02/23/2011 Env Bd Packet - Laserfiche WebLink

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• • FINAL DRAFT 02 -23 -2011 (1) Stormwater Management - A Stormwater Management Permit shall be required for all proposed land development activity including public linear projects except for mill and overlay of public roadway, sidewalk, or trail that does not create additional impervious surface, or unless otherwise exempted in this ordinance, which meets any or all of the following: (a) Creation of more than 10,000 sq. ft. (0.23 acre) of impervious surface, including smaller individual sites that are part of a common plan of development that may be constructed at different tunes. (b) The site is within the 100 -year floodplain; within 1,000 feet of a public water or protected wetland; impacts a wetland; and /or within 300 feet of Rice Creek, Clearwater Creek, Hardwood Creek, or a public ditch. (c) If redevelopment will disturb fifty percent or more of existing impervious surface or increase impervious surface by fifty percent or more. For the purpose of this paragraph, the extent of disturbance is the area of exposure of underlying soils. (d) Any land disturbing activity, regardless of size, that the City determines would otherwise cause an adverse impact to an environmentally sensitive area or other property. (2) Stormwater Management Criteria - Site plans for new development of any kind will be assessed for stormwater quantity control and stormwater quality management. The general policy on stormwater runoff rates is to reduce the impacts of development by maintaining predevelopment hydrological conditions in the following ways: (a) Decrease runoff volume. (b) Decrease erosion and sedimentation. (c) Decrease flow frequency, duration, and peak runoff rates. (d) Increase infiltration (groundwater recharge) or filtration. (e) Maintain existing flow patterns. (f) Reduce time to peak flows by increasing the time of concentration to and through storm sewers. (g) Storage of stormwater runoff on site. (h) Avoid channel erosion. (i) The proposed project must not adversely affect water level off the site during or after construction. 11