Agenda - 06-04-2013-13 (3) - Laserfiche WebLink

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INFORMATION ITEM Memorandum To: Frank Clifton, County Manager From: Gayle Wilson, Solid Waste Director Date: May 21, 2013 Re: UNC /Orange County Landfill Gas Project Summary In March of 2009 the University of North Carolina entered into an agreement with the County of Orange on a Landfill Gas (LFG) to Energy project. The proposed project was to utilize methane gas generated at the Orange County Landfill (OCL) located on Eubanks Road for use as fuel in a LFG generator which was to be located on University property near the intersection of Martin Luther King Blvd. and Homestead Rd in Chapel Hill. The project was to be completed under two different contracts and also included the phasing of the project located on the OCL to coincide with the closure of the Municipal Solid Waste Landfill located south of Eubanks Road. Phase 1— Oranee County Landfill Phases 1 of construction of the landfill gas extraction and collection system involved installing the necessary wells, piping, and flare system package. The fastest part of the construction project was the installation of the wells, and the longest part was the installation of the gas lines. Construction of the gas transmission lines portion of the project started in November of 2010 and concluded in October 2011. The gas transmission line was installed to connect the wellheads of the completed wells to the flare /gas treatment station that was installed to the east of the south landfill near the existing sediment basin. A major part of the transmission line construction required the boring of Eubanks Road to tie the north landfill into the system. The transmission line installation also involved placing several condensate sumps along the transmission line to drain the liquids out of the system before reaching the flare station area. Twenty -one isolation valves were also installed in the system to provide a means for shutting down portions of the system while allowing others to still operate. In January 2011, Shaw Environmental installed 15 gas extraction wells in the south landfill. These wells extend down through the existing waste to within approximately 10 feet of the bottom of the landfill. The wells were constructed using six inch slotted PVC pipe and were backfilled with gravel to within 10 to 15 feet of the surface. The remaining annular space to the surface was sealed off using two different layers of pelletized bentonite that were hydrated with water and had soil placed on either side of the bentonite. Eighteen existing leachate cleanouts on the south landfill were fitted with remote wellheads that allow for the extraction of the gas while providing a way for condensate to drain back to the leachate piping. This gave the extraction system 33 locations scattered throughout the landfill to draw gas. The north landfill was also connected to the system; however wells were not required to be drill. Forty - five passive vents had already been installed on the north landfill prior to the start of this project. Those vents were converted to extraction wells by replacing the well head on the casing pipe.