09-26-2007 Council Agenda - Laserfiche WebLink

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LURING &ASSO(1 -AT.S ,au, nBul September 21, 2007 File: 120093E -0240 Honorable Mayor and City Council City of Little Canada 515 Little Canada Road East Little Canada, MN 55117 -1633 RE: RICHIE PLACE SUBDIVISION CITY OF LITTLE CANADA Dear Mayor and Council Members: Due to the review comments on the original submittal in regards to the stormwater management and drainage calculations for the site, the applicant has modified the layout of the proposed development from the original submittal. The major revision was the combination of the two storm water ponds into a single pond north of the west cul -de -sac extension. The new layout was provided as an addition to the Planning Commission packet for review and was the layout discussed by the Planning Commission. To provide additional information to the City Council we have completed a review of the new stormwater management and drainage calculations based on the new layout. Below is a summary of the comments: Stormwater Management Calculations 1. We have reviewed the storm water routing and associated time of concentrations for the pre - development and post - development condition. While they are generally accurate there are a few minor discrepancies that should be corrected. We will work with the Developers Engineer to address this issue. 2. Additional contour information should be utilized in the HydroCAD calculations for the proposed pond calculations. The contours to be used in the calculations should be set at 2 -foot or less intervals. 3. The weir used in the calculations appears to be incorrect with what is shown on the detail plan sheet. This should be reviewed and corrected as necessary. 4. Documentation should be provided that indicates how the infiltration rates were determined. Ltr- 092107 -CC 10062 Flanders Court NE, Blaine, MN 55449 - Phone: (763) 780 -0450 - Fax: (763) 780 -0452