[HISTORY: Adopted by the Borough Council of the Borough of
Wilmerding 4-7-1992 by Ord. No. 919 (Ch. 26, Part 1, of the 1989 Code).
Amendments noted where applicable.]
A.
Purpose. This chapter is adopted and implemented to achieve the following
general purposes and objectives:
(1)
To manage and control stormwater runoff resulting from land alteration
and disturbance activities in accordance with the watershed stormwater
management plans adopted pursuant to the Pennsylvania Storm Water
Management Act (Act 167 of 1978, as amended).[1]
[1]
Editor's Note: See 32 P.S. § 680.1 et seq.
(2)
To utilize and preserve the desirable existing natural drainage systems
and to preserve the flood-carrying capacity of streams.
(3)
To encourage natural infiltration of rainfall to preserve and recharge
groundwater supplies and stream flows.
(4)
To provide for the design, installation and adequate maintenance
of all permanent stormwater management structures in the Borough.
B.
Applicability. The following activities are included within the scope
of this chapter:
(1)
Land development.
(2)
Subdivision.
(3)
Construction of new or additional impervious or semipervious surfaces
(driveways, roadway, parking lot, buildings and additions thereto,
etc.) which increases the rate of runoff equal to or more than 0.30
cubic feet per second as calculated using the Rational Formula for
a ten-year storm, except that residential construction creating less
than 5,000 square feet of impervious surface shall not apply.
(4)
Diversion or piping of any natural or man-made drainage channel.
(5)
Installation of stormwater systems or appurtenances thereto, except
those areas covered by PennDOT or other governmental agencies.
(6)
Earthmoving activities involving five or more acres of land.
C.
Liability disclaimer.
(1)
Neither the granting of any approval under the stormwater management
provisions of this chapter, nor the compliance with the provisions
of this chapter or with any condition imposed by a Borough official
hereunder shall relieve any person from any responsibility for damage
to persons or property resulting therefrom, or as otherwise imposed
by law, nor impose any liability upon the Borough for damages to persons
or property.
(2)
The granting of a permit which includes any stormwater management
facilities shall not constitute a representation, guarantee or warranty
of any kind by the Borough or by an official or employee thereof of
the practicability or safety of any structure, use or other plan proposed,
and shall create no liability upon or cause of action against such
public body, official or employee for any damage that may result pursuant
thereto.
D.
Compatibility. 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
code, rule, act or ordinance. If more stringent requirements concerning
regulation of stormwater controls are contained in the other code,
rule or ordinance, the more stringent regulation shall apply.
A.
Stormwater management performance districts.
(1)
For purposes of stormwater management, the Borough of Wilmerding
is divided into the following stormwater management districts:
(a)
Turtle Creek.
(2)
One or more of these districts may be further subdivided into subareas
which have similar hydrological characteristics and drain to a common
point.
B.
General standards.
(1)
The following provisions shall be considered the overriding performance
standards against which all proposed stormwater control measures shall
be evaluated and shall apply throughout the Borough of Wilmerding.
(a)
Any landowner and any person engaged in the alteration or development
of land which may affect stormwater runoff characteristics shall implement
such measures as are reasonably necessary to prevent injury to health,
safety or other property. Such measures shall include such actions
as are required:
[1]
To assure that the maximum rate of stormwater runoff is no greater
after development than prior to development activities; or
[2]
To manage the quantity, velocity and direction of resulting
stormwater runoff in a manner which otherwise adequately protects
health and property from possible injury.
(2)
The stormwater management plan for the development site must consider
all the stormwater runoff flowing over the site.
(3)
No discharge of toxic materials shall be permitted into any stormwater
management system.
C.
Watershed standards; Turtle Creek Stormwater Management District.
(1)
The stormwater performance standards contained in this section are
intended to implement the standards and criteria contained in the
Turtle Creek Stormwater Management Plan, adopted and approved in accordance
with the Pennsylvania Storm Water Management Act.[2] If there is any discrepancy between the provisions of
this section and the standards and criteria of the plan, or if the
watershed plan is subsequently amended, then the standards/criteria
of the current watershed plan shall govern.
[2]
Editor's Note: See 32 P.S. § 680.1 et seq.
(2)
Storm frequencies. Stormwater management facilities on all development
sites shall control the peak stormwater discharge for the two-, ten-,
twenty-five- and one-hundred-year storm frequencies. The NRCS[3] twenty-four-hour, Type II rainfall distribution shall
be used for analyzing stormwater runoff for both predevelopment and
post-development conditions. The twenty-four-hour total rainfall for
these storm frequencies in the watershed are:
|
Storm Frequency
(years)
|
Rainfall Depth
(inches)
| |
|---|---|---|
|
2
|
2.50
| |
|
10
|
3.61
| |
|
25
|
4.31
| |
|
100
|
5.71
|
|
(For additional information or data on other storm return periods,
consult the "Rainfall Duration Frequency Tables for Pennsylvania,"
produced by DEP, Office of Resource Management, Bureau of Dams and
Waterways Management, Division of Stormwater, Harrisburg, February
1983).
|
[3]
Editor's Note: Natural Resources Conservation Service of the
United States Department of Agriculture; formerly SCS (Soil Conservation
Service).
(3)
Calculation methods.
(a)
Development sites. For the purpose of computing peak-flow rates
and runoff hydrographs from development sites, calculations shall
be performed using one of the following: NRCS publications, Technical
Release (TR) 55 or 20, HECI, or Penn State Runoff Model.
(b)
Stormwater collection/conveyance facilities. For the purposes
of designing storm sewers, open swales and other stormwater runoff
collection and conveyance facilities, any of the above-listed calculation
methods or the Rational Method may be used. Rainfall intensities for
design should be obtained from the Pennsylvania Department of Transportation
rainfall charts.
(c)
Predevelopment conditions. Predevelopment conditions shall be
assumed to be those which exist on any site at the time of adoption
of the Turtle Creek Stormwater Management Plan. Hydrologic conditions
for all areas with pervious cover (i.e., fields, woods, lawn areas,
pastures, cropland, etc.) shall be assumed to be in "good" condition,
and the lowest recommended NRCS runoff curve number (CN) shall be
applied for all pervious land uses within the respective range for
each land use and hydrologic soil group.
(4)
Release rate percentage.
