(A) If detention facilities are utilized for the development site, the facility(ies) shall be designed such that post-development peak runoff rates from the developed site are controlled to those rates defined by this chapter.
(B) All detention facilities shall be equipped with outlet structures to provide discharge control for the four designated storm frequencies. Provisions shall also be made to safely pass the post-development 100-year storm runoff without damaging or impairing the continued function of the facilities. Should any stormwater management facilities be regulated by 25 Pa. Code Chapter 105 regulations, the facility shall be designed in accordance with those regulations and meet the regulations concerning dam safety which may require the passage of storms larger than the 100-year event.
(C) Shared-storage facilities which provide detention of runoff for more than one development site within a single subarea are encouraged wherever feasible and provided such facilities meet the criteria contained in this section. In addition, runoff from the development sites involved shall be conveyed to the facility in a manner that avoids adverse impacts (such as flooding or erosion) to channels and properties located between the development site and the shared-storage facilities.
(D) Where detention facilities will be utilized, multiple use facilities, such as wetlands, lakes, ballfields or similar recreational/open space uses are encouraged wherever feasible, subject to the approval of the municipality and compliance with 25 Pa. Code Chapter 105 regulations.
(E) Other considerations which should be incorporated into the design of the detention facilities include.
(1) Inflow and outflow structures shall be designed and installed to prevent erosion and bottoms of impoundment type structures should be protected from soil erosion.
(2) Control and removal of debris both in the storage structure and in all inlet or outlet devices shall be a design consideration.
(3) Inflow and outflow structures, pumping stations and other structures shall be designed and protected to minimize safety hazards.
(4) The water depth at the perimeter of a storage pond should be limited to that which is safe for children. Restriction of access (fence, walls and the like) may be necessary depending on the location of the facility and the maximum depths of water.
(5) Side slope of storage ponds shall not exceed a ratio of two and one-half to one horizontal to vertical dimension.
(6) Landscaping shall be provided for the facility which harmonizes with the surrounding area.
(7) Facilities shall be located to facilitate maintenance, considering the frequency and type of equipment that will be required.
(8) Bottoms of detention basins should be graded with sufficient slope to provide positive surface drainage. A subdrainage system may be required depending on the location of the pond bottom relative to ground water levels.
(9) All detention ponds shall be provided with a fence of a height and type subject to the approval of the municipality and shall be designed to assure access for maintenance. In all cases, the fence height shall be a minimum of five feet.
(Ord. 4-2011, passed 10-8-2011)