Laserfiche WebLink
levels upstream of the slurry wall and a maximum of 1 foot decline downstream of the slurry <br />wall. There is one well not owned by Ilall-Irwin that will be located within 600 feet of the <br />mh»ng area (Wickershame #161560). However, since the pit will be lined prior to when mining <br />operations commence, the de-watering activities associated with the wells will not cause injury <br />to this well. The aquifer analysis shows that the water level in the vicinity of well #161560 will <br />increase by 1 foot, thereby increasing the saturated thickness of the well and improving the <br />production of the well. This well is located a distance of 300 feet from the slurry wall and over <br />350 feet from the actual mine site. <br />The proposed facility, when lined, will be used as storage reservoir by the Ground Water <br />Management Subdistrict (GWMSD) of the Central Colorado Water Conservancy District. The <br />GWMSD will use this storage facility to provide augmentation coverage for over 1,000 <br />agricultural wells that include numerous wells for dairies. The need for this gravel reservoir is <br />paramount to the continued operation and compliance with state statute the prevention of injury <br />to senior water rights within Division I. <br />In the highly unlikely event that the slurry wall fails, the result to the area groundwater gradient <br />will equilibrate back to the historic gradient conditions that existed prior to the installation of the <br />slurry wall. Five dedicated monitoring wells will be installed on the outside and adjacent to the <br />slurry wall. The depth to water in alI of these five monitoring wells will be sampled prior to the <br />construction of the slurry wall and monthly thereafter during the mining operation. Prior to the <br />routine operation of the lined reservoir, the pit will have to be pumped dry and tested for a period <br />of 90 days to demonstrate that the State Engineer's leakage standazd is met or exceed. These <br />monitoring wells will be used as a indicator to determine slurry wall failure. The impact resulting <br />from an exceedance in the State Engineer's Offce leakage standard will result in an increased <br />evaporative depletion to the South Platte. The exceedance in the State Engineer's Office leakage <br />standard will be determined in the required Water Court decree accounting for the storage <br />reservoir. If this occurs, the decree will require that all out-of-priority evaporative depletions be <br />fully augmented until such time as the excess leakage is corrected. <br />Sincerely, <br />Enclosures <br />Water Rights • Hydrology • Hydraulics • Water Quality <br />E:\LcaflHaO\Cravel PitstSouth PlattcW issen Pit Aquifer Impact Anafysis.doc <br />3 <br />