All activities regulated herein shall be designed and maintained in accordance with the following requirements:
A. 
Sites. All sites shall limit the rate of stormwater runoff so that no greater rate of runoff from the site is permitted than that occurring prior to development. Predevelopment stormwater runoff shall be computed for storm frequencies of 10 years.
B. 
Conveyance system. All stormwater conveyance elements shall be designed to adequately handle the stormwater flows from the peak rate of discharge from a ten-year post-development storm event.
C. 
Detention facilities. Storage calculations for surface detention facilities shall be designed based on the difference between the 100-year predevelopment and the 100-year post-development storms. The primary outlet from the basin shall be no greater than to allow for a ten-year predevelopment release rate. An emergency spillway shall be provided for the 100-year post-development storm.
D. 
Existing drainageways. Natural drainageways shall be utilized to the maximum extent possible in carrying stormwater runoff, provided that such uses remain consistent with the purpose of this chapter and are not in violation of any existing local, county, state or federal regulations. Where the tract is traversed by a watercourse, drainageway, channel or stream, there shall be provided a drainage easement conforming substantially to the line of such watercourse, drainageway, channel or stream, and of such width as will be adequate to preserve the unimpeded flow of natural drainage or for the purpose of widening, deepening, improving or protecting such drainage facilities. An existing watercourse, drainageway, channel or stream location shall be changed only when approved by the Pennsylvania Department of Environmental Protection, Fish Commission, the United States Army Corps of Engineers and the Northumberland County Soil Conservation Service, whichever and to the extent their respective regulatory jurisdiction applies.
A. 
General. The minimum stormwater control requirements shall require that all facilities provide management measures pursuant to § 143-15 above. The pre- and post-development peak discharge rate shall be computed based on existing and proposed land uses, provided that all land uses in the site after development are in good hydrologic condition. Where existing land uses are agricultural, all predevelopment rates shall be computed based on the land being in good condition. Supporting drainage area and imperviousness area maps and detailed calculations shall be submitted.
B. 
Supplemental standards. The following technical reference materials are hereby incorporated into this chapter for information and to govern the design and hydrologic control provisions of this chapter. The most current edition or subsequent revision to these publications shall prevail.
(1) 
Soil Erosion and Sedimentation Control Manual, Pennsylvania Department of Environmental Protection, dated May of 1990.
(2) 
Soil Survey of Northumberland County, Pennsylvania, USDA NRCS, dated May 1963.
(3) 
Commonwealth of Pennsylvania, Department of Transportation Design Manual Part 2, Chapter 12.
(4) 
Urban Hydrology for Small Watersheds, Technical Release No. 55 (TR-55). USDA NRCS, dated June 1986.
(5) 
Flood Hazard Boundary Map for the City of Sunbury, United States Department of Housing and Urban Development, Federal Insurance Administration, National Flood Insurance Program, Flood Boundary Map.
(6) 
Engineering Field Manual, USDA NRCS Code 378, dated May 1977.
(7) 
Title 25 of the Department of Environmental Protection Part 1, Article II, Chapter 105, titled "Dam Safety and Waterway Management."[1]
[1]
Editor's Note: See 25 Pa. Code Ch. 105.
(8) 
Pennsylvania Department of Environmental Protection and the United States Army Corps of Engineers, Pennsylvania Act 14, P.L. 834.
(9) 
Chapter 73, Pennsylvania Sewage Facilities Act, Article 73.15, titled "Percolation Tests."
(10) 
Standard Specifications for Ponds, Service Manual, USDA NRCS Code 378, dated May 1977.
A. 
Conveyance systems. The Rational Equation, as outlined in the Pennsylvania Department of Transportation Design Manual No. 2, shall be used for areas of 320 acres or less. Areas in excess of 320 acres shall be either the USDA NRCS TR-20 Method or an alternate method as approved by the engineer.
B. 
Stormwater management storage facilities. The TR-55 of the USDA NRCS shall be used in the sizing of all stormwater storage facilities. Alternate methods may be used with the approval of the engineer.
C. 
Stormwater conduits.
(1) 
Stormwater conduits of whatever material utilized shall be installed with a minimum of 15 inches of coverage below design finish grade elevations. Pipe strength shall conform to the minimum standards determined under Pennsylvania Department of Transportation Design Manual No. 2, Chapter 12.
(2) 
Conduits shall be sized to accommodate the entire drainage basin discharge for the respective storm event enumerated under Paragraph C-16, titled "Conveyance Conduit Storm Events."
D. 
Channel velocities. Channel velocities, wherever applicable, shall not exceed the permissible velocities specified under the Department of Environmental Protection Soil and Erosion Control Manual, dated February 15, 1988, Appendix 67.
E. 
Emergency spillway outlets. Emergency spillways and outlets shall be designed for a post-development 100-year peak discharge. A minimum of one foot of freeboard shall be provided around the entire top of the pond embankment. This freeboard shall be provided above the effective spillway design depth. The spillway top of the embankment shall also be provided with a five-foot-wide and level pathway on top.
F. 
Energy dissipation. Energy dissipation shall be provided at the outfall of detention or retention ponds, along outfall channels and at the discharge end of all conveyance conduits. Design shall provide a nonerosion velocity of flow from the structure to a watercourse.
G. 
Easements or rights-of-way. Where a stormwater management plan involves the direction of some or all stormwater off the site, it shall be the responsibility of the developer to obtain from adjacent property owners any easements or other necessary property interests concerning the flowage of water. Approval of a stormwater management plan does not create or affect any such rights.
H. 
Off-site structures. Off-site structures shall not have a contributory drainage area in excess of 400 acres unless, on a case-by-case basis, a larger drainage area is approved by the Department of Environmental Protection, USDA NRCS and the United States Army Corps of Engineers as their respective interests control such facilities.
I. 
Trash rack. Trash racks for vertical pipe inlets and other water receiver structures shall be installed in the design, unless otherwise approved by the City Engineer.
J. 
Construction details. Construction details shall conform to the latest standard of the Pennsylvania Department of Transportation Form 408 Specifications and Roadway Construction Series of Roadway Construction Standards. Infiltration structures and other construction structures, including fencing, shall conform to the applicable standards of the City.
K. 
Conveyance conduit storm events. Conveyance conduits shall be sized utilizing the following storm events:
(1) 
Minor roadway: 10 years.
(2) 
Collector roadway: 10 years.
(3) 
Watercourse crossing minor road: 100 years.
(4) 
Watercourse crossing collection road: 100 years.
L. 
Infiltration rates. Infiltration rates applicable to the design of underground stormwater management facilities shall be computed in accordance with the Pennsylvania Sewage Facilities Act, Article 73.15, titled "Percolation Tests."
Permits and approvals issued pursuant to this chapter do not relieve the applicant of the responsibility to secure required permits or approvals for activities regulated by any other applicable codes, rules, act or ordinances. If more stringent requirements concerning regulation of stormwater or erosion and sedimentation control are contained in other codes, rules, acts or ordinances, the more stringent regulation shall apply.