(a)
Definition. The release rate percentage defines the percentage
of the predevelopment peak rate of runoff that can be discharged from
an outfall on the site after development. It applies uniformly to
all land development or alterations within a subarea. A listing of
the release rate percentage by subarea appears in Appendix A of this
chapter; the subareas are delineated on the Borough Stormwater Management
District Map (refer to this section).[4]
[4]
Editor's Note: Appendix A and the map referenced are on file
in the Borough's office.
(b)
Procedure for use.
[2]
Compute the predevelopment and post-development runoff hydrographs
for each stormwater outfall on the development site using an acceptable
calculation method for the two-, ten-, twenty-five- and one-hundred-year
storms. Apply no on-site detention for stormwater management but include
any techniques to minimize impervious surfaces and/or increase the
time of concentration for stormwater runoff flowing from the development
site. If the post-development peak runoff rate and the runoff volume
are less than or equal to the predevelopment peak runoff rate and
volume, then additional stormwater control shall not be required at
that outfall. If the post-development peak runoff rate and volume
are greater than the predevelopment peak runoff rate and volume, then
stormwater detention will be required, and the capacity of the detention
facility must be calculated in the manner prescribed below.
[3]
Multiply the subarea release rate percentage by the predevelopment
rate runoff from the development site to determine the maximum allowable
release rate from any detention facility for the four prescribed storm
events.
[4]
Design the outlet control facilities and size the volume of
the detention facility using the calculated post-development hydrograph
and accepted hydrograph routing procedures in consideration of the
maximum allowable release rate.
(5)
No-harm evaluation.
(a)
An applicant may seek to exceed the otherwise applicable subarea
release rate percentage by performing the no-harm evaluation. This
evaluation requires an independent engineering analysis to demonstrate
that other reasonable options exist to prevent the occurrence of increased
stormwater runoff discharge rates and/or velocities or that measures
can be provided to prevent increased stormwater discharge rates and/or
velocities from increasing flood elevations and accelerating erosion
at all downstream points in the watershed.
(b)
A no-harm evaluation will be considered only in instances where
the discharge to a stream channel from the development occurs directly
to the Monongahela River or through a properly sized and designed
regional stormwater detention facility.
(c)
The analysis for the no-harm evaluation shall be submitted to
the Borough Engineer and Allegheny Planning Department for review
and approval.
A.
General criteria.
(1)
Applicants may select runoff control techniques, or a combination
of techniques, which are most suitable to control stormwater runoff
from the development site. All controls must be subject to approval
of the Borough Engineer. The Borough Engineer may request specific
information on design and/or operating features of the proposed stormwater
controls in order to determine their suitability and adequacy in terms
of the standards of this chapter.
(2)
The applicant should consider the effect of the proposed stormwater
management techniques on any special soil conditions or geological
hazards which may exist on the development site. In the event such
conditions are identified on the site, the Borough Engineer may require
in-depth studies by a competent geotechnical engineer. Not all stormwater
control methods may be advisable or allowable at a particular development
site.
(3)
The stormwater management practices to be used in developing a stormwater
management plan for a particular site shall be selected according
to the following order of preference:
(4)
Infiltration practices shall be used to the extent practicable to
reduce volume increases and promote groundwater recharge. A combination
of successive practices may be used to achieve the applicable minimum
control requirements. Justification shall be provided by the applicant
for rejecting each of the preferred practices based on actual site
conditions.
B.
Criteria for infiltration systems.
(1)
Infiltration systems shall be sized and designed based upon local
soil and groundwater conditions.
(2)
Infiltration systems shall be greater than three feet deep and shall
be located at least 10 feet from basement walls.
(3)
Infiltration systems shall not be used to handle runoff from commercial
or industrial working or parking areas.
(4)
Infiltration systems may not receive runoff until the entire drainage
area to the system has received final stabilization.
(5)
The stormwater infiltration facility design shall provide an overflow
system with measures to provide a nonerosive velocity of flow along
its length and at the outfall.
C.
Criteria for stormwater detention facilities.
(1)
If detention facilities are utilized for the development site, the
facility(ies) shall be designed such that post-development peak runoff
rates from the developed site are controlled to those rates defined
by the subarea release rate percentage for the two-, ten-, twenty-five-
and one-hundred-year storm frequencies.
(2)
All detention facilities shall be equipped with outlet structures
to provide discharge control for the four designated storm frequencies.
Provisions shall also be made to safely pass, at minimum, the post-development
one-hundred-year storm runoff without breaching or otherwise damaging
(i.e., impairing the continued function of) the facilities.
(3)
Shared storage facilities, which provide detention of runoff for
more than one development site within a single subarea, may be considered
and are encouraged. Such facilities shall meet the criteria contained
in this section. In addition, runoff from the development sites involved
shall be conveyed to the facility in a manner that avoids adverse
impacts (such as flooding or erosion) to channels and properties located
between the development site and the shared storage facilities.
(4)
Where detention facilities will be utilized, multiple-use facilities,
such as wetlands, lakes, ball fields or similar recreation/open space
uses, are encouraged wherever feasible, subject to the approval of
the Borough.
(5)
Other considerations which should be incorporated into the design
of the detention facilities include:
(a)
Inflow and outflow structures shall be designed and installed
to prevent erosion, and bottoms of impoundment-type structures should
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 designed and protected to minimize safety hazardous.
(d)
The water depth at the perimeter of a storage pond should be
limited to that which is safe for children. This is especially necessary
if bank slopes are steep or if ponds are full and recirculating in
dry periods. Restriction of access (fence, walls, etc.) may be necessary
depending on the location of the facility.
(e)
Side slope of storage ponds shall not exceed a ratio of 2.5:1
horizontal to vertical dimension.
(f)
Landscaping shall be provided for the facility which harmonizes
with the surrounding area.
(g)
Facility shall be located to facilitate maintenance, considering
the frequency and type of equipment that will be required.
(h)
Spillway design. The outlets for the retention ponds shall consist
of a combination of principal and emergency spillways. The outlets
must pass the peak runoff expected from the drainage area for a one-hundred-year
storm without damage to the embankment of the pond. Runoff computations
shall be based upon the soil cover conditions which are expected to
prevail during the life of the basin.
