All regulated earth disturbance activities within the municipality
shall be designed, implemented, operated and maintained to meet the
purposes of this chapter, through these two elements: 1) erosion and
sediment control during the disturbance activities (e.g., during construction);
and 2) water quality protection measures after completion of earth
disturbance activities (e.g., after construction), including operations
and maintenance.
A.
No earth disturbance activities within the municipality shall commence
until the requirements of this chapter are met.
B.
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.
(3)
For projects that add impervious area to a parcel, the total impervious
area on the parcel is subject to the requirements of this chapter.
C.
Stormwater flows onto adjacent property shall not be created, increased,
decreased, relocated, or otherwise altered without written notification
of the adjacent property owner(s). Such stormwater flows shall be
subject to the requirements of this chapter.
D.
SWM site plans approved by the municipality, in accordance with § 240-11, shall be on site throughout the duration of the regulated activity.
E.
Erosion and sediment control during regulated earth disturbance activities shall be addressed as required by § 240-17.
G.
All best management practices (BMPs) used to meet the requirements
of this chapter shall conform to the state water quality requirements
and more stringent requirements as determined by the municipality.
H.
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.
I.
Storage facilities should completely drain both the volume control
and rate control capacities over a period of time not less than 24
hours nor more than 72 hours from the end of the design storm.
J.
The design storm volumes to be used in the analysis of peak rates
of discharge should be 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, Silver
Spring, Maryland. NOAA's Atlas 145 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
L.
Additional requirements.
(1)
In conjunction with meeting the requirements of this chapter, the
applicant shall refer to and meet all conditions and requirements
set forth in the Borough of West View's Municipal Separate Storm
Sewer System (MS4) Prohibited Discharge Ordinance.
(2)
In conjunction with meeting the requirements of the chapter, the
applicant shall refer to and meet all conditions and requirements
set forth in the Borough of West View's total maximum daily load
(TMDL) plan as adopted and revised.
M.
Exemptions.
(1)
Regulated activities that disturb areas less than 2,500 square feet
are exempt from the peak rate control and the SWM site plan preparation
requirement of this chapter.
(2)
Agricultural activity is exempt from the rate control and SWM site plan preparation requirements of this chapter provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
(3)
Forest management and timber operations are exempt from the rate control and SWM site plan preparation requirements of this chapter provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
(4)
All Borough development activities, Borough road work, Borough utility
activities, and Public Works activities are exempt from this chapter
in its entirety.
(5)
For a parcel or tract of land held under single ownership, only one
application for a small development, as defined above, shall be permitted
before requiring a stormwater management plan for the entire parcel.
A project cannot be phased to circumvent the stormwater requirements
by using the exemption for small developments.
N.
Small developments.
(1)
At the time of application, the Borough Zoning Officer shall determine
if the development qualifies as a "small development" and, therefore,
is eligible for a simplified stormwater plan submission. For the purposes
of this chapter, a small development is:
(a)
Any development which results (or will result when fully constructed)
in the creation of 5,000 or less square feet of impervious surface
area, including roofs, patios, driveways, and sidewalks.
(b)
The Borough Engineer shall review the proposed provisions for
stormwater management for small developments. The Borough shall determine
if the proposed development site is part of a larger parcel or tract
for which a stormwater management plan was approved previously and,
therefore, subject to any specific stormwater management controls
contained in the prior plan.
(c)
For a parcel or tract of land held under single ownership, only
one application for a small development, as defined above, shall be
permitted before requiring a stormwater management plan for the entire
parcel. A project cannot be phased to circumvent the stormwater requirements
by using the exemption for small developments. When calculating new
impervious area for determining whether a development qualifies as
a "small development," the cumulative total of all impervious areas
constructed within five years of the application date shall be considered.
(2)
The Small Project Stormwater Management Plan Application included
in Appendix 5[2] may be used for projects under 5,000 square feet of proposed
impervious surface. The Small Project Stormwater Management Plan Application
allows documentation of new impervious surface, credits through disconnection
of impervious surfaces and tree planting, and sizing of volume control
BMPs and rate control facilities that may be required.
[2]
Editor's Note: Appendix 5 is included as an attachment
to this chapter.
