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<br /> <br /> <br />a.New development. For new, nonlinear developments that create more than one acre of new <br />impervious surface on sites without restrictions, stormwater runoff volumes will be <br />controlled and the post-construction runoff volume shall be retained on site for 1.1 <br />inches of runoff from all impervious surfaces on the site. <br /> <br />b.Redevelopment. Redevelopment projects (including linear projects), on sites without <br />restrictions that create new impervious surfaces shall capture and retain on site 1.1 <br />inches of runoff from the new impervious surface and show a net pollutant reduction <br />for any reconstructed impervious surfaces. <br /> <br />6.Water Quality <br />b. <br /> <br />a.Total suspended solids. Treatment also must achieve an 80 percent removal of <br />suspended solids. <br /> <br />b.Phosphorus control. Stormwater shall be treated to remove 60 percent of the post- <br />development phosphorus load on an annual basis before discharge to natural water <br />bodies. The amount of total phosphorus removed should be modeled using the Minimal <br />Impact Design Standards (MIDS) calculator or an equivalent water quality modeling <br />program. Where water quality ponding is exclusively used to meet the phosphorus <br />removal requirement, the ponds must be sized to store the site runoff from a two and <br /> <br />one-half inch rainfall below the normal outlet elevation. <br />c. <br /> <br />7.Rate Control. For post-construction rate control modeling a minimum curve number <br />of 84 shall be used on all disturbed/graded soil areas, due to soil compaction impacts, unless <br />Soil Protection/Compaction Remediation specifications have been incorporated into the <br />Proposal (Plan Set, Stormwater Management Plan, etc.) and are approved by the City <br />Engineer. Atlas 14 shall be used in all rate-control estimates. <br />New construction. Projects shall have no increase in runoff from theTotal suspended solids. <br />Treatment also must achieve a 60 percent removal of suspended solids. <br />d. Oil and grease control. For all storm water plans for commercial or industrial <br />developments and all other uses where the potential for pollution by oil or grease, <br />or both, exists, the first one-half inch of runoff will be treated using the best oil <br />and grease removal technology available. This requirement may be waived by the <br />city when the applicant can demonstrate that installation of such practices is not <br />necessary. <br />e. Runoff rate control. Refer to city's design standards. <br />(b) All stormwater facilities shall be designed, installed and maintained to effectively <br />accomplish the following: <br />1. Minimizetwo, <br /> <br />a. predevelopment peak runoff rates for the 2, 10, and 100 year 24 <br />event. <br />hour storm events. <br />2. Minimize predevelopment peak runoff rates for the ten year, 24 hour storm event. At <br />a minimum, the storm sewer system shall be designed for this storm event. Low areas <br />must have an acceptable overland drainage route with the proper transfer capacity <br />when the event is exceeded. <br />3. Minimize predevelopment peak runoff rates for the 100-year, 24-hour storm event. <br /> Page <br />16 <br />