Every applicant for a building permit, subdivision approval, or a permit to allow land disturbing activities that do not meet the threshold of § 154.03 must submit a stormwater pollution control plan to the city at the time of application. No building permit, subdivision approval, or permit to allow land disturbing activities shall be issued until the city approves this plan. At a minimum these pollution abatement control practices must conform to those in the current version of the State Pollution Control Agency’s publication, Protecting Water Quality in Urban Areas.
(A) General policy on stormwater runoff rates. Stormwater runoff rates must not increase over the predevelopment two-year, ten-year and 100-year peak storm discharge rates, based on the last ten years of how that land was used. Also, accelerated channel erosion must not occur as a result of the proposed activity.
(B) The stormwater pollution control plan and the grading plan. The stormwater pollution control plan’s measures, the limit of disturbed surface and the location of buffer areas shall be marked on the approved grading plan, and identified with flags, stakes, signs and the like on the development site before work begins.
(C) Inspections of the stormwater pollution control plan measures. At a minimum, such inspections shall be done weekly and after every storm event that is large enough to result in run off from the site by either the developer or the developer’s designated representative.
(D) Minimum requirements of the stormwater pollution control plan. The Stormwater Pollution Control Plan shall be prepared and signed by a licensed professional engineer and shall contain the following information:
(1) The name and address of the applicant and the location of the activity;
(2) Project description: the nature and purpose of the land disturbing activity and the amount of grading, utilities and building construction involved;
(3) Phasing of construction: time frames and schedules for the project’s various aspects;
(4) A map of the existing site conditions: existing topography, property information, steep slopes, existing drainage systems/patterns, type of soils, waterways, wetlands, vegetative cover, 100-year floodplain boundaries and locations of existing and future buffer strips;
(5) A site construction plan that includes the location of the proposed land disturbing activities, stockpile locations, erosion and sediment control plan, construction schedule and the plan for the maintenance and inspections of the stormwater pollution control measures;
(6) Adjacent areas: neighboring streams, lakes, residential areas, roads and the like, which might be affected by the land disturbing activity;
(7) The site’s areas that have the potential for serious erosion problems;
(8) Erosion and sediment control measures: the methods that will be used to control erosion and sedimentation on the site, both during and after the construction process;
(9) Permanent stabilization: how the site will be stabilized after construction is completed, including specifications, time frames or schedules; and
(10) Calculations: any that were made for the design of such items as sediment basins, wet detention basins, diversions, waterways, infiltration zones and other applicable practices.
(E) General stormwater pollution control plan criteria. The plan shall address the following:
(1) Stabilizing all exposed soils and soil stockpiles and the related time frame or schedule;
(2) Establishing permanent vegetation and the related time frame or schedule;
(3) Preventing sediment damage to adjacent properties and other designated areas such as streams, wetlands, lakes and unique vegetation (e.g., oak groves, rare and endangered species habitats);
(4) Scheduling for erosion and sediment control practices;
(5) Where permanent and temporary sedimentation basins will be located;
(6) Engineering the construction and stabilization of steep slopes;
(7) Measures that will control the quality and quantity of stormwater leaving a site;
(8) Stabilizing all waterways and outlets;
(9) Protecting storm sewers from the entrance of sediment;
(10) What precautions will be taken to contain sediment when working in or crossing water bodies;
(11) Restabilizing utility construction areas as soon as possible;
(12) Protecting public roads from sediment and mud carried from the site by construction and other traffic;
(13) Disposing of temporary erosion and sediment control measures;
(14) How the temporary and permanent erosion and sediment control practices will be maintained; and
(15) How collected sediment and floating debris will be disposed.
