§ 153.43 STORMWATER PERMIT - SUBMITTAL REQUIREMENTS.

   (A)   All requirements per §§ 153.42 and 153.43 must be submitted.

   (B)   Stormwater management plan. The stormwater management plan shall contain the following:

      (1)   Existing and proposed sub-watershed boundaries, upstream and downstream hydrologic flow paths, all on-site water features (including waters of the state), drainage patterns, flow directions, floodplain, and shoreland shown on separate figures;

      (2)   Location and amount of existing and proposed impervious area including roads, trails, parking areas, and building areas;

      (3)   Location, alignment, and elevation of existing and proposed stormwater facilities;

      (4)   Construction plans and specifications for all proposed facilities designed to meet requirements of §§ 153.55 through 153.64;

      (5)   Hydrologic calculations for runoff volume, velocities, and peak flow rates using Atlas 14 precipitation depths and storm distributions for the two-year rainfall event; ten-year, 24-hour storm event; 100-year, 24-hour storm event; and 100-year, ten-day snowmelt event for existing and proposed conditions;

      (6)   All hydrologic, hydraulic, and water quality computations completed to design the proposed facilities, including a demonstration of conformance with the water quality and volume control requirements of § 153.56;

      (7)   Curve numbers used to calculate runoff; curve numbers used to calculate runoff shall be based on TR 55, Second Edition, June 1986, Table 2 2a with the following changes:

         (a)   Cover type "open space" will be based on the amount of topsoil as well as grass cover. Less than six inches of topsoil equals poor condition; and more than six inches of topsoil equals good condition;

         (b)   Curve numbers used for cover types "urban districts" and "residential districts" assume at least six inches of topsoil and six inches of non-compacted subsoil soil based on the standards in § 153.62, Topsoil Management.

      (8)   Existing and proposed normal water level, high water level, and emergency overflow elevations for the site;

      (9)   For sites requiring extended detention, calculations showing the two-year storm discharge reduced by 50% of existing conditions to demonstrate compliance with the extended detention requirement. The minimum outlet diameter shall be six inches;

      (10)   Plans, specifications and computations for stormwater management facilities submitted for review shall be signed by a professional engineer licensed in the State of Minnesota.

   (C)   Operation and maintenance plan. The operation and maintenance plan shall identify the BMPs constructed as part of the project and shall contain the following:

      (1)   Description of inspection and maintenance activities for the stormwater BMPs;

      (2)   Timeline of inspection and maintenance activities for the stormwater BMPs;

      (3)   Contact information for the parties responsible for inspection and maintenance;

      (4)   Signatures of the parties responsible for inspection and maintenance.

   (D)   Additional information as relevant and necessary to evaluate an application may be required. Requests for additional information shall be submitted in writing to the responsible party and shall specify requirements for submittal to the county.

   (E)   At county discretion, less information may be required to constitute a complete application.

(Ord. 99-2022, passed 6-28-22)