04-13-2017 Planning Ccommission Packet

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3 of 4 10062 Flanders Court NE – Blaine, MN 55449 – Ph: (763) 780-0450 Fax (763) 780-0452 9. Hydrant valves should be set 1 foot behind the curb and the hydrant set 5 feet behind the curb. Stormwater Management Plan 1. Sediment removal must be provided prior to storm water discharge into the infiltration basin. A minimum of a 4 foot sump structure with a S afl Baffle must be added to the lines going into the infiltration basin. 2. Drain tile must be extended to the lowest end of the subcut excavation adjacent to Rice Street. 3. A note should be added to the detail indicating that 5% iron filings by weight should be added to the fine filter media. It should also be noted that the elevations on Detail 550 do not match the material depths indicated or the elevations utilized in the HydroCAD calculations. Stormwater Pollution Prevention Plan 1. Any mulch used over seeded areas must be hydro mulch. No straw may be used for mulch. 2. The applicant should provide more detail on the restoration of the infiltration basin and pond system including a planting plan. Typically standard turf is not maintainable in these areas. Drainage Calculations 1. The time of concentration utilized for the existing and proposed conditions should be based on the actual flow routes and no additional time added as direct entry. The proposed conditions should be revised to note the flow route instead of a direct entry calculation. 2. The 10-year discharge rate to Rice Street in the proposed conditions is slightly more than the existing rate. This should be addressed. 3. The outlet in the proposed HydroCAD calculations for Pond P1 is noted as an 18-inch pipe while the plans note this pipe as 15-inches. The discrepancy should be resolved. 4. The outlet in the proposed HydroCAD calculations for Pond P2 has several discrepancies with the plan. The pipe slope of the outlet pipe does not match the plan, the rim elevation of structure MH 200 differs, and three draintile pipes are noted in the plans. This should be revised. 5. The required abstraction volume for the site is 4,542 cubic feet. There is a reference to Appendix F in the submittal documents that the Appendix provides the documentation that the storage volume requirements are met. However, Appendix F was not attached. This documentation should be submitted. This documentation should match the stage-storage charts noted in the HydroCAD calculations at the appropriate storage elevation.