Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• CG w Sampling. Surface soil sampling may be conducted after the GWS to further clarifyresults, with the level and nature of sampling dependent on GWS results. If GWS resultsindicate no evidence of contamination impacts above background levels, no additionalsurface soil sampling will be required other than to address areas too wet to perform agamma walkover survey. Based on historical direct gamma measurements, the area mostlikely to have contamination exceeding surface soil CG w requirements is along the WMA2 border.oIf GWS results indicate contamination impacts above background levels but thatsurface soil contaminant levels exceeding CG w requirements are unlikely, thearea of interest will be systematically sampled using a triangular grid with adensity of one sample per 400 m 2 . One sample will be collected from eachlocation representative of a 0-15 cm depth interval. Locations will be selected toprovide systematic coverage of the area of interest. The purpose is to documentthe maximum activity concentrations present in surface soils within WMA 12South. [contingent]oIf GWS results indicate surface soil contaminant levels exceeding CG wrequirements likely exist, one sampling location will be selected at the highestgross activity level to confirm CG w exceedances and another set of samplinglocations will be identified to spatially bound the extent of contamination (i.e.,along the boundary of what is considered likely above CG w requirements) if thisis not obvious from the GWS data. Two samples will be collected from thelocation targeting high gross activity levels, one representative of a 0-15 cmdepth interval, and one representative of a 15 cm-1 m depth interval. One samplewill be collected from each location intended to laterally bound contamination,representative of a 0-15 cm depth interval. In addition, the location targeting highgross activity levels will have one down-hole gamma scan conducted at thecenter of the location with static measurements taken every 15 cm. Locations willbe selected so that each representative area does not overlap. The purpose is todocument CG w requirement exceedances and bound the lateral extent ofcontamination. [contingent]Rev. 1 J-11