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R <br /> runoff from the landfill. The ditches discharge to a stormwater retention pond <br /> located at the south end of the site. <br /> 2. HYPOTHETICAL RELEASE SCENARIO <br /> The Harney Lane Sanitary Landfill is unlined and stopped receiving waste in <br /> 1991 and was closed in 1994. Ongoing groundwater monitoring shows some <br /> VOC impacts from LFG migration and moderately elevated inorganics in some <br /> groundwater monitoring wells. A landfill gas extraction system was installed in <br /> 1996. The most likely release that will require corrective action is an elevation in <br /> VOCs rather than an elevation of inorganics. Older landfill gas systems were not <br /> designed to control the migration of landfill gas from the unlined bottom of the <br /> landfill. <br /> Using past performance of the module as an indicator of possible future release <br /> mechanisms, escape of landfill gas from the Unit is probable and more likely than <br /> generation of leachate as a mechanism for moving contaminants from the bottom <br /> of the landfill to groundwater. <br /> The hypothetical release scenario for Harney Lane Sanitary Landfill is as follows: <br /> 1. Release occurs from the unlined landfill <br /> 2. Deep landfill gas (carrying VOCs) beyond the influence of the existing <br /> landfill gas extraction wells escapes from the bottom of the landfill. <br /> 3. The escaped landfill gas travels to groundwater resulting in low level <br /> (<50 µg/I) VOC concentration in groundwater. <br /> 3. CORRECTIVE ACTION <br /> A corrective action response was developed to mitigate the impacts envisioned <br /> under the hypothetical release scenario. The extent and complexity of the <br /> corrective action response is proportional to the environment threat of the release <br /> and is consistent with the type and magnitude of corrective action mandated by <br /> the Regional Water Quality Board at the time this document was prepared. <br /> The corrective action envisioned is based on the following assumptions and <br /> premises: <br /> 1. The focus of the corrective action is source control. <br /> 2. The low level release of VOCs to groundwater will not require active <br /> groundwater cleanup (pump and treat, air sparging, etc.). This approach <br /> 73467 3 August 9,2006 <br /> LA 1103C Corrective Action Financial Assurance Cost Estimate <br /> Harney Lane Sanitary Landfill <br />