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PgUlry THOMAS R. FLINN DIRECTOR C9C/FgRN�P THOMAS M. GAU CHIEF DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGER JANES BUSINESS ADMINISTRATOR May 18, 2010 Mr. Todd Del Frate California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive, #200 Rancho Cordova, California 95670-6114 0 P. O. BOX 160 - 1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201 (209) 468-3000 FAX (209) 468-2999 www.sjgov.org/pubworks SUBJECT: BARRIER OVER REFUSE AT FOOTHILL SANITARY LANDFILL Dear Mr. Del Frate: This letter addresses an issue that you and I have discussed before: the barrier between old and new refuse of Module "I" at Foothill Landfill. Our adjustment of the landfill gas (LFG) system at the Foothill Landfill indicates that well GX-2 may not be fully functional (Figure 1). 1 suspect that the refuse beneath the lateral pipe to that well has settled, causing a low spot where condensate can collect (Figure 2). This low area is probably near the well head, which is under the HDPE fabric installed during the Site Improvement Project of 2006. We are nominally in compliance with our AQMD permit, which requires that we maintain vacuum "at the well head". Since this well is beneath the HDPE fabric, the pressure at the adjustment valve is used to measure well pressure, and we continue to show vacuum at that point. Nominal compliance aside, we should keep all wells fully functional, especially those beneath the HDPE fabric. To restore full function to GX-2 we have little choice except to go through the HDPE to the well head. Once we find the well, we will extend the well riser through the fabric, and connect the well to the LFG system with a new pipe (Figure 2). The need to excavate through the HDPE causes us to consider the HDPE fabric and its purpose. The HDPE fabric separates the old refuse in Module "I" (which is does not have a liner) from the new refuse that placed over the Module "I" footprint due to the construction of Module 1 (which is lined). Title 27 of the California Code of Regulations does not address this situation, and does not require a separation or barrier. Title 27 does, however, require barriers in two other situations: base liners under refuse prior to the disposal of refuse over native soil (Section 20330), and closure barriers placed over refuse (Section 21090(a)(2)).