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PUBLIC HtALTH SERVICCTS ;,a U IN cO <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION " <br /> Karen Furst, M.D., M.P.H., Health Officer �. P <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> � 11 <br /> DALE BOYETT <br /> UD <br /> BOYETT PETROLEUM <br /> P O BOX 576277 <br /> MODESTO CA 95357-6277 <br /> WORKPLAN: WorkPlan for Lateral Extent of Groundwater Contamination DATED: April 19,200 <br /> PREPARED BY: WHF,Inc. <br /> APPROVED ❑ with Conditions/See Below <br /> DISAPPROVED ❑ <br /> ADDENDUM /�K Submit by: May 31,2000 <br /> ADEQUATE AND NECESSARY ELEMENTS OF THE WORKPLAN(H&S 25299.37,subd.(c)(3).): <br /> COMMENTS AND CONDITIONS: <br /> 1) Based on the analytical results of the 3/27/00 samples and QMR Deawivr 1999,the concentrations of <br /> MTBE have consistently increased in MW-1 and MW-3. GW gradient direction appears to be toward <br /> the north and northwest. PHS/EHD recommends installing additional MWs north and west of MW- <br /> 1 to a)establish a transect line of MWs in order to evaluate the rate of mass-fluctuation and lateral <br /> migration,b)provide data collection points for calculation of GW/plume transmissivity,and c) as <br /> sentinel wells to define the limit of the plume. <br /> 2) The vertical extent of the contamination has not been defined. PHS/EHD recommends using CPT <br /> to evaluate both the geology and the most strategic depths to obtain discrete grab water samples to <br /> investigate the vertical extent of the contamination. Based on the returning data, PHS/EHD <br /> recommends installing totally penetrated MW(s) with discrete screen length within specific lifts to <br /> define the vertical limit of the contamination in groundwater. <br /> 3) Blue ice should not be used as a means to control temperature in the preservation of samples,unless it <br /> can be demonstrated to PHS/EHD inspector at the field that 5-C or below is achieved consistently. <br /> Otherwise,PHS/EHD recommends using real ice for the preservation of the samples. <br /> 4) Approval of the WorkPlan does not extend to the approval of a feasibility study such as an air <br /> sparging or soil vapor extraction pilot test(AIS/SVE). AIS/SVE Feasibility pilot tests should be <br /> conducted only after the 3-dimensional shape and extent of the contamination has been defined. <br /> 5) The WorkPlan recommended future feasibility study including the evaluation of natural biological <br /> attenuation,and air sparging and vapor extraction wells. It would be most cost-effective to analyze <br /> soil samples from each significantly different lithological lifts for soil physical properties as <br /> permeability,dry bulk density,porosity,moisture,and organic carbon content,and Total Plate Count <br /> of the heterotrophic microbial populations,and the level of nitrogen and phosphate for nutrient <br /> concentrations. <br /> 6) Contingency to advance to greater depths or installation of additional MWs as dictated by field <br /> observations. <br /> 7) Must provide a properly calibrated,working organic vapor detector such as a PID during work <br /> 8) Selection of samples for analyses must include PHS/EHD comments and agreement. <br /> 9) Submit to PHS/EHD an addendum to this WorkPlan by May 31,2000. <br /> 10) Submit application for pre-approval to the State Cleanup Fund if it has not already been submitted. <br /> 11) Schedule work with PHS/EHD before scheduling work with G57 contractor. <br /> REASONS FOR DISAPPROVAL OF THE WORKPLAN(H&S 25299.37,subd.(C)(3).): <br /> DATED May 5,2000 BYa-o"'Z,l'f- <br /> Cc: <br /> CRWQCB,Central Valley Region-Marty Hartzelf <br /> Fax: WHF,Inc.-Bill Fox <br /> A Division of San Joaquin County Health Care Services <br />