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POUIry <br />N <br />� THOMAS R. FLINN <br />DIRECTOR <br />9CIFOPH <br />THOMAS M. GAU <br />CHIEF DEPUTY DIRECTOR <br />MICHAEL SELLING <br />DEPUTY DIRECTOR <br />STEVEN WINKLER <br />DEPUTY DIRECTOR <br />ROGER JANES <br />BUSINESS ADMINISTRATOR <br />June 24, 2010 <br />Mr. Todd Del Frate <br />Engineering Geologist <br />California Regional Water Quality Control Board <br />11020 Sun Center Drive, #200 <br />Rancho Cordova, California 95820-6114 <br />[A <br />P. O. BOX 1810 - 1810 E. HAZELTON AVENUE <br />STOCKTON, CALIFORNIA 95201 <br />(209) 468-3000 FAX (209) 468-2999 <br />www.sjgov.org/pubworks <br />LUId <br />�T1rr'LRVICES <br />SUBJECT: UPDATED ENGINEERING FEASIBILITY STUDY AND AMENDED REPORT OF <br />WASTE DISCHARGE, CORRAL HOLLOW SANITARY LANDFILL <br />Dear Mr. Del Frate: <br />0� <br />Please consider this letter an updated Engineering Feasibility Study and amended Report of Waste <br />Discharge submitted in accordance with your letter dated May 13, 2010. At issue is the continuing <br />detections of volatile organic compounds in the shallow aquifer (concentrations usually less than <br />10 ppb), which we attribute to landfill gas (LFG). The deep aquifer continues to be unaffected. <br />An important feature of the site is that refuse is known to be placed in the CalTrans property east <br />of our site. Landfill gas is not collected from this refuse except for the influence of wells installed <br />on our property. <br />Although the number of VOCs has been reduced by the LFG system which began operation in <br />2001, the five additional wells installed in December 2008 have not had the desired effect <br />(Figure 1). These wells were located to attempt to collect LFG from the refuse in CalTrans <br />property east of the landfill. <br />We continue to apply vacuum to these wells far in excess of our normal adjustment criteria, such <br />that the gas collected from these wells is very low in methane, as follows: <br />�-o-/I c <br />LFG Extraction Well <br />Methane Content <br />EW -40 <br />0.4 <br />EW -41 <br />0.4 <br />EW -42 <br />0.0 <br />EW -43 <br />1.6 <br />EW -44 <br />2.3 <br />4 <br />Gas of this concentration dilutes the fuel reaching the LFG flare, which is presently operating near <br />the lower limits of its fuel requirement. In spite of this excessive gas withdrawal, we continue to <br />find VOCs in the shallow aquifer samples. <br />