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Mr. Jason Wedel <br />March 26, 2014 <br />Page 2 <br />GRADING PLAN and EROSION CONTROL PLAN <br />3. Note that the proposed project exists in an area of Anoka County that was previously <br />unmapped by FEMA. The 2013 revised preliminary Flood Insurance Rate Map (FIRM) <br />data for Anoka County shows Pond B, portions of proposed Street B and Block 4 lots <br />may be in a future special flood hazard area Zone A. The preliminary data can be <br />downloaded from the Minnesota Department of Natural Resources <br />at: ftp://ftp.dnr.state.mn.us/pub/waters/floodplain/County data/Anoka/ <br />4. Note, the seasonally high groundwater elevation of 897.0 is higher than the permanent <br />pool elevation of 895.5, besides constructability issues, the groundwater may seep into <br />the pond, reducing the active storage capacity. <br />5. Benchmark or datum not shown on grading plan. <br />6. Provide inlet sediment control protection for all inlets to ponds (rear yards especially). <br />STORMWATER MANAGEMENT <br />7. The proposed 100-year 24-hour discharge rate (41.85 cfs) exceeds existing peak rate <br />(41.14 cfs). <br />8. Curve Numbers used in the HydroCAD model should match standards outlined in <br />RCWD Rules. The HydroCAD output shows varying curve numbers used despite the <br />report stating only 74 was used for the proposed development. <br />9. Verify the total runoff area as the HydroCAD output shows an increase from existing to <br />proposed conditions, while the watersheds shown on plans did not change. <br />This concludes our stormwater management comments at this time. If you, or the applicant, <br />have any questions regarding these comments, please contact Katy Thompson at (763) 270-3473 <br />or kthompson@wsbeng.com. <br />SAAdvisory Boards & Co issions\Planning & Zoning Bmd\Packets\2014 PacketsW-12-2014 P&Z Packet\5A-CFN\3a MEMO j_wedel sto-tu -em <br />