4.2.b PCSR 05-23-2023 - Laserfiche WebLink

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CU 23-09 Narrative The additional 20-acres of property has been purchased by ERL from Tiller Corporation, now part of Martin Marietta (Tiller). The property is currently used by Tiller for its gravel mining operation, as they retained mineral rights on the property per the terms of the purchase. As has been the practice at the existing Landfill, development of Landfill related components (in this case the proposed stormwater management infrastructure) will follow behind Tiller's mining operations. Tiller has an approved CUP from the City for their mining activity (including the 20-acre subject property). The additional property will allow for ERL to construct one large stormwater basin to replace the currently permitted design which included two sedimentation basins and would have required a lift station to manage stormwater from the Landfill. The modifications will allow for gravity drainage for stormwater management (eliminating the lift station) and reduce the amount of controlled fill placement required for perimeter berm construction. For the previous design, stormwater discharge from the site was under the exterior roadway, then under the City of Elk River trail, and ultimately to an upstream wetland on property owned by ERL. The modified design allows for discharge directly west of the proposed pond to an existing low area, on property also owned by the Landfill, east of the trail (eliminating the need for the City trail crossing). The proposed sedimentation pond includes settling basins at the east and west ends. A safety bench has been incorporated into the design and perimeter access for cleaning / maintenance activities has been considered. The proposed pond has been designed to provide flexibility depending on mining activities in the area. The bottom elevation of the pond will be at maximum an elevation of 964; the actual elevation may be 964 or lower depending on mining activities. The design presented herein represents the minimum storage capacity that would be provided and storm events that would be managed. Actual conditions following mining activities may provide for management of larger storm events by increasing the available storage capacity. See the attached "Conditional Use Permit Application" for additional details