[Ord. No. 872, 11/7/2022]
1.
Any proposed storm drainage plans which affect the drainage basin
of any river or stream shall be approved by the Division of Dams and
Waterway Management of the Pennsylvania Department of Environmental
Protection if the affected drainage area is more than 100 acres.
2.
Easements shall be dedicated to the Borough along all natural or man-made streams and watercourses (as described in § 121, Subsection 8 and/or detention basin areas within a subdivision or land development. These easements should be of sufficient width to convey a 100-year design storm, assuming the upstream drainage basin to be fully developed. Easements shall also be provided where storm drainage swales, culverts or other structures traverse, enter or discharge onto private property. On private property the entire easement area and fencing and landscaping (if any) shall be maintained by the property owner and the Borough shall not maintain and/or repair any improvements within that easement, unless stormwater runoff from public roads or public park land crosses through the easement.
A.
If stormwater runoff from public roads or public lands crosses through
the easement the Borough shall, upon satisfactory installation of
improvements as specified in a developer's improvement agreement
and maintenance agreement, maintain and repair only the structural
stormwater management improvements within the easement such as:
B.
The landowner shall be responsible for all other maintenance and
repairs within this easement. For example, the landowner must:
(1)
Mow the lawn.
(2)
Repair or replace fencing.
(3)
Repair or replace landscaping.
(4)
Repair sinkholes that may develop in the easement.
(5)
Keep the area free of obstructions, structures, vegetation or
accumulated sediment that may block or hinder the function and purpose
of the easement.
(6)
Keep the area free of litter or garbage.
3.
Storm sewers, culverts, and related installations shall be provided
to permit the flow of natural watercourses, to ensure the drainage
of all low points on the subdivided lots or developed land areas and
along the line of streets, and to intercept stormwater runoff along
streets at intervals related to the extent and grade of the area drained.
The system shall also be designed to accommodate or receive and discharge
all runoff from adjacent upstream properties, as if the upstream properties
were developed. Where adequate existing storm sewers are readily accessible,
the developer must connect new stormwater facilities to the existing
system.
4.
Flood Protection. 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, without proper and approved provisions
being made for taking care of these conditions.
5.
When the runoff is increased, due to development, the developer must
secure written approval from the downstream property owners. In lieu
of such written approval, the developer shall follow the other requirements
of this Part, in particular, the sections dealing with detention basins
and downstream facilities, and shall provide the Borough with a notarized
statement satisfactory to the Borough Solicitor, stating that the
Borough shall be held harmless against any claim of damage from the
downstream property owners that may result from the proposed development.
6.
Scour and Erosion Prevention. In areas in which street curbs are
not required by the Borough, drainage may be accomplished by natural
or artificial swales and culverts. Special structures such as check
dams, drop-outlets, or other energy dissipating structures or riprap
may be required to prevent scour or erosion in locations with large
runoff quantities or steep slopes. In no case may a change be made
in the existing topography which would result in a slope exceeding
the normal angle of slippage of the material involved. No paved swales
will be allowed without the approval of the Borough.
7.
Fixed Pipe Collection System. The Borough may require a fixed pipe
collection system with catch basins. Such fixed pipe collection system
with catch basins shall be used in all areas with street curbs and
gutters, when required. The Borough may require foundation pipe underdrains.
8.
Low point drainage.
A.
Developer shall grade and install all necessary drainage facilities
to ensure the drainage of all low points on subdivided lots or within
the subdivision or developed land areas.
B.
Underdrains are required at a minimum for 50 feet upward from a road
low point along each approach road to the low point.
9.
Stormwater Detention Facilities. Where the topography of the tract
being developed or the character of the downstream storm sewer indicate,
as determined by the Borough, stormwater detention facilities shall
be provided within the subdivision proposed. This provision may be
required even if downstream property owners have given written approval.
Such stormwater detention facility shall be designed in accordance
with the following requirements:
A.
The detention facilities shall be designed to meet stormwater runoff
rates after development to the peak runoff rate established for each
district in Subpart 1C, § 127.
