The intent of storm water management design guidelines is to encourage the use of structural, vegetative or managerial practices, commonly referred to as best management practices (BMPs), designed to treat, prevent or reduce degradation of water quality due to storm water runoff. All development projects subject to review under the requirements of this chapter shall be designed, constructed and maintained using BMPs to prevent flooding, protect water quality, reduce soil erosion, maintain and improve wildlife habitat, and contribute to the aesthetic values of the project. The particular facilities and measures required on-site shall reflect and incorporate existing grade, natural features, wetlands and watercourses on the site to the maximum extent feasible.
(A) Storm water drainage. All storm water drainage plans shall meet the standards adopted by the township for design and construction and shall, to the maximum extent feasible, utilize various control techniques, including, but not limited to:
(1) Limitation of land disturbance and grading;
(2) Maintenance of vegetated buffers and natural vegetation;
(3) Minimization of impervious surfaces;
(4) Use of terraces, contoured landscapes, runoff spreaders, vegetated or rock-lined swales;
(5) Use of infiltration devices, soil permitting; and
(6) Shared use of detention basins.
(B) General standards.
(1) Storm water management systems shall be designed to prevent flooding and the degradation of water quality related to storm water runoff and soil erosion from proposed development.
(2) All properties that are subject to this chapter shall provide for on-site storage of storm water. Facilities shall be designed to provide a volume of storage and discharge rate that meets the standards of the township's storm water engineering and design guidelines.
(3) Priority shall be placed on site design that maintains natural drainage patterns and watercourses. Alterations to natural drainage patterns shall not create flooding or degradation in water quality for adjacent or downstream property owners. The County Public Works Commissioner must approve site designs if it is a watercourse under his or her jurisdiction. The County Road Commission and the State Department of Transportation must also approve site designs for watercourses within their jurisdictional rights-of-way.
(4) The use of swales and vegetated buffer strips (containing desirable native plant materials) or other infiltration practices is encouraged as a method of storm water conveyance so as to decrease runoff velocity, allow for biofiltration, allow suspended sediment particles to settle, and to remove pollutants. Tolerance for water saturation, sunlight, pesticides, metals and salt shall be required in determining appropriate plantings in these areas.
(5) Drainage systems shall be designed to be visually attractive. The integration of storm water conveyance systems and retention and detention basins in the overall landscape concept is recommended. Ponds with a naturally contoured, rather than square or rectangular, design and appearance shall be encouraged.
(6) Where large amounts of grease and oil may accumulate, as in the case of commercial/industrial developments and large areas of pervious surfaces for parking, approved oil separators shall be required.
(7) For sites that store or use chemicals, a spill response plan shall be submitted and approved by the township, or the site can provide the township evidence of a State Department of Environmental Quality approved storm water pollution prevention plan and certificate of coverage.
(C) Storm water management and wetlands. Wetlands may be used for storm water management if all the following conditions are met.
(1) Wetlands and their current functions shall be protected from impairment due to the discharges of storm water. Measures such as a vegetated forebay shall be taken to reduce erosive velocities of storm water discharge and remove sediment and other pollutants prior to discharge to a wetland. The volume of a vegetated forebay is defined by the township's storm water management plan.
(2) Wildlife, fish or other beneficial aquatic organisms and their habitat within the wetland will not be impaired.
(3) The wetland has sufficient holding capacity for storm water, based upon calculations prepared by the proprietor and reviewed and approved by the township, and that the additional storm water will not impair the wetland's current functions.
(4) On-site erosion and sediment control shall be provided to protect the natural function of the wetland.
(5) Provisions approved by the township shall be established so as to ensure that the wetland is not disturbed or impaired in the future relative to the needed storage capacity.
(6) Applicable permits from the local government and the State Department of Environmental Quality are obtained.
(D) Site plan standards for impervious surface reduction.
(1) The township recognizes that, due to the specific requirements of any given development, inflexible application of the design standards may result in development with excessive paving, storm water runoff and a waste of space which could be left as an open space.
