1. Design standards shall be those contained within the Stormwater Management Ordinance [Chapter 19].
2. Basin low-flow channels shall be designed to filter sediment and pollutants from site discharge. Appropriate vegetation should be chosen for this purpose and the channel should meander through the basin to maximize the amount of pollutant removal. Impervious low-flow channels are prohibited in basins collecting more than two drainage acres. Each basin design should include landscaping considerations, such as plant lists, to promote pollutant removal.
3. Stormwater management basins with side slopes steeper than 4:1 are prohibited.
4. Residential homes located in the designated growth area as defined in the Township Comprehensive Plan and homes located in the appropriate well-head protection areas shall be provided with roof drain seepage pits unless the soil is determined to be unsuitable for infiltration. Suitable soil infiltration rates would range from 2-6 inches/hour.
5. Subsurface infiltration shall not be permitted in areas where it will adversely affect subsurface sewage disposal or well heads.
6. All natural drainage ways and existing contouring of pre-development drainage patterns shall be preserved to the maximum extent possible, and post-development drainage patterns shall simulate pre-development patterns. Where existing (on/off site) wetlands accept runoff from the site, there shall be no reduction in the runoff volume of surface flows after development. Drainage easements shall be provided to protect these natural drainage courses and wetland areas.
7. Generally, significant horizontal and vertical alignment changes of the collection system shall be achieved through the use of manholes and/or inlets. Inlets shall be placed at the end of the radii of intersecting streets.
8. The minimum slope for unlined, open channels shall be 2%; minimum slope for pipes and lined channels shall be .5%.
9. Energy dissipaters/erosion control devices shall be placed at the outlets of all pipes where flow velocities exceed maximum permitted channel velocities.
10. Vertical pipes, inlets and other surface water receiving structures shall be installed with trash racks, or so designed to control trash accumulation. Headwalls and endwalls, in residential areas, shall be constructed with grates so as to limit access to open pipes.
11. Storm sewer inlets which direct flow off-site and the last inlet prior to a stormwater management facility shall be designed as water quality inlets to provide sediment control and pollutant removal. All such inlets shall be accompanied by a note on the plans concerning maintenance.
12. In wellhead protection areas as identified on the Dover Township Wellhead Protection Overlay Map, water quality inlets shall be provided to collect and remove pollutants from parking lot runoff.
13. Use of parking lots for detention storage may be approved by the Board of Township Supervisors, after review and recommendations from the Township Engineer.
14. No stormwater runoff or natural drainage water shall be so diverted as to overload existing drainage systems, or create flooding or the need for additional drainage structures on other private properties or public lands.
(Ord. 2011-05, 3/14/2011, § 1003)