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1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 I 1 The City of Everett The Floyd & Snider Team Everett Landfill/Tire Fire Site 4.0 Groundwater Pathway 4.1 OBJECTIVES Groundwater pathway monitoring will consist of three phases of monitoring. Evaluation Monitoring will occur for the first three years to supplement current information regarding baseline conditions at the site. Following the Evaluation Monitoring period, Performance Monitoring will occur for a minimum of ten years, and as triggered by certain development actions. Confirmational Monitoring is implemented once development conditions are stable, and Performance Monitoring is finished. The supplemental data regarding baseline conditions that will be collected during Evaluation Monitoring will assist in future assessment during Performance Monitoring of seasonal and long- term changes in groundwater quality. Such changes may result from future site development, remedial actions, or local changes to groundwater recharge or discharge. Evaluation Monitoring will provide area background concentrations of metals in order to finalize those cleanup levels. An appropriate well network and analyte list for Performance Monitoring will be selected after the 3-year Evaluation Monitoring period is completed. The objective of Performance Monitoring as defined by MTCA is to confirm that a cleanup action has attained performance and cleanup standards. Because potential future development is required to meet cleanup standards as defined in the Cleanup Action Plan, the timing of Performance Monitoring will reflect the phasing of specific development actions. Performance Monitoring will occur following Evaluation Monitoring. Additionally, Performance Monitoring will be reset or reinstated after the first significant future pile installation activity occurs on the site. Additional pile installation activities will reset or reinstate Performance Monitoring only if such pile installation occurs in a zone identified for pile restrictions. In addition to groundwater monitoring requirements, inspection of stormwater management facilities will be made to confirm that collected stormwater is not allowed to infiltrate at the landfill site, and is managed appropriately for off -site discharge. Stormwater infiltration is an issue related to groundwater. These inspections will be coordinated with the site inspections defined in Chapter 5 for the Direct Contact Pathway. 4.2 COMPLIANCE CRITERIA Groundwater cleanup levels are identified in the BFS as the most stringent of drinking water and surface water standards. Points of compliance for the shallow and the deep aquifers are conditional. Groundwater in the shallow aquifer (leachate) is collected in the leachate collection system and conveyed off -site for treatment. A small section of the shallow aquifer is present east of the leachate collection system and west of the East Ditch (see Figure 2 1, Site Map). There is residual waste in the strip of land between the leachate collection trench and the East Ditch. dots\ ects ompli OEµM Everett l ndfiMCP maker - final Compliance Monitoring and Contingency Plan docslCompliance Monitoring Plan\CMCP 11-10-170.doc FINAL - March 2001 Page 4-1