(i)
Principal spillway. The principal spillway shall consist of
a solid vertical pipe or box of corrugated steel pipe, or reinforced
concrete joined by a watertight connection to a horizontal pipe (barrel)
extending through the embankment and outletting beyond the downstream
toe of the fill. The principal spillway shall have a minimum capacity
of 0.2 cubic feet per second per acre of drainage area when the water
surface is at the crest of the emergency spillway. The maximum capacity
of the barrel will be the twenty-five-year predevelopment flow. The
construction materials must be approved by the Borough. Refer to Plate
A.[1] The maximum barrel capacity established herein may be
reduced in those areas of the Borough which are regulated or controlled
by any other duly authorized stormwater management plan.
[1]
Editor's Note: Plate A is on file in the Borough's office.
(j)
Design elevations. When the principal spillway is used in conjunction
with an emergency spillway, the crest of the principal spillway shall
be a minimum of 2.0 feet below the crest of the emergency spillway.
The crest of the principal spillway shall be a minimum of three feet
below the top of the embankment. Refer to Plate A.[2]
[2]
Editor's Note: Plate A is on file in the Borough's office.
(k)
Antivortex and trash rack. An antivortex device and trash rack
shall be attached to the top of the principal spillway to improve
the flow of water into the spillway and prevent floating debris from
being carried out of the basin. The antivortex device shall be of
the concentric type as shown in Plate B and Plate C, or approved equal.[3]
[3]
Editor's Note: Plates B and C are on file in the Borough's
office.
(l)
Base. The base of the principal spillway must be firmly anchored
to prevent floating. If the riser of the spillway is greater than
10 feet in height, computations must be made to determine the anchoring
requirements. As a minimum, a factor of safety of 1.25 shall be used
(downward forces equal 1.25 times upward forces). For risers of 10
feet or less in height, the anchoring may be done in one of the two
following ways:
[2]
A square steel plate, a minimum of 1/4 inch thick and having
a width equal to twice the diameter of the riser, shall be welded
to the base of the riser. The plate shall then be covered with 2.5
feet of stone, gravel or compacted soil to prevent flotation. See
Plate D for design details.[5]
[5]
Editor's Note: Plate D is on file in the Borough's office.
(m)
Barrel. The barrel of the principal spillway which extends through
the embankment shall be designed to carry the twenty-five-year predevelopment
flow (or any required reduction thereof) provided by the riser of
the principal spillway with the water level at the crest of the emergency
spillway. The connection between the riser and the barrel must be
watertight. The outlet of the barrel must be protected to prevent
erosion or scour of downstream area. This will include an end section
or end wall with a designed riprap apron.
(n)
Antiseep collars.
[1]
Antiseep collars shall be used on the barrel of the principal
spillway within the normal saturation zone of the embankment to increase
the seepage length by at least 10%, if either of the following conditions
is met:
[2]
The antiseep collars shall be installed within the saturated
zone. The maximum spacing between collars shall be 14 times the projection
of the collar above the barrel. Collars shall not be closer than two
feet to a pipe joint. Collars should be placed sufficiently far apart
to allow space for hauling and compacting equipment. Connections between
the collars and the barrel shall be watertight. The length of the
barrel within the saturation zone can be obtained by entering Plate
E with variable "Y." "Y" is the depth of water at the principal spillway
crest in feet. This chart will provide saturated length. This number
is entered in Plate F to size the antiseep collar. Refer to Plate
G for details of the antiseep collar.[6]
[6]
Editor's Note: Plates E, F and G are on file in the Borough's
office.
(o)
Emergency spillway. The emergency spillway shall consist of
an open channel constructed adjacent to the embankment over undisturbed
material (not fill). The spillway shall have a control section at
least 20 feet in length. The control section is a level portion of
the spillway channel at the highest elevation in the channel. The
emergency spillway shall be designed to carry the peak rate of runoff
expected from a one-hundred-year storm, less any reduction due to
the flow through the principal spillway. The spillway channel shall
return the flow of water to a defined channel downstream from the
embankment. The maximum allowable velocities in the emergency spillway
channel will depend on the type of lining used. For vegetated linings,
allowable velocities are listed in Table 4.[7] For nonerodible linings, such as concrete, asphalt paving
and riprap, design shall return the flow to the natural channel at
noneroding velocities. See Plates H and I for design of the emergency
spillway.[8]
(p)
Embankment. The material for the embankment shall consist of
all excavation on the project except such material as may be determined
unsuitable by the Borough's representative, which includes, but
is not limited to, frozen material and excessively wet or dry material.
Acceptable material shall conform to the current PennDOT Publication
408, Section on Embankment Material, or as approved by the Borough
representative.
(q)
Rock lining. The rock lining material used in stormwater management
facilities should be a minimum of Class R-5 to a nominal thickness
of 24 inches according to PennDOT Publication 408, Section on Rock
Lining, or as approved by Borough's representative.
(r)
Fence. A chain-link fence must be installed around the pond
at a height of six feet. A three-foot-wide gate with lock and keys
must be provided to allow access for future maintenance. Fence details
and specifications shall be submitted to the Borough.
(s)
Access road. The subdivider shall provide a ten-foot-wide access
road constructed of 2B stone at a depth of four inches. Such access
road shall run from the paved Borough street to the retention pond.
D.
Criteria for collection/conveyance facilities.
(1)
All stormwater runoff collection or conveyance facilities, whether
storm sewers or other open or closed channels, shall be designed in
accordance with the following basic standards:
(a)
All sites shall be graded to provide drainage away from and
around the structure in order to prevent any potential flooding damage.
(b)
Lots located on the high side of streets shall extend roof and
french drains to the curbline storm sewer (if applicable). Low side
lots shall extend roof and french drains to a storm sewer collection/conveyance/control
system or natural watercourse in accordance with the approved stormwater
management plan for the development site.
(c)
Collection/conveyance facilities shall not be installed parallel
and close to the top or bottom of a major embankment to avoid the
possibility of failing or causing the embankment to fail.
(d)
All collection/conveyance facilities shall be designed to convey
the twenty-five-year storm peak flow rate from the contributing drain
area and to carry it to the nearest suitable outlet such as a stormwater
control facility, curbed street, storm sewer or natural watercourse.
(e)
Where drainage swales or open channels are used, they shall
be suitably lined to prevent erosion and designed to avoid excessive
velocities.
(2)
Wherever storm sewers are proposed to be utilized, they shall comply
with the following criteria:
(a)
Where practical, designed to traverse under seeded and planted
areas. If constructed within 10 feet of road paving, walks or other
surfaced areas, drains shall have a narrow trench and maximum compaction
of backfill to prevent settlement of the superimposed surface or development.
