ARCHIVED REPORTS_1993_1 - Laserfiche WebLink

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II. Project Description The surface water detention facility would be located in the southwest comer of the site. The design and construction of the facility would meet the requirements of the San Joaquin County design standards and sized to handle a 100-year, 24-hour storm incident on the closure area of both the existing and expanded areas. The detention pond would be excavated below the current existing grade and pump its discharge to Little Johns Creek. The pump would be designed to empty the detention basin within 48 hours. The detention basin facility would be fenced to PY Y prevent unauthorized access. Landfill Gas Control When organic waste is placed in a landfill,it initially contains oxygen,and decomposes aerobically in the presence of oxygen for a short time,producing only carbon dioxide. Anaerobic decomposition,which takes place after the oxygen is depleted,produces both methane and carbon dioxide. The two primary concerns over landfill gas production are that landfill gas is usually odorous and that methane can be present at concentrations where it would be flammable or explosive. While neither carbon dioxide nor methane are odorous,some trace landfill gasses are odorous(including hydrogen sulfide). Landfill gas is usually saturated with water vapor and is typically at an elevated temperature due to the decomposing activities in the landfill. Thus, when the landfill is collected in pipelines a liquid condensate is generated. Pacific Energy(PEn)currently operates a methane gas recovery system at the landfill to power an electrical generation plant located at the northwest comer of the landfill. Enough landfill gas is collected to produce 760 kilowatts per hour of electrical power. This energy is sold to Pacific Gas and Electric Company(PG&E). Pacific Energy is responsible for its liquid condensate and returns it to the landfill. On June 3, 1992 the Local Enforcement Agency,the San Joaquin County Public Health Services,through the authority of the landfill's Solid Waste Facility Permit,ordered the City to stop returning condensate to the landfill by October 9, 1993. An alternative disposal method is under review. The existing landfill does not have a liner nor is there any other form of landfill gas collection other than that done by PEn. There have been no significant odor complaints according to City personnel(R.W. Beck,and Associates, 1992). California Integrated Waste Management Board staff have taken combustible gas readings at the property boundary and have found the readings to be below five percent for at least two years. H.16