Agenda - 02-17-2009 - 4l - Laserfiche WebLink

Browse Search

Mr. Thomas C.Allen, II NC DEHNR DAQ August 25, 1998 Page 2 We understand that the DAQ will now accept recalculated NMOC emissions using the U.S. EPA's AP-42 emissions factors and the LandWin emissions modeling computer program developed by U.S. EPA for gas emissions estimation. Neither were used in the original calculations performed by the DAQ. Please note that our estimate of the in-place MSW waste volume for the Northern disposal unit has been substantially reduced from that previously reported. Further research into the disposal records and history of the northern site documented that substantial volumes of inert material were placed in the northern landfill. The inert wastes, identified by class, tonnage, and year in the attached spreadsheet. (Table 2), were excluded for the gas generation calculation. Recalculation of NMOC emissions were performed for the combined MSW disposal units using the LandWin model. This simple computer program was developed specifically for estimating MSW landfill gas generation rates under the New Source Performance Standards and Emission Guidelines for Municipal Solid Waste Landfills(NSPS). The landfill gas emission model is based on a first-order decomposition rate equation that estimates annual emissions over a period of time based on the input of site variables and established default values specified by the user. The LandWin software uses identical equations to the methods used by the DAQ in their calculations, by Orange Regional Landfill staff in preparing the Initial Capacity Report, and by ALMES in their demonstrating the non-applicability of NSPS to this site. The calculations are sensitive to the gas generation rate factors, e.g. whether the NSPS/Clean Air Act(CAA) default parameters or the US EPA's AP-42 emissions factors are used. The current AP-42 emissions factors for MSW landfill gas generation as referenced in the US EPA literature are as follows: k 0.04 1/yr L. = 4411 ft3 CH4/Mg of waste in place CN„oc = 2420 ppmv as hexane(co-disposal) Ca,,,ICC = 595 ppmv as hexane (no co-disposal). The recalculated NMOC emission rates for northern, southern, and combined MSW units are presented in 'Table 1. Gas generation rate estimates were completed for NMOC's using both the AP-42 and NSPS/CAA emissions factors for comparison. These emissions modeling results are presented in Attachments A and B. respectively. The emissions analysis demonstrates that actual NMOC emissions are currently well below the 100 ton/year threshold established by the DAQ to trigger the Title V operating permit program. The calculations further show that predicted NMOC emissions are considerably below those previously calculated by the DAQ based on NSPS defaults. Recalculated NMOC values for the Orange Regional Landfill document that the landfill's potential to emit is well below all applicable regulatory thresholds for the currently permitted waste footprint and design capacity. Substantial future expansion would be required at the site to approach the regulatory limit on emissions. Note that the Orange Regional Landfill is currently operating in a new lined Subtitle ALMES&ASSOCIATES,INC. CONSULTING ENGINEERS P:\pecuments\ChapHl-595V974 45∎n297-945.APen.LA;y.?-'L5-98,dcc 897945-595