(F) Minimum stormwater pollution control measures and related inspections. The following minimum control measures are required where bare soil is exposed; (due to the diversity of individual construction sites, each site will be individually evaluated; where additional control measures are needed, they will be specified at the discretion of the city; the city will determine what action is necessary to prevent excessive erosion from occurring on the site):
(1) All grading plans and building site surveys must be reviewed by the city for effectiveness of erosion control measures in the context of the site topography and drainage;
(2) Sediment control measures must be properly installed by the builder before construction activity begins. The structures may be adjusted during dry weather to accommodate short-term activities, such as those that require very large vehicles. As soon as this activity is finished or before rainfall, the erosion and sediment control structures must be returned to the configuration specified by the city. A sediment control inspection must then be scheduled, and passed before a footing inspection will be done;
(3) Diversion of channeled runoff around disturbed areas, if practical, or the protection of the channel;
(4) If a stormwater management plan involves directing some or all of the site’s runoff, the applicant or his or her designated representative shall obtain from adjacent property owners any necessary easements or other property interests concerning the flowing of the water;
(5) The scheduling of the site’s activities to lessen their impact on erosion and sediment creation;
(6) Minimize amount of exposed soil; and
(7) Control runoff as follows: Unless precluded by moderate or heavy snow cover (mulching can take place if a light snow cover is present), stabilize all exposed inactive disturbed soil areas within 100 feet of any water of the state, or within 100 feet any conveyance (curb, gutter, storm sewer inlet, drainage ditch and the like) to a water of the state with sod, seed or weed free mulch. This must be done if the developer will not work the area for seven days on slopes greater than three feet horizontal to one foot vertical (3:1), 14 days on slopes ranging from 3:1 to 10:1 and 21 days for flatter slopes.
(8) Generally, sufficient silt fence will be required to hold all sheet flow runoff generated at an individual site, until it can either infiltrate or seep through silt fence’s pores.
(9) Temporary stockpiling of 50 or more cubic yards of excess soil on any lot or other vacant area may require a grading permit for the earth moving activity in question.
(10) For soil stockpiles greater than ten cubic yards the toe of the pile must be more than 25 feet from a road, drainage channel and stormwater inlet or property line. If for any reason a soil stockpile of any size is located closer than 25 feet from a road, drainage channel, stormwater inlet or property line, and left for more than seven days, it must be covered with tarps or controlled in some other manner.
(11) All sand, gravel or other mining operations taking place on the development site shall have a national pollutant discharge elimination system general stormwater permit for industrial activities and all required State Department of Natural Resources permits.
(12) Temporary rock construction entrances may be required wherever vehicles enter and exit a site.
(13) Parking is prohibited on all bare lots and all temporary construction entrances, except where street parking is not available.
(14) Public streets must be cleaned and swept whenever tracking of sediments occurs and before sites are left idle for weekends and holidays. Establishment of a regular sweeping schedule is encouraged.
(15) Water, impacted by the construction activity, that is being removed from the site by pumping must be treated by temporary sedimentation basins, geotextile filters, grit chambers, sand filters, up-flow chambers, hydro-cyclones, swirl concentrators or other appropriate controls. The water shall not be discharged in a manner that causes erosion or flooding of the site, receiving channels, adjacent property or a wetland.
(16) All storm drain inlets must be protected during construction until control measures are in place with either silt fence or an equivalent barrier that meets accepted design criteria, standards and specifications of the State Pollution Control Agency.
(17) Catch basins; all newly installed and rehabilitated catch basins must be provided with a sump area for collecting coarse-grained material, when required by the city. The basins must be cleaned when they are half filled with material.
(18) Roof drain leaders; if possible, all newly constructed and reconstructed buildings must route roof drain leaders to pervious areas (not natural wetlands) where the runoff can infiltrate. The discharge rate shall be controlled so that no erosion occurs in the pervious areas.
(19) Follow-up inspections must be performed by the developer or subsequent owner on a regular basis to ensure that erosion and sediment control measures are properly installed and maintained. In cases where cooperation is withheld, construction stop orders may be issued by the city, until erosion and sediment control measures meet specifications. A second erosion and sediment control/grading inspection must then be scheduled and passed before the final inspection will be done.
(20) Inspection and maintenance: all stormwater pollution control management facilities must be designed to minimize the need of maintenance, to provide easy vehicle and personnel access for maintenance purposes and be structurally sound. These facilities must have a plan of operation and maintenance that ensures continued effective removal of the pollutants carried in stormwater runoff. The city or its designated representative shall inspect all stormwater management facilities during construction. Thereafter, the developer or subsequent owner shall inspect at least once every five years. The developer or subsequent owner will keep all inspection records on file for a period of six years.
(G) Permanent stormwater pollution controls.
