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STATE OF CALIFORNIA GEORGE DEUKMEJIAN,Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION _� _, 3443 RGUTIER ROAD r SACRAf 1ENTO,CA 95827-3098 Mr. Ted Knowles 17 February 1989 1140 West Hammer Lane Stockton, CA 95209 SOIL REMEDIATION PROPOSAL FOR FORMER KNOWLES GAS STATION AT 1140 WEST HAMMER LANE, STOCKTON Thank you for submitting the 6 February 1989 Soil Remediation Proposal (SRP) for our review. The in-situ venting system proposed by Groundwater Technology, Incorporated (GTI) to remediate soil at your site is acceptable to us provided that the system is shown to operate effectively during the "full - scale test. " Prior to installation, GTI is to supply us with the details on the procedures they propose to use when conducting this full -scale test of the soil venting system. The screened intervals of the proposed recovery wells extend across sand, silt, and clay layers, which means, due to its higher permeability, the sand layer will yield the m)st vapors. How will the testing evaluate the systems ability to yield vapors from the silt and clay layers? Will it be necessary to install recovL:ry wells which are screened in discrete layers or can it be shown that the system will recover vapors from all the layers? _ Please have GTI supply us with the testing details by 10 March 1989. All required permits for installation and operation of the system must be obtained from the appropriate local agencies . In addition, the extent of soil contamination beneath the tank pit is based on data from one soil boring (SB-1) . In order to better define the vertical extent, and to show the initial concentrations prior to soil venting, we request that at least two soil samples collected from each of the four vapor recovery well installation borings be submitted to the laboratory for TPH as gasoline and BTX and E analyses. Soil samples collected from 30 feet below grade down to the vertical extent of the boring are of special of interest. If petroleum hydrocarbons are detected in the soil samples collected at 45 feet below grade (the proposed vertical extent of the borings) , the boring is to be advanced until no hyd-ocarbons are detected, or until ground water is - encountered. If you have any questions, )lease call me at (916) 361-5725. �c�a.r� W Gvrx� EDWARD W. JAMES Wrr.r6,0_ /Wic 172.e Engineering Geologist EWJ:ewj cc: Ms. Diane Hinson, San Joaquin Local Health District, Stockton Mr. James Grasty, Groundwater Technology, Incorporated, Sacramento