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n C l L Summary The Waste Industry Air Coalition (WIAC) is comprised of the Solid Waste Association of North America (SWANA) and the National Solid Wastes Management Association. Members of these associations have reported that the AP -42 landfill gas (LFG) defaults, derived from analyses made on average 13 years ago, overestimate the current trace LFG constituent levels. The WIAC previously submitted three reports addressing LFG trace constituents. An initial report submitted in August 1999' showed a continuous Iong term hazardous air pollutants (HAP) decline at six California landfills (see LFG Constituent Declines below). HAP levels typically declined five fold or more over a ten year period. A second WIAC report was submitted November 19992 showing that Hydrogen Chloride levels in recent source tests are more than four times less that the AP -42 default. A third WIAC report was submitted in May 20003 showing that the average of recent non -methane organic compound (NMOC) analyses at 144 landfills was 30% less than the current AP -42 defaults. This fourth report presents a nationwide WIAC survey of recent trace LFG constituent analyses. The WIAC obtained test results from 75 landfills that were made on average within the last two years. The WIAC survey found that the current trace constituent levels are two to four times less than the AP -42 defaults. For the compounds associated with greater health risk at high concentrations, the differences were yet larger. These findings support those from the previous three reports that the AP -42 defaults substantially overstate current LFG constituent levels. The decline in LFG constituent levels over time may be due to a variety of factors including: ® improvement of analytical methodologies that better identify and quantify trace constituents; • federal introduction of waste management regulations that strictly regulate hazardous waste disposal; • federal introduction of municipal solid waste landfill regulations that detect and prevent ` disposal of unacceptable hazardous wastes;'and • industry transition to processes and products requiring less or no hazardous materials. In view of the detected decline, it is strongly recommended that the AP -42 defaults be revised to reflect the current LFG constituent levels. From the California landfill results, showing a continuous long term declining trend in the LFG constituents, it can be reasonably anticipated that additional declines will occur. As a result, two further recommendations are offered. First, older AP -42 data should be purged, to eliminate unrepresentative results, and replaced with current data. The most recent AP -42 revision in 1995 only added new but did not purge older values. Second, U.S. EPA should recognize landfills as a unique source for which its AP -42 defaults will need to change over time. U.S. EPA should consider additional future updates of the AP -42 to address the anticipated declines. 1 "Documentation of Large MSW Landfill Gas Constituent Declines From US EPA AP -42 Default Values", Ray Huitric, County Sanitation Districts of Los Angeles County, and submitted by John Skinner, Executive Director and CEO, SWANA, on August 30, 1999. z Correspondence titled "Submission of Hydrogen Chloride Test Data from Landfill Gas Fired Combustion Devices" dated November 1999 from Edwin P. Valis, Jr., Project Manager, EMCON to Roy Huntley, Emission Factor and Inventory Group, OAQPS, U.S. Environmental Protection Agency. 3 Correspondence titled "Preliminary Data on Non -Methane Organic Compound (NMOC) Concentrations in Landfill Gas" dated May 9, 2000 from Edward W. Repa, Director of Environmental Programs, NSWMA to Roy Huntley, Emission Factor and Inventory Group, OAQPS, U.S. Environmental Protection Agency.