(3)
Should the applicant choose not to use the Small Project Stormwater
Management Plan Application (Appendix 5),[3] a plan addressing peak rate and volume controls must be
submitted and shall include a plan which describes narratively and
graphically the type and location of proposed on-site stormwater management
techniques or the proposed connection to an existing storm sewer system.
The plan should show accurately site boundaries, five-foot interval
contours, location of watershed and/or subarea boundaries on the site
(if applicable), and any watercourses, floodplains or existing drainage
facilities or structures located on the site. Where the applicant
is proposing to connect to an existing storm sewer, the applicant
shall submit documentation showing that sufficient capacity exists
in the storm sewer from the point of connection to the point of outlet
in the natural drainage system. The plan and supporting documentation
must be prepared by a registered professional engineer.
[3]
Editor's Note: Appendix 5 is included as an attachment
to this chapter.
O.
Volume controls.
(1)
The low-impact development practices provided in the BMP Manual shall be utilized for all earth disturbance activities to the maximum extent practicable. Water volume controls shall be implemented using the Design Storm Method in Subsection O(1)(a) or the Simplified Method in Subsection O(1)(b) below. For regulated activity areas equal or less than one acre that do not require hydrologic routing to design the stormwater facilities, this chapter establishes no preference for either methodology; the applicant may select either methodology on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology, and other factors.
(a)
The Design Storm Method (CG-1 in the BMP Manual[4]) is applicable to any size of regulated activity. This
method requires detailed modeling based on site conditions.
[1]
Do not increase the postdevelopment total runoff volume for
all storms equal to or less than the two-year, twenty-four-hour duration
precipitation.
(b)
The Simplified Method (CG-2 in the BMP Manual[5]) provided below is independent of site conditions and
should be used if the Design Storm Method is not followed. This method
is not applicable to regulated activities greater than one acre or
for projects that require design of stormwater storage facilities.
For new impervious surfaces:
[1]
Stormwater facilities shall capture at least the first two inches
of runoff from all new impervious surfaces.
[2]
At least the first one inch of runoff from new impervious surfaces
shall be permanently removed from the runoff flow — i.e., it
shall not be released into the surface waters of this commonwealth.
Removal options include reuse, evaporation, transpiration, and infiltration.
[3]
Wherever possible, infiltration facilities should be designed
to accommodate infiltration of the entire permanently removed runoff;
however, in all cases at least the first 0.5 inch of the permanently
removed runoff should be infiltrated.
P.
Rate controls.
(1)
Postdevelopment discharge rates shall not exceed the predevelopment
discharge rates for the one-, two-, five-, ten-, twenty-five-, fifty-,
and one-hundred-year storms. If it is shown that the peak rates of
discharge indicated by the postdevelopment analysis are less than
or equal to the peak rates of discharge indicated by the predevelopment
analysis for one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year,
twenty-four-hour storms, then the requirements of this section have
been met. Otherwise, the applicant shall provide additional controls
as necessary to satisfy the peak rate of discharge requirement.
Q.
Design storms.
(1)
The SCS Type II Rainfall Distribution shall be used for all analyses.
The rainfall depth to be utilized for design storm frequencies shall
be as follows:
Design Storm
(year)
|
Rainfall Depth, 24 Hours
(inches)
|
---|---|
1
|
1.97
|
2
|
2.35
|
5
|
2.88
|
10
|
3.30
|
25
|
3.90
|
50
|
4.40
|
100
|
4.92
|
(2)
Individual site standalone detention facilities shall be constructed
for all single-family lot developments or single-family lots located
in land developments which for terrain reasons cannot utilize the
development's detention systems. Individual site standalone detention
facilities shall consist of gravel filled sumps, ponds, tanks or other
approved facilities, sized in accordance with standard details in
the Borough Construction Standards.
(3)
Storage volumes for total impervious areas greater than 5,000 square
feet shall be calculated using the methods outlined in this section.
(4)
All stormwater detention facilities shall be located at least 10
feet from foundation walls in a location approved by the Borough.
All pipe from roof drains to a point 10 feet from the structure shall
be a minimum Schedule 40 PVC pipe or approved equal.
(5)
Predevelopment conditions. The cover type for all sites will be considered
to be the hydrologic conditions at the time of the development application.
