Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPpurpose is to resolve the question of whether surface soil CG w requirementexceedances exist for areas where GWS results are ambiguous. [contingent]oIf any 0-15 cm interval yields a sample result indicating a surface soil CG wrequirements exceedance and that sample location is not laterally bounded either byexisting sampling locations with results less than surface soil CG w requirements or byGWS data that clearly indicate contamination is not a concern, additional samplinglocations will be selected so that the contamination encountered is spatially bounded.The purpose is to laterally bound contamination that is above CG w requirements.[contingent]• Central Western Area of WMA 2. The assumption is that because of surface coveradded to the site as part of WVDP activities, surface contamination that pre-dated theWVDP may now be covered by clean material and may not readily detectable by GWSscans. Figure B.22 shows the area of WMA 2 where this is a concern. (Note that thecontamination status of soils beneath building slabs will be addressed by remedialsupport surveys after slabs have been removed.) This area is approximately 1.7 acres insize. Systematic sampling locations arranged on a triangular grid with a 20-m gridspacing will be used to evaluate the contamination status of soils beneath the existingground cover. Approximately 20 sampling locations will be required. Each location willhave one sample collected to a depth of 1-m. In addition, each will have a down-holegross activity scan with one measurement taken each 15 cm. [required]B.9.4Subsurface Soil SamplingSubsurface soil sampling within WMA 2 has three purposes: (1) to determine presence andvertical extent of contamination impacts above background levels in WMA 2 along the edge ofand outside the planned deep excavation, (2) to estimate waste stream volumes in support of theplanned WMA 2 deep excavation, and (3) to provide geotechnical and contamination statusinformation for the footprints of the slurry and sheet walls.Much of the WMA subsurface has been impacted by the North Plateau Groundwater Plume tovarying degrees. A significant amount of historical data collection has already taken place toRev. 1 B-21