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r� <br />n <br />• <br />Environmental Consultants <br />and Contractors <br />March 11, 2013 <br />File No. 07206050.10 <br />Mr. Joyesh Chandra <br />County of San Joaquin <br />Post Office Box 1810 <br />Stockton, California 95201 <br />4707 Greenleaf Circle 209 545-8490 <br />Suite F FAX 209 545-8391 <br />Modesto, CA 95356 www.scsfieldservices.com <br />Subject: First Quarter 2013, Perimeter Monitoring Probe Landfill Gas (LFG) Testing at the <br />Corral Hollow Landfill, Tracy, California <br />Dear Mr. Chandra: <br />This letter provides results of gas monitoring probe (GW) testing for the first quarter of 2013 <br />(January through March) performed by SCS Field Services (SCS). All testing, monitoring <br />protocols and reporting were performed in general conformance with Title 27 California Code of <br />Regulations (CCR) Article 6. Briefly, these regulations require that solid waste disposal site <br />owners/operators implement LFG control or monitoring provisions to ensure that methane gas <br />concentrations in soils at the property boundary do not exceed the lower explosive limit (LEL, or <br />5 percent by volume) and that interiors of on-site structures do not exceed 1.25 percent by <br />volume in air. Below is a summary of our quarterly monitoring activities. <br />On January 29, 2013, no methane gas (the combustible component of LFG) in excess of the LEL <br />was detected at any location tested. These results indicate that at the time of our testing, the <br />subject site perimeter subsurface monitoring probes were in compliance with the requirements of <br />Title 27 CCR Article 6. <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 />Gas monitoring well testing procedures are as follows: <br />Connect sample tubing, open test valve, observe pressure, and record data. <br />0 <br />