ARCHIVED REPORTS_1996_1 - Laserfiche WebLink

Home Browse Search

.N 1 -LANDFILL EXPANSION ISSUES Page 1-28 An opportunity to decrease the size of the surface water perimeter ditch. One disadvantage is that there would be two surface water facilities, each with pumping equipment and each requiring maintenance. 1.7 LANDFILL GAS CONTROL SYSTEM 1.7.1 Introduction As the organic content of solid waste decomposes, it generates landfill gas. This gas contains numerous constituents that are explosive, toxic, and smell unpleasant. Landfill gas can migrate either by vertical or lateral movement. Many physical and environmental factors,e.g.,surrounding earth materials, gas production rates within the refuse, and barometric pressures, affect the direction and rate at which the gas will migrate. Also influencing gas migration is the existence of a liner and the cover material. Simply put, gas will migrate toward the path of least resistance. The primary goal of the landfill gas control system is to reduce landfill gas emissions during landfill operations as well as after closure of the landfill. This system will consist of intermediate and surface gas collection piping in trenches that lead to surface headers, which are then connected to transmission lines leading to the Blower/Flare facility. At the Blower/Flare facility, the vacuum that draws the gas through the system is generated and the collected gas is burned under controlled conditions. Landfill gas is generally saturated with water vapor and d can cant'significant amounts of dust and grit. Normally occurring temperatures in the landfill can reach 130oF or higher depending on the microbial activity present in the solid waste. Thus, the gas is typically at an elevated temperature compared to ambient conditions surrounding the pipeline. This condition results in water condensing in the pipeline,which necessitates that condensate management become an integral aspect of landfill operations. 1.7.2 Existing Conditions Pacific Energy currently operates a methane gas recovery system at the landfill. The collected gas is used to power an electrical generation plant located at the northwest comer of the landfill. Pacific Energy takes enough landfill gas so that the power plant produces up to 760 kilowatts per hour of electrical power; this energy is sold to Pacific Gas and Electric Company (PG&E) under a long-term agreement. Pacific Energy pays the City of Stockton a royalty based on a percentage of the gross revenue from the power that is generated at the plant. Pacific Energy is responsible for its liquid condensate and they operate under Waste Discharge Requirement Order No.88-208. At this time, the condensate is returned to the landfill,where it is disposed via leach-type trenches located three to five feet below the surface. On June 3, 1992, the Local Enforcement Agency, through the authority of the landfill's Solid Waste Facility Permit, ordered the City to stop returning landfill gas condensate to the landfill by October 9, 1993. Pacific Energy has submitted several plans to the regulatory agencies but, as of the time of this report, the alternative method of disposal is still under review. As the existing Austin Road landfill does not have a liner, there is no control of lateral migration of landfill gas nor is there any collection of any landfill gas other than that done by Pacific Energy. R.W.SOCK and Associates 1811.002 City of Skx*mn