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V 1 � THOMAS R. FLINN DIRECTOR c,. P 4CiF�P� THOMAS M. GAU CHIEF DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGER JANES BUSINESS ADMINISTRATOR Mr. Todd Del Frate March 12, 2010 California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive, #200 Rancho Cordova, California 95670-6114 P. PBOX 1810 -1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201 (209) 468-3000 FAX (209) 468-2999 wvvw.sjgov.org/pubworks SUBJECT: PROPOSED REMOVAL OF SOIL GAS WELL SG -8, FOOTHILL LANDFILL Dear Mr. Del Frate: ®��I Soil gas well SG -8 was among 11 single -probe soil gas monitoring wells installed by the County in 2003 (Figure 1). The purpose of these wells was to provide subsurface monitoring of landfill gas migration in compliance with the regulations in place at that time, and to allow monitoring of the soil gas volatile organic compounds (VOC) per Monitoring and Reporting Program (MRP) R5-2003-0020. SG -8 was installed directly south of Module 1, in the footprint of the next planned Module (Module 2). In 2009, the County installed triple -probe migration monitoring wells near the property boundary in accordance with Title 27 California Code of Regulations Section 20925, thereby removing the need for subsurface migration monitoring at SG -8 and other single -probe wells. MRP R5-2003-0020 does not specify the number of soil gas wells, and VOC data gathered in the six years since monitoring began does not indicate relevance to groundwater quality. According to the development plan for the landfill, the landfill operator continues to remove soil from the footprint of Module 2, as needed for soil cover in Module 1. He has avoided destroying SG -8 by excavating around it, creating a small hill with the enclosure for that well at the top. However, this well must be removed in the near future to make way for Module 2. Because it is close to the active face, it is ideally located to provide cover soil during the next wet season. It would be timely and efficient to begin utilizing that soil next winter. Therefore, we propose to make the soil of this small hill available for use as daily cover starting next winter, which will result in the removal of that well. Monitoring for subsurface migration of landfill gas will continue at the wells installed in 2009, and measurement of subsurface VOC concentrations will continue at the other single -probe wells installed in 2003.