(b)
Preferably installed after excavating and filling in the area
to be traversed is completed, unless the drain is installed in the
original ground with a minimum of three feet of cover and/or adequate
protection during the fill construction.
(d)
Designed to adequately handle the anticipated stormwater flow
and be economical to construct and maintain. The minimum pipe size
shall be 15 inches in diameter.
(e)
Drain pipe, trenching, bedding and backfilling requirements
shall conform to the requirements of the Borough and/or applicable
PennDOT Specifications, Form 408.
(f)
All corrugated metal pipe shall be polymer-coated and with asbestos
bonding and paved inverts where prone to erode. Pipe within a Borough
right-of-way shall be reinforced concrete pipe with a minimum diameter
of 15 inches.
(g)
Storm inlets and structures shall be designed to be adequate,
safe, self-cleaning and unobtrusive and consistent with Borough standards.
(h)
Appropriate grates shall be designed for all catch basins, stormwater
inlets and other entrance appurtenances.
(i)
Manholes shall be designed so that the top shall be at finished
grade and sloped to conform to the slope of the finished grade. Top
casings of structures located in roads or parking areas shall be machined
or installed to preclude "rattling."
(j)
Where proposed sewer connects with an existing storm sewer system,
the applicant shall demonstrate that sufficient capacity exists in
the downstream system to handle the additional flow.
(k)
Storm sewer outfalls shall be equipped with energy-dissipation
devices to prevent erosion and conform with applicable requirements
of the Pennsylvania Department of Environmental Protection for stream
encroachments (Chapter 105 of Pennsylvania DEP Rules and Regulations).
(l)
Stormwater inlets. The maximum spacing between stormwater inlets
shall be designed according to the ten-year storm flow and the capacity
of the inlets, taking into account gradient of roadway, maximum allowable
street flooding and drainageway capacity. When a possibility of clogging
of grates, side opening, or combination inlets exists, use the capacity-reduction
factors shown on Table 1 applied to theoretical capacity of the inlet.[9] The maximum amount of water that should be bypassed on
to the next downstream inlet for inlets on continuous grades is 10%.
[9]
Editor's Note: Table 1 is on file in the Borough's office.
(m)
Pipes. Horizontal and vertical curves with radii of 100 feet
or greater are allowed for all pipe sizes. Friction losses to the
pipe shall be calculated using the Manning formula: v = (1.49/n) AR2/3 S1/2. Values for "n"
are found in Table 2.[10] The minimum value for "v" in pipes shall be three feet
per second. The maximum value for "v" in pipes shall be based on engineering
judgment and experience. Pressure flow is permitted in storm sewers.
The elevation of the hydraulic gradient shall be at least one foot
below ground level. Pressure heads up to 25 feet can be used with
concrete pipe with rubber-gasketed joints.[11]
(o)
Open channels. Maximum allowable velocities of flow in swales,
open channels and ditches, as relating in slope and grass cover, are
shown in Table 4.[13] Higher velocities require invert stabilization. If they
do not present a hazard, velocity dissipaters may be approved by the
Borough or its representative.
[13]
Editor's Note: Table 4 is on file in the Borough's office.
(p)
Where seepage pits, seepage tanks, seepage trenches and/or french
drains are proposed, the developer shall include an analysis of the
potential for accelerated sinkhole development in the specific geology
of the site due to the concentration of water introduction to the
subsurface.
A.
Erosion/sedimentation plan shall be provided in accordance with the
Pennsylvania Erosion/Sedimentation Regulations (25 Pa. Code Chapter
102), the standards and guidelines of the County Conservation District.
B.
Proposed erosion/sedimentation measures shall be submitted with the
stormwater management plan as part of the preliminary and final applications.
A.
Maintenance responsibilities.
(1)
The stormwater management plan for the development site shall contain
an operation and maintenance plan prepared by the developer and approved
by the Borough Engineer. The operation and maintenance plan shall
outline required routine maintenance actions and schedules necessary
to ensure proper operation of the facility(ies).
(2)
The stormwater management plan for the development site shall establish
responsibilities for the continuing operation and maintenance of all
proposed stormwater control facilities, consistent with the following
principles:
(a)
If a development consists of structures or lots which are to
be separately owned and in which streets, sewers and other public
improvements are to be dedicated to the Borough, stormwater control
facilities should also be dedicated to and maintained by the Borough.
(b)
If a development site is to be maintained in single ownership
or if sewers and other public improvements are to be privately owned
and maintained, then the ownership and maintenance of stormwater control
facilities should be the responsibility of the owner or private management
entity.
(c)
The Borough Council, upon recommendation of the Borough Engineer,
shall make the final determination on the continuing maintenance responsibilities
prior to original approval of the stormwater management plan. The
Borough Council reserves the right to accept the ownership and operating
responsibility for any or all of the stormwater management controls.
B.
Maintenance agreement for privately owned stormwater facilities.
(1)
Prior to final approval of the site's stormwater management
plan, the property owner shall sign and record a maintenance agreement
covering all stormwater control facilities which are to be privately
owned. The agreement shall stipulate that:
(a)
The owner shall maintain all facilities in accordance with the
approved maintenance schedule and shall keep all facilities in a safe
and attractive manner.
(b)
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.
(c)
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.
(d)
Maintenance by a private entity shall be secured by performance
security in an amount equal to 110% of the cost as determined by the
Borough to be necessary to adequately maintain said system.
(e)
If the owner fails to maintain the stormwater control facilities
following due notice by the Borough to correct the problem(s), the
Borough may perform the necessary maintenance work or corrective work,
and the owner shall reimburse the Borough for all costs.
(2)
Other items may be included in the 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
Solicitor and Borough Council.
C.
Maintenance by individual lot owners. When any stormwater management
facility is located on an individual lot, and when maintenance thereof
is the responsibility of that landowner, a description of the facility
or system and the terms of the required maintenance shall be incorporated
on a plat of the property. The plat shall be recorded with the County
Recorder of Deeds within 90 days following Borough approval. In addition,
the Borough may require as a condition of approval that any deed conveying
any interest in such lot contain language indicating that the conveyance
is subject to an express covenant by the grantee that the grantee
will maintain the stormwater management facility.
A.
