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4 0° <br />Water Boards <br />EOMUNU G BROWN JR <br />GOVERNOR <br />RN.. MATTHEW RODRIQUEZ <br />-Ili's SECRETARY FOR <br />ENVIRONMENTAL PROTECTION <br />Central Valley Regional Water Quality Control Board <br />26 September 2018 <br />Bonny Carter <br />Director of Facilities and Planning <br />Tracy Unified School District <br />1875W. Lowell Avenue <br />Tracy, CA 95376 <br />ADDITIONAL GROUNDWATER INVESTIGATION WORK PLAN, FORMER DELTA ISLAND <br />SCHOOL, 11022 WEST HOWARD ROAD, STOCKTON, SAN JOAQUIN COUNTY <br />Central Valley Water Board staff has reviewed the 20 September 2018 Additional Groundwater <br />Investigation Work Plan (work plan) prepared by GHD Services Inc. (GHD) on behalf of the Tracy <br />Unified School District for the former Delta Island School property in San Joaquin County. The work <br />plan was submitted pursuant to our meeting with you on 6 September 2018 during which we <br />requested additional groundwater sampling for dissolved arsenic since previous groundwater samples <br />contained arsenic above the Maximum Contaminant Level (MCL) of 10 micrograms per liter, but may <br />not have been field-filtered to remove sediments. <br />GHD proposes to advance four borings and collect a grab groundwater sample from each boring at <br />the locations shown on Figure 2 of the work plan. The proposed locations generally correspond with <br />the locations of the four previous groundwater samples. Each boring will be drilled to a depth of <br />20 feet, or 10 feet below first encountered groundwater and a temporary PVC well casing with 10 feet <br />of screen will be inserted into each borehole before sample collection. Grab groundwater samples will <br />be collected using a peristaltic pump, clean stainless-steel bailer, or new disposable bailer, and field <br />filtered using a 0.45-micron filter. The samples will be submitted to a California-certified laboratory for <br />analysis for dissolved arsenic by EPA Method 200.8. GHD will prepare a report documenting the field <br />activities, sample results, conclusions, and recommendations. <br />Central Valley Water Board staff concurs with the work proposed in the work plan. Please the results <br />report by 10 December 2018. As proposed, any necessary well drilling permits will be obtained prior <br />to the field work. Please provide us with a minimum of 72 hours' notice prior to initiation of the field <br />work so that we have an opportunity to observe the work. <br />Feel free to contact me with any questions or concerns regarding this letter at (916) 464-4622 or <br />Bill.Brattainwaterboards.ca.qov. <br />Original signed by <br />William Brattain, P.E. <br />Water Resource Control Engineer <br />Private Sites Cleanup Unit <br />cc: Fred Blickle, GHD Services Inc., Emeryville <br />;7. 1 D. P.E. ••• Pi. iv ESO., EXECUTIVE OFFICER <br />11020 Sun Center Drive E200, Rancho Cordova, CA 95670 I www waterboards ca.gov/centralvalley <br />OELYCEORAPER