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J <br /> 1 <br /> w . <br /> i <br /> LEE & PIERCE inc. <br /> consulting engineers <br /> i 546 ABBOTT STREET, SUITE 20 <br /> SALINAS, CA 93901 -4323 <br /> BILL PELICH, P.E. CIVIL <br /> I JOHN LANE, R.G. , R.E.A. SALINAS (831 ) 758-0096 <br /> LEE MARCUM FAX (831 ) 758-1213 <br /> July 5, 2006 <br /> Mr. Nuel Henderson <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Subject: Revised Workplan for Vertical Groundwater Investigation <br /> Beneto Inc., 749 E. Charter Way, Stockton, CA, Site 1060 <br /> Dear Mr. Henderson: <br /> This Workplan is submitted on behalf of Beneto, hie. in response to the San Joaquin County <br /> Environmental Health Department (EHD) directive letter dated September 27, 2005 . In the <br /> directive, EHD requested the installation of discrete-depth, short-screened wells to verify the <br /> results of a CPT investigation conducted by California Geophysical Group, Inc. (CGG) and <br /> Gregg Drilling and Testing, Inc. Specifically, the wells will be installed to investigate water <br /> quality beneath the site in permeable zones identified at depths of approximately 85-92 feet <br /> below ground surface (bgs) and approximately 132- 135 feet bgs. <br /> This workplan will supersede and supplant the January 30, 2006 workplan and addenda (March <br /> 21 , 2006 and April 18, 2006) prepared by CGG related to the deep well investigation. The new <br /> wells will be identified as monitoring wells MW17B and MW18C. The sections below describe <br /> the proposed methodology of drilling, sampling and constructing the wells. Figure 1 shows the <br /> location of the site. <br /> WORKPLAN <br /> New monitoring wells MW17B and MW18C will be constructed in the source area at the <br /> 6 approximate locations shown on Figure 2. Since the deep wells will pass through highly <br /> 8 contaminated shallow groundwater, precautions will be taken to ensure that the annular seals will <br /> be adequate to prevent cross-aquifer contamination. The proposed drilling and construction <br /> methodology is intended to minimize the possibility of inter-aquifer transfer of groundwater <br /> during drilling and after completion of the well. The pilot borings will be drilled with mud rotary <br /> U:\L&P\Benem\WKPLAN_deepwell s.doc <br />