Twenty percent of all existing impervious surface shall be considered
meadow in good condition. All hydrologic parameters used to calculate
peak flow rates shall use the appropriate specifications pertaining
to these conditions.
R.
Method of computation.
(1)
All computations used in conjunction with the analysis and design
of stormwater management facilities shall be based on one or more
of the following methods:
(2)
These methods of runoff computation developed and used by the Soil
Conservation Service and other authorities are hereby adopted by the
Borough.
(3)
The use of the Basic Rational Method in estimating runoff may be
employed in the design of the storm sewer system within the development.
The storm sewer system shall be interpreted as the conduits, culverts,
inlets and appurtenant features for the conveying of stormwater to,
through or from a development site to the point of final discharge
or control facility. The Rational Method shall not be used in the
analysis of stormwater runoff from the development in its entirety
or in conjunction with the design of any retention/detention facilities
or other runoff control measures.
S.
Stormwater detention facilities.
(1)
All detention facilities shall be equipped with multistage outlet
structures to provide discharge control for the one-, two-, five-,
ten-, twenty-five-, fifty-, and one-hundred-year storm frequencies.
Provisions shall also be made for safely passing the postdevelopment
one-hundred-year storm runoff flows without damaging (i.e., impairing
the continued function of) the facilities.
(2)
Shared-storage facilities, which provide detention of runoff for
more than one development site, may be considered within a single
subarea. Such facilities shall meet the design criteria contained
in this section. In addition, runoff from the development sites involved
shall be conveyed to the facility in a manner so as to avoid adverse
impacts, such as flooding or erosion, to channels and properties located
between the development site and the shared-storage facility.
(3)
Other considerations which should be incorporated into the design
of the detention facilities include:
(a)
Inflow and outflow structures shall be designed and constructed
to prevent erosion. Bottoms of impoundment-type structures shall be
protected from soil erosion.
(b)
Control and removal of debris, both in the storage structure
and in all inlet or outlet devices, shall be a design consideration.
(c)
Inflow and outflow structures, pumping stations and other structures
shall be protected and designed to minimize safety hazards.
(d)
Provide fencing at least six feet in height around the entire
perimeter of all ponds/basins.
(e)
Side slopes of storage ponds shall not exceed a ratio of three
to one (3:1) horizontal to vertical dimension.
(f)
Landscaping shall be provided for the facility which harmonizes
with the surrounding area.
(g)
All stormwater detention facilities shall be screened from view
of existing roads or streets located within the Borough, which is
a minimum of six feet in height with sufficient access for maintenance
vehicles. The screening material must be approved by the Borough.
Landscaping of the pond embankment shall not be permitted at any time.
(h)
The facility shall be located to facilitate maintenance, considering
the frequency and type of equipment that will be required. The facility
shall be equipped with an access road at least 10 feet wide and with
a maximum of grade of 15%.
(i)
All pond outlet structures shall have suitable antiseep collars,
gaskets, barriers and/or seals to prevent leakage and piping of water
through the pond embankment. All storm pipe installed through a pond
embankment shall be constructed of reinforced concrete pipe.
(j)
Provide a minimum of one foot of freeboard above the one-hundred-year
design storm event as it passes through the emergency spillway.
(k)
A geotechnical investigation report for the construction of
the stormwater detention/retention and infiltration facilities must
be provided including design recommendations for embankment construction,
interior and exterior slopes, drainage swales and infiltration areas.
T.
Single-family lots.
(1)
Retention/detention facilities shall be constructed for all existing
single-family lot developments or single-family lots located in land
developments which for terrain reasons cannot utilize the development's
retention/detention systems. Retention facilities shall consist of
gravel filled sumps, ponds, tanks or other approved facilities, sized
in accordance with standards of this chapter.
(2)
Storage volumes for roof areas greater than 5,000 square feet shall
be calculated using the methods outlined in.
U.
Easements. Easements for stormwater management facilities shall be
required to have a minimum width of 20 feet. Where a subdivision or
land development is, or will be, traversed by a watercourse, there
shall be provided a stormwater or drainage easement of a width sufficient
for the purpose, but not less than 20 feet. The stormwater detention
facilities must be provided within a drainage easement. An access
easement must be provided from the public right-of-way to the stormwater
detention facility with a minimum width of 20 feet.
