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A. Storm Water Detention. The post - construction BW(s) chosen <br />must be able to detain storm water runoff for protection of the <br />stream channels, stream erosion control, and improved water quali- <br />ty. <br />B. Properly Sized BMPs. The BNIP(s) chosen must be sized to treat <br />the water quality volume (WQv) and ensure compliance with <br />Ohio's water quality standards in Chapter 3745 -1 of the Ohio Ad- <br />ministrative Code. The WQv shall be equivalent to the volume of <br />runoff from a 0.75 -inch rainfall. <br />C. Runoff Rate: The peak runoff rate from the development area shall <br />not be greater after development than it was before development. <br />The applicant shall provide calculations proving no increase in the <br />runoff rates from the one -, two -, five -, 10 -, 25 -, 50- and 100 -year <br />storms. <br />D. Runoff Volume: hrcreases in the runoff volume shall be offset by <br />further restricting runoff rates. <br />(3) Based on the increase in runoff volume, the applicant shall detenmine <br />the critical storm for the development area. 'The runoff rate from the <br />critical storm shall be restricted to the one -year pre - development storm <br />runoff rate. The critical storm shall be calculated as follows: <br />A. Determine the total volume of runoff from a one -year frequency, <br />24 -hour storm, occurring on the development area before and after <br />development. <br />B. From the volumes in subsection (z)(3)A determine the percent of <br />increase in volume of runoff due to development according to the <br />equation (Q after divided by the Q before) X 100 and, using this <br />percentage, select the critical storm from this table: <br />Table 4: Critical Storm Selection <br />The Percentage Increase In Volume Of Runoff Is: <br />Equal To Or Greater <br />han <br />And Less Than <br />he 24 -Hour "Crib- <br />al Storm" <br />for Discharge Will Be <br />10 <br />1 Year <br />10 <br />20 <br />Years <br />0 <br />50 <br />5 Years <br />50 <br />100 <br />10 Years <br />100 <br />250 <br />25 Years <br />50 <br />500 <br />50 Years <br />500 <br />- - -- <br />100 Years <br />(4) Detention Or Retention Basin Exemption For Redevelopment Or For <br />Expansion Of Existing Facilities: <br />A. For any development regulated by this regulation, the construction <br />of a detention or retention basin may not be required for the devel- <br />52 <br />