B.
Spillways shall be provided for possible overflows, and such spillways
shall be protected from erosion. Spillways shall be designed for the
100-year storm.
C.
Pipe outlet arrangements shall provide complete outletting of all
detained water, unless provisions for permanent ponding have been
approved. Privately owned infiltration practices meeting the DEP standards
for BMPs, approved as part of a site's PCSM Plan shall be considered
to meet this requirement.
D.
A detention basin, unless proposed for infiltration, shall be lined
with an impervious soil or a synthetic impervious liner in those areas
where it is determined by the design engineer that pervious soils
may result in sink holes and other unsatisfactory conditions.
(1)
The minimum liner allowed is 30 mil PVC. Actual individual liner
specifications shall be provided by the manufacturer for each individual
basin and installation shall be completed in accordance with the manufacturer's
specifications.
(2)
The liner must be installed to a minimum height of the 100-year
water elevation in the facility.
E.
The detention facility shall be planted with low maintenance grass
or a substitute satisfactory to the Borough. Detention basins shall
be planted with ground cover in accordance with Borough standards.
F.
To minimize the visual impact of detention basins, any required basin
shall be designed to avoid the need for safety fencing. To meet this
requirement, basins shall be designed to the following specifications:
(1)
Maximum depth of detained runoff shall be 24 inches for a two-year
and ten-year storm event; and
(2)
Maximum depth of detained runoff shall be 36 inches for a 100-year
storm event; and
(3)
Interior slopes shall not be steeper than a ratio of 4:1 horizontal
to vertical;
(4)
A water surface limit shall be no closer than 100 feet to any
residential building and no closer than 25 feet to any other type
building;
(5)
Basin, including exterior slopes, shall be no closer than 20
feet to a property line.
G.
These depths and slopes may be exceeded by permission of the Borough
Council, on a case-by-case basis, if lot runoff, topography, and/or
existing downstream systems make the required pond area unreasonable
large. In such a case, a fence and landscape screens will be required
unless the facility is remote from all existing or proposed residential
areas.
H.
An access ramp of 10:1, 10 feet wide, shall be provided to allow
maintenance equipment to reach the basin floor. The ramp shall coincide
with the required gate if fencing is needed. If the detention basin
is designed to accept storm runoff from public land or public roads,
the ramp shall be paved from the nearest public street to 10 feet
into the base of the detention basin with a driveway consisting of
a six-inch crushed stone base, two inches of 19 mm Superpave binder
course and 1 1/2 inches of 9.5 mm Superpave wearing course constructed
to a width of 10 feet. This paved ramp may be utilized as part or
all of the emergency spillway (if appropriately graded and located).
I.
If provided, fencing must be four-foot-high galvanized chain link
fence vinyl coated (green, brown or black) with a double wide gate
five feet wide each, 10 feet total in width) at such a location as
to provide ready access to the detention basin by maintenance forces
with maintenance equipment or suitable equivalent approved by the
Borough.
J.
Landscaping, subject to the approval of the Borough, shall be provided
adjacent to the detention facility so as to provide a buffer between
the facility and the adjacent development. Detention basins shall
be screened in accordance with Borough standards.
K.
The minimum slope of the bottom of a detention basin shall be 2%
toward the outlet structure, except for privately owned infiltration
practices, meeting the DEP standards for BMPs, approved as part of
a site's PCSM Plan.
10.
All streets shall be designed so as to provide for the discharge
of surface water from their rights-of-way.
11.
Design criteria.
A.
Unless a more conservative design is required by another regulation,
or is required because of conditions particular to an individual development,
the following storm criteria shall be used to design storm collection
and conveyance systems:
|
Area
|
Design Storm Return
|
|---|---|
|
Residential areas
| |
|
Fixed pipe
|
10-year*
|
|
Total conveyance
|
100-year
|
|
Nonresidential areas
| |
|
Fixed pipe
|
25-year
|
|
Total conveyance
|
100-year
|
|
Culvert crossing of any road
| |
|
In culvert
|
25-year
|
|
Total conveyance
|
100-year
|
|
NOTES:
| |
|
*
|
To be sized on based on the maximum allowed impervious coverage
for the subdivided lot(s) to be developed per the Borough Zoning Ordinance
and applicable Zoning District.
|
B.
