Conceptual Site Model - Argonne National Laboratory

WVDP Phase 1 CSAP• Three locations along each piece of buried infrastructure within WMA 7 but outside theNDA geomembrane cover will be selected for soil excavation. These locations will beselected to maximize the possibility that contamination will be encountered (e.g.,locations where historical or current GWS data indicate surface contamination exists).During excavation, exposed soils will be monitored by scans for evidence of elevatedgross activity. The purpose of this sampling is to evaluate the presence of contaminationassociated with buried infrastructure. [required]oIf elevated readings are encountered below a depth of 1 m, soils exhibiting thehighest levels of gross activity will be sampled and analyzed.oIf elevated readings are not encountered below a depth of 1 m, a samplerepresentative of soils deeper than 1 m will be collected. In the case ofinfrastructure that did not carry waste, the sample will be from soils immediatelyabove the line. In the case of infrastructure that did carry waste, the sample willbe from soils immediately beneath the line.• If contamination above background conditions is encountered at any selected location,trenching will continue to depth until background conditions are observed. An additionalsample will be collected from the base of the trench to verify background conditions. Thepurpose is to vertically bound observed contamination. [contingent]• If buried infrastructure soil sampling identifies contamination impacts greater thanbackground, biased sampling will continue following the line until at least twoconsecutive locations yield soil samples below surface soil CG w requirements. Locationspacing will be based on engineering judgment, including the geometry of the line, thelevel of contamination encountered, and surface evidence of contamination. The purposeof this sampling is to bound the extent of contamination associated with buriedinfrastructure, as necessary. [contingent]G.9.7 Additional ContingenciesSampling and/or GWS data may indicate that contamination exists or extends beneath surfacescurrently covered by existing structures, concrete, asphalt, or gravel. In this case, “surface soil”Rev. 1 G-16