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site. Firestone Blvd., an existing road immediately south of the site, also should be protected <br />against excessive mounding on that side of the site. <br />To the east of the site, there are several existing groundwater lakes used for recreational and <br />piscatorial purposes. The use of these lakes would be impacted by a substantial reduction in <br />groundwater levels in the azea. <br />2. Trigger Points for Mitigation or Re-evaluation of Up-Front Mitigation <br />Trigger points refer to the elevation at which the operator will implement the mitigation <br />measures described below, or re-evaluate the up-front mitigation measures installed prior to <br />lining of the site. The trigger points are given in relation to the established baseline or up-front <br />mitigation for each monitoring point, but are based on elevations which will prevent adverse <br />impacts to existing surrounding stmctures. The following aze the trigger points for each of the <br />five monitoring locations: <br />A. Monitoring Well Nos. 1 and Z: These wells will be used to evaluate the up-front <br />mitigation to be installed on the west side of the site (see below). An increase in <br />elevation of one foot or more above the elevation of the perimeter drain at the locations <br />of the monitoring well will trigger re-evaluation of the installed mitigation measure. <br />B. Monitoring Well No. 3: This well will be used to evaluate the up-front mitigation to be <br />installed on the south side of the site (see below). An increase in elevation of one foot <br />or more above the elevation of the perimeter drain at the location of the monitoring well <br />will trigger re-evaluation of the installed mitigation measure. <br />C. Southwest Lake: This lake will be used to evaluate the up-front mitigation to be <br />installed on the west side of the site (see below). An increase in elevation of one foot or <br />more above the elevation of the perimeter drain at the lake will trigger re-evaluation of <br />the installed mitigation measure. <br />D. Eastern Lakes: A decrease in elevation of four feet or more below the established <br />baseline will be used as the trigger point for mitigation. <br />3. Specific Mitigation Measures <br />The following are the specific mitigation measures the operator will take up-front, prior to lining <br />of the site, in relation to each of the trigger points listed above. <br />A. Monitoring WeII Nos. 1 and 2: The operator will install a perimeter drain along the <br />western side of the site, adjacent to the clay liner. The perimeter drain will collect <br />excess groundwater between the clay liner and the highway, and will be dischazged <br />directly into the St. Vrain River. The drain will extend into the southwest lake to collect <br />mounding occurring in the vicinity of the lake, and hold the lake to pre-existing water <br />levels. <br />B. Monitoring Well No. 3: The operator will install a perimeter drain along the southern <br />edge of the site, along the existing alignrnent of Firestone Blvd. The perimeter drain <br />will dischazge directly into the existing lake located in the SW '/< of the NE '/< of Section <br />2, Township 2 North, Range 68 West, currently owned by Weld County. <br />Weld Comry Hokestra Pit <br />DMG l12 Permit Amendment <br />Page 14 <br />