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.(Q'� gncon <br /> 1433 North Market Boulevard •Sacramento.California 95834-1943 • (916)928-3300 . Fax(916)928-3341 <br /> DEC 05 1,997 December 3, 1997 <br /> Project 20C42-001.026 <br /> ENV+F„-; �,`:TAL HEALTH <br /> PERMIT/SERVICES <br /> Ms.Gail Wiggit <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3098 <br /> Re: Well 17A1 Decommissioning; Tesoro Distribution Terminal, Stockton, California <br /> Dear Ms. Wiggit: <br /> EMCON recommends proceeding with decommissioning Tesoro well 17A1 based on the <br /> information obtained from the recently conducted video log and third quarter 1997 <br /> sampling event. <br /> The video log appears to confirm the identity of the well as Well 17A1. As we discussed, <br /> the video log clearly shows that the well casing (8-inch diameter) is corroded at two <br /> locations at a depth of approximately 53 feet below ground surface (bgs). A second casing <br /> (10-inch diameter), which corresponds to the outer casing specifications on the Department <br /> of Water Resources (DWR Well Data Form, was visible through the corroded inner <br /> casing. The well is silted in at approximately 54 feet bgs, corresponding to the corrosion <br /> holes in the casing. <br /> As EMCON reported in the Third Quarter Groundwater Monitoring Report, free product <br /> was encountered during the initial attempt to decommission the well (July 18, 1997). Free <br /> product was removed from the well, sampled, and properly disposed of during this <br /> monitoring event. Sample results showed the free product consisted primarily of <br /> hydrocarbons in the C14 to C38 range (see attached chromatograms). Based on visual <br /> observations and the fuel finger print scan, the free product appears to be a result of lube <br /> oil leakage from the well pump. <br /> EMCON will decommission the well consistent with California Well Standards <br /> Bulletins 74-81 and 74-90. We will attempt to perforate the inner and outer casing to the <br /> current well depth of approximately 54 feet below ground surface (bgs), and pressure grout <br /> the well and well annulus from the bottom to the surface with a cement grout. The total <br /> well depth will be sounded. and the volume of the inner well casing the annual space <br /> uCLWCCn t da,iugS wui ire cai�—dWti to Lietermine the amount of grout required. Grout will <br /> SACN:\PJ00C4N1C4200126AA-97,cJb:6 Rev.0,1713/97 <br />