Section 12A-88 Stormwater management plan required.

(b) A stormwater management plan must be submitted and approved by the director before issuance of a land disturbance permit and before approval of a final plat or a development plan. The stormwater management plan shall be prepared and certified by a registered professional engineer licensed in the State of Missouri.

(c) The stormwater management plan must show all components of the storm drainage system including street curbs, inlets and piping, junction boxes, engineered and natural channels and stormwater management facilities (for example, retention and detention ponds, bioswales, bioretention areas, etc.). The stormwater management plan may be prepared in conjunction with or separate from the soil erosion plan.

(d) It is recommended that a preliminary stormwater management plan be submitted early in the review process to allow time for city staff to discuss plan concepts with the developer. The stormwater management plan will be discussed as part of the concept review for any proposed development.

(e) The stormwater management plan must comply with all requirements of the city’s current Stormwater Management and Water Quality Manual.

(2) Calculations. Hydrologic and hydraulic design calculations for the pre-development and post-development for the design conditions specified in the Stormwater Management and Water Quality Manual. These calculations shall include: description of the design storm frequency, intensity and duration; time of concentration; soil curve numbers; peak runoff rates and total volumes for the watershed area; infiltration rates where applicable; culvert capacities; flow velocities; data on the increase in rate and volume of runoff for the design storms referenced in the Stormwater Management and Water Quality Manual; and, documentation of sources for all computation methods and field test results.

(3) Soils information. When a stormwater management facility relies on the hydrologic properties of the soils (such as an infiltration basin) the developer shall submit a soils report. The soils report shall be based on onsite boring logs or pit profiles. The number and location of required soil boring or soil pits shall be determined based on what is needed to determine the suitability and distribution of soil types present at the location of the facility.

(4) Landscaping information. The developer must include a detailed landscaping and vegetative restoration plan as part of the stormwater management plan. Details on maintenance of the vegetation shall be included in the operation and maintenance plan. The landscaping plan component must be prepared by an individual who can demonstrate knowledge of landscape design or by Missouri Department of Conservation personnel.

(g) The stormwater management plan must include a written operation and maintenance manual for the permanent stormwater management facilities, including landscaping and vegetative cover, proposed as part of the development. This is required whether the facilities are to be publicly or privately maintained. Approval of the operation and maintenance manual is a part of the overall plan approval process.