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[SWMU B-31]

Known (Updated): Approximately 650 feet of active sanitary sewer pipe (8-inch PVC) east of Building 92 (Figure B31-1) were thought to have been 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-31 unit consists of the bedding material only.

Excavation was conducted at the site with the intention of removing all of the shot and associated contaminated soils from the ground. Seven test pits were dug to determine where along the line the lead-contaminated sand and shot were believed to be located. These test pits (T1 through T7) were each approximately 6 feet deep, 10 feet long and 5 feet across. The pits are approximately 100 feet apart. No lead-contaminated sand or shot was encountered.

Previous Investigations (Updated): Surface soil and subsurface soil samples were collected at B-31 in 1996 and 1997 at locations shown in Figure B31-1. However, these data are in question due to ITS’ questionable laboratory practices.

Data Needs: As described above, the extent of pipe bedding consisting of shot with lead material, if any, needed to be determined. In July 1997, it was found that no shot with lead material was used along this portion of the sewage line.

Closure Activities: Excavations were made to determine the extent of pipe bedding made up of shot and lead-contaminated sand; none was found. Confirmation sampling was recently conducted also. The activities that were conducted are as follows:

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

2. A total of seven test pits were dug along the line to identify which portion of the line had shot and lead-contaminated sand bedding. No shot with lead-contaminated sand was identified.

3. A LeadCheck® field test kit was used to determine if elevated lead levels occur in the underlying soil. This test kit was used solely as a field aid for determining if any of the potentially contaminated material existed. Analytical samples for laboratory analysis were collected as described in item 5 below.

4. Since the line is active, the trench was filled back in quickly to prevent pipe damage. CSSA personnel will backfill the trench with clean fill.

5. To verify that no shot and lead-contaminated soils had been used, confirmation soil samples were collected at a rate of one per test pit. Each test pit measures approximately 10 feet long by 5 feet across by 6 feet deep, and they are approximately 100 feet apart. These samples were analyzed for copper, lead, and zinc using methods listed in the table below. These metals were the contaminants identified during the previous phase of work as exceeding background levels. Results are pending.