7.1. SR 02-21-2017 - Laserfiche WebLink

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and water erosion, with between one-third and two-thirds of the original surface layer removed from erosion. Slopes on the subject property range from 2-18%, with the majority of slopes less than 10%. Mining will create steeper slopes with an excavation face of 1.5:1 (Horizontal to vertical). Erosion from the excavation slopes is inconsequential. Surface water drainage from active mining areas will be directed to low areas within the Tiller mining operation. Collected surface water infiltrates into the underlying soils and/or evaporates and there is no site discharge. Surface water drainage will not be directed off-site. As part of restoration, excavated slopes will be backfilled to a maximum of 4:1 (25%). Reclamation grades over the entire subject parcel will range from 2% - 25%. Reclaimed slopes will be covered with topsoil and seeded to establish vegetation and stabilize the surface. 17. Water quality: surface water runoff a. Compare the quantity and quality of site runoff before and after the project. Describe permanent controls to manage or treat runoff. Describe any stormwater pollution prevention plans. Both the quantity and quality of site runoff will remain similar before and after construction. During active mining, the runoff from the subject property will be managed internally and will not drain off the site. The existing mining facility operates under a Minnesota NPDES permit for gravel mining facilities. The Storm Water Pollution Prevention Plan (SWPPP) for the existing site will be amended to include the subject property. The SWPPP includes best management practices including spill prevention, fuel storage, erosion control and eliminating site discharges of stormwater. b. Identify routes and receiving water bodies for runoff from the site; include major downstream water bodies as well as the immediate receiving waters. Estimate impact runoff on the quality of receiving waters. The site is located within the Elk River Watershed that ultimately drains to the Mississippi River. During active mining, stormwater will be handled internally. Sedimentation basins, diversion berms, silt fence and other appropriate controls are actively utilized to control sedimentation and treat stormwater. After final reclamation of the subject property and the existing mining facility, reclamation grades will direct water to the west towards several small landlocked isolated wetland basins, with overflow continuing to the west under the abandoned Great Northern railbed into a small creek that is tributary to Elk River. Elk River eventually flows into the Mississippi River located approximately 2.5 miles south of the subject property. 18. Water quality: wastewaters a. Describe sources, composition and quantities of all sanitary, municipal and industrial wastewater produced or treated at the site. Operations on the subject parcel will not generate any sanitary or municipal or industrial wastewater. The existing facility generates washwater discharge from the washing operation and small quantities of sanitary wastewater. b. Describe waste treatment methods or pollution prevention efforts and give estimates of composition after treatment. Identify receiving waters, including major downstream water bodies, and estimate the discharge impact on the quality of receiving waters. If the project involves on-site sewage systems, discuss the suitability of site conditions for such systems. The existing permitted facility generates industrial wastewater from the aggregate washing process. The washing process does not utilize any chemicals. Washwater discharge is directed into a series of sedimentation ponds and the water is recycled back into the plant. Washwater is not discharged off- site. There is an office with a septic tank and drainfield located within the processing area of Tiller’s existing facility. c. If wastes will be discharged into a publicly owned treatment facility, identify the facility, describe