(1)
Stormwater management easements are required for all areas used for
off-site stormwater control, unless a waiver is granted by the Borough.
(2)
Stormwater management easements shall be provided by the property owner if necessary for: 1) access for inspections and maintenance; or 2) preservation of stormwater runoff conveyance, infiltration, and detention areas and other BMPs, by persons other than the property owner. The purpose of the easement shall be specified in any agreement under § 240-24.
(3)
Facilities, areas, or structures used as stormwater management BMPs
shall be enumerated as permanent real estate appurtenances and recorded
as deed restrictions or conservation easements that run with the land.
(4)
Operation and management plans for stormwater management approved
pursuant to 25 Pa. Code § 102 after the date of this chapter
shall be recorded as a restrictive deed covenant that runs with the
land.
(5)
If a conservation easement is provided, the long-term ownership,
access, maintenance, and use restrictions must be identified on the
recording plan.
V.
Flood-prone areas.
(1)
Land identified as flood-prone on maps issued by the Federal Insurance
Administration shall be subject to the regulations of the National
Flood Insurance Program and shall comply with the provisions of the
Borough Floodplain Ordinance.[6]
(2)
The one-hundred-year floodplain shall be delineated by one of the
following methods:
(a)
The Flood Insurance Study (FIS) by the Federal Emergency Management
Agency (FEMA).
(b)
A hydrologic report prepared by an individual registered in
the Commonwealth of Pennsylvania to perform such duties. Calculations
and channel hydraulic characteristics used to determine floodplain
limits shall be provided.
(3)
Municipal liability disclaimer. Approval of a stormwater management
plan by the Borough shall not be construed as an indication that said
plan complies with the requirements, laws, or standards of any agency
of the commonwealth, which may or may not govern said activity.
The following permit requirements may apply to certain regulated
earth disturbance activities, and must be met prior to commencement
of regulated earth disturbance activities, as applicable:
A.
All regulated earth disturbance activities DEP subject to permit requirements by regulations under 25 Pa. Code Chapter 102;
C.
Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by DEP under 25 Pa. Code Chapter 105.
D.
Any stormwater management facility that would be located on a state
highway right-of-way, or require access from a state highway, shall
be subject to approval by the Pennsylvania Department of Transportation
(PennDOT); and
Stormwater management facilities shall be constructed in accordance
with the following minimum specifications:
A.
All workmanship and materials shall conform to the Borough Construction Standards as provided in the Borough of West View Code, Chapter 240. In addition, all workmanship and materials shall conform to the latest edition of PennDOT Form 408.
B.
All connections to existing storm sewer pipes shall be made by construction
of a suitable junction box (inlet or manhole) to provide access for
clean-out. No blind connections shall be permitted.
C.
All pond outlet structure pipes shall have suitable gaskets to prevent
leakage and piping of water through the pond embankment.
D.
All pipe outlets shall discharge onto a stone rip-rap blanket to
prevent erosion of soil. Rip-rap will be sized considering pipe exit
velocities.
E.
Controls shall be installed at initial stages of earthmoving and
otherwise as outlined in the staging of earthmoving activities section
of the erosion and sedimentation control plan.
F.
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.
Maintenance is an essential part of the successful functioning
of a stormwater management system and the following shall be required:
A.
Maintenance during development. Maintenance during development of
a project shall be the responsibility of the developer and/or landowner
and shall usually include, but shall not be limited to:
(1)
Removal of silt from all debris basins, traps or other structures
or measures when 40% of capacity is filled with silt.
(2)
Disposal of collected silt in a manner which will not adversely affect
the environment.
(3)
Periodic maintenance of temporary control facilities such as replacement
of straw bale dikes, straw filters or similar measures.
(4)
Establishment or re-establishment of vegetation by seeding and mulching
or sodding of scoured areas where vegetation has not been successfully
established. A developer or landowner retains this obligation as to
property he or she has developed or improved even if the proper season
for "seeding" occurs initially sometime after the project is otherwise
completed in whole or as to a particular phase.
(5)
Installation of necessary controls sufficient to protect against
problems caused by storm events within design frequencies.
(6)
Removal of all temporary measures upon completion of the project.
B.