(1) The applicant shall install or construct, or pay the city fees for all stormwater management facilities necessary to manage increased runoff, so that the two-year, ten-year and 100-year peak storm discharge rates existing before the proposed development, are not increased. These predevelopment rates shall be based on the last ten years of how that land was used. Accelerated channel erosion must not occur as a result of the proposed land disturbing or development activity. An applicant may also make an in-kind or a monetary contribution to the development and maintenance of community stormwater management facilities designed to serve multiple land disturbing and development activities undertaken by one or more persons, including the applicant.
(2) All calculations and information used in determining these peak storm discharge rates shall be submitted along with the stormwater pollution control plan.
(3) The applicant shall consider reducing the need for stormwater management facilities by incorporating the use of natural topography and land cover such as natural swales and depressions as they exist before development to the degree that they can accommodate the additional flow of treated (e.g., settled) water without compromising the integrity or quality of the wetland or pond.
(4) The following stormwater management practices must be investigated in developing the stormwater management part of the stormwater pollution control plan in the following descending order of preference:
(a) Protect and preserve as much natural or vegetated area on the site as possible, minimizing impervious surfaces, and directing runoff to vegetated areas rather than to adjoining streets, storm sewers and ditches;
(b) Flow attenuation by use of open vegetated swales and natural depressions;
(c) Stormwater wet detention facilities (including percolation facilities); and
(d) A combination of successive practices may be used to achieve the applicable minimum control requirements specified in division (G) above. The applicant shall provide justification for the method selected.
(H) Minimum design standards for stormwater wet detention facilities. At a minimum these facilities must conform to the most current technology as reflected in the current version of the State Pollution Control Agency’s publication, Protecting Water Quality in Urban Areas and the current requirements found in the same agency’s NPDES permits for stormwater associated with construction activities.
(I) Minimum protection for natural wetlands.
(1) Runoff must not be discharged directly into wetlands without appropriate quality (i.e., treated) and quantity runoff control, depending on the individual wetland’s vegetation.
(2) At the minimum, a 30-foot wide protective buffer strip of predevelopment vegetation, if possible, shall surround all wetlands. The buffer strip’s width shall be increased at least four feet for every 1% of slope of the surrounding land. The city may choose to extend the size of the buffer strip to protect sensitive wetlands from degradation.
(a) Detailed buffer design is usually site specific. Therefore the city can require a larger buffer than the minimum.
(b) For newly constructed buffer sites the design criteria should follow common principles and the example of nearby natural areas. The site should be examined for existing buffer zones and mimic the nearby slope structure and vegetation as much as possible. Buffer design and protection during construction should do any or all of the following: slow water runoff, trap sediment, enhance water infiltration, trap fertilizers, pesticides, pathogens, heavy metals, trap blowing snow and soil, and act as corridors for wildlife. How much stress is put on these functions will determine the buffer zone’s final configuration.
(c) The applicant or developer or subsequent owner shall maintain the buffer strip for the first year.
(d) Because drain tiles will short-circuit the benefits of vegetated buffer strips, drain tiles on the development site should be identified and rendered inoperable.
(e) Buffer strips may be made into perpetual conservation easements.
(3) Wetlands must not be drained or filled, wholly or partially, unless replaced by either restoring or creating wetland areas of at least equal public value. Compensating for the impact by replacing or providing substitute wetland resources or environments with those of at least equal public value. Compensation, including the replacement ratio and quality of replacement should be consistent with the requirements outlined in the rules adopted by the Board of Water and Soil Resources.
(4) Work in and around wetlands must be guided by the following principles in descending order of priority:
(a) Avoid the direct or indirect impact of the activity that may destroy or diminish the wetland;
(b) Minimize the impact by limiting the degree or magnitude of the wetland related activity and its implementation;
(c) Rectify the impact by repairing, rehabilitating or restoring the affected wetland environment with one of at least equal public value; and
(d) Reduce or eliminate the adverse impact over time by preservation and maintenance operations during the life of the activity.
(J) Models/methodologies/computations. Hydrologic models and design methodologies used for the determining runoff characteristics and analyzing stormwater management structures must be approved by the city. Plans, specifications and computations for stormwater management facilities submitted for review must be sealed and signed by a licensed professional engineer. All computations must appear in the plans submitted for review, unless otherwise approved by the city.
(Ord. 23-003, passed 3-13-2023)