(2) The township may permit deviations from ordinance requirements during the site plan review process to reduce impervious surfaces, as determined by the Township Zoning Administrator or Planning Commission. These deviations can be either prescribed by ordinance or proposed through creative land development techniques that are permitted by this chapter. The township may permit deviations whenever it finds that the deviations are more likely to meet the intent and standards of this chapter and accommodate the specific characteristics of the use in question.
(3) The township may attach conditions to the approval of a deviation that bind the approval to the specific use in question. Measures that reduce impervious surface and increase infiltration may include, but are not limited to, the following.
(a) Streets and access.
1. Design residential streets with the minimum required pavement width needed to support travel lanes, on-street parking and emergency (as defined by applicable emergency response agencies), maintenance and service vehicle access and function based on traffic volumes.
2. Reduce the total length of residential streets by examining alternative street layouts to determine the best option for increasing the number of homes per unit length.
3. Design street right-of-way widths/private road easements to reflect the minimum required to accommodate the travel-way, the sidewalk and vegetated open channels.
4. Minimize the number of street cul-de-sacs and reduce the radius of cul-de-sacs to the minimum required to accommodate emergency and maintenance vehicles. Alternative turnarounds shall be considered, including the use of mountable curbing and grass shoulders for the occasional event of access by fire trucks and other large commercial trucks. Provide landscape center islands wherever cul-de-sacs exist.
5. Where density, topography, soils and slope permit, use vegetated open channels in the street right-of-way/private road easements to convey and treat storm water runoff.
6. Use alternative driveway surfaces and shared driveways that connect two or more sites. (Use agreements should accompany any application.)
7. Promote more flexible design standards for residential subdivision sidewalks. Where practical, consider locating sidewalks on only one side of the street and providing common walkways linking pedestrian areas.
(b) Parking.
1. Base parking requirements on the specific characteristics of the use, land-banking in open space parking required to satisfy ordinance requirements.
2. Reduce the overall imperviousness associated with parking lots by providing compact car spaces, minimizing stall dimensions, incorporating efficient parking lanes, depressed center islands with curb cuts and using pervious materials in the spillover parking areas where possible.
3. Encourage shared parking between compatible users.
4. Encourage use of grass pavers or pervious pavers for little-used parking areas, for example, church parking lots that are used only once a week and the like.
(c) Site design.
1. Direct rooftop runoff to pervious areas such as yards, open channels or vegetated areas and avoid routing rooftop runoff to the roadway and the storm water conveyance system.
2. Incorporate a green roof or a roof garden to create a vegetated roof system that retains and filters storm water prior to drainage off building rooftops.
3. Create naturally vegetated buffer systems, which may vary in width as determined by the township along all drainageways. Critical environmental features such as the 100-year flood plain, steep slopes and wetlands shall be considered.
4. Minimize clearing and grading of woodlands and native vegetation to the least amount needed to build lots, allow access and provide fire protection.
5. Conserve trees and other vegetation at each site by planting additional vegetation, clustering tree areas and promoting the use of native plants.
6. Incorporate shared use of detention/retention basins, where feasible.
(E) Storm water facility maintenance.
(1) Whenever a landowner is required to provide restricted discharge, on-site storm water detention and/or surface drainage to wetlands, or whenever other protective environmental measures including monitoring devices and oil and sediment separators are required, the measures or facilities shall be provided and maintained at the landowner's expense. The landowner shall provide assurance to the township that the landowner will bear the responsibility of providing and maintaining the methods or facilities, by written agreement, suitable for recording at the office of the County Register of Deeds, that will act as a perpetual restriction on the land, the form and content of which shall be approved by the Township Attorney. A maintenance plan shall be provided including notation and description of maintenance requirements and timelines.
(2) Refer to the township storm water management plan and guidelines for a sample maintenance plan.
(Ord. 06-14-Z, passed 10-3-2006; Ord. 06-14, passed 10-17-2006)