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Table 3: 24-Hour Critical Storm <br />If the Percentage of Increase in Volume of <br />Runoff is: <br />The Critical Storm will be: <br />Equal to or Greater Than: and Less Than: <br />---- 10 1 year <br />10 20 2 year <br />20 50 5 year <br />50 100 10 year <br />100 250 25 year <br />250 500 50 year <br />500 --- 100 year <br />For example, if the percent increase between the pre- and post-development runoff volume fora 1-year <br />storm is 35%, the Critical Storm is a 5-year storm. The peak discharge rate of runoff for all storms up to <br />this frequency shall be controlled so as not to exceed the peak discharge rate from the 1-year frequency <br />storm under pre-development conditions in the development drainage area. The post-development <br />runoff from all less frequent storms need only be controlled to meet pre-development peak discharge <br />rates for each of those same storms. <br />E. Storm Water Management on Redevelopment Projects: Comprehensive Storm Water <br />Management Plans for redevelopment projects shall reduce existing site impervious areas <br />by at least 20 percent. Aone-for-one credit towards the 20 percent net reduction of impervious <br />area can be obtained through the use of pervious pavement and/or green roofs. <br />Where site conditions prevent the reduction of impervious area, storm water <br />management practices shall be implemented to provide storm water quality control <br />facilities for at least 20 percent of the site's impervious area. <br />2. When a combination of impervious area reduction and storm water quality control <br />facilities are used, the combined area shall equal or exceed 20 percent of the site. <br />Where projects are a combination of new development and redevelopment, <br />the total water quality volume that must be treated shall be calculated by a <br />weighted average based on acreage, with the new development at 100 <br />percent water quality volume and redevelopment at 20 percent. <br />4. Where conditions prevent impervious area reduction or on-site storm water <br />management for redevelopment projects, practical alternatives as detailedfor <br />redevelopment projects, practical alternatives as detailed in Section 1128.10 may be <br />approved by the Village Engineer. <br />1128.10 ALTERNATIVE ACTIONS <br />