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ENVIRONMENTAL, HEALTH DEPARTMENT <br /> SAN JOAQUINCOUNTY <br /> unitsupervisors <br /> Donna K. Heran, R.E.H.S. <br /> 304 East Weber Avenue, Third Floor Cad Borgman, R.E.H.S. <br /> Direcfa' Mike Huggins, R.E.H.S., R.D.I. <br /> Al Olsen, R.E.H,S. Stockton, California 95202-2708 <br /> Douglas W. Wilson, R.E.H.S. <br /> Program Afnnager Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. <br /> 4liFO RN <br /> Laurie og Cotuāž¢a, R.E.}LS, Fax : (209) 464-0138 Robert McClellan, .E,H.S, <br /> Progrnm Afmmger Mark Barcellos, R.E.H.S. <br /> RODGER LISTON WAA 0 7 200ri <br /> DARPETRO INC USA SERVICE STATION <br /> 3450 EL CAMINO <br /> CERES CA 95307 <br /> RE: DARPETRO, INC Site Code: 1060 <br /> 749 E CHARTER WAY <br /> STOCKTON, CA 95202 <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Work Plan (WP), dated 16 October 2004, to install three groundwater <br /> monitoring wells and one assessment boring . EHD has also received a letter dated 15 <br /> October 2004 confirming a decision between EHD and your consultant California <br /> Geophysical Group, Inc. (CGG), to omit the soil gas survey of the site at this time. <br /> CGG proposes in WP to advance one boring to a target depth of 50 feet below surface <br /> grade in the former UST pit to collect soil samples at 5-foot intervals and grab ground <br /> water samples at 10-foot intervals until two consecutive ground water samples test 'non- <br /> detect' for gasoline components, the chemical analyses to be performed by an on-site <br /> mobile laboratory. In addition, CGG proposes to install three ground water monitoring <br /> wells, MW-14 , MW-15 and MW-16 near the southwest corner of Charter Way and Grant <br /> Street and east-southeast and north-northeast of the former UST pit to assess the lateral <br /> extent of impacted shallow groundwater. EHD approves installation of the three <br /> proposed groundwater monitoring wells, but with the provision that the sand filter pack <br /> extend only 2 feet above each screen interval . The grout seal shall be properly mixed <br /> portland cement with a maximum of 5% bentonite, approved for grouting by the <br /> manufacturer, mixed in the cement. <br /> EHD cannot approve advancement of the assessment boring at this time as the methods <br /> for advancing the boring and collecting soil and groundwater samples have not been <br /> specified . Also, EHD is still concerned that the approach for determining the total depth <br /> of the proposed boring in the former UST pit area utilizing a mobile lab may not be a <br /> cost-efficient method . EHD recommends that you do a cost estimate comparison for <br /> utilizing a mobile laboratory with the attendant drill rig standby time while analyzing <br /> samples vs. advancing a boring to a specified target depth likely to achieve vertical <br /> delineation, collecting groundwater samples and submitting them to a non-mobile <br /> laboratory facility. EHD notes that the State Water Board Cleanup Fund (Fund) may <br /> decline reimbursement of costs if the Fund decides the expenses submitted are <br /> excessive. EHD also recommends consideration of use of a cone penetration testing <br /> (CPB) rig to advance the boring and to collect groundwater samples from each interval <br /> of potential high permeability and submitting the samples to a non-mobile analytical <br /> laboratory facility. Please provide a work plan addendum to EHD by 18 April 2005 that <br />