at one additional medium priority SWMU (B-21), as well as additional actions which will be taken at four medium priority SWMUs listed above (B-8, B-31, B-32, and B-33). The locations of these sites are shown in Figure 5.1. A brief description of each of the sites addressed in this amendment is provided in Table 5.2.

This document was prepared by Parsons Engineering Science (Parsons ES) for CSSA under the U.S. Air Force Air Mobility Command (HQ AMC) Contract F11623-94-D-0024, delivery order RL33, dated September 30, 1996 and modified June 27, 1997. This section is an amendment to the RL17 work plan (Sections 1 through 4). It describes the scope of investigation and closure activities at the additional SWMUs.

5.1 - Description of RL33 Study

5.1.1   Purpose

The objectives of the work at the nine SWMUs (B-8, B-20, B-21, B-24, B-28, DD area, B-31, B-32, and B-33) are similar to the objectives listed in Section 1. In short, the overall objectives are to collect sufficient data to determine if each of these sites can be closed; and if they can, to close them. Since the four additional high priority SWMUs (B-20, B-24, B-28, and DD area) and B-8 potentially contain UXO, there will be the added dimension of UXO removal at these sites. Once the UXO has been removed, the closure potential of each SWMU will be assessed with regards to closure standards of 30 TAC 335 Subchapter S. Then, if the SWMUs meet RRS1 closure requirements, an effort will be made to obtain certified closure from the TNRCC. A detailed description of the closure standards and their associated requirements is provided in Section 2.2.

5.1.2   Scope of RL33 Work

This amendment describes the following tasks:

It should be noted that some of these tasks have already been initiated. UXO and scrap metal removal at B-20 commenced in November 1994, and continued until soil sifting operations were completed in March 1997. UXO removal at B-24, B-28, and the DD area were completed in September 1997.

5.2 - Rationale and Methodology

The following sections describe the rationale and methodology of the additional field actions at sites B-8, B-31, B-32, B-33, as well as the actions at B-20, B-21, B-24, B-28, and the DD area.

Sections 2.3.1 through 2.3.10 include a general description of the field investigation. Field activities not described in Section 2, including soil sifting and shot and sand removal, have been added.

5.2.1   Field Efforts

The field efforts to be conducted at the nine sites addressed in this amendment are summarized in Table 5.3.

5.2.2   Field Sampling

The procedures for field sampling will follow those described in Section 2 and the FSP (Parsons ES, 1996a). Media to be sampled include those listed in Table 5.4.

The number of samples to be collected at each site is described in the site-by-site descriptions. Sample collection and handling techniques will follow the Sampling Analysis Plan (SAP) for SWMU Closures at Camp Stanley Storage Activity (Parsons ES, 1996a). Analytical techniques will follow procedures described in Test Methods for Evaluating Solid Waste, U.S. Environmental Protection Agency, SW-846 and Version 1.1 of the HQ AFCEE QAPP (AFCEE, 1996).

As described in the Amendment to Project Plans for Remedial Investigation at B-20 Former Open Burn/Open Detonation Area (Parsons ES, 1997a), four types of field quality control (QC) samples will be collected during the investigative effort. QC samples to be collected include equipment blanks, field duplicate samples, trip blanks, and matrix spike/matrix spike duplicate (MS/MSD) samples. Sample descriptions, identifications, and frequencies required are described in detail in the SAP (Parsons ES, 1996a).

5.2.3   Soil/Rock Borings

Soil borings will tentatively be drilled at site B-24 and the DD area. (Soil borings were previously drilled and sampled at B-8, B-20, B-28, B-31, B-32, and B-33.) If trench and sifted soil sampling indicates that contaminants exceed RRS1 or RRS2 (depending on the closure standard to be pursued) at B-24 and the DD area, borings will be drilled to determine the extent of contamination. The number and tentative locations of borings planned for these sites are shown in the site by site descriptions.

Total boring depth will be at least 5 feet deeper than the deepest extent of known waste management activities. Based on known information at these sites, depths are not expected to exceed 20 feet.

5.2.4   Groundwater Sampling

In the event that groundwater is encountered in shallow borings and contamination is detected at the unsaturated-saturated interface through laboratory analysis, a minimum of three borings will be completed as groundwater monitoring wells within each such investigated SWMU. CSSA and AFCEE concurrence for sampling groundwater will be obtained in the event surface contamination exists, but the unsaturated-saturated interface is not contaminated. The proper techniques for installation and development of monitoring wells, purging and sampling groundwater, and specific chemical analyses to be performed are outlined in the SAP.

5.2.5   Soil Sifting

As described previously, soil sifting is necessary at B-8, B-20, B-24, B-28, and the DD area to remove UXO and scrap metal. Sifting has already been accomplished at B-20, B-28, and the DD area. Sifting at B-20 was conducted in April and May 1997, at B-28 in June and July 1997, and at the DD area in May 1997. The procedures followed during the B-20 sifting operations are described in detail in the Soil Sifting Technical Approach. The general approach for sifting at the other sites is described below.

