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1 <br /> ENVIRONMENTAL HEALTAEPARTMENT <br /> Pp UJN C SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Director 304 East Weber Avenue, Third Floor Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202 Douglas W.Wilson,R.E.H.S. <br /> • cq. _�c• Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> c,F okd Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Mark Barcellos,R.E.H.S. <br /> FEB 1 4 2002 <br /> PAUL SUPPLE <br /> ARCO PRODUCTS COMPANY <br /> P O BOX 6549 <br /> MORAGA CA 95470 <br /> RE: ARCO Station #4932 SITE CODE: 1136 <br /> 16 E. Harding Way <br /> Stockton CA 95204 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed the <br /> "Response to SJC/PHS Letter dated December 7, 2001 and Work Plan for Additional Site <br /> Assessment and Feasibility Testing" dated January 15, 2001 that was submitted on your <br /> behalf by SECOR International Incorporated (SECOR) and has the following comments. <br /> In response to the Responses: the issue of deadlines was discussed. Both work plans <br /> that had been submitted by SECOR on your behalf had stated approximate deadlines for <br /> submittal of the reports of findings following completion of the proposed work. Both work <br /> plans were approved in whole by SJC/EHD, no conditions modifying the proposed <br /> approximate deadlines for submittal of the reports of findings were made by SJC/EHD. As <br /> such, SJC/EHD expected the reports would be submitted by the latest of the approximate <br /> dates proposed by SECOR and approved by SJC/EHD. <br /> As concerns the pumping test that was performed but not reported. SECOR stated that <br /> the test was not formal aquifer testing, but was done to give SECOR an idea of <br /> approximate flow rates to enable them to design a formal aquifer test. However, the <br /> performance of a formal aquifer test at a later date was not proposed in the work plan. <br /> Though the work should have been addressed with an addendum, SJC/EHD recognizes <br /> that at times changes in field conditions require changes in investigative procedures. The <br /> pumping test simply should have been reported. <br /> One item that SECOR did not respond to was the lack of comparison of groundwater <br /> contaminant concentrations following the MPE test to the concentrations from before the <br /> test was conducted. This was a task that SECOR had proposed to complete. <br /> The Work Plan for Additional Site Assessment and Feasibility Testing proposes the <br /> installation of three additional shallow groundwater monitoring wells, the installation of <br /> three deep groundwater monitoring wells, the installation of one groundwater extraction <br /> well, and the performance of a three-day groundwater extraction feasibility test. <br /> The proposed shallow wells will be built to 40-feet below surface grade (bsg) with a <br /> maximum screen interval of 20 feet. They will be located off-site to obtain lateral shallow <br /> plume definition in the down gradient direction. The proposed deep wells will be built to <br /> 77-feet bsg with a maximum screen interval of 5 feet. One deep well will be located on- <br /> site; the other two will be located off-site to the north/north-east. Soil samples will be <br /> collected every five feet during the drilling of the boreholes for the wells; selected samples <br />