AOC 60 RFI Work Plan Addendum

Area of Concern 60

RFI Work Plan Addendum

Soils: Trinity and Frio soils (frequently flooded).

Known: The site is located west of the tunnel and entrance roadway in the East Pasture, towards the south fence line. The site was identified on a 1966 aerial photograph as a trench-type anomaly, and is approximately 0.6 acres in size.

Previous Investigations: None.

Data Needs: Map, geophysical survey and analytical data (VOCs, SVOCs, explosives and metals) for subsurface data.

Rationale for Analytical Program: Based on a trench-type anomaly in the vicinity of the tunnel in the East Pasture, chemicals of potential concern include VOCs, SVOCs, metals and explosives. 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 are included at this site because waste burning may have occurred.

Closure Activities: The following activities constitute an initial investigation of the area of concern 60. 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 order.

1. Field map AOC 60 as described in Section 2.4.1 of the Work Plan Overview.

2. Remove any vegetation necessary to complete field activities listed below. If any potential UXO is observed during field activities, work will cease until UXO specialists are brought on site to identify and remove UXO.

3. Conduct a geophysical survey, as described in Section 2.4.1 of the Work Plan Overview, of the mapped site to identify any anomalies. A ground penetrating radar (GPR) device and an EM-31 instrument will be used to complete the geophysical survey. The locations of four of the corners of the survey points will be recorded using a GPS unit. Analysis of the EM data will follow field activities.

4. If the survey information indicates an anomaly is present, complete two soil borings to characterize the subsurface soils surrounding the anomaly. Two soil samples will be collected from each boring. The total depth of each boring will be approximately 10 feet. 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.

5. 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 described 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.

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

7. 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.