General requirements. No final subdivision/land development plan
shall be approved, no permit authorizing construction issued, or any
earthmoving or land disturbance activity initiated until the final
stormwater management plan for the development site is approved in
accordance with the provisions of this chapter.
B.
Exemptions for small developments.
(1)
At the time of application, the Borough shall determine if the subdivision/land
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 any subdivision or land development
which results in (or will result in when fully constructed) the creation
of 5,000 or less square feet of impervious area.
(2)
Applications for small developments shall include a plan which describes
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, the boundaries, five-foot interval contours,
locations 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. Contingent upon the approval of
the Borough Engineer, alternative methods may be used where applicable.
The Borough reserves the right to require that the plan be prepared
by a registered professional engineer, surveyor or landscape architect.
(3)
The Borough Engineer shall review and approve the proposed provisions
for stormwater management in accordance with the standards and requirements
of this chapter.
C.
Stormwater plan contents.
(1)
General format. The stormwater plan shall be drawn to a scale of
not less than one inch equals 200 feet. All sheets shall contain a
title block with name and address of applicant and engineer, scale,
North arrow, legend and date of preparation. The plan should show
the location of the project relative to highways, Borough boundaries
or other identifiable landmarks.
(2)
Existing and proposed features. The plan shall show the following:
(a)
Watershed location. Provide a key map showing the location of
the development site within the watershed(s) and watershed subarea(s).
On all site drawings, show the boundaries of the watershed(s) and
subarea(s) as they are located on the development site and identify
watershed name(s) and subarea number(s).
(b)
Floodplain boundaries. Identify one-hundred-year floodplains
on the development site (as appropriate) based on the Borough Flood
Insurance Study Maps.
(c)
Natural features. Show all bodies of water (natural or artificial)
watercourses (permanent and intermittent), swales, wetlands and other
natural drainagecourses on the development site or which will be affected
by runoff from the development.
(d)
Soils. Provide an overlay showing soil types and boundaries
within the development site (consult County, NRCS and United States
Geological Survey for information).
(e)
Contours. Show existing and final contours at intervals of two
feet; in areas with slopes greater than 15%, five-foot contour intervals
may be used.
(f)
Land cover. Show existing and final land cover classifications
as necessary to support and illustrate the runoff calculations performed.
(g)
Drainage area delineations. Show the boundaries of the drainage
areas employed in the runoff calculations performed.
(h)
Stormwater management controls. Show any existing stormwater
management or drainage controls and/or structures, such as sanitary
and storm sewers, swales, culverts, etc., which are located on the
development site or which are located off site but will be affected
by runoff from the development.
(i)
Location of existing and proposed overhead and underground utilities
including water and sewer lines.
(3)
Professional certification. The stormwater management plan (including
all calculations) must be prepared and sealed by a registered professional
engineer, surveyor or landscape architect with training and expertise
in hydrology and hydraulics. Documentation of qualifications may be
required by the Borough.
(4)
Runoff calculations. Calculations for determining predevelopment
and post-development discharge rates and for designing proposed stormwater
control facilities must be submitted with the stormwater management
plan. All calculations shall be prepared using the methods and data
prescribed by § 260-2 of this chapter.
(5)
Stormwater controls. All proposed stormwater runoff control measures
must be shown on the plan, including methods for collecting, conveying,
storing stormwater runoff on site which are to be used both during
and after construction. Erosion and sedimentation controls shall be
shown in accordance with applicable Borough and County Conservation
District requirements. The plan shall provide information on the exact
type, location, sizing, design and construction of all proposed facilities
and relationship to the existing watershed drainage system.
(a)
If the development is to be constructed in stages, the applicant
must demonstrate that stormwater facilities will be installed to manage
stormwater runoff during each stage of development.
(b)
A schedule for the installation of all temporary and permanent
stormwater control measures and devices shall be permitted.
(6)
Easements, rights-of-way, deed restrictions. All existing and proposed
easements and rights-of-way for drainage and/or access to stormwater
control facilities shall be shown and the proposed owner identified.
Show any areas subject to special deed restrictions relative to or
affecting stormwater management on the development site.
(7)
Other permits/approvals. A list of any approvals/permits relative
to stormwater management that will be required from other governmental
agencies (e.g., an obstructions permit from Pennsylvania DEP) and
anticipated dates of submission/receipt should be included with stormwater
plan submission. Copies of permit applications may be required by
the Borough where they may be helpful for the plan review.
(8)
Maintenance program. The application shall contain a proposed maintenance
plan for all stormwater control facilities in accordance with the
following:
(a)
Identify the proposed ownership entity (e.g., municipality,
property owner, private corporation, homeowners' association or other
entity).
(b)
Include a maintenance program for all facilities, outlining
the type of maintenance activities, probable frequencies, personnel
and equipment requirements and estimated annual maintenance costs.
(c)
Identify method of financing continuing operation and maintenance
if the facility is to be owned by other than the Borough or governmental
agency.
(d)
Submit any legal agreements required to implement the maintenance
program and copies of the maintenance agreement as required by this
chapter.
(9)
Financial guarantee. Submit financial guarantees in accordance with
the provisions of this chapter.
A.
Preapplication phase.
(1)
Before submitting the stormwater plan, applicants are urged to consult
with the Borough, County Planning Department and County Conservation
District on the requirements for safely managing the development site
in a manner consistent with the Borough ordinances and applicable
watershed stormwater management plan. These agencies may also be helpful
in providing necessary data for the stormwater management plan.
(2)
Applicants are encouraged to submit a sketch plan with a narrative
description of the proposed stormwater management controls for general
guidance and discussion with the Borough and other agencies.
(3)
The preapplication phase is not mandatory; any review comments provided
by the Borough or other agencies are advisory only and do not constitute
any legally binding action on the part of the Borough or any county
agency.
B.
Stormwater plan reviews.
(1)
Submission of plans. Stormwater plan applications shall be submitted
with the preliminary and final subdivision/land development applications.
(2)
Notification of affected municipalities. The Borough shall notify
municipalities upstream and downstream of the development site which
may be affected by the stormwater runoff and proposed controls for
the site. Copies of the plans will be made available to the municipalities
upon request. Comments received from any affected municipality will
be considered by the Borough Engineer and county agencies in their
review.
(3)
County planning review.
(a)
A copy of the stormwater plan, along with all runoff calculations,
shall be forwarded to the Allegheny County Planning Department. A
report of the findings will be returned to the Borough within 30 days.
