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Rifle Gravel Pit #1 March 2021 <br /> 5.2.1.2 Water Handling and Dewatering <br /> Stormwater Management <br /> Scott will apply for coverage under Permit No. COR400000, CDPS General Permit (for) <br /> Stormwater Discharges Associated with Construction Activity at least 10 days prior to the <br /> commencement of construction activities disturbing greater than or equal to 1 acre. This <br /> permit has several requirements that address water quality and stormwater management, <br /> including monitoring and reporting, and the development and implementation of a <br /> Stormwater Management Plan (SWMP). <br /> During the initial stages of mining, Scott will not disturb the tailwater channel in its existing <br /> location and implement BMPs to prevent mining operations from discharging into or <br /> commingling with these waters. Scott will install a low-water crossing at the existing tailwater <br /> channel crossing or collect the channel in a pipe. <br /> Dewatering <br /> Scott will also apply for coverage under Permit No. COG603000 (Discharges Associated <br /> with Subterranean Dewatering or Well Development) or Permit No. COG608000 <br /> (Discharges to Surface Water from Well Development and Pumping Test Activities)to <br /> manage dewatered water. The specific permit will be determined once the water is sampled <br /> and analyzed. <br /> Scott negotiated a temporary license agreement with the owner of the neighboring Shideler <br /> property (Parcel 217908100527)to the east that will allow Scott to bury a 12" dewatering <br /> pipeline that will collect and convey pumped dewatered water to the Colorado River <br /> (Attachment A drawings). This pipeline will have an energy dissipation structure upstream of <br /> the discharge point to the Colorado River and an armored outfall to prevent erosion and <br /> sedimentation discharges into the Colorado River. <br /> The trenching and installation of the proposed dewatering pipeline will create temporary <br /> impacts to federally jurisdictional wetlands located on the Shideler property (Parcel <br /> 217908100527), and will also require a permanent outfall structure on the bank of the <br /> Colorado River, which will constitute a permanent impact to that jurisdictional water. A range <br /> of alternatives has been considered for this project and every effort has been made to avoid <br /> the discharge of dredged or fill material into waters of the United States. However, there are <br /> no practicable alternatives that avoid a minor and temporary filling of wetlands, which have <br /> been minimized 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 1-2) 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 property; therefore, the wetland conditions will <br /> quickly re-establish in the pipeline route. The NWP 39 will be acquired prior to construction. <br /> 16 <br />