Introduction

Background
In accordance with Contract Number DACA31-00-D-0011, Delivery Order Nos. 18 and 27, URS Corporation (URS) was tasked by United States Army Corps of Engineers (USACE), Baltimore District to perform soil sampling and reporting at Solid Waste Management Unit (SWMU) 6, cid Wastewater Lagoon, located in the Main Manufacturing Area (MMA) at the Radford Army Ammunition Plant (RFAAP), Radford, Virginia. The objective was to collect and analyze subsurface soil samples from WMU 6 and perform an evaluation of the resultant data with respect to Resource Conservation and Recovery Act (RCRA) hazardous waste characteristics and United States Environmental Protection Agency, Region III (USEPA) Risk-Based Concentrations (RBCs).

Soil sampling at SWMU 6 was necessary to properly manage excavated soils that will be generated as part of the Production Base Support (PBS) project to construct nitrocellulose (NC) settling tanks at SWMU 6. The planned depth of excavation is 25 feet. The SWMU 6 sampling program results will allow RFAAP to properly manage the excavated material during construction and to prevent future sampling under the tanks once the construction is complete.

RFAAP submitted the SWMU 6 Soil Sampling Results Report to USEPA on May 11, 2001. Approval of the Report was granted in a letter dated June 12, 2001. As a point of clarification, the Report makes reference to
reactivity (percent nitrocellulose) and reactivity (percent explosives). The Report should reference total reactivity regardless of the source. Section 7.0, Summary and Conclusions, of the SWMU 6 Soil Sampling Results Report (URS, 2001), indicated that RFAAP would present a comparison of SWMU 6 inorganic data to the Point Estimates derived from the facility-Wide Background Study (IT Corp., 2002). This document represents a Decision Document based on the results of that comparison. The objective of this Summary Report is to provide the basis for an agreement between RFAAP, USEPA, and Virginia Department of
Environmental Quality (VDEQ). Specifically, pursuant to the results presented in the SWMU 6 Sampling Results Report (URS, 2001) and based on the analyses presented herein, a RCRA Facility Investigation (RFI) is not required for SWMU 6 per the USEPA RCRA Corrective Action Permit, RFAAP, Part II, Section D.7.a. and b.

Facility-Wide Background Study
Subsequent to USEPA approval of the SWMU 6 Soil Sampling Results Report, IT Corporation (IT Corp.) completed a Facility-Wide Background Study at the MMA and the New River Unit (NRU) of RFAAP (note that this work was completed in accordance with Work Plan Addendum No. 10). Task objectives were to characterize naturally occurring background soil inorganic constituent concentrations within the MMA and the NRU (IT Corp., 2002). Scope of work activities included the collection of background soil samples to establish a baseline for inorganic compounds of concern at RFAAP. Background sample locations were selected based on soil types and collected in areas not impacted by Installation activities. Associated soils were evaluated based on formation properties and chemical and physical characteristics.

The final set of Point Estimates for the background data set is based on calculated 95% Upper Tolerance Limits (UTLs) for a single, Facility-wide data set that represents surface and subsurface soil from the MMA and NRU areas. These values are included in the Facility-Wide Background Study as a point of reference for point-by-point comparisons for site screening. For several constituents, the 95% UTLs are below the RBCs,
which were used to screen chemicals of potential concern (COPCs) at this SWMU (see Section 3.0). Thus, by utilizing an additional screening tool (i.e., the 95% UTLs), the potential for identifying naturally occurring elements as contaminants is minimized.