(b)
If the Planning Department review identifies that the plan fails
to comply with the watershed standards and criteria or that a possibility
exists for harmful downstream impacts from the development site, the
applicant will be advised so that the necessary modifications can
be made to the stormwater management controls for the development
site. The Borough Engineer shall not approve the development site's
stormwater management plan until modifications are made and the plan
receives a positive review from the County Planning Department.
(4)
Borough Engineer's review. The Borough Engineer shall approve
or disapprove the stormwater management plan based on the requirements
of the Borough ordinances, the standards and criteria of the watershed
plan and good engineering practice. The Engineer shall submit a written
report, along with supporting documentation, stating his reasons for
approval or disapproval.
(5)
Status of the Engineer's determination. The approval/disapproval
of the site's stormwater management plan by the Borough Engineer
shall be considered final. The Borough Council shall not reverse the
Engineer's determination by approving or disapproving the site's
stormwater management plan or any specified control measure in contradiction
to the Engineer's action. The Borough Council may request modifications
or alternative approaches to the stormwater management controls, provided
these are agreed to by the Borough Engineer and the applicant's
engineer.
(6)
Permits required from other governmental agencies. Where the proposed
development requires an obstruction permit from the Pennsylvania DEP
or an erosion/sedimentation permit from the County Conservation District,
then final stormwater management plan approval shall be conditional
upon receipt of such permits. However, no building permit shall be
issued, nor construction started, until the permits are received and
copies filed with the Borough.
A.
Upon final stormwater plan approval and receipt of all necessary
permits, the applicant may commence to install or implement the approved
stormwater management controls.
B.
If site development or building construction does not begin within
two years of the date of final approval of the stormwater management
plan, then before doing so, the applicant shall resubmit the stormwater
management plan to verify that no condition has been changed within
the watershed that would affect the feasibility or effectiveness of
the previously approved stormwater management controls. Further, if
for any reason development activities are suspended for two years
or more, then the same requirements for resubmission of the stormwater
management plan shall apply.
A.
If the request for a plan modification is initiated before construction
begins, the stormwater plan must be resubmitted and reviewed according
to the procedures contained in § 260-7 above.
B.
If the request for a plan modification is initiated after construction
is underway, the Borough Engineer shall have the authority to approve
or disapprove the modification based on field inspection, provided,
1) the requested changes in stormwater controls do not result in any
modifications to other approved Borough land use/development requirements
(e.g., building setbacks, yards, etc.); and 2) the performance standards
in § 260-2 are met. Notification of the Engineer's
action shall be sent to the Borough Council, which may issue a stay
of the plan modification within five days and require the permittee
to resubmit the plan modification for full stormwater plan review
in accordance with § 260-7 above.
A.
The Borough Engineer or a designated representative shall inspect
the construction of the temporary and permanent stormwater management
system for the development site. The permittee shall notify the Engineer
48 hours in advance of the completion of the following key development
phases:
(1)
At the completion of preliminary site preparation including stripping
of vegetation, stockpiling of topsoil and construction of temporary
stormwater management and erosion control facilities.
(2)
At the completion of rough grading but prior to placing topsoil,
permanent drainage or other site development improvements and ground
covers.
(3)
During construction of the permanent stormwater facilities at such
times as specified by the Borough Engineer.
(4)
Completion of permanent stormwater management facilities including
established ground covers and plantings.
(5)
Completion of final grading, vegetative control measures or other
site restoration work done in accordance with the approved plan and
permit.
B.
No work shall commence on any subsequent phase until the preceding
one has been inspected and approved. If there are deficiencies in
any phase, the Borough Engineer shall issue a written description
of the required corrections and stipulate the time by which they must
be made.
C.
If during construction the contractor or permittee identifies any
site condition, such as subsurface soil conditions, alterations in
surface or subsurface drainage, which could affect the feasibility
of the approved stormwater facilities, he/she shall notify the Borough
Engineer within 24 hours of the discovery of such condition and request
a field inspection. The Borough Engineer shall determine if the condition
requires a stormwater plan modification.
D.
In cases where stormwater facilities are to be installed in areas
of landslide-prone soils or other special site conditions exist, the
Borough may require special precautions such as soil test and core
borings, full-time inspectors and/or similar measures. All costs of
any such measures shall be borne by the permittee.
A.
Guarantee of completion. A completion guarantee in the form of a
bond, cash deposit, certified check or other negotiable securities
acceptable to the Borough shall be filed. The guarantee shall cover
all streets, sanitary sewers, stormwater management facilities, water
systems, fire hydrants, sidewalks and other required improvements;
it shall be in the amount and form prescribed by the Municipalities
Planning Code (Section 509).[1]
[1]
Editor's Note: See 53 P.S. § 10509.
B.
Release of completion guarantee. The completion guarantee shall be
returned or released upon written certification by the Borough Engineer
or a designated agent that improvements and facilities have been installed
and completed in accordance with the approved plan and specifications.
The procedures for requesting and obtaining a release of the completion
guarantee shall be in a manner prescribed by the Municipalities Planning
Code (Section 510).[2]
[2]
Editor's Note: See 53 P.S. § 10510.
C.
Default of completion guarantee. If improvements are not installed
in accordance with the approved final plan, the Borough Council may
enforce any corporate bond or other security by appropriate legal
and equitable remedies. If proceeds of such bond or other security
are insufficient to pay the cost of installing or making repairs or
corrections to all the improvements covered by said security, the
Borough Council may, at its option, install part of such improvements
in all or part of the development and may institute appropriate legal
or equitable action to recover the improvements. All proceeds, whether
resulting from the security or from any legal or equitable action
brought against the developer, or both, shall be used solely for the
installation of the improvements covered by such security and not
for any other Borough purpose.
D.
Dedication of public improvements.
(1)
When streets, sanitary sewers, stormwater management facilities,
waterlines or other required improvements in the development have
been completed in accordance with the final approved plan, such improvements
shall be deemed private until such time as they have been offered
for dedication to the Borough and accepted by separate ordinance or
resolution or until they have been condemned for use as a public facility.
(2)
Prior to acceptance of any improvements or facilities, the Borough
Engineer shall inspect it to ensure that it is constructed in accordance
with the approved plan and is functioning properly. In the case of
any stormwater control facility, it must be free of sediment and debris.
