[Home]
TO0019 Work Plan Addendum, SWMU B-30
December 2003
Site Description and History
SWMU B-30 was previously an at-grade limestone quarry area that was later reportedly used for disposal of miscellaneous construction debris. A field survey performed during September 1993 indicated scrap concrete, roofing shingles, and other construction waste at the site area. The approximate 0.36-acre area appears disturbed in aerial photographs dating back to 1966. The vegetation at the site consists of sparse native grasses and shrubs. In addition, the site is covered with mounds of dirt and construction debris that made access to the various sampling locations difficult during the field investigation. A tree line is present to the south of the site area, and a limestone embankment lies in the northern portion of the site. Figure B30-2 is an aerial photograph from 2003, showing the location of SWMU B-30.
Summary of Previous Investigation Results
Geophysical Survey
A 1996 EM geophysical survey of the site identified two anomalous areas. One anomaly was located just to the south of SS01, and was located near some surface concrete slabs and debris, while there was no obvious protruding waste at the second, eastern anomaly (shown in Figure B30-2). Most likely, the anomaly near SS01 is the result of metal rebar in the concrete slabs. The anomaly near SB01 may be related to subsurface waste; however, no waste was encountered in SB01.
Soil Borings
In March 2000, three surface soil samples were collected and three borings were drilled at SWMU B-30. One of the three surface soil samples (RW-B30-SS03) had constituent concentrations exceeding RRS1 criteria. Metals slightly exceeded background levels in three subsurface samples, and common laboratory contaminants methylene chloride and bis(2-ethylhexyl)phthalate exceeded RLs in five samples.
Analytical results for sample number RW-B30-SS03 reported 47.3 mg/kg copper, 86.46 mg/kg lead, and 93.2 mg/kg zinc. This sample was collected near a pile of discarded roofing shingles.
For two of the three borings, three metals were detected at concentrations slightly exceeding RRS1 standards in samples collected from the Glen Rose Limestone Formation. Sample number RW-B30-SB01 (12.5-13.0 ft bgs) had reported concentrations of barium and cadmium at 11.1 mg/kg and 0.13 mg/kg, respectively. The RRS1 standards for barium and cadmium in Glen Rose Limestone material are 10.0 mg/kg and 0.1 mg/kg, respectively. Sample number RL-B30-SB03 (2.5-3.0 ft bgs) had a reported nickel concentration of 7.9 mg/kg, slightly higher than the RRS1 standard of 6.8 mg/kg for Glen Rose Limestone.
Bis(2-ethylhexyl)phthalate and methylene chloride were the only organics exceeding RLs, and they are considered to be associated with laboratory and/or sampling equipment contamination. The low reported concentrations of these compounds, the knowledge that methylene chloride and bis(2-ethylhexyl)phthalate are common lab contaminants, and the fact that the exceedances are limited to small number of samples forms the basis of the conclusion that these compounds do not pose a concern at SWMU B-30.
Closure Plan and Sampling Recommendations
Closure of SWMU B-30 under RRS1 requires removal of waste visible on the ground surface, disposal of any buried waste, and removal of contaminated soil at the site. The waste, including roofing shingles, tiles, and construction rubble, must be removed from CSSA for off-post disposal to pursue RRS1 closure with respect to the soil unit. 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.
The anomaly located near RW-B30-SB01 should be excavated to determine if it is caused by buried waste. After waste on the ground surface has been removed from the vicinity of the western anomaly, a test pit should be excavated to confirm that there is no underlying buried waste. In addition, soil in the vicinity of RW‑B30‑SS03 and RW‑B30‑SB03 should also be excavated and disposed of.
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 B-30 is approximately 2,300 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 copper, nickel, and zinc (SW‑6010B), 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
Remove waste on ground surface of site. If practical, separate metal debris for recycling.
Excavate test pit in the vicinity of RW-B30-SB01 to determine what caused the anomaly. Excavate any waste encountered.
Excavate soils in the vicinity of RW-B30-SB03 and RW-B30-SS03, where above-background concentrations of copper, lead, and zinc were detected.
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.
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 B‑30.
Collect samples of the excavation sidewalls and bottom. Samples will be analyzed for copper, lead, nickel, and zinc; these parameters exceeded RRS1 criteria in the samples collected at the site in 2000.
Continue excavation until RRS1 soil criteria or competent bedrock, whichever comes first, is reached.
Re-grade the site with clean fill and reseed.
Validate data and prepare Closure Report for SWMU B-30.