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ENVIRONMENTAL HEALT]abEPARTMENT <br /> � SAN JOAQUIN COUNTY <br /> 2 2 Donna K. Heran, R.E.H.S. Unit Supervisors <br /> Director 304 East Weber Avenue,Third Floor Carl Borgman,R.E.H.S. <br /> Al Olsen, R.E.H.S. Stockton,California 95202-2708 Mike Huggins, R.E.H.S., R.D.I. <br /> ;P.• Program Manager Tele hone: 209 468-3420 Douglas W. Wilson, R.E.H.S. <br /> • c4�iFoaa p ( ) Margaret Lagorio,R.E.H.S. <br /> Laurie A. Cotulla, R.E.H.S. Fax: (209)464-0138 Robert McClellon, R.E.H.S. <br /> Program Manager <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 Soil 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/EHD approves the proposed borings to 60 feet bsg and the collection of grab <br /> groundwater samples. SJC/EHD recommends these borings be continuously cored to <br /> obtain 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 borings 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 />