(3)
The owner shall submit as-built plans for all facilities proposed
for dedication. Drawings shall bear the seal of a registered engineer
indicating the as-built improvements have been constructed in accordance
with the approved plans.
E.
Maintenance guarantee. Prior to acceptance of any improvements or
facilities, the applicant shall provide a financial security to secure
the structural integrity and functioning of the improvements. The
security shall: 1) be in the form of a bond, cash, certified check
or other negotiable securities acceptable to the Borough; 2) be for
a term of 18 months; and 3) be in an amount equal to 15% of the actual
cost of the improvements and facilities so dedicated.
A.
The Borough Council may adopt by resolution, from time to time, a
reasonable schedule of fees to cover the cost of plan reviews, inspections
and other activities necessary to administer the provisions of this
chapter. All fees shall be set in accordance with the applicable provisions
of the Municipalities Planning Code, and any dispute over the fee
amount shall be resolved in the manner prescribed by the Municipalities
Planning Code.[1] No approval to begin any work shall be issued until the
requisite fees have been paid.
[1]
Editor's Note: See 53 P.S. § 10101 et seq.
A.
Right of entry. Upon presentation of proper credentials, duly authorized
representatives of the Borough may enter at reasonable times upon
any property to investigate or ascertain the condition of the subject
property in regard to any aspect regulated by this chapter.
B.
Notification. In the event that the applicant, developer, owner or
his/her agent fails to comply with the requirements of this chapter
or fails to conform to the requirements of any permit, a written notice
of violation shall be issued. Such notification shall set forth the
nature of the violation(s) and establish a time limit for the correction
of the violation(s). Upon failure to comply within the time specified,
unless otherwise extended by the Borough, the applicant, developer,
owner or his/her agent shall be subject to the enforcement remedies
of this chapter.
C.
Preventative remedies.
(1)
In addition to other remedies, the Borough may institute and maintain
appropriate actions by law or in equity to restrain, correct or abate
a violation, to prevent unlawful construction, to recover damages
and to prevent illegal occupancy of a building or premises.
D.
Enforcement remedies.
(1)
Any person who has violated or has knowingly permitted the violation
of the provisions of this chapter shall, upon being found liable therefor
in a civil enforcement proceeding commenced by the Borough, pay a
fine of not less than $100 and not more than $600 plus court costs,
including reasonable attorneys' fees, incurred by the Borough. No
judgment shall commence or be imposed, levied or be payable until
the date of the determination of a violation by the Magisterial District
Judge.
(2)
If the defendant neither pays nor timely appeals the judgment, the
Borough may enforce the judgment pursuant to applicable rules of civil
procedure.
(3)
Each day that a violation continues shall constitute a separate violation
unless the Magisterial District Judge further determines that there
was a good faith basis for the person violating this chapter to have
believed that there was no such violation. In such case there shall
be deemed to have been only one such violation until the fifth day
following the date of the Magisterial District Judge's determination
of a violation; thereafter, each day that a violation continues shall
constitute a separate violation.
(4)
All judgments, costs and reasonable attorney fees collected for the
violation of this chapter shall be paid over to the Borough.
(5)
The Court of Common Pleas, upon petition, may grant an order of stay,
upon cause shown, tolling the per-diem fine pending a final adjudication
of the violation and judgment.
(6)
Nothing contained in this section shall be construed or interpreted
to grant to any person or entity other than the Borough the right
to commence any action for enforcement pursuant to this section.
E.
Additional remedies. In addition to the above remedies, the Borough
may also seek remedies and penalties under applicable Pennsylvania
statutes or regulations adopted pursuant thereto, including, but not
limited to, Storm Water Management Act (32 P.S. §§ 680.1
through 680.17), the Dam Safety and Encroachments Act (32 P.S. §§ 693.1
through 693.27) and the Erosion and Sedimentation Regulations (Chapter
102 of Title 25 of the Pennsylvania Code). Any activity conducted
in violation of this chapter or any Pennsylvania-approved watershed
stormwater management plan may be declared a public nuisance by the
Borough and abatable as such.
F.
Additional legal proceedings. In addition to the fines for violations,
costs and penalties provided for by this section, the Borough may
institute proceedings in courts of law or equity to collect damages
to require owners and/or occupants of real estate to comply with the
provisions of this chapter.
G.
Municipal lien. The cost of removal, fine and penalties hereinabove
mentioned may be entered by the Borough as a lien against such property
in accordance with existing provisions of law.
H.
Existing rights and penalties preserved. The collection of any penalty
under the provisions of this chapter shall not be construed as stopping
the Commonwealth of Pennsylvania, the County, the Borough or any aggrieved
person from proceeding in courts of law or equity to abate a violation
of this chapter. Moreover, it is hereby declared to be the purpose
of this chapter to provide additional and cumulative remedies to abate
nuisances.
I.
Appeals. Any person aggrieved by any action of the designee of the
Borough may appeal to the Borough Council within 30 days of that action.
As used in this chapter, the following terms shall have the
meanings indicated:
The Storm Water Management Act (Act of October 4, 1978, P.L.
864, No. 167; 32 P.S. §§ 680.1 through 680.17, as amended
by Act of May 24, 1984, No. 63).
A landowner or developer who has filed an application for
development, including his/her heirs, successors and assigns.
A perceptible natural or artificial waterway which periodically
or continuously contains moving water or which forms a connecting
link between two bodies of water. It has a definite bed and banks
which confine the water.
An underground reservoir or tank for storage of rainwater.
The Allegheny County Conservation District.
A closed conduit for the free passage of surface drainage
under a highway, railroad, canal or other embankment.
See "storm frequency."
The magnitude of precipitation from a storm event measured
in probability of occurrence (e.g., fifty-year storm) and duration
(e.g., twenty-four-hour), and used in computing stormwater management
control systems.
Unless otherwise noted, the official designee of the Borough
for action on behalf of the Borough under the terms of this chapter
shall be the Borough Engineer.
The slowing, dampening or attenuating of runoff flows entering
the natural drainage pattern or storm drainage system by temporarily
holding water on a surface area in a detention basin or within the
drainage system.
A pond or reservoir, usually small, constructed to impound
or retard surface runoff temporarily.
The person, persons or any corporation, partnership, association
or other entity or any responsible person therein or agent therefor
that undertakes the activities associated with changes in land use.
