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1 The City of Everett The Floyd & Snider Team Everett Landfill/Tire Fire Site The leachate collection system also collects groundwater from this narrow strip of land and conveys it off -site, preventing discharge to surface water. The shallow aquifer point of compliance is located on the strip of land between the East Ditch and the leachate collection trench and the compliance criteria for the shallow aquifer is based on hydraulic control through operation of the leachate collection system. Demonstration of hydraulic control is through monitoring of water levels in shallow aquifer monitoring wells and the leachate trench to show that hydraulic gradients are toward the leachate collection system, which would indicate no shallow aquifer discharge to surface water. The compliance criteria does not preclude the potential for removal of the source of contamination (landfilled materials) within the narrow strip of land east of the leachate collection trench and west of the site boundary (inner eastern railroad track) during future development actions. If the potential source of contamination is removed from this area or a hydraulic barrier is installed on the west edge of the East Ditch, hydraulic control of shallow groundwater east of the leachate collection system trench would not be necessary. Although no water quality monitoring of the shallow aquifer is proposed as long as the leachate collection trench is operated, future monitoring may occur if there is a desire to demonstrate that the shallow aquifer has achieved the compliance criteria. If future monitoring is implemented and it demonstrates that cleanup levels have been met in the shallow aquifer, the leachate collection system would be turned off. ' Because the shallow aquifer is discharging to the leachate collections stem, groundwater q 9 9 Y quality compliance will be measured in the deeper aquifer. Groundwater in the deep aquifer discharges directly and indirectly to the Snohomish River, a designated potential source of drinking water. The proposed point of compliance for the deep aquifer is located downgradient of the landfill, between the landfill and the point of discharge into the Snohomish River, outside the boundary of landfilled materials, and no further than 100' east of the easterly railroad tracks. No existing deep aquifer groundwater monitoring wells are located at the point of compliance. The proposed number and location of new compliance wells are discussed in section 4.3.1. Table 2 (see end of Section 4) summarizes the proposed cleanup levels, as well as proposed analytical methods presented in the BFS. As discussed in Section 6.3.2 of the BFS, concentrations of some metals at the site (e.g. arsenic, lead, zinc) may reflect upgradient, area background conditions. Evaluation Monitoring will include monitoring at new, upgradient ' monitoring wells, which will define area background concentrations and allow finalization of cleanup levels. 4.3 INSPECTION REQUIREMENTS Periodic visual inspection of the site, under both existing and future conditions, is required to P 9 q verify that stormwater infiltration is minimized. In undeveloped areas and under existing conditions, an inspection will be made to confirm that grading of landfill cover does not allow significant areas of ponded water to accumulate on the site. Under potential future developed conditions, an inspection of stormwater management facilities is required to ensure that stormwater is being managed to minimize infiltration and to appropriately convey the water off- dots% ompli OEuMo Everett LandflMCP maker -final Compliance Monitoring and Contingency Plan docslCompliance Monitoring PIan1CMCP 11-1 QOO.doc FINAL - March 2001 Page 4-2