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mit EDMUND G. BROWN JR. <br /> GOVERNOR <br /> OALIlOM MIA MATTHEW RODRIDUEZ <br /> Water Boards SECRETARY FOR <br /> ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> RECtIVED <br /> 27 July 2015 AUG 3 2®15 <br /> ftWr'01VW <br /> Mr. Taj M. Bahadori, PE PERMIT/S RVICESL <br /> TH <br /> Senior Civil Engineer <br /> San Joaquin County Public Works, Solid Waste Division <br /> 1810 E. Hazelton Avenue <br /> Stockton, CA 95201 <br /> ADDENDUM TO REVISED ENGINEERING FEASIBILITY STUDY, FOOTHILL SANITARY <br /> LANDFILL, SAN JOAQUIN COUNTY <br /> The Foothill Sanitary Landfill is owned by San Joaquin County Department of Public Works and <br /> operated by Foothill Landfill Inc. (hereinafter jointly known as Discharger) and is regulated by <br /> Waste Discharge Requirements Order R5-2015-0058 and Cleanup and Abatement Order <br /> R5-2004-0706. On 1 August 2014, staff issued a Notice of Violation (NOV) requesting the <br /> Discharger revise their Engineering Feasibility Study (EFS) and propose additional corrective <br /> action measures to address landfill gas migration within the vadose zone. The source of the <br /> contaminants (volatile organic compounds) has been identified as the unlined Module I. Landfill <br /> gas and groundwater data submitted by Discharger confirms the release is ongoing. <br /> The Discharger submitted a Revised EFS dated 19 December 2014 that addressed the issues <br /> outlined in the 17 October 2014 email from staff. The current Module I LFG system consists of <br /> nine (9) vertical LFG extraction wells with applied vacuum coming from the on-site gas to <br /> energy plant. The vadose zone surrounding Module I is currently only being monitored by 10 <br /> soil gas probes. The number of extraction wells and the vadose zone probes were noted as an <br /> area of concern in the 1 August 2014 NOV. <br /> On 21 May 2015, staff responded to the Revised EFS. Staff's response requested the <br /> Discharger prepare an EFS addendum addressing the following concerns: <br /> • The plan did not include details of how field work and data collection will be measured, <br /> recorded, and what order the test will proceed for the Radius of Influence investigation. <br /> • The plan did not include reconstruction of soil gas probes SG-3A, SG-5A, SG-7, SG-10, <br /> and SG-11A during the first phase of this project. <br /> In a letter dated 17 July 2015, the Discharger proposes to proceed with the installation of <br /> additional corrective action measures in two Phases. Phase 1 will consist of installing four (4) <br /> LFG extraction wells to the active LFG system, along with reconstruction of four (4) soil vapor <br /> gas probes. The Discharger also proposes to perform a ROI investigation and modeling to help <br /> determine the location of additional LFG extraction wells and soil gas monitoring probes. <br /> KARL E. LONGLEY SCD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/centralvalley <br /> ICA RECYCLED PAPER <br />