04-08-2019 Council Packet - Laserfiche WebLink

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Ms. Katie Larsen 03/29/2019 Page 5 Lyngblomsten Preliminary Plat Engineering Review Catch basin structures have been re-verified Storm sewer systems and catch basins will be reviewed with the final design submittal. Additional CB’s will be required to maintain the storm sewer pipe within 2 feet from the road. 14. On Sheet C1.51, in section D of the “General Construction Sequence”, the applicant shall add the following note prior to note 3 “Locally Strip topsoil…” a. “Prior to site disturbance, construct a construction detention pond (in the location of the proposed pond) to help treat soil runoff during construction.” The SWPPP excerpt has been modified 15. On Sheet C1.51, in section D of the “General Construction Sequence”, the applicant shall add the following note prior to note 11 “Complete stabilization of the…” a. “Prior to final stabilization, verify the proposed pond is constructed to final grade. Clean out any accumulated deposited sediments during construction.” The SWPPP excerpt has been modified. 16. On Sheet C1.51, in section G of the “General Construction Sequence”, the applicant shall add the following note. a. “Street Sweeping (with a pickup broom only) will be provided as needed or at the direction of the owner/engineer.” The SWPPP excerpt lines been modified 17. On Sheet C1.51, the applicant shall include erosion control blanket on the pond slopes above the NWL. The plan has been modified 18. On Sheet C1.51, the applicant shall include erosion control blanket on all back-yard swales and 50’ around all back-yard catch basins. The plan has been modified. 19. At the 24 inch diameter westerly pipe outlet we recommend connected the pond outlet to the existing pipe via a manhole with and open grate. If this were to be accomplished, there should not be an opportunity to drain the existing swale. The manhole has not been provided 20. Storm sewer shall have 15 feet of separation from a structure and include a 20’ easement. The applicant should consider a utility and trail corridor between the private road and main road. (between Lots 10-11, Lots 11-12) 21. Our review is based on the assumption that the senior living complex has a finished floor elevation of 910.5 and a 12 foot parking garage below. The ground water in this area is an 897 to 899. They are not meeting the 4 foot of separation from groundwater. It is being proposing to mitigate this with a drain tile and pump system, backup power, and cut off wall. The City could consider reducing the low floor free board requirement of 4 feet separation from groundwater upon submittal of a geotechnical report and design by a licensed engineer. This report shall define ground water level elevations for the senior living complex and include plans demonstrating that potential ground water inflow will adequately be mitigated. The proposed trench grate and draintile will need to be pumped or discharged downstream of the pond. It is recommended to construct an improved outlet for the site, downstream of the pond. It is our understanding that this option would have construction impacts in an existing developed area. • Water Supply The proposed site is currently not served by municipal water and on site wells shall be abandon per MDH. This area of the City, Woodridge Estates, is currently a low pressure area. The City’s Comprehensive Plan and water system model identifies the need for a 12-inch diameter trunk