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`.01/03/2008 15:18 2098350 Valley Organics, Inc. Green Waste Composting Facility, Lathrop, CA WORKPLAN FOR WELL RADIUS SEARCI4 AND GROUNDWATER SAMPLING Purpose and Scone 2098350675 PAGE 06 8112.000.000 December 4, 2007 Page 2 The purpose of this Workplan is to present the sampling and analysis rationale and investigation protocols specific for the Site. The objective of the Workplan is to provide data to be utilized in future evaluation of potential affects on groundwater in the local area, The Workplan includes descriptions of the following activities: • Groundwater Sampling Location and Rationale • Groundwater Sample Collection Procedures • Documentation Requirements A field sampling matrix table and examples of field forms to be used during f=ield activities accompany this Workplan. Field forms include: • Boring Log Form • Sample Label Example • Chaim -of Custody Record GEOLOGY AND I IYDROGEOLOGY The Site, situated in the north -central portion of the San Joaquin Valley geomorphic province, is in an area characterized as flood plain and delta deposits, The San Joaquin Valley is a large asymmetrical trough bounded by granitic, metamorphic and marine sedimentary rocks of pre Tertiary age that have been in -filled with up to 6 vertical miles of sediment (USGS, 1986). Most of the sediments deposited in the Sacramento -San Joaquin Delta prior to 25 million years ago were accumulated in marine environments and the younger deposits (25 million years ago to recent) are generally described as non -marine, however, some of the younger deposits likely formed in shallow seas and estuaries as marine deposits. According to Atwater, the Delta region or the Central Valley, in which the Site is located, experienced stages of the following during late Quaternary time: • Wetlands and flood plain creation as the tidewater rose in the valley from the west • Areas of erosion when tidewaters receded • Deposition of alluvial fans that were reworked by wind to create extensive sand dunes • Alluvial fan deposition from streams emanating from the adjacent mountain ranges. The Geologic Map of the San Francisco -San lose Quadrangle compiled by Wagner et al. (1991) lists the main geologic Pori -nation at the Site as Holocene -aged Modesto Forniation (Qin).