CCP 02-10-1992 - Laserfiche WebLink

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I Ie pond level of 946.5 under current conditions will not require any grading of the pond. I I 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 I 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 I maximum pond height of elevation 947.3. The upper channel in the northwest I corner of pond A-7a must be filled in and replaced with a 15" RCP pipe with an invert elevation of 945.3. An orifice plate with a 13" diameter opening is I 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 I the 15" RCP storm sewer and orifice plate could be completed when the entire .. drainage area of 16.67 acres is developed. I 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. I 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 I water runoff for the entire drainage area of 16.67 acres. The top of the weir I 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 I 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 I elevation 944.7. ~. I I