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Emcon <br /> 1433 North Market Boulevard•Sacramento.CA 5834-1943•(916)928.3300•Fax(916)928-3341 <br /> nr; i• , ,'� A,''O i� • ZJ <br /> June 25, 1998 <br /> Project 20C42-001.026 <br /> Mr. Ron Rowe <br /> San Joaquin County Environmental H Wth <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> Re: Abandonment of Tesoro Well 17A1 at the Stockton Bulk Terminals, Stockton, <br /> California <br /> Dear Mr. Rowe: <br /> EMCON appreciated the opportunity to meet with you and Margaret Lagorio on June 18, <br /> 1998, to discuss the abandonment of Well 17AL During the meeting, you reiterated that <br /> pressure grouting was a "preferred" method for well abandonment rather than the approach <br /> used by EMCON, which included tremieing grout into the well, filling the casing with <br /> grout, pulling the well casing from the borehole, and bringing the grout level to ground <br /> level. We discussed several reasons why the approach EMCON selected provides the <br /> greatest probability for successful sealing. <br /> The purpose of this letter is to el rate on the rationale used for selection of the <br /> abandonment procedure as discussed with you at the June 18, 1998 meeting. Attached are <br /> letters prepared by both EMCON and Water Development Corporation in response to your <br /> March 3, 1998 letter. These letters should serve as background information and provide <br /> additional details. <br /> Unsealed abandoned wells constituta potential hazard to preservation of groundwater <br /> resources. The sealing of such wellsIter <br /> case in point well 17A1, must eliminate the hazard <br /> and prevent both potential groundw contamination and intermingling of groundwater <br /> zones. A destruction permit was issued by San Joaquin County Public Health Services to <br /> abandon well 17A1 to a depth of 55 feet. The permit called for the casing to be perforated <br /> at three foot intervals and pressured grouted. <br /> The goal of sealing well 17A1 or any abandoned well is to restore the downhole conditions <br /> to the geohyrologic conditions that existed prior to drilling and constructing the well. The <br /> intent of abandoning well 17A1 wa� to fill the borehole in such a manner that vertical <br /> movement of water within the well 'casmg, including vertical movement of water within <br /> the annular space surrounding the well casing, is prevented. This sealing procedure will <br /> SACSI:.\PIG,OC42\OC420012.6AG-95Vba=s:I <br />