Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAPper 200 m 2 area. If a wetland area is less than 200 m 2 in size, one sample will becollected. [contingent]• Hot Spots. If GWS data indicate the presence of contamination that possibly exceeds“hot spot” (CG emc ) standards or an isolated elevated area is identified that appearsindicative of a discrete release, the location of concern will be sampled with a biasedsample. If biased samples are collected from a particular location, they will be collectedfrom two depth intervals: 0-15 cm, and 15 cm-1 m. The 0-15 cm samples will beanalyzed for the 12 radionuclides of potential interest in addition to the 18 ROI. Onedown-hole gamma scan will be conducted from each biased location. The purpose ofthese samples is to resolve GWS anomalies, evaluate the appropriateness of the currentROI list, and verify the absence of additional ROI. [contingent]• 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.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 activity concentrations present in surface soils within WMA 9. [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 cmRev. 1 H-7