The term "developer" is intended to include, but not necessarily be
limited to, the terms "subdivider," "owner" and "builder" even though
the individuals involved in successive stages of the project may vary.
Any activity, construction, alteration, change in land use
or practice that affects stormwater runoff characteristics.
The flow or rate of flow from a canal, conduit, channel or
other hydraulic structure.
A channel and a ridge constructed to a predetermined grade
across a slope and designed to collect and/or divert runoff from slopes
which are subject to erosion.
In general, the removal of surface water from a given area;
commonly applied to surface water and groundwater.
A right granted by a landowner to a grantee allowing the
use of private land for stormwater management purposes.
Any structure or activity which in any manner changes, expands
or diminishes the course, current or cross section of any watercourse,
floodway or body of water.
Wearing away of the lands by running water, winds and waves.
The application of measures to reduce erosion of land surfaces.
Materials covering the ground surface.
Subsurface water occupying the saturation zone, from which
wells and springs are fed.
Replenishment of groundwater naturally by precipitation or
runoff or artificially by spreading or injection.
A line joining points whose vertical distance from the center
of the cross section of the fluid flowing in a pipe are proportional
to the pressure in the pipe at the point.
The slope of the hydraulic grade line.
Not allowing or allowing only with great difficulty the movement
of water; impermeable.
Any of the following activities:
The improvement of one lot or two or more contiguous lots, tracts
or parcels of land for any purpose involving:
A group of two or more residential or nonresidential buildings,
whether proposed initially or cumulatively, or a single nonresidential
building on a lot or lots regardless of the number of occupants or
tenure; or
The division or allocation of land or space, whether initially
or cumulatively, between or among two or more existing or prospective
occupants by means of or for the purpose of streets, common areas,
leaseholds, condominiums, building groups or other features.
A subdivision of land.
Any activity involving the changing, grading, transportation,
fill and any other activity which causes land to be exposed to the
danger of erosion.
The upkeep necessary for efficient operation of physical
properties.
The Borough of Wilmerding, Allegheny County, Pennsylvania.
A watershed where natural surface configurations, runoff
characteristics and defined drainage conveyances have attained the
conditions of equilibrium.
U.S. Department of Agriculture, Natural Resources Conservation
Service (formerly SCS).[1]
The means of controlling the relationship between the headwater
elevation and the discharge, placed at the outlet or downstream end
of any structure through which water may flow.
The maximum rate of flow of water at a given point and time
resulting from a specified storm event.
Maximum flow.
Pennsylvania Department of Environmental Protection.
Standard which establishes an end result or outcome which
is to be achieved but does not prescribe specific means for achieving
it.
A partnership, corporation, homeowners' association, condominium
association or any other similar association as distinguished from
an individual lot owner.
A rainfall-runoff relation used to estimate peak flow, expressed
by the following formula:
|
Q = CIA
|
|
Where:
| ||||
|
Q
|
=
|
peak runoff rate in cfs (cubic feet per second)
| ||
|
C
|
=
|
runoff coefficient
| ||
|
I
|
=
|
design rainfall intensity (inches/hour) lasting for a critical
time, Tc, or longer
| ||
|
Tc
|
=
|
time of concentration
| ||
|
A
|
=
|
drainage area in acres
| ||
The average interval of time, stated in years, within which
a given storm event will be equaled or exceeded once.
The watershed factor determined by comparing the maximum
rate of runoff from a subbasin to the contributing rate of runoff
to the watershed peak rate at specific points of interest.
A basin, usually enclosed by artificial dikes, that is used
to retard stormwater runoff by temporarily storing the runoff and
releasing it at a predetermined rate.
The average interval in years over which an event of a given
magnitude can be expected to recur.
That part of precipitation which flows over the land.
The surface components of any watershed which affect the
rate, amount and direction of stormwater runoff. These may include,
but are not limited to, vegetation, soils, slopes and man-made landscape
alterations.
Mineral or organic solid material that is being transported
or has been moved from its site of origin by air, water or ice and
has come to rest.
The process by which mineral or organic matter is accumulated
or deposited by moving water, wind or gravity.
An area excavated in earth, filled with loose stone or similar
material, and into which surface water is directed for infiltration
into the ground.
A subsurface concrete tank surrounded by stone, into which
surface water is directed for infiltration into the ground.
A surface such as stone, rock or other materials which permits
some vertical transmission of water.
A method of runoff computation developed by the Coil Conservation
Service (now NRCS), and found in its publication "Urban Hydrology
for Small Watersheds," Technical Release No. 55, January 1975, revised
1986.
See "detention pond" and "retention pond."
The average interval in years over which a storm event of
a given precipitation volume can be expected to occur.
A sewer that carries intercepted surface runoff, street water
and other drainage but excludes domestic sewage and industrial waste.
That portion of precipitation which runs over the land.
Natural or man-made structures that collect and transport
stormwater through or from a drainage area to the point of final outlet,
including, but not limited to, any of the following: conduits and
appurtenant features, canals, channels, ditches, streams, culverts,
streets and pumping stations.
The plan for managing stormwater runoff adopted by Allegheny
County and Westmoreland County as required by the Storm Water Management
Act.
Basins, pipes, swales, terraces, etc., designed and installed
to collect, transport, detain and/or retain stormwater.
The division or redivision of a lot, tract or parcel of land
by any means into two or more lots, tracts, parcels or other divisions
of land, including changes in existing lot lines for the purpose,
whether immediate or future, of lease, partition by the court for
distribution to heirs or devisees, transfer of ownership or building
or lot development; provided, however, that the subdivision by lease
of land for agricultural purposes into parcels of more than 10 acres,
not involving any new street or easement of access or any residential
dwelling, shall be exempted.
A low-lying stretch of land which gathers or carries surface
water runoff.
The time, in hours, surface stormwater runoff takes to travel
from the hydraulically most distant point in the drainage basin to
the point under design consideration. This time is the combined total
of overland flow time and flow time in pipes or channels, if any.
Any channel for conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
The entire region or area drained by a river or other body
of water, whether natural or artificial. A "designated watershed"
is an area delineated by the Pennsylvania DEP and approved by the
Environmental Quality Board, for which counties are required to develop
watershed stormwater management plans.
The plan for managing stormwater runoff throughout a designated
watershed adopted by Allegheny County and Westmoreland County as required
by the Pennsylvania Storm Water Management Act.
