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• O.P'p U I ry• C y< THOMAS M.GAU P.O.BOX 1810-1810 E.HAZELTON AVENUE DIRECTOR STOCKTON,CALIFORNIA 95201 (209)468-3000 FAX(209)468-2999 www.sjgov.org/pubworks FRITZ BUCHMAN W'D1T°Ung for YOU DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER RECEIVED DEPUTY DIRECTOR ROGER JANES February 29, 2012 BUSINESS ADMINISTRATOR 0 2 2012 Mr. Robert McClellon, Program Coordinator Environmental Health Department EWRONMENTAL HEALTH 600 East Main Street PERMIT/SERV Stockton, California 95202 SUBJECT: IMPROVEMENT OF PERIMETER LANDFILL GAS MONITORING WELLS AT SAN JOAQUIN COUNTY-OWNED LANDFILLS Dear Mr. McClellon:01 ett I Thank you and Gino Yekta for your review of our proposed improvement to the perimeter landfill gas migration monitoring wells at San Joaquin County-owned landfills. The improvement (insertion of a small-diameter tube within the existing probe pipes) will greatly reduce the time required for monitoring, increase the reliability of the measurement of the subsurface gas composition, and ensure that combustible gas does not enter the soil of adjacent properties. This letter is written in response to the email received February 22, 2012 from Mr. Gino Yekta of CalRecycle's Closure branch which granted approval of our proposed improvements under certain conditions. We are pleased to meet these conditions, as follows: 1. Monitoring is not compromised by the insertion of the tubes. Monitoring is not compromised. In fact, monitoring will be improved by reducing the amount of air that must be removed from the well to measure subsurface soil gas concentrations. 2. We provide "Certification from the Operator/consultant that the new design will function the same way as the original design. I am pleased to provide the certification below. Measurement of the concentration of gasses in the soil will be by the same method as before: bringing a small amount of air to the surface where we use a hand-held instrument to measure gas concentrations. Measurement will be more reliable because the smaller tube means reduced potential for dilution of the subsurface gas by air intrusion and the time required for monitoring, an issue raised by Mr. Yekta. 3. /f issues are discovered with the new design, the Operator will immediately change to the original design. Yes, if we find problems with this design that cannot be solved, then we will immediately and easily remove the tubes, restoring the probes to their original condition.