As required by the city's phase II municipal separate storm sewer (MS4) National Pollutant Discharge Elimination System (NPDES) permit, issued by the state department of environmental management (ADEM), the city must develop, implement, and enforce a stormwater management program designed to reduce the discharge of pollutants from its MS4 to the maximum extent practicable to protect water quality and to satisfy the appropriate water quality requirements of the federal Clean Water Act (CWA).

(Zoning Ord. 2019, § 316(intro. ¶), 6-24-2019; Ord. No. 490, 12-10-2012)

Any person or entity proposing to construct buildings or develop land within the city shall apply to the planning commission for approval of a stormwater management plan. No building permit shall be issued, or land developed, except upon approval of such plan. The following activities shall be excluded from the requirements of this section:

(1)

Minor land disturbing activities such as home gardens, home landscaping, repairs, or related activities.

(2)

Construction of single-family residences, when they are constructed by or under contract with the owner for his own occupancy.

(3)

Agricultural practices or construction of farm buildings, when conducted in compliance with all applicable best management practices.

(4)

Private and commercial forestry activities, when conducted in compliance with all applicable best management practices.

(5)

Construction or maintenance projects undertaken or financed, in whole or in part, by:

a.

The state department of transportation;

b.

Any county or municipality of the state;

c.

The Soil Conservation Service;

d.

The U.S. Department of Agriculture;

e.

Any public utility under the regulatory jurisdiction of the public service commission.

(Zoning Ord. 2019, § 316(a), 6-24-2019; Ord. No. 490, 12-10-2012)

For sites one acre and above (or such requirements as subsequently adopted by ADEM), the developer shall furnish proof of obtaining an ADEM stormwater discharge permit and shall be responsible for maintaining the stormwater best management practices until the completion of the project.

(Zoning Ord. 2019, § 316(b), 6-24-2019; Ord. No. 490, 12-10-2012)

(a)

The stormwater runoff calculations shall be based on a 25-year storm frequency; however, if the property or drainage structure is located in a 100-year floodplain, the calculations shall be based on a 100-year storm frequency.

(b)

The post-construction runoff shall be less than or equal to pre-construction runoff, based on the required design storm frequency.

(c)

The content of the stormwater management plan shall consist of measures that will safely convey runoff to a stable outlet, using storm drain piping, diversions, ditches or swales, retention structures, or similar conservation measures. These measures shall minimize flooding and damage to downstream facilities resulting from increased post-construction runoff from the site. The plan shall also provide provisions to minimize erosion from construction activities by the use of silt fencing, hay bales, check dams, sediment ponds, etc. These measures for conveyance of runoff and erosion control shall be operational as soon as possible after the start of construction.

(Zoning Ord. 2019, § 316(c), 6-24-2019; Ord. No. 490, 12-10-2012)

Developments where the area contributing runoff is 25 acres or less shall be designed using the rational method of calculating runoff. developments where the area contributing runoff is between 25 and 200 acres shall be designed using either the rational method of calculating runoff or other methods as approved by the planning commission. For developments where the area contributing runoff is 200 acres or more, the applicant shall use state regression equations or submit a method of evaluation for the calculation of runoff to the planning commission for review and approval. All such development proposals shall be prepared by a licensed professional engineer.

(Zoning Ord. 2019, § 316(d), 6-24-2019; Ord. No. 490, 12-10-2012)

The planning commission may request assistance from qualified experts in determining whether the applicant's proposed measures comply with these requirements.

(Zoning Ord. 2019, § 316(e), 6-24-2019; Ord. No. 490, 12-10-2012)

The planning commission may waive any one or all items in this section only if it is recommended by staff review to do so.

(Zoning Ord. 2019, § 316(f), 6-24-2019; Ord. No. 490, 12-10-2012)