Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPD.9.3Subsurface Soil SamplingThe purpose of subsurface soil sampling within WMA 4 is to determine presence and verticalextent of contamination impacts above background levels. Much of the WMA 4 subsurface ispotentially impacted by contamination associated with the North Plateau Groundwater Plume.Significant historical data collection has been dedicated to characterizing the extent and level ofthis plume. The sampling described by this section is not intended to further characterize theNorth Plateau Groundwater Plume. It is intended to characterize surface contamination thatextends to depths greater than a meter outside the known North Plateau Groundwater Plumefootprint and/or contamination overlain by a thin layer of clean soil.• If any 0-15 cm surface soil sample result indicates contamination impacts abovebackground levels and there was not a 15 cm-1 m sample collected from that location, a15 cm-1 m sample will be collected from that location following the protocols used forthe original 0-15 cm surface soil sample. In addition, each soil location will have onedown-hole gamma scan conducted at the center of the location with static measurementstaken every 15 cm. [contingent]• If a 15cm -1 m sample result exceeds background levels, then an additional sample froma depth of 1-2 m will be collected and analyzed from that location. In addition, downholegamma data will be collected from the location with static measurements collectedfor every 15 cm depth interval. If that sample has contamination above backgroundconditions, then the next deeper 1 m interval will be sampled and analyzed and a downholegamma scan performed. This process will continue until background conditions arereached. [contingent]D.9.4Drainage Feature SamplingWMA 4 contains two primary drainage features. The first runs from the northwestern corner ofWMA 4 towards the east, along the CDDL, discharging on the east side of WMA 4 at the WVDPfence line. This feature is known as the Swamp Ditch. The portion of the Swamp Ditch that runsalong the north side of the CDDL is carried by a buried pipe. The second drainage feature runseast along the southern edge of the CDDL before turning north and connecting with the SwampDitch. For drainage features within WMA 4, the surface soil CG w requirements apply. SurfaceRev. 1 D-11