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ATC Associates Inc. <br /> AkTC 1117 Lone Palm Avenue, Suite 201 <br /> (: <br /> \v, Modesto, California 95351. <br /> 209-579-2221 <br /> AS s o c I ATE 6 I N C . fax: 209-579-2225 <br /> None of the analytes of interest were detected in the groundwater samples collected <br /> from 82 feet bgs at CPT1 and 105 feet bgs at CPT2 . MTBE was detected in the <br /> groundwater sample collected from 22 feet bgs at CPT2 at a concentration of 1 .2 tag/L . <br /> Toluene , xylenes , and MTBE were detected in the groundwater sample collected from <br /> 57 feet bgs at CPT3 at concentrations of 2 . 0 Ng/L , 2 .8 pg/L , and 21 pg/L, respectively . <br /> TPHd was not detected in any of the groundwater samples . <br /> In April and May 2008 , ATC installed monitoring wells MW8 through MW14 . The wells <br /> were completed at depths varying from 17 to 121 . 5 feet bgs . <br /> GEOLOGY <br /> The Site is located within the central portion of the Great Valley Physiographic Province , <br /> The Great Valley is a large elongated northwest-trending asymmetric structural trough <br /> bounded by the Sierra Nevada Mountains to the east and by the Coastal Mountain <br /> Ranges to the west. The Great Valley is underlain by a thick sequence of sediments <br /> ranging in age from Jurassic to Recent. The Site is located in the delta area of the San <br /> Joaquin Valley and underlain by sediments deposited by the San Joaquin River <br /> consisting of gravel, sand , silt, and clay. <br /> Flood Basin Deposits are exposed in the Delta area of the San Joaquin Valley. These <br /> deposits are basin-ward , fine-grained forms of the Laguna , Riverbank, Modesto , and <br /> Recent formations and , therefore , range in age from Pliocene to Recent. They are <br /> generally much finer grained with a higher percentage of fine sand and clays than their <br /> depositional equivalents to the east and west. Occasional gravel beds occur along the <br /> present waterways and are probably representative of the type of underlying lithology <br /> distribution . This unit ranges in thickness from 0 to 1 ,400 ± feet. Groundwater in this <br /> unit occurs under unconfined to confined conditions . The unit, in general , has low <br /> permeability and may create semi-confined to confined conditions when interlayered <br /> with the Alluvium and Modesto/Riverbank Formations. Occasional pockets of fresh <br /> water are found in the Delta deposits , but generally contain poor quality water. This unit <br /> is designated as Dos Palos Alluvium by (Wagner et al . 1990) (State of California <br /> Department of Water Resources (DWR) , Bulletin 118, updated in 2003) . <br /> According to the Geologic Map of the Sacramento Quadrangle, California, 1:250, 000, <br /> published by the California Division of Mines and Geology, 1981 , the site is underlain by <br /> alluvial deposits of the Modesto Formation . <br /> HYDROGEOLOGY <br /> The Site is located within the Eastern San Joaquin Subbasin of the San Joaquin River <br /> Hydrologic Region . The Eastern San Joaquin Subbasin is defined by the aerial extent <br /> of unconsolidated to semi consolidated sedimentary deposits that are bounded by the <br /> Mokelumne River on the north and northwest; San Joaquin River on the west; <br /> Stanislaus River on the south ; and consolidated bedrock on the east. The Eastern San <br /> KIR 2009 WP for Pilot Testing.doc ATC Associates Inc. <br /> S:\Enviromnental\62514 — KIR ATC Project No. 54.62514.0001 <br /> Page 4 <br />