(A) For all regulated activities, unless preparation of a SWM site plan is specifically exempted in § 52.036:
(1) Design and implementation of an approved SWM site plan is required; and
(2) No regulated activities shall commence until the borough issues written approval of an SWM site plan, which demonstrates compliance with the requirements of this chapter.
(B) SWM site plan approved by the borough, in accordance with § 52.056, shall be on site throughout the duration of the regulated activity.
(C) The borough may, after consultation with DEP, approve measures for meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with, state law including, but not limited to, the Clean Streams Law, 35 P.S. §§ 691.1 et seq..
(D) For all regulated earth disturbance activities, erosion and sediment control BMPs shall be designed, implemented, operated and maintained during the regulated earth disturbance activities (e.g., during construction) to meet the purposes and requirements of this chapter and to meet all requirements under Pa. Code Title 25 and the Clean Streams Law. Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Manual (E&S Manual), No. 363-2134-008 (April 15, 2000), as amended and updated.
(E) For all regulated activities, implementation of the volume controls in § 52.037 is required.
(F) Impervious areas.
(1) The measurement of impervious areas shall include all of the impervious areas in the total proposed development even if development is to take place in stages.
(2) For development taking place in stages, the entire development plan must be used in determining conformance with this chapter.
(G) Stormwater flow onto adjacent property shall not be created, increased, decreased, relocated or otherwise altered without a written agreement from the adjacent property owner(s). Such stormwater flows shall be subject to the requirements of this chapter.
(H) All regulated activities shall include such measures, to the maximum extent practicable, to:
(1) Protect health, safety and property and the public welfare;
(2) Meet the water quality goals of this chapter by implementing measures to:
(a) Minimize disturbance to floodplains, wetlands and wooded areas;
(b) Maintain or extend riparian buffers;
(c) Maintain natural drainage patterns;
(d) Avoid erosive flow conditions in natural flow pathways;
(e) Minimize the creation of impervious surfaces;
(f) Minimize thermal impacts to waters of this Commonwealth; and
(g) Disconnect impervious surfaces by directing runoff to pervious areas, wherever possible.
(3) Incorporate the techniques for low impact development practices.
(I) Discharge roof drains and sump pumps to infiltration or vegetative BMPs or satisfy the criteria for DIAs.
(J) Infiltration BMPs should be spread out, made as shallow as practicable, and located to maximize use of natural on-site infiltration features while still meeting the other requirements of this chapter.
(K) Stormwater storage facilities should completely drain both the volume control and rate control capacities over a period of time not less than 24 hours and not more than 72 hours from the end of the design storm.
(L) (1) The design storm volumes to be used in the analysis of peak rates of discharge will be the 24-hour values as shown in the following table:
Storm Frequency | 24-Hour Depth in Inches |
2-year | 2.45 |
10-year | 3.44 |
25-year | 4.07 |
100-year | 5.13 |
(2) Or the 24-hour values obtained from the Precipitation-Frequency Atlas of the United States, Atlas 14, Volume 2, Version 3.0, U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), National Weather service, Hydrometeorological Design, Studies Center, Silver Spring, Maryland. NOAA’s Atlas 14 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/
(M) For all regulated activities, SWM BMPs shall be designed, implemented, operated and maintained to meet the purposes and requirements of this chapter and to meet all requirements under Pa. Code Title 25, the Clean Streams Law and the Stormwater Management Act.
(N) Various BMPs and their design standards are listed in the BMP Manual.
(O) Off-site areas which drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site.
(P) Any stormwater management facility designed to store stormwater runoff and not eligible for a waiver from permit requirements pursuant to 25 Pa. Code § 105.12 requiring a berm or earthen embankment shall be designed to provide an emergency spillway to handle flow up to and including the 100-year post-development conditions. The height of embankment must be a minimum one-foot above the maximum pool elevation computed when the facility functions for the 100-year post-development inflow.
(Q) Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls or stream enclosures), and any work involving wetlands pursuant to 25 Pa. Code Chapter 105 regulations, as amended or replaced, shall be designed, permitted and constructed in accordance with Chapter 105.
(R) Any drainage conveyance facility and/or channel that does not fall under Chapter 105 regulations, must be able to convey, without damage to the drainage structure or roadway, runoff from the 25-year design storm. Conveyance facilities discharging to or exiting from stormwater management facilities shall be designed to convey the design flow to or from that structure.
(S) Storm sewers must be able to convey post-development runoff from a ten-year storm event without surcharging inlets, where appropriate.
(T) Adequate erosion protection shall be provided along all open channels, and at all points of discharge.
(U) The design of all stormwater management facilities shall incorporate sound engineering principles and practices and shall not result in the creation or continuation of adverse hydrologic or adverse hydraulic conditions within the watershed.
(1980 Code, Ch. 24, Part 3, § 301) (Ord. 1403, passed 7-18-2011, § 301)