CCP 01-13-1992 - Laserfiche WebLink

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pond level of 946.5 under current conditions will not require any grading of the . pond. Under future developed conditions, pond A-7a must have a storage volume that will hold the runoff from the entire drainage area (A-7) while allowing a peak discharge out of the pond of 4.8 cfs. With these criteria. pond A-7a requires 1.95 acre-feet of storage for the 100 year 24 hour storm and will have a maximum pond height of elevation 947.3. The upper channel in the northwest corner of pond A-7a must be filled in and re~laced with a 15" RCP pipe with an invert elevation of 945.3. An orifice plate with a 13" diameter opening is required to reduce the flow out of the pond to 4.8 cfs. The pond must also be graded to contain water up to an elevation of 947.3. However, construction of the 15" RCP storm sewer and orifice plate could be completed when the entire . drainage area of 16.67 acres is developed. The Rice Creek Watershed District is requiring that the baffled weir for pond A-7A be constructed when the 24" RC pipe is installed into the pond. The weir in pond A-7a is designed with the same requirements as the weir serving the wetland preservation area. This weir will treat the 1 year 24 hour storm water runoff for the entire drainage area of 16.67 acres. The top of the weir will be at elevation 946.10 and requires a minimum length of weir of 24 linear feet. Page 4 of the plans illustrates the details of the weir at pond A-7a and its location. The installation of the weir will require grading the channel side and bottom. The bottom of the channel under the weir should be at elevation 944.7. .