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Area of Concern 58

RL83 Work Plan Addendum

Soils: Brackett soils (12-30 percent slopes).

Known: The site is a suspected trench observed on a 1973 aerial photograph. AOC 58 is located southwest of monitoring well MW-2 approximately 60 feet east of AOC 42, and is approximately 0.2 acres in size..

Previous Investigations: None.

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

Rationale for Analytical Program: Based on a suspected trench observed on a 1973 aerial photograph, chemicals of potential concern include VOCs, SVOCs, 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 are included at this site since waste burning may have occurred. Explosives are not included since no UXO has been observed.

Closure Activities: The following activities constitute an initial investigation of AOC 58:

  1. Field map AOC 58 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 with approximately 21 survey points on a 10-foot grid. The approximate locations of the survey points are shown on Figure AOC58-1. 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. Collect three grab surface soil samples at a depth of six inches below surface grade. The samples will be biased toward any anomalies found during geophysical survey activities. Each sample will be analyzed for VOCs, SVOCs, and metals. For planning activities, the approximate locations of the surface soil samples are shown on Figure AOC58-1. 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.