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ENVIRONMENTAL HEALTH DEPARTMENT <br /> p �;" SAN JOAQUIN COUNTY <br /> Donna K Hera n, RE H S Vnd Supervisors <br /> < Director 304 East Weber Avenue,Third Floor Carl Rorgman,R E H S <br /> Al Olsen, R E H S Stockton,California 95202-2708 Mire Huggins, a E H S, R D I <br /> Ci4{'����`P Prograni Manager Telephone (209)468-3420 Douglas W Wilson, R E!-i S <br /> Laune A Cotulla, R E H.S. Mnrgarct Lasorio,R E H S <br /> Program Manager Fax (209) 464-0138 Robert McCiellon, R E li 5 <br /> Website www sjgov org/ehd/ Jeff Carruesco,R E H S <br /> AUG 1 2005 <br /> DARIN ROUSE PAUL SUPPLE <br /> CHEVRON PRODUCTS COMPANY ATLANTIC RICHFIELD COMPANY <br /> PO BOX 6004 BLDG V PO BOX 6549 <br /> SAN RAMON CA 94583 MORAGA CA 94570 <br /> RE Chevron #9-4275 and ARCO #2133 <br /> CUF Claim #CP0034 <br /> 2905 and 2908 Ben Holt Drive <br /> Stockton CA 95207 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed "Work <br /> Plan for Sod and Groundwater Delineation and Addendum to Work Plan for Well <br /> Destruction and UST Removal"dated May 27, 2005, submitted on your behalf by Secor <br /> International Incorporated (SECOR) and has the following comments <br /> The work plan proposes to complete delineation of the vertical and lateral extent of the <br /> . soil and groundwater contamination at the above referenced commingled plume site with <br /> the installation of six onsite soil borings to 60 feet below surface grade (bsg)for the <br /> collection of hydropunch grab groundwater samples, and the installation of two offsite soil <br /> borings to 25 feet bsg Three of the six deep borings will be located on the Chevron <br /> property, following collection of the hydropunch samples from these borings SECOR <br /> proposes to backfill the boreholes with grout to 20 feet bsg and convert them to shallow <br /> groundwater monitoring wells The remaining three deep borings will be located on the <br /> ARCO property and will be fully destroyed by backfilling with neat cement grout following <br /> collection of the hydropunch samples One of the proposed offsite borings will be <br /> converted to shallow groundwater monitoring well MW-10 located north of the Chevron <br /> site The proposed location of the second shallow boring, identified as AS-11, is to the <br /> east of the ARCO site <br /> SJC/EHE approves the proposed bonngs to 60 feet bsg and the collection of grab <br /> groundwater samples SJC/EHD recommends these bonngs be continuously cored to <br /> obtaln an accurate soil profile to identify potential contaminant migration pathways and to <br /> aid in the development of the commingled plume site conceptual model If samples <br /> collected from 60 feet bsg exhibit field indications of contamination the bonngs should be <br /> extended and samples collected from deeper units If Chevron/ARCO chooses not to do <br /> this, and deep contamination is documented in the analytical data,further assessment of <br /> the vertical extent of the plume will be required SJC/EHD also approves the backfill and <br /> conversion of the three borings proposed for location on the Chevron property to shallow <br /> groundwater monitoring wells <br /> AUG 0 2 2005 <br /> By ----------- <br />