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Environmental Consultants 4707 Greenleaf Circle 209 545-8490 <br /> Suite F FAX 209 545-8391 <br /> Modesto,CA 95356 <br /> www.scsfieldservices.com <br /> • <br /> April 18, 2007 <br /> File No. 07206052.00 <br /> Mr. Dan Johnson <br /> County of San Joaquin <br /> P.O. Box 1810 <br /> Stockton, California 95201 <br /> Subject: First Quarter 2007, Perimeter Gas Monitoring Probe and Structure Roof Vent <br /> Landfill Gas (LFG)Testing at the Harney Lane Landfill, Lodi, California <br /> Dear Mr. Johnson: <br /> This letter provides results of perimeter monitoring probes(GW) and structure roof vent testing <br /> for the first quarter of 2007 (January through March) performed by SCS Field Services (SCS). <br /> All testing, monitoring protocols and reporting were performed in general conformance with <br /> Title 27 California Code of Regulations(CCR)Article 6. Briefly, these regulations require that <br /> solid waste disposal site owners/operators implement LFG control or monitoring provisions to <br /> ensure that methane gas concentrations in soils at the property boundary do not exceed the lower <br /> explosive limit(LEL, or 5 percent by volume)and that interiors of on-site structures do not <br /> exceed 1.25 percent by volume in air. Below is a summary of our quarterly monitoring <br /> activities. <br /> Summary,Conclusions and Recommendations <br /> As of the date of our testing, no methane gas (the combustible component of LFG) in excess of 5 <br /> percent by volume was detected at any location tested(i.e., vent risers of structures and <br /> perimeter subsurface GW probes). These results indicate that at the time of our testing the <br /> subject site perimeter subsurface GW probes and the structure vent risers were in compliance <br /> with requirements of Title 27 CCR Article 6. <br /> Gas Testing Instrumentation and Methods <br /> Testing for methane gas, oxygen gas, carbon dioxide gas and pressure was performed using a <br /> Landtec Gem-2000 Gas Analyzer calibrated to methane gas. This instrument measures <br /> combustible gas concentrations in air directly on either of two scales, the first as percent by <br /> volume of the lower explosive limit(LEL)of methane gas in air(0 to 5 percent); the other as <br /> percent by volume (0 to 100 percent) in the gas sampled. The detection limit for this instrument is <br /> approximately 0.10 percent by volume. <br />