2019-07-09_REVISION - M2004044 (30)

Home Browse Search

was submitted to the Division as part pages 17-19 of an adequacy response to Mr. Larry Oehler dated November 22, 2004. The plan was reviewed and approved by the Division as part of the original permit for the site. A copy of the approved Groundwater Monitoring and Mitigation Plan is described below. The hydrogeologic conditions have changed since the 2004 report. However, many of the changed conditions were considered in the 2004 model. The Challenger Pit north of the West Mine Area has been reclaimed as a lined storage reservoir.The triangular shaped parcel north of the East Mine Area has been backfilled with fines. The Greenhouses in the northeast comer of the West mining area and the small property located entirely within the east mining area are now owned by the City of Aurora and will be mined and reclaimed as part of the water storage reservoir., The 2004 report presented eight hydrogeologic scenarios that address the various conditions and associated ground water impacts of the for the life of Tucson South Mine. Scenario 6 described on pages 9 and 10, illustrated on Figures 9 and 10, represent the current conditions with two exceptions. The wells at the Greenhouse property, now owned by aurora,will be removed during mining and the South Mine Area rather than being wet mine will be dewatered. The changes due to the Aurora property are moot and do not have a material impact on the model simulations. However,the dewatering of the South Mine Area will likely impact wells west of the South Mine Area. Al will implement its Ground Water Mitigation Plan to address potential impacts to these wells. The model indicates that after installation of the slurry wall, ground water will mound up to approximately six feet along the western and southern edges of the West Mine Area. Given the rise in ground ware level west of the slurry wall,the mining operations will not increase seepage from the Brighton or Brantner ditches. The model also indicates that there will be little to no mounding south of the South Mine Area after reclamation. This is due to the presence of the Brighton Return Ditch that acts like a drain limiting the rise in ground water level. Similarly,the model indicates that there will be minimal rise in ground water level south of the East Mine Area. This is likely due to the close proximity of the south Platte River. Todd Creek Farms Metropolitan District#1 (Todd Creek)operates several water supply wells between the South Platte River and the slurry wall of the East Mine Area.Todd Creek is aware of the future slurry wall and has an agreement with Al acknowledging the construction of the slurry wall and potential impacts to well yields. Groundwater flows from south-southwest to north-northeast, roughly parallel to the South Platte River. Consequently, there will be very little"shadow effect" (decline in ground water level) in the Morgan Smith Natural Area. The proximity of the River also minimizes the impacts of groundwater levels in the Morgan Smith Natural Area. The modeling (Scenario 6 figures 9 and 10) indicates there will be a shadow effect north of the mine in the narrow strip of unmined alluvial aquifer beneath Tucson Street. The drawdown estimated by the model assumes the wells at the Aurora property Greenhouse and one domestic well north of the mine were pumping. Given that the greenhouse wells will not be pumping the drawdown will likely be less than the of six to eight feet estimated by the model. There is one remaining domestic alluvial water well in this strip of land. Potential impacts to the well will be addressed by the Ground Water Mitigation Plan. Ground Water Monitoring and Mitigation Plan Groundwater monitoring and evaluation of potential mining or reclamation impacts shall be conducted as part of the Groundwater Monitoring and Mitigation Plan. The monitoring plan was reviewed and approved by the Division with the original permit and will be used during mining and reclamation activities. The plan is outlined below. To establish a baseline,Aggregate installed 17 monitoring wells at the mining site and is measuring water levels monthly prior to beginning of mining, and quarterly thereafter. (Note: MW-11 was removed during Todd Creek Metropolitan District's construction of a water pipeline and MW-2 on the Bloom property can no longer be found. Aggregate Industries Tucson South Resource Permit#M-2004-044112 Permit Amendment Page G-5