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Mt. Ross Atkinson March 30,2001 Page 2 Objectives The objectives set forth for this limited shallow groundwatcr investigation are as follows: ' Collect representative groundwater samples in the vicinity of the waste reject the stockpiles located at MonietLifetile's Lathrop and French Camp, California facilities. • Determine if total chtomium and/or chromium VI is present in shallow groundwater at either facility at concentrations in excess of the PHGs. The applicable regulatory criteria cited in the January 18,2001 letter (Califortlia PHG in Drinking Water)is 0.2 µg/L for chromium VI. These objectives will be accomplished under the following scope of work: ' Using a limited access direct push drill rig,install up to five soil probe holes neat the waste reject tile stockpile areas with the collection of one groundwater sample from each probe lavation (Figure 2 and 3)_ The sampling locations may be adjusted in the field due to access restrictions identified at the time of sampling. ■ Submit groundwater samples to a California state-certified laboratory for the analysis of chromium VI using EPA Test Method 7199 and total chronuiutn using EPA Test Method 6010. • Evaluate the analytic it results,report sampling results and make recommendations for additional sampling,if warranted. Geology and Hydrogeology This section describes the geologic and hydxogeologic conditions in the vicinity of the facilities and the surrounding area. The following descriptions are based on published literatuxe. The Lathrop and French Camp facilities are located about 7 miles south of Stockton, California,within the Central Valley geomorphic province. The Central Valley geomorphic province is divided into the Sacramento Valley and the San Joaquin Valley. The Central Valley is a large, northwestward-trending, asymmetric structural trough that has been filled with several miles thick of sediment (USGS 19861). The U.S. Geological Survey (USGS) describes the boundaries of the Sacramento Valley as stretching from Red Bluff to the north to approximately the Lodi area (the Sacramento-San Joaquin Delta), to the east by the Sierra Nevada, and the Coast Ranges to the west. The San Joaquin Valley is bounded by the Delta on the north and the Coast Ranges and the Tehachapi Mountains to the south. 1 US Geological Survey,Page,1t.W.,1956,Geology of the Fresh-Ground-Water Basin of the Ccnttal Valley,California,with Tcxwxe Maps and Sections,USGS Profcssipnal Paper 1401-C. PA.P\jobs\20597\102253 Q'ouod—ft,wP,do< EVV-d 810/EOO d ZZ1-i OV60V2V6V6 113ACIVO ONV NAOda-woad wr89:01 1001-0E-AV