[AOC 35]
AOC 35 AETC Work Plan Addendum
(Updated February 2001)
Soils: Krum Complex and Trinity and Frio Soils.
Known: The site consists of approximately 0.6 acres immediately surrounding Well 16, and is located in the northeast area of the Inner Cantonment.
Previous Investigations (Updated February 2001): Under Order 67, EM and GPR geophysical surveys were performed at seven potential source areas around Well 16. A total of 16 anomalies were found. In May 1995, field studies were increased to areas within a 2,000-foot radius of Well 16. An additional EM geophysical survey was conducted but no anomaly was found in this area, labeled Well 16 at the time (now included as AOC 35).
In June and July 1995, twenty-one soil gas survey samples were collected and analyzed for chlorinated and aromatic volatile organics. PCE was the only target analyte detected (0.37 ug/L was the highest concentration). In August and September 1995, Parsons ES completed surface geologic mapping activities and analysis of geophysical logs from the water wells at and around CSSA. Two distinct fault zones were mapped: one fault zone is near Well 16 and the other fault zone is north of Well 1.
In January 1996, Dr. Charles Young, a geophysical consultant, completed ground penetrating radar surveys around CSSA. Blackhawk Geosciences completed a seismic reflection survey from Well 16 southeast to Well 1.
In November 1999, a geophysical survey was conducted, as described in Section 2.4.1 of the Work Plan, to further identify any anomalies. A ground penetrating radar (GPR) device and an EM-31 instrument was used to complete the geophysical survey. While anomalies associated with known buried utilities or metallic objects on the ground were identified, no additional anomalies associated with suspected waste management were detected.
Data Needs (Updated February 2001): Geophysical survey and analytical data (VOCs – TCE, PCE, and DCE) for surface soils. The need for subsurface samples was de-scoped with the August 2000 SOW amendment due to the lack of anomalies associated with past waste management activities.
Rationale for Analytical Program: Based on the site’s vicinity to well 16 and previous investigations around well 16, chemicals of potential concern include VOCs (TCE, PCE and DCE).
Original Scope of Work (May 2000): The following activities constitute an initial investigation of AOC 35. This work will be completed as part of the requirements under the RCRA 3008(h) Order under AETC delivery order 5068.
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.
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 approximate locations of the survey points are shown on Figure AOC35-1. 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.
If the surveying information indicates an anomaly is present, complete 5 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 (SW8260) for PCE, TCE, and DCE only. QA/QC samples will be collected as described in Section 2.4 of the FSP.
If the geophysical survey does not identify subsurface anomalies, the funding for the soil borings may be replaced with surface samples to satisfy closure criteria with significant cost savings to CSSA. A modification by the AETC contracting officer will be required to change the basic statement of work (SOW). Until such a modification is in effect, no change to the pre-defined scope of work may be directed.
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 investigations 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 requirements, a technical report describing the results of the investigation and recommended additional investigation and/or remediation will be prepared.
Revised Scope of Work (August 2000): Since the November 1999 geophysical survey information did not identify subsurface anomalies in this area, the funding for the soil borings will be replaced with surface samples to satisfy closure criteria with significant cost savings to CSSA. The SOW was revised on August 2, 2000, and is reflected in this version of the work plan.
Five surface soil samples will be collected to characterize the soils in this area (Figure AOC35-2). Each sample will be analyzed for PCE, TCE, and DCE-isomers only, under Method SW8260B for VOCs. QA/QC samples will be collected as described in Section 2.4 of the FSP.
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 investigations 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 requirements, a technical report describing the results of the investigation and recommended additional investigation and/or remediation will be prepared. (The overall objective is to collect sufficient data to determine if the site can be closed; and if possible, to close it. Initially, RRS1 for the closure will be used. If closure to RRS1 is not viable, then the data will be compared to TRRPS for an acceptable closure. Clean closures using RRS1 standards will be obtained whenever technically and economically possible.)