CORRESPONDENCE_2007-2009 - Laserfiche WebLink

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Foothill Sanitary Landfill utilizes several methods to control run-on and run-off. The natural topography of the area controls run-off and run-on into the site. Run-on from surrounding properties is minimal because the working area is a significant distance from the property boundary. The facility utilizes drainage channels along the landfill perimeter to conduct storm water runoff from Module I. The channels discharge into sedimentation/detention basins for sediment control, and to reduce storm water flows off site. Containment Systems Module "I" is unlined and therefore does not have a leachate collection and recovery system (LCRS). The base of this Module 1 is composed of a geocomposite clay layer (GCL) under a 60 - mil HDPE geomembrane in conformance with CCR Title 27 and RCRA Subtitle D with an overlying LCRS. The recovered leachate is at no time applied to Module I. The liner of Module 1 was extended over the southern portion of Module "I" in 2006. This extension included placing GCL and HDPE composite liner over existing waste as required by the RWQCB. A landfill gas collection system was completed in 2007, collecting LFG primarily from Module "I". HYPOTHETICALRELEASE SCENARIO The "foreseeable release" from the Foothill Landfill is based on the containment features now in place and the history of compliance at the site. Module 1 is fitted with a geomembrane base liner and LCRS. Future expansions will have the same or better containment systems. In contrast, Module "I" does not have a base liner. For this reason, Module "I" has a higher probability of a release and is therefore assumed to be the source of the hypothetical release. Historic monitoring provides evidence of groundwater impacts due to landfill gas not inorganic constituents as would be seen with leachate escaping from the bottom of the landfill. Module "I" is undergoing partial closure in 2006, which further reduces the chance of leachate generation. Using past performance of the module as an indicator of possible future release mechanisms, escape of landfill gas from the module is more likely than generation of leachate as a mechanism for moving contaminants from the bottom of the landfill to groundwater. Hypothetical Corrective Action The corrective action will be based on the data indicating a release at that time, as approved by the Regional Water Quality Board. Corrective Action Financial Assurance Cost Estimate 3 September 30, 2008 Foothill Sanitary Landfill Public Works/Solid Waste Div.