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! HU Wr l <br /> PUBLIC HEALTH SERVIC,hS )OPOu!N C <br /> .o� <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION 7 ` J. <br /> Karen Furst, M.D., M.P.H., Health Officer °"ciFoa�`P <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> JUN 0 1 2000 <br /> KAREN PETRYNA <br /> C/O EQUIVA LLC <br /> PO BOX 7869 <br /> BURBANK CA 91510-7869 <br /> RE: TEXACO STATION <br /> SITE CODE: 1055 <br /> 440 W CHARTER WAY <br /> STOCKTON CA <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) has recently <br /> reviewed a "Response Letter/Amended Workplan" from Cambria Environmental Technology dated May <br /> 11, 2000 regarding the site referenced above. The Cambria letter is provided in response to an April 17, <br /> 2000 directive from PHS/EHD to the responsible party. PHS/EHD has discussed the site with your <br /> consultant(Cambria)on several occasions. <br /> At one time several feet of petroleum hydrocarbon free-product was documented in monitor wells at this <br /> site. The above referenced site is geographically located at the center of a complex groundwater plume <br /> investigation currently involving six sites. PHS/EHD has recommended that you focus your resources on <br /> delineating your plume boundaries and defining potential plume blending intersections (cormningled <br /> plumes) recognizing the potential for contaminants to migrate to and from nearby sources (all comers of <br /> Lincoln and Charter Way). PHS/EHD has also asked you to evaluate data from surrounding sites on a <br /> routine basis to more cost effectively understand regional contaminant impacts and hydrogeologic findings. <br /> Recognizing these issues PHS/EHD has respectfully requested your assistance in previous correspondence. <br /> On May 24, 2000 PHS/EHD and a representative from the Central Valley Regional Water Quality Control <br /> Board(CVRWQCB) met to discuss this site in detail. As a result of this meeting both PHS/EHD and the <br /> CVRWQCB agree that the scope of work proposed in the May 11, 2000 letter is insufficient to adequately <br /> characterize the soil and groundwater plume at this site in a timely manner. <br /> A transect approach to plume definition has been recommended in conversations with your consultant. No <br /> monitor wells or boreholes are present at this site at depths greater than 60 feet below grade surface (bgs). <br /> Down-gradient wells are impacted with benzene and MtBE clearly indicating the lack of vertical and lateral <br /> plume definition. Numerous boreholes and wells in close proximity to this site document the presence of <br /> fuel hydrocarbons in groundwater at depths greater than 85 feet bgs. PHS/EHD and the CVRWQCB are <br /> closely evaluating the placement and construction details of boreholes and wells to assist in the process of <br /> delineating a large, widespread commingled groundwater plume. PHS/EHD has recommended to Cambria <br /> on May 19 and 26", 2000 that two continuous core boreholes be placed along the eastern property line <br /> (parallel with MW-5, .VEW-4, and MW-3) and a second transect consisting of two continuous core <br /> boreholes be installed parallel with MW-9, MW-11 and MW-10 on the down-gradient parcel to the east. <br /> PHS/EHD recommends that your consultant advance the continuous core Cone Penetration Tests (CPT) to <br /> at least 80 feet bgs or greater collecting soil and groundwater samples as needed to define your plume. <br /> 1 <br /> A Division of San Joaquin County Health Care Services <br />