Landfill Gas Considerations. Cell 8 currently operates under an Alternate Operating Scenario (AOS) approved by the State of Maryland. The alternate operating scenario consists of actively collecting LFG from leachate collection system components, rather than from typical LFG extraction xxxxx and/or trenches. Note that the alternate scenario is implemented in Cell 8 only. All other Cells of the Facility are closed, capped, and operate normally (i.e., the LFG collection system consists of typical extraction xxxxx and/or trenches). Since liquid addition is known to enhance LFG generation, the system will be designed to collect and control LFG in accordance with 40 CFR Part 60 Subpart WWW. To support this level of LFG collection and control, each horizontal trench pipe will have a flanged connection at the end opposite from the injection point. This connection will allow the County to install either a passive or an active system to combust the collected LFG. The need to collect and control LFG will be evaluated as the project progresses, based on methane surface emission monitoring, and observations of odors. Collection and control will occur if methane surface emissions exceed 500 ppm or odors from the test area are observed. Exceedances will be handled in accordance with the protocol outlined in 40 CFR Part 60 WWW. The potential for surface emissions is greatest just over the test area. Recognizing, however, that LFG generated from the test area could potentially migrate beyond the test area, the County will monitor surface emissions over the entire plateau area that encompasses the test area. This plateau area measures 180 feet by 300 feet and is essentially centered on the test area and borders the landfill sideslope (see Attachment IV). Note that the landfill sideslope is covered with a clayey intermediate cap (hydraulic conductivity of about 10-4 to 10-5 cm/s), reducing the potential for sideslope surface emissions. Note also that the integrity of the sideslope cap is maintained with vegetative growth. Surface monitoring in the above-mentioned plateau area will be in accordance with the New Source Performance Standards (NSPS), 40CFR Subpart WWW (refer to Table 3).
Landfill Gas Considerations. The design capacity of the Facility's Subtitle D landfill exceeds the New Source Performance Standard (NSPS) thresholds, and thus the facility must comply with 40 CFR Part 60 Subpart WWW. Cell 8 currently operates under an Alternate Operating Scenario (AOS) approved by the State of Maryland under its NSPS Program, and the County has included the AOS in its application for a Part 70 Permit (also known as a Title V permit) under the federal Clean Air Act (hereinafter referred to as the Title V Permit). The AOS provides that at Cell 8 LFG is collected via existing leachate collection system components, rather than from separate LFG extraction xxxxx and/or trenches. The AOS also postpones the requirement for quarterly measurement of surface methane emissions under 40 CFR Part 60 Subpart WWW. (Note that the AOS applies to Cell 8 only. Each of the other Cells is part of an active LFG collection system comprising separate extraction xxxxx and/or trenches, and are monitored quarterly for LFG). Recognizing that liquids addition enhances the generation of LFG, the County agrees to take all necessary steps to control, and monitor, LFG in the area of the bioreactor experiment. To accomplish these steps, and as further detailed below, the County 1) will request an amendment to its AOS under which it will be required to conduct quarterly surface methane emissions monitoring, beginning with a baseline measurement taken prior to the first introduction of liquids, and 2) in accord with the requested amendment will, as the project progresses, evaluate the need to install additional LFG control devices, in the area of the bioreactor project in accordance with the NSPS for municipal landfills, 40 CFR Part 60 Subpart WWW. (A copy of
