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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 /> May 31, 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: Second 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 second quarter of 2007 (April through June)performed by SCS Field Services (SCS). All <br /> testing, monitoring protocols and reporting were performed in general conformance with Title 27 <br /> California Code of Regulations (CCR)Article 6. Briefly,these regulations require that solid <br /> waste disposal site owners'/operators implement LFG control or monitoring provisions to ensure <br /> 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. Subsequent to this monitoring, SCS understands <br /> that the San Joaquin County Local Enforcement Agency(LEA) conducted monitoring on May 4, <br /> 2007 and found probe GW No. 1-Intermediate indicating 7.4%methane. Effective June 4, <br /> 2007, SCS will monitor probes GW No. 1 through 4 and the adjacent nine structures weekly per <br /> the County's direction. <br /> Gas Testiniz 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 />