§ 446.01 Stormwater performance standards.
§ 446.02 Manholes.
§ 446.03 Inlets.
§ 446.04 Castings.
§ 446.05 Stormwater roof drains.
§ 446.06 Unnatural drainage.
§ 446.07 Watercourses.
§ 446.08 Bridges and culverts.
§ 446.09 Intersections of private driveways and public streets.
§ 446.10 Testing.
§ 446.01 Stormwater performance standards.
[Amended 12-11-2014 by Ord. No. 556]
A.
Applicants are encouraged to design conveyance systems that encourage
infiltration and improve water quality wherever practicable.
B.
Wherever conveyance channels are necessary, drainage shall be maintained
by an open channel with landscape banks designed to carry the one-hundred-year,
twenty-four-hour stormwater runoff from upstream contributory areas.
If the runoff from stormwater collection and conveyance facilities
would drain over land to a stormwater detention facility, the twenty-five-year
frequency storm event may be used. The Township Engineer with the
approval of the Township may increase the design storm, as conditions
require. All open channels shall be designed with one foot of freeboard
above the design water surface elevation of the design runoff condition.
C.
Flood relief channels shall be provided and designed to convey the
runoff from the one-hundred-year, twenty-four-hour storm, such that
a positive discharge of this runoff is to a natural drainagecourse
with a defined bed and bank.
D.
Manholes and/or inlets shall not be spaced more than 300 feet apart
for pipe sizes up to 24 inches in diameter and not more than 450 feet
apart for larger pipe sizes.
E.
Where drainage swales are used in lieu of or in addition to storm
sewers, they shall be designed to carry the required runoff without
erosion and in a manner not detrimental to the properties they cross.
Drainage swales shall provide a minimum grade of 1% but shall not
exceed a grade of 9%. Drainage swales used strictly for conveyance
are not the same as open vegetated channels.
F.
Street curbing for the purpose of stormwater conveyance is discouraged.
On streets that must contain curbing, storm sewers shall be placed
in front of the curbing. To the greatest extent possible, storm sewers
shall not be placed directly under curbing. At curbed street intersections,
storm inlets shall be placed in the tangent section of the road.
G.
Use of grassed swales or open vegetated swales in lieu of curbing
to convey, infiltrate and/or treat stormwater runoff from roadways
is encouraged. Inlets shall be placed at the center of the shoulder
swale draining the street and shall be located no closer than four
feet from the edge of the cartway.
H.
When requested by the Township the developers shall obtain or grant
a minimum twenty-foot-wide drainage easement over all storm sewers,
drainage swales, channels, etc., that are a component of the stormwater
management system when located within undedicated land. All permanent
detention basins and/or other stormwater management facilities providing
stormwater control for other than a single residential lot shall be
located within a defined drainage easement that allows proper legal
access and maintenance vehicle access.
I.
No property owner shall obstruct or alter the flow, location or carrying
capacity of a stream, channel or drainage swale to the detriment of
any other property owner, whether upstream or downstream. All subdivision
and/or land development plans containing streams, channels, drainage
swales, storm sewers or other conveyance systems that cross property
boundaries, existing or proposed, or whose discharge crosses such
boundaries shall contain a note stating the above.
J.
Water quality inlets. Storm drainage systems that collect runoff
from parking areas and/or loading areas exceeding 5,000 square feet
of impervious coverage and discharge to stormwater management systems,
including surface, or subsurface infiltration systems, shall have
a minimum of one water quality inlet per each acre of drainage area.
The purpose of water quality inlets is to remove oil, grease, and
heavy particulates or total suspended solids, hydrocarbons and other
floating substances from stormwater runoff; methods other than water
quality inlets may be permitted if the applicant demonstrates to the
Township's satisfaction that any such alternative will be as
effective and as easily maintained. Periodic cleaning of these systems
shall be addressed in the operation and maintenance plan submitted
to the Township.
K.
Suitable drainage structures, culverts, storm sewers, swales and
related installations shall be provided along roads to ensure removal
of stormwater from all gutters, at all low points and at intervals
elsewhere not exceeding 600 feet, such that the width of stormwater
flow in any gutter does not exceed 1/4 of the total cartway width.
