May 2000

Soils: Tarrant Association (gently undulating).

Known: Historically used as an area to burn classified documents and other trash from CSSA. Approximately 1.2 acres in size, SWMU B-4 is located approximately 50 feet southeast of SWMU O-1. Three trenches have been identified at the site.

Previous Investigations: Under Order 67, available records at CSSA were reviewed for an evaluation of potential groundwater contamination sources. Six geophysical anomalies were observed during an EM geophysical survey (2 February 1995) and the area was labeled as SWMU B-4. A GPR survey was completed on 15 and 16 February 1995, and the results confirmed the identification of at least three trenches. Due to the size of the area, the three trenches were identified as SWMU B-4. The other three anomalies were labeled as SWMU-B4A, and eventually have been relabeled as AOC 52.

Also under Order 67, six soil borings were completed between 10 and 14 March 1995. Waste material found in the borings included coal, fibrous material, nails, a piece of non-oxidized metal, rusted hinges, wire, screen and charred material. No ordnance was observed in the borings. Soil/rock samples were collected during drilling activities, and one groundwater sample was collected from SB5 on 15 March 1995. Cadmium, chromium, copper, lead, and nickel were all detected in the soil/rock samples above background criteria. No metals were detected above background criteria in the groundwater sample. Results are summarized in Table B4-1 and Table B4-2.

Two phases of soil gas surveys were completed during July and November 1995. PCE was observed on 13 and 14 July 1995 in the area that borders SWMU O-1. PCE was detected at concentrations less than 1 µg/L in November 1995.

Data Needs: Phase II RCRA Facility Investigation required at this site. Analytical data, including groundwater and subsurface soils/rock analyzed for VOCs, SVOCs, explosives, and metals, are needed for verification and clarification of previous data.

Rationale for Analytical Program: Based on previous analytical results and prior use, the chemicals of potential concern include VOCs, SVOCs and metals. No VOCs or SVOCs were detected in soil samples in March 1995; but PCE in soil gas was detected in areas bordering SWMU O-1 in 1995. Cadmium, chromium, copper, lead and nickel were all detected in soil samples above background levels in 1995. Therefore, VOCs, SVOCs, and metals analysis are part of the analytical program for this site.

Closure Activities: The following activities constitute an additional investigation at SWMU B-4:

1. Twelve soil borings will be advanced to further characterize the surface and subsurface soils surrounding the area. Five soil borings will be completed within Trench 1, four soil borings will be completed within Trench 2, and three soil borings will be completed in Trench 3. Approximate locations of the 12 borings are shown on Figure B4-1. Four soil/rock samples will be collected from each boring; one at the surface (6 inches below ground surface), one at a depth of five feet, one at a depth of 10 feet, and one from the underlying limestone bedrock. If the rock cores need to be broken to fit into the sample jars, then a stainless steel trowel will be used as a pick to break the rock cores. Each boring will be advanced up to five feet into the limestone bedrock. The total depth of each boring will be approximately 15 feet. Each sample will be analyzed for VOCs, SVOCs, explosives, and metals. When possible, samples for VOC analysis will be collected using brass rings inside the split spoon. QA/QC samples will be collected as described in Section 2.4 of the FSP.

2. If water is discovered in the soil borings, up to one boring per trench will be completed as a groundwater monitoring well as detailed in Section 2.4.1 of the Work Plan Overview. Groundwater will be sampled, where present, and each sample will be analyzed for VOCs, SVOCs, explosives, and metals. QA/QC samples will be collected as described in Section 2.4 of the FSP.

3. The locations of the soil borings will be recorded using a GPS unit.

4. IDW will be handled as specified in the FSP.

5. If the results of the above work indicate that the site can be closed under RRS1 without further investigation and/or remediation, a technical/closure report will be prepared and submitted in accordance with TNRCC closure requirements. If the site does not meet RRS1 closure requirement, a technical report describing the results of the investigation and recommended additional investigation and/or remediation will be prepared.