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Bloom, Page 2, 1131105 <br />GENERAL COMMENTS <br />Items that should be addressed regarding the submitted modeling and plan set are as follows. <br />1. A utility plan, including the location of all proposed storm sewer, should be submitted for <br />review. <br />2. A detail of the detention pond outlet structure should be provided for review. <br />— 3. An infiltration rate of 1 inThr was used for the proposed detention basin in the HydroCAD <br />— modeling submitted. For B soils, a lower infiltrationrate between 03 – 0.6 zn/�' is <br />recommended. <br />_ 4. If infiltration is to be provided by the detention basin, notes should be added to the plan <br />set indicating that the soils will not be compacted and that light equipment will be used to <br />construct the basin. <br />5. The 100-yr high water level of the proposed detention basin should be modeled as <br />impervious in the subcatchment to the detention basin in the HydroCAD modeling. <br />6. A detail of the sediment control structure on the east side of the wetland should be <br />provided for review. <br />Changes to the HydroCAD model will affect the modeled rates and volumes. However, for the <br />purposes of this review, the submitted information has been used to evaluate the development. <br />RATE CONTROL <br />Peak discharge rates for developments must be at or below existing rates for the 2, 5, 1 D, and <br />100 year storm events. <br />Based on the HydroCAD modeling output submitted for existing conditions and proposed <br />conditions, the following peak discharge rates were determined: <br />Storm Event, 24-hr Existing Conditions Proposed Conditions <br />f cfs <br />2 2.80" 2.13 4.35 <br />5 (3.50") 3.86 6.28 <br />� 4 4.20" 5.83 8.22 <br />i0� 6.00" 11.53 14.27 <br />Table L Comparison of Peal{ Discharge Rates <br />As shown in Table 1, proposed discharge rates will exceed those of existing rates. This is <br />primarily due to the various areas of unrestricted discharge from the site. Therefore, the site <br />does not meet the District's rate control criteria. Providing controls for this discharge, which <br />could include practices such as rooftop storage, underground storage, rain gardens, infiltration <br />"Our mission is toprotect, manage, and improve the water resources of the Capitol Region Watershed District. ° <br />