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NN,. %W e' Dopaco, Inc. - 2 - 18 September 2012 800 W. Church St., Stockton San Joaquin County The following table shows the CPT-MIP-2012-13 groundwater sample results by depth and tolueneNOCs concentrations in micrograms per Liter (ug/L). Depth Toluene 2-Butanone 4-Meth -2 Pentanone Acetone 18.5' 410,000 <63,000 <63,000 <63,000 32'-33' 510,000 74,000 250,000 <71,000 32'-33' 500,000 170,000 340,000 110,000 1 =duplicate sample The grab groundwater sampling location for CPT-2012-13 was moved 5' to the south of that actual MIP/CPT boring location, due to an obstruction on the surface. The Report stated that the discrepancy between the MIP toluene results (<1 ppm) and the maximum groundwater toluene results (510 ppm) was due to the fine grained lithology above 35' below ground surface (bgs) causing the highly localized distribution of the toluene in the subsurface. All calibrations of the MIP sensors showed proper functioning before and after testing for each CPT location. A 2005 soil and groundwater investigation reported toluene in a grab groundwater sample at 6,800,000 ug/L at B-1, which is shown on the Report Figure 5 as approximately 10' north-northwest of CPT-MIP-2012-13. Of the remaining CPT/MIP grab groundwater sample toluene results located near CPT-MIP-2012-13, toluene was only detected at CPT-MIP-2012-14 (34 ug/I, 37'-38' bgs) at 5' south, and CPT-MIP-2012-15 (1 ug/I at 32.5'-33.5' bgs) at 25' south. The groundwater data from the Report and previous investigations data show that the groundwater plume is defined to the north, west, and east of CPT-MIP-2012-13. The subsurface geology was determined by CPT logs and detailed in geologic cross sections, which showed fine grained sediments (silts and clays) from surface down to a coarse grained sediment (sand) starting at 33' bgs (CPT-MIP-2012-13) and extending down to 42' bgs (9' thick). The sand (permeable zone) thins to 3' thick (38' bgs to 41' bgs) at 20' to the west (CPT-MIP-2012-11), expands to 8' thick (36' to 43' bgs) at CPT-MIP-2012-14, and to 10' thick (33' to 45' bgs) at CPT-MIP-2012-15. The Report and previous investigations logs show the sand pinches out to the west and east of the source area. Groundwater flow direction was not calculated by the grab sample borings. The Report states toluene is limited in lateral extent and the groundwater sampling shows as little as 5' laterally may be the difference between impacts in groundwater in the source area and non-detects in soils based on the MIP. The Report recommends the following wells be installed and screened from 30' to 35' bgs, due to the Report's 58% success rate in finding water above 30' bgs (The Workplan recommended screening across first water previously detected between 15' to 20' bgs). Well Location Possible Flow Direction Nearest boring DMW-1 35'west of source area upgradient CPT-MIP-2012-11 DMW-2 45' east of source area downgradient Geos ntec 6 2011 DMW-3 80' southwest of source area downgradient to crossgradient CPT-MIP-2012-16 DMW-4 60' south of source area crossgradient CPT-MIP-2012-10