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FW)) <br />gOio <br />EDMUND G BROWN JR. <br />cov[nNon C o <br />°O° 207 <br />Water Boards .14,0,00-grk4S <br />Central Valley Regional Water Quality Control Board c- ()E-V \ACC.5 <br />MATTHEW RODRIOLLEZ <br />SECRETARY FOR <br />ENVIRONMENTAL PROTECTION <br />6 December 2012 <br />Belinda May, LTC <br />Environmental Compliance Officer <br />10620 Mather Road <br />Mather, CA 95655-4176 <br />WORK PLAN FOR GROUNDWATER INVESTIGATION AND GROUNDWATER <br />MONITORING WELL INSTALLATION, FIELD MAINTENANCE SHOP #24, <br />STOCKTON CALIFORNIA ARMY NATIONAL GUARD COMPLEX, SAN JOAQUIN <br />COUNTY <br />Central Valley Regional Water Quality Control Board staff (Central Valley Water Board <br />staff) has reviewed the Work Plan for Groundwater Investigation and Groundwater <br />Monitoring Well Installation (Work Plan) received on 7 November 2012. The Work Plan <br />provides the rationale and procedures to investigate the Field Maintenance Shop <br />groundwater plume and source area. This investigation is proposed in support of <br />potential implementation of an in-situ chemical oxidation remedy Central Valley Water <br />Board staff comments on the Work Plan are provided below. <br />COMMENTS <br />1. Page 10, Section 3.3, Membrane Interface Probe Borings: It is unclear how the 2 500 <br />square foot "source area" was selected for investigation. The area is oval in shape <br />and appears to be oriented along a line between existing monitoring wells FMS-MW2 <br />and FMS-MVV5. The "source area does not include the entire footprint of the former <br />underground storage tanks (USTs) nor the location of dual phase extraction well FMS- <br />DPE2, which is screened in relatively high concentrations of petroleum hydrocarbons. <br />Revise the Work Plan to explain how the "source area" was selected for investigation <br />and explain why some areas with significant contamination are not included. <br />The primary goal of the Work Plan is to collect additional data necessary to support <br />potential in-situ chemical oxidation. Therefore, Central Valley Water Board staff <br />recommends including the entire area of known and suspected high residual <br />petroleum hydrocarbons concentrations in the proposed "source area" investigation. <br />KARL E. LONGLEY ScD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br />11020 Sun Center Drive *200, Rancho Cordova, CA 95670 I www.waterboards.ca .govicentralvaliay <br />Cip RECYCLED PAPER