The preliminary plan or lot location plan shall indicate the areal
extent of the 100-year storm.
12.
Design Preparation. Designs of storm drainage systems and stormwater
management facilities shall be prepared by a licensed professional
engineer. Complete detail calculations shall be submitted to the Borough
for approval. Calculations shall cover the entire drainage basin involved,
including consideration of areas upstream and/or outside the proposed
subdivision or developed land areas. All designs must be approved
by the Borough.
13.
The developer shall provide written assurance, satisfactory to the
Borough, that the storm drainage systems and stormwater management
facilities will be properly maintained. Such assurances shall be in
a form to act as a covenant that will follow with the land, and shall
provide municipal maintenance in case of default, and further provide
for assessment of costs and penalties in case of default in municipal
takeover.
14.
As an alternate to the above § 131, Subsection 13, the Borough may, at their own option, assume responsibility of the storm drainage system and stormwater management facilities and require dedication of the basin by the developer. If the storm drainage system or stormwater management facility is dedicated or offered to the Borough for long term maintenance, the following regulations shall apply:
A.
The dedicated area shall not be considered part of the open space
and recreation dedication requirements as required in the Subdivision
and Land Development Ordinance.
B.
The detention basin top of berm shall be a minimum width of eight
feet, if applicable.
C.
The developer shall provide for the special financial burden the
Borough will be accepting if the Borough accepts the maintenance of
a stormwater management facility. To help mitigate this future financial
burden the developer shall give to the Borough a cash payment in the
amount of $60,000 per acre, on a pro-rata basis based on consumer
price index, for any stormwater management facility site or area dedicated
to the Borough and being accepted by the Borough. This requirement
is minimum and can be modified by a resolution of Borough Council,
as necessary, to reflect actual long-term costs of detention basin
maintenance in the Borough.
[Ord. No. 872, 11/7/2022]
1.
The collection system shall be designed by the Rational Method of
Design in accordance with American Society of Civil Engineers Manual
No. 37 except where noted, using the formula Q = CiA, unless otherwise
approved by the Borough.
A.
Capacity: "Q" is the required capacity in cubic feet per second for
the collection system at the point of design.
B.
Runoff coefficient: "C" is the runoff coefficient applicable to the
entire drainage area. It shall be based on consideration of soil conditions,
average slope of the drainage area and the ultimate development of
the entire drainage area according to comprehensive plans. For the
various types of ultimate development, the runoff coefficient shall
be taken from the table in Appendix C,[1] unless sufficient engineering data has been presented
to the Borough Engineer by the developer which information in the
judgement of the Borough Engineer and Borough Council is sufficient
to warrant the use of an alternate runoff coefficient.
[1]
Editor’s Note: Said appendix is on file in Borough offices.
C.
Rainfall intensity formula: "i" is the rainfall intensity in inches
per hour and shall be determined from rainfall intensity charts for
this area, based on time of concentrations, including overland flow
time, Manning's Formulae for channelized flow time and pipe flow
time. The design rainfall frequency shall be taken from the PennDOT
Intensity-Duration-Frequency Field Manual, Region 4, as presented
in Appendix C.
D.
Drainage area: "A" is the drainage area, in acres, tributary to the
point of design, and shall include areas tributary from outside sources
as well as from within the subdivision or developed land area itself.
2.
Flow Velocity. Storm sewer lines shall be designed to produce a minimum
velocity of 3.0 feet per second when flowing full or have a minimum
pipe slope of 0.5%. The maximum permissible velocity shall be 15.0
feet per second.
3.
Manholes. Manholes shall be spaced at intervals not exceeding 300
feet and shall be located wherever branches are connected or sizes
are changed and wherever there is a change in alignment or grade.
