Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• Three trenching locations will be selected along the WMA 6 drainage ditch. The trencheswill be separated by approximately 20 m to provide coverage for the stretch of thechannel that was reported to have been contaminated. The purpose of the trenching is toidentify subsurface contamination associated with the original sewage discharge channel.Trenching will be orthogonal to the orientation of the current ditch, and will be from awest to east direction starting at the ditch. Trenching will continue eastward for aminimum of 6 m or until there is no further evidence of contamination deeper than 1 m.Trenching will be to a minimum depth of 2 m, or to a depth such that there is no furtherevidence of contamination. Soils will be screened for elevated activity as trenchingprogresses. A minimum of three soil samples will be collected from each trench, onefrom the start of the trench targeting soils at a depth of approximately 1.5 m from soilsbelieved to be un-impacted based on gross activity data, one from soils that exhibit thehighest levels of gross activity, or from soils that appear to be representative of theoriginal sewage discharge channel if no evidence of elevated activity is observed, and onefrom soils on the western edge of the trench from a depth of approximately 1.5 metersfrom soils believe to be un-impacted based on gross activity data. If significantcontamination is identified by gross activity measurements, a fourth sample will berequired from soils at the bottom of the trench beneath the zone where contamination wasidentified to verify background conditions. [required]• If all three trenches identify contamination, then trenching will continue down the lengthof the original sewage discharge channel until the channel either terminates or untilbackground soils are encountered. Trench spacing will be approximately 20 m. Samplingwill be conducted as previously described. [contingent]• 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 surface soil sample indicates contamination impacts above background levels for the15 cm-1 m depth interval, an additional sample from a depth of 1-2 m will be collectedRev. 1 F-17