CORRESPONDENCE_2008 (7/08 TO 12/08)

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Mr. Dan Johnson December 30, 2008 Page 2 area (i.e., utility lines, irrigation valve boxes, vaults, basements, wall spaces, etc.) and is exposed to an ignition source, it can be explosive at concentrations between 5 and 15 percent by volume. At higher concentrations, methane is flammable. However, the presence of methane gas in site soil does not mean there is an immediate threat of explosion because flames cannot typically propagate through soil. SURFACE EMISSIONS MONITORING On November 17, 2008, surface emissions monitoring was performed over the surface of the subject site. The intent of the monitoring was to identify any specific locations or areas of the landfill surface with organic compound concentrations exceeding SJVAPCD Rule 4642 threshold limit value of 1,000 ppmv measured as methane. EMISSIONS TESTING INSTRUMENTATION/CALIBRATION Instruments used to perform the landfill surface emission testing consisted of the following: • Landtec SEM -500 portable Flame Ionization Detector (FID). This instrument measures methane in air over a range of 1 to 50,000 ppmv. The SEM -500 meets SJVAPCD requirements and was calibrated in accordance with Rule 4642 Section 6.1.1.1 test methods. Instrument calibration logs are shown in Attachment 1. SURFACE EMISSIONS MONITORING PROCEDURES Surface emissions monitoring was conducted in accordance with SJVAPCD Rule 4642 Section 6.1.1.2. Monitoring was performed with the SEM -500 inlet held within 3 inches of the landfill surface while a technician walked a grid in parallel paths not more than 90 feet apart over the surface of the landfill. Cracks, holes and other breaks in the surface were also tested. Surface emissions readings were monitored approximately every 30 seconds and recorded if they exceed 1,000 ppmv. Recorded wind speed results are shown in Attachment 2. Wind speed averages were observed to remain below 10 miles per hour and no instantaneous speeds exceeded 15 miles per hour. No rainfall had occurred within 72 hours of the monitoring events. Therefore, site meteorological conditions were within modified Rule 4642 requirements on the test date (see attached waiver letter).