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(5) plots of native vegetation and/or buffers in place of sod <br />(6) reforestation and revegetation <br />(7) trees and tree box filters <br />(8) reduction of impervious area <br />(9) rain water harvesting <br />(C) Other Practices. Other traditional stormwater BMPs may be approved on a site <br />by site basis to achieve the goals of water quality and quantity, and rate control. These practices shall conform <br />to the standards outlined in the resources referenced above. <br />(D) All stormwater runoff shall be pre-treated prior to discharge to any surface water. <br />(E) Maintenance Plan. A plan shall be established to maintain all temporary and permanent BMPs in a <br />working and efficient condition. This may include removal of invasive species, sediment, debris, or any other <br />foreign or obstructive object or condition that prevents the BMPs from performing as designed. <br />(F) Exemption. The mill and overlay or rehabilitation of a public roadway that does not create additional <br />impervious surfaces; and sidewalk or trail projects are exempt from these stormwater requirements. These <br />projects may be subject to other regulations. <br />157.22. Drainage. <br />Site alteration, grading, placement and installation of BMPs and other related activities shall be implemented in <br />such a way that drainage from the site shall not exceed the pre -developed rates and will not adversely affect <br />neighboring properties. <br />157.23 Calculations. <br />Hydrologic and hydraulic design calculations must be submitted for the pre -development and post -development <br />conditions for the 2, 10, and 100 year events as well as the 10 day snow melt event. Such calculations shall <br />include: (i) description of the design storm frequency, intensity and duration, (ii) time of concentration, (iii) Soil <br />Curve Numbers or runoff coefficients, (iv) peak runoff rates and total runoff volumes for each watershed area, <br />(v) infiltration rates, where applicable, (vi) culvert capacities, (vii) flow velocities, (viii) data on the increase in <br />rate and volume of runoff for the design storms used, and (ix) documentation of sources for all computation <br />methods and field test results. <br />157.24. Volume Control and Pollutant Management <br />For non -linear projects, water quality volume (calculated as an instantaneous volume) must be calculated as one (1) inch <br />times the sum of the new and the fully reconstructed impervious surface. <br />For linear projects, water quality volume (calculated as an instantaneous volume) must be calculated as the larger of one (1) <br />inch times the new impervious surface or one-half (0.5) inch times the sum of the new and the fully reconstructed <br />impervious surface. Where the entire water quality volume cannot be treated within the existing right-of-way, a reasonable <br />attempt to obtain additional right-of-way, easement, or other permission to treat the stormwater during the project planning <br />process must be made. Volume reduction practices must be considered first. Volume reduction practices are not required if <br />the practices cannot be provided cost effectively. If additional right-of-way, easements, or other permission cannot be <br />obtained, the owner/operator of construction activity must maximize the treatment of the water quality volume prior to <br />discharge from the City's MS4. <br />The requirements of this section may be altered and alternative treatment BMPs approved under the following <br />limitations: <br />3 1 a'' a e <br />