L.
No stormwater pipe (public or private) shall be less than 15 inches
in diameter that conveys surface runoff. All stormwater pipes shall
be concrete unless otherwise approved by the Township. The minimum
pipe slope shall be such that a minimum of two ft/sec velocity is
maintained. Where a culvert or pipe is used to replace a stream, the
cross-sectional area shall be at least as large as the original stream
channel. All stormwater BMPs shall be constructed in accordance with
the Township's "standard details." Minimum pipe cover shall conform
to the manufacturer's recommendations. Stormwater conveyance
pipes utilized in BMPs shall have a pipe size of four-inch diameter
or larger.
M.
Where open watercourses for stormwater drainage are used the following
standards shall apply:
1.
Artificial channels shall be of trapezoidal cross section, with the
channel width at the bottom at least 10 times the maximum water depth
which would be produced by the one-hundred-year design storm and with
rough, permeable and flexible sides and bottom. No artificial channel
shall be used to replace a natural stream.
2.
At all points in the drainage system the velocity shall be less than
the erosion threshold of the conveyance material, including at the
outlet from the construction area or subdivision site.
N.
All stormwater collection and conveyance facilities (pipes, swales,
and structures) shall be designed for a one-hundred-year design storm
event, unless the runoff would naturally drain overland to a stormwater
detention facility, in which case a twenty-five-year design storm
event may be used. All drainage facilities shall be designed to contain
the energy grade line for the peak flow rate for the design storm
within the structures a minimum of two feet below surface elevation.
The hydraulic grade line must be within the pipe. Swales and channels
shall provide at least one foot of freeboard above the energy grade
line. Backwater effects of pipes discharging under surcharge conditions
shall be included in the calculations.
O.
All workmanship and materials shall conform to the Township's
construction standards. In addition, all workmanship and materials
shall conform to the latest edition of PennDOT Form 408 and be supplied
by manufacturers of suppliers listed in PennDOT's Bulletin 15.
P.
All connections to existing storm sewer pipes shall be made by construction
of a suitable junction box (inlet or manhole) to provide access for
cleanout. No blind connections shall be permitted.
Q.
All pipe outlets shall discharge onto a stone riprap blanket to prevent
erosion of soil. Riprap shall be sized considering pipe exit velocities.
R.
The discharge of stormwater runoff shall be to a well-defined drainagecourse,
which has a defined bed and bank. If stormwater runoff cannot be discharged
to a defined drainagecourse, documentation of written permission from
each downstream property owner shall be provided for all properties
between the source of discharge and the defined drainagecourse.
S.
Inlets of each type shown in the Township construction standards
shall be installed. Inlets at street intersections shall be placed
on the tangent and not on the curved portion of the intersection radii.
T.
Manhole and inlet castings shall conform to the Pennsylvania Department
of Transportation Form 408 and PennDOT Standards for Roadway Construction.
Inlet grates shall be bicycle safe. Frames and grates shall be cast
iron or structural steel. Concrete frames shall not be permitted.
U.
All roof drains shall discharge to an on-lot sump, or to a storm
sewer system which is controlled by a detention pond. Outlets from
roof drain sumps shall not discharge directly to fill slopes. Outlets
shall not discharge directly to the gutter line of any street. All
pipes from roof drains shall be a minimum four-inch Schedule 40 ABS,
PVC or SDR 26 pipe. Four-inch Schedule 40 PVC or ABS pipe is required
for a distance of 10 feet from the foundation of the dwelling. No
stormwater drainage system shall be permitted to be constructed through
any curbing on any public street. Minimum pipe size for sump stormwater
piping is four inches.
V.
All bridges and culverts shall be designed to support expected loads
and to carry expected flows and shall be designed to meet current
standards of the Pennsylvania Department of Transportation. All bridges
and culverts shall be subject to all permits required by the Pennsylvania
Department of Environmental Protection, Bureau of Dams and Waterways.
W.
Disposal of stormwater from roof and driveway drains:
1.
Unless otherwise approved by the Township, no stormwater from roofs
or driveway drains shall be discharged to the street surface or curb
underdrain.
