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k4 KLEINFELDER • 1 EXECUTIVE SUMMARY Kleinfelder, on behalf of PCCP Mariposa Lakes, LLC, performed a hydrogeologic investigation of the proposed Mariposa Lakes Development site to establish current and background conditions in the uppermost regional aquifer beneath the site. The investigation also included obtaining preliminary data related to physical characteristics of the deeper aquifer. The resulting data describing the baseline conditions will be used in support of the pending Environmental Impact Report (EIR). Kleinfelder guided the installation, development, and sampled eight groundwater monitoring wells between February 7 and February 14, 2005 for the collection of background groundwater quality data within the uppermost regional aquifer. The monitoring well network has been installed to assess the background groundwater quality prior to the installation or development of any man-made water features. The depth to groundwater within the upper most regional aquifer ranged from 78.86 to 90.17 feet below ground surface (bgs). The groundwater elevation at the site ranged from 33.02 feet Mean Sea Level (MSL) to 38.86 feet MSL. The groundwater gradient is • estimated to be towards the north/northeast with groundwater depressions noted north, east, and west of the site, based on the San Joaquin County Flood Control and Water Conservation District (SJCFCWCD) Map, 2003. Groundwater samples collected from the monitoring wells were analyzed for general minerals, physical parameters, radiochemistry, coliform bacteria, and organic chemicals by (EPA Methods 504, 525.1, 505, 507, 515.3, 524.2, 525.2, 547, 548.1549.2, and 632). The constituents with concentrations reported above regulatory water quality goals were as follows: Nitrate detected in samples from MW-2 and MW-4 at concentrations of 63.4 and 51.5 milligrams per liter (mg/L), respectively, exceeded the California drinking water standards maximum contaminant level of (PMCL) of 45 mg/L. Nitrate as NO3 concentrations are generally associated with septic leach field systems, livestock operations, or as a fertilizer component. Atrizine was detected in the groundwater sample collected from MW-2 with a concentration of 1.9 micrograms per liter (µg/L). The California MCL for Atrazine is 1.0 µg/L. Atrazine is a common agricultural pesticide. Diuron, was detected in the groundwater sample collected from MW-6 with a concentration of 0.2 µg/L. The water quality goal [Suggested No Adverse Response Level (SNARL)] for Diuron is 10 µg/l. Diuron is a common agricultural • herbicide. 63138.H01/ST06R312/JDZ:ly Page 1 2f 20 April 7, 2006 ©2006 Kleinfelder, Inc.