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REMEDIATION PLAN For Control of Landfill Gas Migration at the Closed Harney Lane Sanitary Landfill Purpose The purpose of this Plan is to establish the procedures by which control of off-site sub-surface migration of combustible gas from the Harney Lane Landfill will be re-established. Background The Harney Lane Landfill is provided with 12 perimeter landfill gas migration monitoring wells, each of which is a"nested" set of three probes, installed at varying depths within the well (Figure 1). These wells are monitored quarterly at a minimum in accordance with the applicable sections of Title 27. The structures of Migrant Labor development adjacent to the landfill are provided with foundation vent pipes that allow the measurement of the concentration of combustible gas beneath the slab of those buildings. Normal monitoring includes quarterly monitoring the foundation vents of the structures immediately adjacent to the landfill. The foundation vents may be monitored more frequently if needed. The landfill is provided with a landfall gas (LFG) collection system installed to prevent off-site migration of LFG and to mitigate groundwater impact by LFG. LFG is collected from 80 LFG wells, each of which is provided with sampling ports and a valve to measure the quality of LFG collected and to adjust the flow rate accordingly. Collected LFG is carried in pipes installed beneath the landfill surface to the LFG flare station,where the LFG is combusted. The vacuum to collect the LFG is provided by a blower, also located in the flare station. The objective of LFG system operation is to control subsurface emissions of LFG, thus controlling LFG migration. This is accomplished by maximizing LFG collection at each well while avoiding excessive overdraw of the refuse. Excessive overdraw may cause a subsurface refuse fire. A significant aspect of LFG system operation is that landfill gas condensate(primarily water with trace LFG contaminants) forms daily within the collection pipes. Unless measures are taken, this condensate will block the LFG piping and prevent the collection of LFG. To avoid this blockage, LFG systems are designed with sloping pipes, allowing the condensate to drain to pre-selected low spots, where a sump and pump is located. The condensate is pumped from the sumps to the LFG flare station, where it is injected into the flare for destruction. Proper functioning of a LFG system depends, among other things, on the proper slope of the LFG pipes. The piping used in this system is non-rigid HDPE, which will conform to the contours of the surface in which it is buried. Another significant aspect is the continual settlement of the landfill surface as the refuse decomposes. Because the refuse does not decompose at the same rate in all locations, some areas will settle faster than others, causing low spots. At the Harney Lane Landfill, a trench fill method was used to place the refuse, thus providing a scalloped effect, where the refuse in the center of the Remediation Plan for LFG Migration 1 San Joaquin County Public Works/Solid Waste Harney Lane Sanitary Landfill October 4,2004