The following general and specific standards shall apply.
(A) General standards.
(1) When possible, existing natural drainage ways, wetlands and vegetated soil surfaces must be used to convey, store, filter and retain storm water run-off before discharge to public waters.
(2) Development must be planned and conducted in a manner that will minimize the extent of disturbed areas, run-off velocities, erosion potential and reduce and delay run-off volumes. Disturbed areas must be stabilized and protected as soon as possible and facilities or methods used to retain sediment on the site.
(3) When development density, topographic features and soil and vegetation conditions are not sufficient to adequately handle storm water run-off using natural features and vegetation, various types of constructed facilities such as diversions, settling basins, skimming devices, dikes, waterways and ponds may be used. Preference must be given to designs using surface drainage, vegetation and infiltration rather than buried pipes and human-made materials and facilities.
(B) Specific standards.
(1) Impervious surface coverage of lots must not exceed 25% of the lot area. However, up to 75% impervious surface coverage may be allowable within zoned light and medium industrial districts, located within the existing (as of November 2013) Mud Lake shoreland district and shoreline (as defined by extending a line east from Southview Avenue South and extending a line south from 3rd Street SE), as a conditional use, if all of the following requirements are met:
(a) One inch of runoff from all impervious surfaces is permanently treated. Preference should be given to volume reduction techniques that include infiltration basins, rain gardens, enhanced infiltration swales, filter strips, disconnected impervious area, and other conservation designs. Treatment by infiltration is required if type A or B soils are present. Otherwise, the runoff must be treated to reduce the total suspended solid (TSS) load by 90 percent and the total phosphorus load by 65%;
(b) A 50-foot wide, permanently vegetated buffer is established along the affected public waters, if one does not presently exist. The buffer shall include vegetation typical of good quality wetlands within the region, and a long-term maintenance plan, including provisions for replacing dead or diseased vegetation, shall be developed and recorded for the maintenance of the established wetland buffer vegetation. Removal of trees and shrubs necessary to accommodate stairways, landings, chairlifts, access paths, and recreational use areas can occur. Except for the access path and recreational use area, a natural ground cover must be preserved or established in the 50-foot nearshore area;
(c) A storm water management plan is developed by a state licensed professional engineer with experience in meeting National Pollution Discharge Elimination System (NPDES) construction permit requirements. The storm water plan must include a long-term operations and maintenance plan recorded with the property; and
(d) Storm water and vegetation management plans are approved by the Commissioner of the Department of Natural Resources.
(2) When constructed facilities are used for storm water management, documentation must be provided by a qualified individual that they are designed and installed consistent with the field office technical guide of the local soil and water conservation districts.
(3) New constructed storm water outfalls to public waters must provide for filtering or settling of suspended solids and skimming of surface debris before discharge.
(Ord. 209.5, passed 12-14-1994; Ord. 308, passed 12-18-2013)