AETC Work Plan Addendum

Soils: Krum Complex and Trinity and Frio Soils.

Known: The site is located east of Well 16 between the North Outer Road and the cantonment fence, and is approximately 0.5 acres in size.

Previous Investigations (Updated): Under Order 67, a geophysical survey was conducted in May 1995 at all "open" areas within a 2,000-foot radius of Well 16. One anomaly was found in this area (labeled Well 16 East at the time) and is now included as AOC 40. The anomaly is subtle and may be caused by a subsurface disturbance or an overhead power line.

In June and July 1995, nine soil gas survey samples were collected and analyzed for chlorinated and aromatic volatile organics. PCE was detected in this area (0.87 ug/L was the highest concentration detected).

Data Needs: Analytical data (VOCs – TCE, PCE, and DCE) for surface and subsurface soils.

Rationale for Analytical Program: Based on the site’s vicinity to well 16 and previous investigations at the site, chemicals of potential concern include VOCs, (PCE, TCE and DCE). Metals, explosives, and SVOCs are not included at this site based on soil gas survey and geophysical survey results.

Closure Activities: The following activities constitute an additional investigation of AOC 40. This work will be completed as part of the requirements under the RCRA 3008(h) Order under AETC delivery order 5068.

Collect five surface grab samples to a maximum depth of 2 feet to characterize surface soils surrounding the area. The surface samples will be collected from the area and biased toward the anomaly and the soil gas survey points with the highest PCE readings. Figure AOC40-1 depicts the proposed locations for the surface samples. This work is being performed in conjunction with sampling efforts at AOCs 36, 38, and 39. Each sample will be analyzed for VOCs (PCE, TCE, and DCE). QA/QC samples will be collected as described in Section 2.4 of the FSP.

Complete one soil boring to characterize the subsurface soils surrounding the area. One boring will be completed in geophysical anomaly A. Three soil samples will be collected from the 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. Currently, this task is not included in AETC DO5068.

Handle IDW as specified in the FSP.

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.