For storm sewer lines of at least 36 inches diameter, manholes may
be spaced at intervals greater than 300 feet with the approval of
the Borough.
4.
Storm Sewer Line Location. Storm sewer lines shall be located between
the center line of the street and the curb line and shall parallel
the centerline of the street as far as practical. Storm sewer lines
shall not be located under curbs or across corners of streets at intersections.
5.
Catch Basin Limits. Not more than two catch basins shall be interconnected
before being connected to a manhole or "access type" catch basin.
6.
Open Swales. Open swales shall be designed on the basis of Manning's
Formula as indicated for collection systems with the following considerations:
A.
Roughness Coefficient. The roughness coefficient shall be 0.040 for
earth swales, and 0.015 for paved swales.
B.
Bank Slopes. Slopes for swale banks shall not be steeper than one
vertical for three horizontal.
C.
Flow Velocity. Design velocity in grass or vegetated swales shall
not exceed four feet per second.
D.
Right-of-way. A swale right-of-way of sufficient minimum width to
include a ten-foot access strip in addition to the width of the swale
from bank top, shall be shown as an easement for drainage purposes.
The Borough may under unusual conditions, require a wider swale right-of-way.
7.
General Design Standards.
A.
Curb Inlets. Curb inlets shall be located at curb tangents on the
uphill side of street intersections. Design and location of curb inlets
shall be approved by the Borough. The collection capacity of curbed
inlets is to be determined using PennDOT standard efficiency charts
for the capture capacity of Type C inlets. All inlets shall be labeled
with an embedded plastic disk indicating a prohibition against pollutants.
B.
State Approvals. Drainage structures that are located in state highway
rights-of-way shall be approved by the Pennsylvania Department of
Transportation and a letter from that office indicating such approval
shall be provided to the Borough.
C.
Pipe Materials. All storm piping shall be new Class III reinforced
concrete piping with O-ring joints or smooth-lined HDPE pipe with
watertight joints. All storm piping shall meet all requirements of
PennDOT. Piping shall be saw cut at the ends, as needed, and not hammered
or broken.
D.
Minimum Pipe Size. Minimum pipe size shall be 15 inches.
E.
Inlet and Manhole Construction. Inlet and manhole castings and concrete
construction shall be equivalent to Pennsylvania Department of Transportation
Design Standards.
F.
Roof Drainage. Stormwater roof drains and pipes shall not discharge
water over a sidewalk, driveway or paved area.
G.
Concentrated stormwater discharges shall be designed to minimize
the impact of development on downstream properties. Flow retarding
and dissipating facilities are required to meet this goal. Such structures
shall be no closer than 50 feet to downstream off-site properties
or drainage easement boundaries.
H.
Open pipe ends must be fitted with concrete endwalls or wingwalls.
I.
No open pipe shall be allowed to end within the existing or proposed
Borough road or state road right- of-way, except in cases where new
driveways must cross existing deep roadside swales adjacent to existing
roads. In the case of these exemptions to the standard, the pipe shall
be located as far off the edge of the pavement as possible (at least
14 feet from the road center line) and shall be at least 12 inches
in diameter.
J.
Any riprap dissipation area or riprap swale area shall be constructed
with mixed stone sizes in accordance with PennDOT criteria for riprap
and all such areas shall be lined with PennDOT approved geotextile
fabric.
K.
A maximum of five cubic feet per second (cfs) will be permitted along
the curb or roadside swale, prior to discharge away from the street
surface by way of roadside swale or underground piping, unless it
is proven to the satisfaction of Borough Council by engineering calculations
that road slopes or other factors would allow a higher capacity.
L.
All pipe endwalls or wingwalls and all detention basin/stormwater
management facility intake and discharge structures shall be protected
from frost related movement and scour activity by the construction
of a concrete footer with a minimum depth of 30 inches below ground
level.
M.
Upstream open culvert headwalls or wingwalls for pipes shall be fitted
with slanted durable protective grates.
