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Mr. Frank DeMaris October 18, 2010 Page 4 of 7 2,100 °F with 1,800°F nominal), and a minimum residence time of 1.0 second. It is rated at 5.64 MMBtu/hr with an exhaust gas flow rate of 10,653 actual cubic feet per minute (acfm). This flare uses about 68 scth of propane to ignite. It is equipped with fully modulating air dampeners for primary air mixing.The combustion chamber is round with a cross sectional area of 8.7 square feet and a chamber volume of 261 cubic feet. A process flow diagram of the gas pre-treatment system is provided in Appendix E. Waste Gas Flare Emissions • The NOx emission factor for the waste gas flare will remain at 0.041 pounds per million British Thermal Units (lb/MMBtu)because it is the lowest factor this type of flare can meet. We recognize that an ultra low NOx flare defined as LAER can meet 0.025 lb/MMBtu; however, for the reasons stated above regarding the variation in VOC concentration levels in the purge air that occurs during the regeneration cycle,the waste-gas flare for Foothill will be required to be operated at a high temperature in order to destroy the highly concentrated stream of VOCs that occurs during certain periods of the regeneration cycle. Therefore, it is not technologically feasible to meet the ultra low NOx emission factor of 0.025 lb/MMBtu that we have seen in SCAQMD as LAER, due to the thermal NOx that will be generated. • The CO emission factor of 0.2 lb/MMBtu is considered BACT as shown in the previously submitted BACT analysis;therefore,the factor will remain the same as the original application. The SJVAPCD has not established a BACT requirement for CO for LFG flares. There are approximately nine BACT determinations in the California Air Resource Board(CARB) database for flares. There were three CO determinations ranging from 0.18 lb/MMBtu to 0.4 lb/MMBtu. Because the NOx emission factor is as low as possible for this type of flare, it would be difficult to lower the CO emission factor below established BACT levels without jeopardizing the NOx level. • As provided in the original application,the SOx emissions based on 150 ppmv inlet concentration will remain. The BACT analysis provided indicated that treatment options are considered technologically feasible but are not cost effective at 150 ppmv or lower. The BACT cost- effectiveness tables for SOx are provided in Appendix C. However, it is important to note that the SOx emissions in the waste gas flare originate from both the hydrogen sulfide content in the raw LFG and the hydrogen sulfide content in the purge air that was collected on the media bed during its adsorption cycle. The hydrogen sulfide concentration levels in the raw LFG will remain fairly constant,while the hydrogen sulfide levels in the purge air will vary during its regeneration cycle, as previously described. a The particulate matter less than 10 microns(PM-10)/particulate matter(PM)emission factor has been revised to 0.2 lb/MMBtu based on field testing of similar waste gas flares. Ameresco's experience with waste gas flares operating in conjunction with our siloxane pretreatment system, has shown a wide variation with PM-10 emissions from source tests. PM content cannot be controlled due to the variability of particulate concentration levels in the purge air that occurs throughout the regeneration cycle of the siloxane pretreatment system. The revised emissions estimate can be found in Appendix A. Note a 1995 BACT determination made by the SJVAPCD