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[SWMU B-32]

SWMU B-32 Work Plan Addendum
RL33 Project, March 1998

Known (Updated): Approximately 90 feet of active sanitary sewer pipe (4-inch PVC) west and north of Building 2 (Fire House) is bedded in lead-contaminated sand containing shot which was generated at the Building 90 test firing room. It is estimated that the bedding extends to a depth of approximately 3 feet and is approximately 2 feet wide. The B-32 unit consists of the bedding material only.

Previous Investigations (Updated): Surface soil and subsurface soil samples were collected at B-32 in March and August 1996, respectively. Sample locations are shown in Figure B32-1. Analytical results are in question due to ITS Laboratory’s practices.

Data Needs: As mentioned previously, the extent of pipe bedding that consists of shot and lead-contaminated sand needed to be determined, and the shot and associated contaminated material needed to be remediated. It is estimated that approximately 36 cubic yards of contaminated material must be remediated. It is planned that excavated material will be characterized and disposed of, as described in the waste analysis plan.

Closure Activities: Shot and lead-contaminated sand making up the pipe bedding at B-32 was excavated, and will be characterized and disposed of. Specific activities are described in detail below.

1. CSSA personnel diverted the sanitary line to allow excavation underneath the pipe.

2. Shot and lead-contaminated sand was removed with a backhoe and manually with a shovel where necessary. Materials were placed on plastic sheeting, bermed, and covered for later disposal.

3. A LeadCheck^® field test kit was used to determine if elevated lead levels occur in the underlying soil. The test kit can only identify lead in soil at concentrations of 400 mg/kg or greater; therefore, samples for laboratory analysis were also collected. The field test kit was used solely as a rough field check to determine if additional contaminated soil needed to be removed. The contaminated soil will be removed until the field test kit indicated that additional excavation is not necessary. The target cleanup levels are the background values for the Crawford and Bexar stony soils.

4. CSSA personnel will backfill the trench with clean fill sand.

5. To determine if all shot and lead-contaminated soils have been removed, confirmation soil samples will be collected at a rate of approximately one per 40 linear feet of pipe bedding. These samples were analyzed for the metals listed in the table below. In addition, the sample collected near B32-SS3 was also analyzed for explosives compounds (SW-8330), since this is the location that 2,6-DNT was detected during previous investigations.

The methods to be used to stabilize the waste prior to disposal are described in the Waste Analysis Plan.