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Rifle Gravel Rt #' January 2021 (Amendmen, to rile No M-2020-008) <br /> 8.0 Exhibit G -- Water Information <br /> Figure 4, Exhibit C depicts the rivers, creeks, water courses, and ditches on the site and <br /> adjacent lands. <br /> Mining of an aggregate deposit like the Rifle Pit will involve affecting local groundwater and <br /> surface water. During active mining operations, local dewatering efforts will pump <br /> groundwater to allow for aggregate mining. <br /> 8.1 Dewatering <br /> SCI negotiated a temporary license agreement with the Shideler's (Parcel 217908100527) <br /> to the east that will allow SCI to bury a 12" dewatering pipeline that will collect and convey <br /> pumped dewatered water to the Colorado River(Attachment A drawings). This pipeline will <br /> have an energy dissipation structure upstream of the discharge point to the Colorado River <br /> and an armored outfall to prevent erosion and sedimentation discharges into the Colorado <br /> River. <br /> The trenching and installation of the proposed dewatering pipeline will create temporary <br /> impacts to federally jurisdictional wetlands located on the Shideler's (Parcel 217908100527), <br /> and will also require a permanent outfall structure on the bank of the Colorado River, which <br /> will constitute a permanent impact to that jurisdictional water. A range of alternatives has <br /> been considered for this project and every effort has been made to avoid the discharge of <br /> dredged or fill material into waters of the United States. However, there are no practicable <br /> alternatives that avoid a minor and temporary filling of wetlands, which have been minimized <br /> to the extent possible by careful selection of the proposed pipeline route. <br /> An aquatic resources report and wetland delineation will be submitted to the ACOE in <br /> support of a nationwide permit application 39 (NWP 39) for Commercial and Institutional <br /> Developments. The NWP 39 application will encompass the initial pit development stages <br /> (Stages 1-3) and the dewatering pipeline. All impacts from the dewatering pipeline are <br /> temporary; in accordance with NWP 39 conditions, during installation in wetland areas <br /> heavy equipment will work on mats to minimize surface disturbance, and topsoil will be <br /> segregated and reapplied following pipeline installation. No changes are proposed to the <br /> existing hydrologic conditions on the Shideler's, therefore the wetland conditions will quickly <br /> re-establish in the pipeline route. The NWP 39 will be acquired prior to construction. <br /> Coverage under a Nationwide Permit No. 7 will also be obtained for the outfall to the <br /> Colorado River. SCI also submitted a Watershed Permit Application to the City of Rifle to <br /> address the dewatering discharge within their Watershed Protection Area. <br /> 8.1.1 Dewatering Pumping Information <br /> The rate of groundwater discharge (pumping) associated with dewatering is expected to <br /> approach about 7 cfs. Mr. Bill Hahn (Hahn Water Resources, LLC) predicted the anticipated <br /> dewatering operations (through modeling) however this is an estimate based upon borings <br /> and groundwater level data. Mr. Hahn presented one possible dewatering configuration that <br /> might be employed for dewatering associated with the first stage (year) of mining. Figure 10 <br /> 29 <br />