2.
Acceptable methods of disposal include properly designed dry sumps,
grassed or other round surfaces with adequate consideration being
given to erosion protection, storm sewers, or any other method approved
by the Township.
§ 446.02 Manholes.
For pipe sizes of 24 inches or less, manholes shall be spaced
at a maximum of 400 feet and for larger pipe sizes, the maximum distances
between manholes shall be 600 feet. In addition, manholes shall be
installed at all points of changes in horizontal alignment and vertical
grade. Inlets may be substituted for manholes where practical.
§ 446.03 Inlets.
Inlets of the type shown in the Township Construction Standards
shall be installed. Inlets at street intersections shall be placed
on the tangent and not on the curved portions.
§ 446.04 Castings.
Manholes and inlet castings shall conform to the Pennsylvania
Department of Transportation (PennDOT) Form 408 and PennDOT Standards
for Roadway Construction. Inlet grates shall be bicycle safe. Frames
and grates shall be cast iron or structural steel. Concrete frames
shall not be permitted.
§ 446.05 Stormwater roof drains.
All roof drains shall discharge to an on-lot sump or to a storm
sewer system which is controlled by a detention pond. Outlets from
roof drain sumps shall not discharge directly onto fill slopes. Outlets
shall not discharge directly to the gutter line of any street.
All pipes from roof drains shall be a minimum four-inch Schedule
40 ABS, PVC or SDR 35 pipe. Four-inch Schedule 40 PVC or ABS pipe
is required for a distance of 10 feet from the foundation of the dwelling.
No stormwater drainage system shall be permitted to discharge into
any sanitary sewer system. No pipes shall be permitted to be constructed
through any curbing on any public street.
§ 446.06 Unnatural drainage.
All points of concentrated flow discharge shall outlet directly
to a well-defined drainage channel, with a defined bed and bank. Whenever
construction stops or concentrates the natural flow of storm drainage
in such a way as to affect adjoining properties, approval of the owners
shall be obtained in writing. Approval of plans by the Township shall
not authorize or sanction drainage affecting adjoining properties.
§ 446.07 Watercourses.
Open watercourses shall not be permitted within the rights-of-way
of streets. The stopping, filling up, confining or other interference
with, or changing the course of, drains, ditches, streams and watercourses
in the Township shall not be permitted unless approval in writing
is obtained from the Board of Commissioners. A permit must be obtained
from the Department of Environmental Protection (DEP) of the Commonwealth
of Pennsylvania for construction or changes in a watercourse subject
to the regulations of the Pennsylvania Department of Environmental
Protection.
§ 446.08 Bridges and culverts.
All bridges and culverts shall be designed to support expected
loads and to carry expected flows and shall be designed to meet current
standards of the Pennsylvania Department of Transportation. All bridges
and culverts shall be subject to all permits required by the Pennsylvania
Department of Environmental Protection, Bureau of Dams and Waterways.
§ 446.09 Intersections of private driveways and public streets.
[Ord. No. 509,
passed 9-12-2007; amended 12-11-2014 by Ord. No.
556]
Stormwater drainage facilities shall be placed where each private
driveway intersects with a public street. The design shall be approved
by the Township and shall meet the following requirements:
A.
The facility shall be placed to maintain the flow line of the stormwater
drainage facility in the public street.
B.
Where an apron gutter is to be utilized, said apron gutter shall
be designed and constructed in accordance with the Township construction
standards.
C.
Where reinforced concrete, metal or tile pipe is to be used beneath
the driveway, said pipe shall not be less than 15 inches in diameter
and shall extend across the full width of the driveway and beyond
the driveway for a distance determined by the Township. The pipe shall
be installed with flared end sections and shall be designed to support
H-15 loading and any other imposed loadings necessary without structurally
damaging the system. The installation of the pipe shall be in accordance
with the Township construction standards.
§ 446.10 Testing.
[Amended 12-11-2014 by Ord. No. 556]
All construction materials used in storm sewers shall be tested
by a qualified testing laboratory, if required by the Township. The
cost for such tests shall be borne by the developer.