After acceptance of the plan by the Borough. In the event that the
Borough accepts public improvements in the plan, except in cases where
an agreement between the developer and the Borough has been executed
to the contrary, the maintenance shall be the responsibility of the
Borough and shall include, where necessary:
(1)
Mowing to maintain adequate stands of grass and to control weeds.
Chemical weed control may be used if state and Borough regulations
are met. Selection of seed mixtures shall reflect the type of maintenance
desired by the Borough.
(2)
Removal of silt from all permanent structures which trap silt or
sediment to keep this material from building up in grassed waterways
and other permanent structures, thereby reducing their capacity.
(3)
Removal of trees and shrubs from pond embankments.
(4)
Repair of animal burrows and removal of animals causing same.
C.
If the Borough does not accept the facilities, it shall be the responsibility
of the developer to inspect all permanent facilities to see that corrective
action is taken where necessary.
(1)
Stormwater facilities located on private property shall be maintained
by the owner or his agent; however, this does not relieve the owner
or his agent of the obligation to inspect his own facilities. The
Borough reserves the right to enter upon private property to make
periodic reasonable inspections and to require the owner to take necessary
corrective actions. An easement shall be recorded granting access
over private property to the stormwater facilities.
(2)
The owner shall convey to the Borough easements and/or rights-of-way
to assure access for periodic inspections by the Borough and maintenance
if required.
(3)
The owner shall keep on file with the Borough the name, address and
telephone number of the person or company responsible for maintenance
activities; in the event of a change, new information will be submitted
to the Borough within 10 days of the change.
(4)
The owner shall establish any special maintenance funds or other
financing sources, in accordance with the approved maintenance plan.
D.
The owner shall pay the amount due to the Special Stormwater Facility
Maintenance Fund.
(1)
Persons installing stormwater storage facilities will be required
to pay a specified amount to the West View Borough Stormwater Facility
Maintenance Fund to help defray the costs of periodic inspections
and annual maintenance expenses. The amount of the deposit shall be
determined as follows:
(a)
If the storage facility is to be privately owned and maintained,
the deposit shall cover the cost of periodic inspections performed
by the Borough for a period of 10 years, as estimated by the Borough.
After that period of time, inspections will be performed by the Borough
and billed directly to the owner.
(b)
If the storage facility is to be owned and maintained by the
Borough, the deposit shall cover the estimated annual costs for maintenance
and inspections for 10 years, as estimated by the Borough.
(c)
The amount of the deposit to the maintenance fund covering annual
inspection and maintenance costs shall be converted to present worth
of the annual series values. The Borough Manager shall determine the
present-worth equivalents, which shall be subject to the final approval
of the Borough Supervisors.
(2)
If the storage facility is proposed, which also serves as a recreation
facility, such as a lake or ball field, the Borough may reduce or
waive the amount of the maintenance fund based on the value of the
land for public recreation purposes.
(3)
If at some future time any storage facility (whether publicly or
privately owned) is eliminated due to the installation of storm sewers
or another storage facility (i.e., a distributed storage facility),
the unused portion of the maintenance fund will be applied to the
cost of abandoning the facility and connecting to the storm sewer
system or other facility. Any amount of the deposit remaining after
the costs of abandonment are paid will be returned to the owner.
E.
If the owner fails to maintain the stormwater control facilities,
following due notice by the Borough to correct the problems, the Borough
shall perform the necessary maintenance or corrective work. The owner
shall reimburse the Borough for all costs.
F.
Additional items may be included in the maintenance agreement where
determined necessary to guarantee the satisfactory maintenance of
all facilities. The maintenance agreement shall be subject to the
review and approval of the Borough's Solicitor.
A.
No regulated earth disturbance activities within the municipality
shall commence until approval by the municipality of an erosion and
sediment control plan for construction activities.
B.
DEP has regulations that require an erosion and sediment control
plan for any earth disturbance activity of 5,000 square feet or more,
under 25 Pa. Code § 102.4(b).
C.
In addition, under 25 Pa. Code Chapter 92,[1] a DEP "NPDES Construction Activities" permit is required
for any earth disturbance one acre or more. This includes earth disturbance
on any portion of, part of or during any stage of a larger common
plan of development.
