(A) The following storm water management practices must be considered and investigated by the applicant in developing a Storm Water Management Plan:
(1) Natural infiltration of precipitation on-site, if the property is located outside of an area that is considered to be sensitive to ground water contamination. The city encourages the infiltration of the first one-half inch of run-off in permeable soils (NRCS hydrologic group A and B soils);
(2) Flow rate reduction by the use of open vegetated swales and natural depressions;
(3) Storm water retention facilities;
(4) Storm water detention facilities. Detention facilities must be designed and constructed according to specifications approved by the City Engineer; and
(5) A combination of practices may be used in order to achieve the minimum control requirements of this subchapter. The applicant must provide justification for the method(s) selected.
(B) When possible, existing natural drainage ways, wetlands and vegetated soil surfaces must be used in a Storm Water Management Plan to convey, store, filter and retain storm water run-off before it is discharged to public waters.
(C) 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 must be used to retain sediment on the site.
(D) 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. The city encourages the use of best management practices, such as using surface drainage, vegetation and infiltration rather than buried pipes and human-made materials and facilities.
(E) When constructed facilities are to be used for storm water management, documentation must be provided by an engineer or an individual qualified to design and review the particular facility, that the facilities are designed and constructed in accordance with all applicable local, state and federal laws and regulations.
(F) Newly constructed storm water outfalls where the discharge eventually flows to public waters must provide for filtering or settling of suspended soils and skimming of surface debris before discharge.
(G) Storm Water Management Plans must be consistent with adopted watershed management plans and ground water management plans prepared in accordance with M.S. Chapter 103B, as it may be amended from time to time, and must be reviewed and approved by the local watershed authority, if required.
(H) Hydrologic models and design methodologies in a Storm Water Management Plan to be used for the determination of run-off and the analysis of storm water management facilities must be reviewed and approved by the City Engineer. Plans, specifications and computations for storm water management facilities must be signed by a licensed professional engineer. All computations must appear on the plans submitted for review, unless otherwise required by the City Engineer.
(Prior Code, § 430.13) (Ord. 2008-05, passed 5-21-2008)