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Ll Hydrogeology Local geology consists of inter -bedded sands, silts and clays with sporadic gravelly layers. The measured hydraulic conductivity of the native soils underlying the Unit range between 1 x 10-4 and 2 x 10 -7 centimeters/second. Groundwater is first encountered at approximately approximately 36 feet below msl, 145 to 157 feet below the ground surface. Groundwater is unconfined and flow is toward the west by southwest with a hydralic gradient of 0.00062 ft/ft. The current groundwater monitoring system is comprised of five monitoring wells, one upgradient well (G-1) and four down gradient wells (G-31), G-4, G-5, and G-6). Environmental Monitoring In July 2002 volatile organic compounds (VOCs) including benzene were confirmed at well G-4 at concentrations reported at 2.3 µg/L. As a result of this detection an additional monitoring well (G-6) was installed. Monitoring results at well G-6 have indicated no groundwater impact at that location. Since January 2003 analytical results have not indicated any detection of VOCs above the trace level. The cause of the impact at G-4 was associated with landfill gas. As a result of these detections, the County submitted an addendum to the Engineering Feasibility Study with associated Amended Report of Waste Discharge (December 21, 2004). The addendum proposed installing an active LFG collection system to remediate future releases. The LFG system was installed in 2006. Run-off/Run-on Facilities A perimeter berm around the waste management unit prevents any run-on to the unit. This perimeter berm, along with a series of ditches, also controls all surface run-off during storm events, and directs surface run-off from the landfill to an interim sedimentation basin on the east side of the site (Figure 1). From this sedimentation basin, and from portions of the eastern side of the landfill, storm water runs into the wetlands on the northern third of the property. Water flows from the wetlands into the tributary of the South Paddy Creek on the eastern property boundary. The primary path for water entering the site is from a tributary of South Paddy Creek east of the site. Water entering from this source flows into the wetlands on the north end of the site and around the unit. Corrective Action Financial Assurance Cost Estimate 2 September 30, 2008 North County Recycling Center and Sanitary Landfill Public Works/Solid Waste Div.