[1]
Editor's Note: Chapter 92 of Title 25 of the Pennsylvania
Code was reserved 10-8-2010, effective 10-9-2010. It was replaced
by Chapter 92a, National Pollutant Discharge Elimination System (NPDES)
Permitting, Monitoring and Compliance.
D.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or County Conservation District must be provided to the municipality. The issuance of an NPDES Construction Permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements of Subsection A.
E.
A copy of the erosion and sediment control plan and any required
permit, as required by DEP regulations, shall be available at the
project site at all times.
F.
A copy of the erosion and sediment control plan and any required
permit, as required by PADEP regulations, shall be available at the
project site at all times.
G.
Measures shall be designed and used during construction as per approved plans from the ACCD and in accordance with the details presented in the PADEP Chapter 102 Revised Erosion and Sedimentation Control Program Manual. The following DEP Construction Details shall be included and made a part of the construction plans:
H.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office of Allegheny County Conservation District must be provided to the Borough. The issuance of an NPDES Construction Permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements of Subsection A.
I.
A copy of the erosion and sediment control plan and any required
permit, as required by DEP regulations, shall be available at the
project site at all times.
A.
No regulated earth disturbance activities within the municipality
shall commence until approval by the municipality of a plan which
demonstrates compliance with state water quality requirements after
construction is complete.
B.
The BMPs must be designed, implemented and maintained to meet state
water quality requirements, and any other more stringent requirements
as determined by the municipality.
C.
To control postconstruction stormwater impacts from regulated earth
disturbance activities, state water quality requirements can be met
by BMPs, including site design, which provide for replication of preconstruction
stormwater infiltration and runoff conditions, so that postconstruction
stormwater discharges do not degrade the physical, chemical or biological
characteristics of the receiving waters. As described in the DEP Comprehensive
Stormwater Management Policy (#392-0300-002, September 28, 2002),
this may be achieved by the following:
(1)
Infiltration: replication of preconstruction stormwater infiltration
conditions;
(2)
Treatment: use of water quality treatment BMPs to ensure filtering
out of the chemical and physical pollutants from the stormwater runoff;
and
(3)
Stream bank and streambed protection: management of volume and rate
of postconstruction stormwater discharges to prevent physical degradation
of receiving waters (e.g., from scouring).
D.
DEP has regulations that require municipalities to ensure design,
implementation and maintenance of best management practices ("BMPs")
that control runoff from new development and redevelopment after regulated
earth disturbance activities are complete. These requirements include
the need to implement postconstruction stormwater BMPs with assurance
of long-term operations and maintenance of those BMPs.
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. All open channels shall be designed
with one foot of freeboard above the design energy gradeline 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
this flow is conveyed to a natural drainagecourse with a defined bed
and bank.
D.
The distance between manholes shall not exceed 300 feet apart for
pipe sizes up to 24 inches in diameter and not more than 450 feet
apart for larger pipe sizes. Inlet spacing shall not exceed 300 feet.
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.
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 shoulder swale draining
the street and shall be located no closer than four feet from the
edge of the cartway.
G.
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
Borough'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
Borough.
H.
Suitable drainage structures, culverts, storm sewers, swales and
related installations shall be provided along roads to insure 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.
I.
No stormwater pipe (public or private) shall be less than 15 inches
in diameter. All stormwater pipes shall be concrete unless otherwise
approved by the Borough. The minimum pipe slope shall be such that
a minimum of two feet per second 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 Borough'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.
J.
When requested by the Borough 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.
K.
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 gradeline 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 gradeline.
Backwater effects of pipes discharging under surcharge conditions
shall be included in the calculations.
L.
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.
(3)
Provide a minimum of one foot of freeboard above the twenty-five-year
design storm event for drainage swales.
M.
All workmanship and materials shall conform to the latest edition
of PennDOT Form 408 and be supplied by manufacturers or suppliers
listed in PennDOT's Bulletin 15.
N.
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.
O.
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. Concrete frames shall not be permitted.
P.
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 PVC or SDR 26
pipe. Four-inch Schedule 40 PVC 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.
Q.
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.
R.
Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP.
S.
Disposal of stormwater from roof and driveway drains:
(1)
Unless otherwise approved by the Borough, 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 Borough.