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PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D ., M.P.H., Health Officer <br /> O [Py 'CIFOPI,\ <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 952(C <br /> 209/468-3420 <br /> PAUL SUPPLE APR 0 7 1998 <br /> ARCO PRODUCTS COMPANY <br /> PO BOX 6549 <br /> MORAGA CA 94570 <br /> RE: ARCO #548 SITE CODE: 1127 <br /> 1612 E. Hammer Ln , <br /> Stockton , CA. , 95210 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS-EHD) has <br /> reviewed the "Workplan to Conduct an Off-site Subsurface Investigation' dated January 28, <br /> 1998 as submitted by EMCON Consulting and offers the following comments. <br /> Installation of the proposed monitoring wells in the adjacent parcel to the south of the site <br /> will require an access agreement signed by the property owner. This document is to be on <br /> file with PHS-EHD prior to issuing a boring permit. Please take the appropriate steps to <br /> obtain this agreement and forward a copy to Michael Infurna, Senior REHS, temporarily <br /> assigned to this site for review of workplans and field inspections. <br /> PHS-EHD staff will conduct a field inspection during drilling activities and will determine <br /> which soil samples will be selected for analysis at the laboratory. At a minimum, an <br /> adequate number of soil samples must be analyzed to support conclusions regarding the <br /> lateral and vertical delineation of soil contamination . Prior to any evaluation for a "No <br /> Further Action' determination, PHS-EHD will require a complete evaluation of the <br /> contaminated soil remaining in place including the mass, volume, and average petroleum <br /> concentration. <br /> As discussed at the February 18, 1998 ARCO/PHS-EHD meeting, EPA Method 8260 is to <br /> be run on all groundwater and soil samples collected until PHS-EHD determines that they <br /> are no longer required . Please include this oxygenate laboratory analysis in a revision to <br /> this soil boring/monitoring well installation workplan and make certain that all future quarterly <br /> monitoring reports include this analysis also. <br /> In reviewing this site, it is noted that the depth to groundwater has been above the <br /> monitoring well screened intervals since March, 1993. As of August 12, 1997 (the last <br /> quarterly report received) , the depth to groundwater was more than 15 feet over the top of <br /> MW- 1 's screened interval. This condition is not consistent with determining the true <br /> petroleum concentrations in the shallow aquifer. Additional monitoring wells must be placed <br /> throughout the site that are constructed so that the screened interval of the well "captures" <br /> the depth to groundwater at the time the well is built. This additional requirement shall be <br /> included in a revised workplan or in an addendum before PHS-EHD approves this phase of <br /> investigation. A destruction procedure for MW-3 and a replacement plan should be included <br /> in the revision as well as the well destruction permit application and $60 fee. <br /> A Division of San Joaquin County Healch Can: Services <br />