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As required by the WDRs, this revised Master Well Workplan' is consistent with:
<br /> Attachment F to the WDRs "Requirements for Monitoring Well Installation
<br /> ' Workplans and Monitoring Well Installation Reports", California Well Standards
<br /> Bulletin 74-90, and San Joaquin County Well Standards. Additionally, this
<br /> workplan includes the Sampling and Analysis Plan (SAP) and recommended
<br /> quality assurance protocols for continued groundwater monitoring to ensure that
<br /> background water quality is adequately characterized and that potential future
<br /> water quality impacts from the discharge, if any, are detected.
<br /> 1.3 Local Hydrogeologic Conditions
<br /> ' The Lathrop area is located in the basin-trough geologic zone of the San Joaquin
<br /> Valley, which consists of continental Pleistocene and Holocene stream-laid and
<br /> ' still-water depositsz. These deposits are derived from a mixture of Sierra Nevada
<br /> and Coast Range rocks3. The near surface deposits are mapped primarily as
<br /> Quaternary alluvial flood plain deposits4. The local depositional environment is a
<br /> ' sedimentary river basin, and the shallow sediments are primarily flood plain and
<br /> over bank deposits of sand, silt and clay. The near surface deposits are
<br /> characterized by discontinuous inter-bedded silty sand, sandy silt, silty clay, clay,
<br /> ' and sand deposits5. Soils are derived from mixed Sierran and Coast Range
<br /> source materials, and are characterized by poor drainages.
<br /> ' The Lathrop area groundwater basin is comprised of an approximately 150-feet,
<br /> thick upper water-bearing zone overlying a 75 to 1,000 feet thick lower water-
<br /> bearing zone. The lower water-bearing zone provides a source of drinking water
<br /> ' to the City of Lathrop. The hydraulic connection between the upper and lower
<br /> ' On February 14, 2007 HydroFocus, Inc. submitted the"Master Well Installation and/or
<br /> Destruction Workplan"to the RWQCB on behalf of the City of Lathrop. RWQCB staff responded
<br /> ' with their April 10, 2007 letter"Incomplete Report, Master Groundwater Well Installation and/or
<br /> Destruction Workplan,WDRs Order No. R5-2006-0094, City of Lathrop, San Joaquin County".
<br /> Their April 10`h letter included a list of suggested changes and/or revisions to the workplan and its
<br /> appendices. This revised "Master Well Installation and/or Destruction Workplan" includes all
<br /> requested changes to the workplan and associated "Groundwater Sampling and Analysis Plan".
<br /> For reference, a listing of responses to the numbered changes and/or revisions is included as
<br /> Appendix A to this revised report. In their April 10, 2007 letter, RWQCB staff requested that three
<br /> ' reports describing the status of groundwater monitoring wells located at River Islands be
<br /> resubmitted separately as stand alone reports (they were originally included as an Appendix).
<br /> Accordingly,the three reports are not included with this revised workplan. The three reports shall
<br /> be submitted by ENGEO, Inc.
<br /> ' 2 Jennings, C.W. and Strand, R.G., 1958, "Geologic map of California, Santa Cruz Sheet",
<br /> California Division of Mines and Geology, Sacramento, California.
<br /> 3 Miller, R.E., Green, J.H., Davis, G.H..,1971, U.S. Geological Survey Professional Paper497-E.
<br /> ' 4 Atwater, B. F., 1982, Geologic maps of the Sacramento-San Joaquin Delta, California, US
<br /> Geological Survey Miscellaneous Field Studies Maps, MF-1401.
<br /> 5 Kleinfelder, "Hydrogeology of the Mossdale and Reiter Property, Lathrop, California", November
<br /> 24, 2004.
<br /> 6 Soil Conservation Service, 1992, Soil Survey of San Joaquin County
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