Agenda - 11-03-2004-9c - Laserfiche WebLink

Browse Search

a~- Orange County Trigon Project No. 0.36-00.Ot6B Hillsborou h Landfill Site Iuly 24.2000 .3.3 LANDFILL GAS 3.3.1 Background Landfill gas is a product of biodegradation of refuse in landfills, and consists of primarily methane, carbon dioxide, water vapor and traces of other non-methane organic compounds (NMOCs). The amount of gas generated and its composition is dependent on the type of mate[ial disposed, the age and capacity of the landfill, local climate and rainfall, and other parameters The U..S. EPA has established performance standards for the collection and treatment of landfill gas and other emission guidelines for relatively large landfills (i.e., 2.5 million tons of waste or 2.5 million cubic yazds), Smaller landfills are not regulated by these federal standards However, constmction and other site improvements in and around landfilled areas, regardless of size, need to take into account the potential for landfill gas generation and the hazards that it may pose. 3.3.2 Landfill Gas Assessment Refuse was observed while advancing the geotechnical borings across about ten acres of the property. Assuming that on average, the refuse is ten feet deep across the area where it was observed, the closed Hillsborough Landfill would be expected to contain from 100,000 to 200,000 cubic yards of waste. Consequently, a landfill of this size is considered small with limited potential to generate substantial amounts of landfill gas. At approximately one-tenth of the tT.S• EPA threshold, it is also not subject to the federal regulations that would require collection and treatment of the landfill gas. Trigon monitored for the presence of landfill gas (measured as methane) using a Foxboro organic vapor analyser and a MSA Gasscope landfill monitor while advancing the test borings for the geotechnical evaluation. Methane was concentrated in borings that contained refuse, especially in the landfill area close to the creek. No methane gas was detected in borings elsewhere at the site that were free of refuse and debris. TRIGON LNC/NEERING CONSULTANTS, !NC- Page 7