Farallon has managed the design, construction, start-up, and expansion and provided consulting advice for the 11-year continuing operation of the vacuum gas-control system at the Roosevelt Regional Landfill in Klickitat County, Washington. A vacuum gas-extraction system with horizontal and vertical wells, manifolds, and blowers first fed landfill gas as fuel to a 10.5-megawatt electrical generation facility. Farallon participated in the design and start-up of a $60 million upgrade with a new facility adding 26 megawatts, which began first phases of electrical generation in 2010. Related work has included preparing landfill gas-generation estimates and forecasts demonstrating major hydrogen sulfide concentration decline over the life of the landfill, in support of obtaining Clean Air Act Title V operating permits. Current landfill gas flow is 5,000 cubic feet per minute, with an ultimate capacity rating of 19,000 cubic feet per minute.
Farallon also evaluated leachate production rates and management technologies and designed a pumping and landfill leachate re-injection system that successfully disposes of 9.5 million gallons of leachate per year. Following an evaluation of the intermediate landfill cover and landfill surface configuration, Farallon recommended minimizing flat landfill top decks and maximizing landfill side slopes and intermediate cover in areas that will receive additional solid waste, to reduce rainfall infiltration and leachate generation. Farallon performed additional evaluations of surface water retention pond capacities and performance.
