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construction/demolition waste, and agricultural waste. The site is bordered by <br /> agricultural land. <br /> 1.2.1 Hydrogeology <br /> To a depth of approximately 80 feet, soil consists of unconsolidated silts, clays, <br /> and sands. The measured hydraulic conductivity of the native soil underlying the <br /> landfill ranges between 10-6 to 10-8 centimeters/second. <br /> Groundwater is first encountered approximately 120 below the ground surface. It <br /> is unconfined and fluctuates approximately 4 feet seasonally. Groundwater flow <br /> is toward the south with a gradient of approximately 0.002 foot per foot. <br /> Groundwater flow velocity has been reported at 67 feet per year. <br /> The current groundwater monitoring system is comprised of four monitoring <br /> wells, one upgradient well (MW-1) and three down gradient wells (MW-2, MW-3 <br /> and MW-3). <br /> 1.2.2 Environmental Monitoring <br /> Volatile organic compounds (VOCs) were first detected in 1991 in MW-2. The <br /> cause of the impact was believed to be landfill gas migration. A landfill gas <br /> (LFG) collection system was installed in 1996 to mitigate groundwater impacts <br /> and control LFG migration. After installation of the LFG collection system <br /> monitoring data indicates continuing decreases in VOCs in MW-2. The VOCs <br /> (tetrachloroethene (PCE), 1,2 dichloropropane, and dichlorodifluoromethane) <br /> have been reported in MW-2. In October 2005 the concentration of PCE, <br /> 1,2 dichloropropane, and dichlorodifluoromethane were 1.4 µg/I, 0.67 µg/I, and <br /> 1.9 µg/I respectively. <br /> An increasing chloride trend has been developing in MW-2, MW-3 and MW-4. <br /> Concentrations do not exceed the recommended secondary maximum <br /> contaminant level (MCL)for drinking water (25.0 mg/1) in wells MW-2 and MW-3. <br /> Concentrations in MW-2 and MW-3 were reported at 24 mg/I and 13 mg/I <br /> respectively in October 2005. However, concentrations of chloride do exceed the <br /> secondary MCL MW-4 (reported at 130 mg/I in MW-4 in October 2005). <br /> 1.2.3 Run-off/Run-on facilities <br /> Harney Lane Sanitary Landfill utilizes several methods to control run-on and run- <br /> off. A perimeter berm/road surrounds the site and prevents water from entering. <br /> The facility utilizes drainage ditches along the berm/road to handle storm water <br /> 73467 2 August 9,2006 <br /> LA 1103C Corrective Action Financial Assurance Cost Estimate <br /> Harney Lane Sanitary Landfill <br />