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CONDOR EARTH <br />188 Frank West Circle, Suite I <br />Stockton, CA 95206 <br />209.234.0518 <br />Fax 209.234.0538 <br />www.condorearth.com CONDOR <br />July 11,2017 <br />Alan Buehler <br />Engineering Geologist <br />Central Valley Regional Water Quality Control Board <br />11020 Sun Center Drive, #200 <br />Rancho Cordova, CA 95670 <br />Subject: Second Addendum to Work Plan for Additional Subsurface Investigation and Well <br />Installation, San Joaquin County Public Works, Hazelton Complex <br />1810 E. Hazelton Avenue, Stockton, CA (RB Case #390489) <br />Condor Project No. 596006 <br />Dear Mr. Buehler: <br />Condor Earth (Condor) has prepared this Second Addendum to the Work Plan for Additional Subsurface <br />Investigation and Well Installation (Work Plan) dated June 19, 2017, to address revised locations for <br />proposed deep borings CPT-1 and CPT-2, proposed shallow boring SB-4, and proposed monitoring wells <br />MW-8, MW-9, and MW-10 at the San Joaquin County Public Works Hazelton Complex (Site) located at <br />1810 E. Hazelton Avenue, Stockton, California. <br />Proposed Revised Locations Borings/Wells <br />Based upon our recent email exchange, Condor is proposing to relocate proposed borings/wells as <br />described below. Proposed locations are shown on the revised Figure 6, attached. <br />CPT-1: In order to minimize potential "drag-down" of contaminants into deeper zones, proposed <br />deep boring CPT-1 will be located approximately 80 feet downgradient of well MW-2 (the <br />monitoring well with the highest concentrations of benzene and MTBE), at the estimated extent <br />of the 100 micrograms per liter (p,g/L) contour for benzene and MTBE; <br />CPT-2: Proposed deep boring located approximately 80 feet east-northeast of proposed boring <br />CPT-1, which is at the approximate downgradient extent of the dissolved contaminant plume; <br />SB-4: Proposed shallow boring located just south of former UST-3 and just west of UST-5 to <br />evaluate the nature of residual petroleum hydrocarbons in soil at depths of approximately 2, 5, <br />and 10 feet below ground surface (bgs); <br />OW-7: Proposed ozone injection well to be installed between the southern dispenser and UST-2, <br />where ozone injection well OW-7 was previously proposed but not installed; <br />MW-8: Proposed shallow compliance well downgradient of the source area and between existing <br />monitoring wells MW-3 and MW-4;