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EcM G.Bn .le. <br /> ee+w,a <br /> c�a,o u,• MAm M nOmapYEX <br /> Water Boards <br /> Central Valley Regional Water Quality Control Board <br /> 15 April 2014 <br /> Dave Vossler <br /> GHD, Inc. <br /> 3831 N. Freeway Boulevard, Suite 220 <br /> Sacramento, CA 95834 <br /> WORK PLAN FOR FORMER SIEBOLD CONSTRUCTION, 820 SOUTH AMERICAN STREET, <br /> STOCKTON, SAN JOAQUIN COUNTY, EMERGENCY ABANDONED AND RECALITRANT <br /> ACCOUNT CASE#R09-121 <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the Work Plan for Additional Subsurface Delineation (Workplan) received <br /> as an email attachment on 20 March 2014 from you for Emergency, Abandoned, and <br /> Recalcitrant(EAR) Account Case# R09-121. The Workplan was prepared in response to the <br /> 30 January 2014 email exchanges between Central Valley Water Board staff and <br /> representatives from GHD which detailed the need for a work plan to provide horizontal and <br /> vertical delineation of the groundwater pollution at the Seibold site in order to move the case <br /> towards closure. It is our understanding from subsequent discussions with you that sufficient <br /> EAR Account funding exists to complete the proposed work. I concur with the tasks proposed in <br /> the Workplan with the conditions stated below. <br /> Our comments on the Work Plan are as follow; <br /> 1. GHD proposes three groundwater monitoring wells (MW-5 through MW-7) onsite and <br /> offsite in the Workplan text. However, Figure 2 shows the locations for four proposed <br /> groundwater monitoring wells. Central Valley Water Board staff concur that four well <br /> locations should be sufficient to provide delineation of the groundwater pollution at this <br /> Site, however the proposed MW-1 location needs to be moved closer to MW-2 and be <br /> screened in a deeper zone to provide vertical delineation. I concur with the well location <br /> east of MW-2 and the two well locations north of the site as proposed. <br /> 2. Figure 3 shows a cross section of the 2" diameter monitoring wells constructed of <br /> polyvinyl chloride casing, screened from 25 feet to 50 feet below ground surface (' bgs). <br /> Depth to groundwater since 2012 has varied from 26' bgs to 27' bgs. The proposed top <br /> of the new wells screens are one to two feet above groundwater that GHD measured in <br /> 2012 and 2013. Screen intervals should be limited to 15 feet in length, with 5 feet set <br /> above the current water table interface and 10 feet below to allow for fluctuations in <br /> water levels over time. <br /> 3. Vertical delineation must also be determined before closure of this case is possible. <br /> Therefore, a deeper well should be installed near well MW-2 to provide vertical <br /> KM E. L*N*a ScO.P.E.,a I PmEu C.Omw"P.E.,eCEE,u®wmv qr n <br /> ttmssunc.nrom.�ms.�wmeoaaoacEssen I w .w0vb=rc1L aso Vmft.saw <br /> Q Mwrm.ao wa <br />