[SWMU Bldg. 43]

SWMU Building 43

TO0019 Work Plan Addendum, December 2003

Site Description and History

SWMU Building 43 was previously used as a makeshift ammunition demolition facility (Figure Building 43-2).  The site includes a small building and the surrounding area.  The building is a three-walled structure made of cinder blocks.  A small brick and steel burn area is located at the back of the building.  The building dimensions are approximately 10 ft by 10 ft.  Miscellaneous solid waste and ammunition were burned inside the burn box.  Metal debris, shotgun shells, and casings are scattered across the ground surface of the site.  Large sections of the site are covered in molten conglomerations of bullets, spent casings, and other unidentified metal pieces.  One large section of debris leads away from the back of the building towards the western edge of the site.  Another section was located near the trees at the northern edge of the site.  Additional scattered metal pieces surround the building.

Summary of Previous Investigation Results

Geophysical Survey

In 1996, a geophysical survey was conducted at SWMU Building 43.  No geophysical anomalies, aside from the anomaly caused by the building itself, were detected at the site.

Unexploded Ordnance Sweep

In August 1997, SWMU Building 43 was swept for UXO.  A small amount of ammunition-related debris was found and removed.  However, no UXO was found and none is thought to exist in the vicinity of SWMU Building 43.

Soil Gas Survey

In 1995, a soil gas survey was conducted in the large area between SWMUs B-3 and B-4.  A small number of these points were located in the vicinity of SWMU Building 43.  Because the 1995 soil gas survey had PCE detections at low levels (up to 0.43 μg/L) in the area around Building 43, a soil gas survey focusing on the SWMU Building 43 area was conducted in August 1996.

The 1996 soil gas survey had detections of PCE at concentrations ranging from 0.04 μg/L to 1.0 μg/L.  TCE was detected at one point, at a concentration of 0.04 μg/L.   Due to the very low concentrations of VOCs detected in soil gas, the proximity of the groundwater PCE plume associated with neighboring SWMUs B-3 and O-1, and the lack of PCE or TCE detections in soil samples collected at the site, these low VOC concentrations detected in soil gas at SWMU Building 43 are presumed to be associated with groundwater contamination in the vicinity of Well CS-MW16.  No point source for these COCs within SWMU Building 43 could be identified.

Surface Soil Samples and Soil Borings

Six borings were advanced at SWMU Building 43 in February and March 2000.  Samples were analyzed for VOCs, SVOCs, explosives, and metals.  No VOCs, SVOCs, or explosives were detected above RLs.  However, arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc levels in surface soil exceeded CSSA background criteria.  The RFI results indicate that only surface soil is impacted.

In March 2003, ten additional surface soil samples were collected to further define the horizontal extent of soils contamination.  The presence of metals (barium, cadmium, copper, lead, mercury, and zinc) in the topmost foot of soil throughout the site was identified at concentrations exceeding the applicable RRS1 closure standards.  The lateral extent of the metals contamination in surface soil has not been fully defined, although it appears that barium, copper, zinc, and lead concentrations decrease to the east and south of the site.  Mercury, however, appears in the eastern and southeastern portions of the site in concentrations above RRS1 closure standards.  Subsurface samples indicate that metals contamination is limited to surface soils.

Laboratory analyses of swipe samples from charred surfaces within Building 43 found no dioxin or furans in concentrations above RRS1 closure standards.

Closure Plan and Sampling Recommendations

Since the horizontal extent of excavation is not completely defined, additional sampling will be needed.  If the horizontal extent remains its current size and soil from the top foot of soil is to be excavated, approximately 250 CY of material will be removed.  Verification soil samples will be collected outside the excavated area and analyzed for arsenic (SW-7060A); cadmium (SW-7131A); barium, chromium, copper, nickel and zinc (SW-6010B); mercury (SW-7471A); and lead (SW-7421).  Waste characterization samples will be collected from the stockpiled waste and analyzed for TCLP metals.

Closure of SWMU Bldg 43 under RRS1 requires removal of waste and contaminated soil at the site.  To accomplish this removal, Building 43 must be removed, following required coordination and approval from the Texas Historical Commission.  Groundwater and competent bedrock will be addressed as part of the groundwater operable unit.  The soil excavation will extend to the depth that waste or waste residue is encountered or to bedrock, whichever comes first.

Excavated material should be characterized with TPH and TCLP metals (Texas Eleven) analyses prior to disposal.  The estimated volume of waste material and waste residue present at SWMU Bldg 43 is approximately 250 CY.  Based on waste at most other SWMUs at CSSA, it is likely that this waste is non-hazardous.

Confirmation samples will be collected following removal/remediation to verify that no contamination remains.  Analysis should include arsenic (SW-7060A); cadmium (SW-7131A); barium, chromium, copper, nickel and zinc (SW-6010B); mercury (SW‑7471A); and lead (SW-7421), based on results of the historic sample analyses.  Samples will be collected at a frequency of one per 100 linear ft of sidewall, with a minimum of one sample per wall.  If the bottom of the excavation is bedrock, bottom samples will be collected at a frequency of one per 20,000 ft2 of bottom surface, with a minimum of two per excavation area.  If the bottom of the excavation is soil, bottom samples will be collected at a frequency of one per 100 ft (100-ft grids).

Following excavation of waste and waste residue, any resulting trenches will be backfilled with clean fill and the site restored.

Summary Of Planned Work

  1. Remove waste on ground surface of site.  If practical, separate metal debris for recycling.

  2. Excavate soils around Building 43 and in the surrounding area where above-background concentrations of arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel and zinc were detected.

  3. Collect samples of excavated soils for waste characterization purposes.  One composite sample consisting of five aliquots will be collected per 1,000 CY of soil.  Analyze samples for TPH and TCLP antimony, arsenic, barium, beryllium, cadmium, chromium, lead, mercury, nickel, selenium, and silver.

  4. Dispose of all waste and soils containing metals concentrations above CSSA background levels at Covel Gardens Landfill under waste profile CG-25591.  This profile will be amended to include waste from SWMU Building 43.

  5. Collect samples of the excavation sidewalls and bottom.  Samples will be analyzed for arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel and zinc; these parameters exceeded RRS1 criteria in the samples collected at the site in 2000 and 2003.

  6. Continue excavation until RRS1 soil criteria or competent bedrock, whichever comes first, is reached.

  7. Re-grade the site with clean fill and reseed.

  8. Validate data and prepare Closure Report for SWMU Building 43.