2002-078 Council Resolution - Laserfiche WebLink

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Drainage Review Page 2 July 3, 2002 for Stoneybrook 3. The City's design standards for storm sewer are the following: Minimum Full Velocity — 3 fps Minimum Mainline Storm Sewer Size —15" RC pipe Minimum Culvert Size —1 5" RC pipe The submitted design seemed to use a minimum full velocity of 2.5 fps and minimum pipe size of 12" RC pipe. The storm sewer chart included in the new plan set reflects the above requirements. 4. The City's Local Water Management Plan calls for ponds to be built with a 15 foot, 10:1 side slope bench. The pond detail submitted show a 10 foot, 10:1 side slope bench. This detail need to be corrected and the proposed pond adjusted to a 15 foot wide bench. The pond detail has been revised to show a 15 -foot, 10:1 side slope bench. 5. The supporting information, soil types, and land use, used to determine the curve numbers needs to be submitted. Supporting information was included in the response letter. 6. An SCS TR -55 method should be used to determine the Time of Concentrations, not the Lag method. Response letter reiterates the Time of Concentration from the HydroCAD Model, which was a Lag method computation. An SCS TR -55 method is the preferred method to calculate Time of Concentrations. 7. Pond 6 is landlocked, according to the model. The 100 -year flood elevation for the pond will need to be determined allowing for a 100 -year snowmelt, 10 -day runoff of 7.2 inches and a Curve Number of 100. The flood elevation has been revised to reflect a 100 -year, l0 -day snowmelt situation. The supporting computations need to be submitted.