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Area of Concern 62

RFI Work Plan Addendum

Soils: Trinity and Frio soils.

Known: The site is located south SWMU B-28, north of AOC 42, east of Salado Creek and west of monitoring well MW-2. The site was identified during geophysical survey activities, and is approximately 0.4 acres in size.

Previous Investigations: Under Order 67, records were reviewed at CSSA during a preliminary evaluation for groundwater investigation. A geophysical survey was conducted in May 1995 at all the “open” areas within a 2,000-foot radius of Well 16. The four anomalies were discovered and labeled A through D. Anomaly A may be associated with the trash pile present in the same area and is designated as AOC 62. Anomalies B, C and D may be additional trenches and are designated as AOC 42.

In June and July 1995, fourteen soil gas survey samples were collected, and an additional 19 follow-up samples were collected and analyzed for chlorinated and aromatic volatile organics. PCE was detected in this area (0.19 ug/L was the highest concentration detected).

Data Needs: Map and analytical data (VOCs and metals) for surface and subsurface soils.

Rationale for Analytical Program: Based on prior investigations at the site, chemicals of potential concern include VOCs and metals. Metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc) are included due to the potential metallic nature of the waste. VOCs analysis is included in the analytical program to detect typical contaminants associated with a disposal area. SVOCs and explosives are not included at this site since no evidence of waste burning or UXO has been found.

Closure Activities: The following activities constitute an additional investigation of the area of concern 62. This work will be completed as part of the requirements under the RCRA 3008(h) Order, but it is not currently included in any delivery orders.

  1. Field locate and map AOC 62 as described in Section 2.4.1 of the Work Plan Overview.

  2. Complete five soil borings to characterize the subsurface soils surrounding the area anomaly. The borings will be biased toward the anomaly found during geophysical survey activities. Three soil samples will be collected from each boring; one at the surface, one at the middle of the boring, and one at the total depth. The total depth of each boring will be approximately 10 feet or until 2 feet is drilled into the bedrock. Each sample will be analyzed for VOCs and metals. QA/QC samples will be collected as described in Section 2.4 of the FSP.

  3. Collect five grab surface soil samples. The samples will be biased toward the anomaly found during geophysical survey activities. Each sample will be analyzed for VOCs and metals. QA/QC samples will be collected as described in Section 2.4 of the FSP.

  4. Water is not expected to be encountered in the borings at the site. However, if water is discovered in any of the soil borings, all borings will be sampled and may be completed as groundwater monitoring wells 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 and metals. QA/QC samples will be collected as described in Section 2.4 of the FSP.

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

  6. If the results of the above work indicate that the site can be closed under RRS1 without any 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 requirements, a technical report describing the results of the investigation and recommended additional investigation and/or remediation will be prepared.