1. The waste materials and the soil matrix will be removed from the trench(es) at each of the sites and stockpiled within the site boundary for sifting operations. Trenches at B-8, B-24, and B-28 were identified during previous investigations via geophysical surveys. The trench at the DD area was identified during surface UXO identification activities in March 1997.

2. Soils and waste materials will be placed on a conveyor belt which feeds into a sifter. The sifter will remove all debris and rocks greater than 1 inch in diameter. This size screen will ensure removal of the smallest UXO items (20 millimeter projectiles) found at these sites.

3. Soil samples for chemical analysis will be collected from sifted soils at a frequency of one sample per 500 yd³. Samples will be analyzed for potential contaminants of concern (identified for each site in the site by site descriptions).

4. Soils which are below background levels, identified through lab analysis, will be replaced within the areas that they were taken from.

5. Soils which are above established background levels will be left on the surface for future remediation or disposal.

5.2.6   Shot and Sand Removal

Shot and sand possibly containing lead at B-32 and B-33 will be removed, stabilized, and properly characterized in a manner that complies with 30 TAC 335 Subchapter R requirements. Although shot removal was also planned for B-31, it was determined during recent work that no shot or lead-contaminated sand actually exist there. Furthermore, a bench-scale stabilization treatability study conducted using 5-gallon samples from B-20, B-32, and B-33 indicated that stabilization using the procedures described here did not successfully reduce leachable lead concentration to nonhazardous levels.

The shot soils and sand to be removed and included in the stabilization and disposal efforts are contaminated primarily with lead; however, other metals/contaminants may be present. Results of ongoing investigations will be utilized in determining the contaminants of concern for all disposal efforts. The anticipated disposal material will be sampled for proper waste characterization in accordance with TNRCC requirements. The Waste Disposal Technical Approach (Waste Analysis Plan) is included as Appendix C. Waste stabilization and transport to a disposal facility will be carried out by Eagle Construction and Environmental Services, Inc. A standard operating procedure (SOP) for the stabilization of soils from Eagle Construction and Environmental Services, Inc. is included as Appendix D.

The general approach which will be taken for completing the stabilization and disposal task is described in detail below.

1. Stabilization of waste material will be accomplished by mixing the soil/sand material with Portland cement, at a 14% by weight ratio, and water. The materials will be mixed in a 20-cubic yard container. After the material has been sufficiently mixed, it will be removed and placed on plastic sheeting at an appropriate location within the SWMU boundary.

2. After the ammunition and sand have been excavated for stabilization, soils from underneath that material will be overexcavated and stockpiled for disposal. At least one sample will be collected from the overexcavated soils to characterize for disposal; however, stabilization is not anticipated to be necessary. The extent of overexcavation to be conducted will be estimated using a LeadCheckâ soil field test kit, which is capable of detecting lead at 400 mg/kg or greater. These results will only be used qualitatively. Quantitative results will be obtained for each site as described in items 3 and 4 below.

3. Samples of the bottom of the trenches will be collected at a rate of one per 100 linear feet and analyzed to determine if all of the contaminated material has been removed. Analytical methods to be used at each site are described in the site by site descriptions. Previous investigation results will be used to identify contaminants of concern.

4. In general, soils that are stabilized will be sampled at a frequency of one per batch, with each batch consisting of approximately 20 yd³. Overexcavated soils which are not stabilized will be sampled at a maximum frequency of one per 50 yd³ or a minimum frequency of one per 500 yd³. All material intended for disposal will be properly characterized, per 30 TAC 335 Subchapter R requirements. Previous investigation results will be used to identify contaminants of concern.

5. Overexcavation and stockpiling at the ammunition disposal areas will continue until contaminant levels reach RRS1 criteria. When chemical levels reach RRS1 criteria or below, overexcavation will be considered to be complete.

Table 5.5 identifies the estimated volume of soil excavated from each of the SWMUs.

5.3 - Solid Waste Management Unit Closure Activities

Additional activities will be carried out at the SWMUs shown in Figure 5.1. Work in addition to that described in Sections 1 through 4 will be carried out at SWMUs B-8, B-31, B-32, and B-33. Work will also be conducted at B-20/21, B-24, B-28, and the DD area. All data collection activities will follow appropriate procedures noted in the SAP. Known information and expected activities at these units are summarized in the site by site descriptions.

The field activities described in Section 2.4.1, with the exception of reviewing historical records, conducting geophysical surveys, and conducting soil gas surveys, will be carried out during the additional investigations. In addition, soil sifting and removal of shot and sand will be carried out. A thorough description of these activities is included the B-20 Soil Sifting Technical Approach, the Waste Disposal Technical Approach, and the waste disposal subcontractors SOPs. Health and safety concerns are addressed in the amendment to the project Health and Safety Plan.

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