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Groundwater Monitoring Plan <br />1. Purpose ofAlonitoringPlan <br />The operation may modify the pre-existing groundwater flow in the azea, but is not expected to <br />be severe or otherwise detrimental to existing structures or water rights. The purpose of the <br />monitoring plan is to ensure that such impacts are not or will not adversely affect existing <br />structures. Because most of the proposed mitigation measures will be installed prior to lining of <br />the site, the monitoring will be used to evaluate the effectiveness of the installed mitigation <br />measures. <br />2. Establishment Baseline Data <br />Baseline data - i.e., data taken prior to lining of the site -may be useful in determining an <br />acceptable range of groundwater levels following lining of the site. Excessive and substantial <br />changes in the groundwater levels in the area may be evidenced by three to four feet above the <br />maximum or three to four feet below the minimum in the range of natural groundwater levels at <br />locations within the permit boundary. <br />Several months of baseline data aze not necessary in situations such as this, as singular data <br />points collected prior to commencement of operations, though not representative of the full range <br />of groundwater levels at a given point, are necessarily within the normal range of groundwater <br />levels at that point. Thus, imposition of a trigger level based on data points that are <br />representative of only a subset of the full range of groundwater elevations would only serve to <br />decrease the range of deviations from existing groundwater elevations that are acceptable <br />without putting in place mitigation measures. hi other words, the acceptable range of <br />groundwater levels during operations will only be nazrowed by the use of less baseline data, and <br />therefore be more protective of existing structures. <br />Further, baseline data is irrelevant where the protection of existing structures is the pazamount <br />concern. What is important in such cases is knowledge of the elevation or change of flow of <br />groundwater at which an existing structure will be impaired. Such knowledge exists completely <br />independent of knowledge of existing structures. <br />With the foregoing in mind, baseline data will be established by collection of data from the <br />monitoring locations prior to lining of the site, but may only include two to three months of data <br />leading up to said lining. The baseline data will be submitted to the DBMS prior to installation <br />of the liners. <br />3. Locations of Monitoring Points <br />In total, there will be five points of monitoring surrounding the site. The proposed locations of <br />the monitoring wells, as shown on Exhibit-Gl, were chosen primarily in relation to, and for <br />the protection of existing structures. The structures of particular concern include the road base of <br />I-25 to the west, the unlined recreational lakes to the east, and wells and commercial structures to <br />the South. <br />The two monitoring wells (Nos. 1 and 2) to the west of the site, which will be located between <br />the clay liner and the I-25 right-of--way, will monitor for excessive groundwater mounding which <br />We(d Counry Hokestra Pit <br />DMG 112 Permit Amendment <br />Page 12 <br />