A.
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 212-14:
B.
SWM site plans approved by the municipality, in accordance with § 212-25, shall be on site throughout the duration of the regulated activity.
C.
These standards apply to the landowner and any person engaged in
regulated activities.
D.
For all regulated earth disturbance activities, erosion and sediment
control BMPs shall be designed, implemented, operated, and maintained
during the regulated earth disturbance activities (e.g., during construction)
to meet the purposes and requirements of this chapter and to meet
all requirements under Title 25 of the Pennsylvania Code and the Clean
Streams Law. Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual), No. 363-2134-008, as amended and updated.[1]
E.
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; except that the volume controls in § 212-15 and the peak rate controls of § 212-16 do not need to be retrofitted to existing impervious areas that are not being altered by the proposed regulated activity.
F.
Stormwater flows onto adjacent or downstream property shall not be
created, increased, decreased, relocated, impeded, or otherwise altered
without written notification of the affected property owner(s). Notification
shall include a description of the proposed development and the stormwater
flows that are being created, increased, decreased, relocated, impeded,
or otherwise altered. Adjacent property shall, at a minimum, include
any property having a shared boundary with the subject property of
the SWM site plan; however, if, in the judgement of the designated
plan reviewer, additional properties are being affected, additional
notifications may be required. Proof of notification (signed postal
receipt, for example) shall be included as part of the SWM plan submission
to the municipality. Such stormwater flows shall be subject to the
requirements of this chapter.
G.
All regulated activities shall include such measures as necessary
to:
(1)
Protect health, safety, and property.
(2)
Meet the water quality goals of this chapter by implementing measures
to:
(a)
Minimize disturbance to floodplains, wetlands, and wooded areas.
(b)
Maintain or extend riparian buffers.
(c)
Avoid erosive flow conditions in natural flow pathways.
(d)
Minimize thermal impacts to waters of this commonwealth.
(e)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible.
(3)
Incorporate methods described in the Pennsylvania Stormwater Best
Management Practices Manual (BMP Manual).[2] If methods other than green infrastructure and LID methods
are proposed to achieve the volume and rate controls required under
this chapter, the SWM site plan must include a detailed justification,
acceptable to the designated plan reviewer, demonstrating that the
use of LID and green infrastructure is not practicable.
H.
Infiltration BMPs should be dispersed throughout the project site
at strategic locations, 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.
Normally dry, open-top, storage facilities should completely drain
both the volume control and rate control capacities over a period
of time not less than 24 and not more than 72 hours from the end of
the design storm.
J.
The design storm precipitation depths to be used in the analysis
of peak rates of discharge shall be as obtained in PennDOT's
Drainage Manual, Publication 584, Appendix 7A; or obtained from the
latest version of the Precipitation-Frequency Atlas of the United
States, National Oceanic and Atmospheric Administration (NOAA), National
Weather Service, Hydrometeorological Design Studies Center, Silver
Spring, Maryland. NOAA's Atlas 14[3] can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
K.
For all regulated activities, SWM BMPs shall be designed, implemented,
operated, and maintained to meet the purposes and requirements of
this chapter and to meet all requirements under Title 25 of the Pennsylvania
Code, the Clean Streams Law, and the Storm Water Management Act.
M.
The municipality may, after consultation with the DEP, approve measures
for meeting the state water quality requirements other than those
in this chapter, provided that they meet the minimum requirements
of, and do not conflict with, state law, including, but not limited
to, the Clean Streams Law.
B.
Earth disturbances between 0.25 acre (10,890 square feet) and one acre of earth disturbance must submit an SWM site plan to the municipality which shall consist of the following items and related supportive material needed to determine compliance with §§ 212-15 through 212-17. The applicant can use the protocols in the small project stormwater management site plan if the municipality has adopted Appendix C.[1]
(1)
General description of proposed stormwater management techniques,
including construction specifications of the materials to be used
for stormwater management facilities.
(2)
An erosion and sediment control plan, including all reviews and letters
of adequacy from the Conservation District, where appropriate.
(3)
Limits of earth disturbance, including the type and amount of impervious
area that is proposed; proposed structures, roads, paved areas, and
buildings; and a statement, signed by the applicant, acknowledging
that any revision to the approved drainage plan must be approved by
the municipality and that a revised erosion and sediment control plan
must be submitted to the municipality or Conservation District for
approval.
(4)
All stormwater management facilities must be located on a plan and
described in detail; and all calculations, assumptions, and criteria
used in the design of the stormwater management facilities must be
shown.
[1]
Editor's Note: Appendix C is included as an attachment to
this chapter.
C.
Agricultural activity is exempt from the SWM site plan preparation
requirements of this chapter, provided the activities are performed
according to the requirements of 25 Pa. Code, Chapter 102.
D.
Forest management and timber operations are exempt from the SWM site
plan preparation requirements of this chapter, provided the activities
are performed according to the requirements of 25 Pa. Code, Chapter
102.
E.
Roadway resurfacing and maintenance projects, which do not increase
impervious area, and underground infrastructure projects are exempt
from the provisions of this chapter, provided the activities meet
the requirements of all other municipal, state and federal requirements.
G.
The municipality may deny or revoke any exemption pursuant to this
section at any time for any project that the municipality believes
may pose a threat to public health and safety or the environment.
H.
Voluntary green stormwater infrastructure (GSI) retrofit projects
that are solely intended to better manage runoff from existing development
and are not part of new development or redevelopment are exempt from
the stormwater management provisions of this chapter. This does not
exempt such projects from any other municipal, state, or federal regulation.
The green infrastructure and low-impact development practices
provided in the BMP Manual[1] shall be utilized for all regulated activities wherever
possible. Water volume controls shall be implemented using the Design
Storm Method in Subsection A or the Simplified Method in Subsection
B below, or alternative design criteria as allowed by 25 Pa. Code,
Chapter 102.
A.
The Design Storm Method (CG-1 in the BMP Manual)[2] is applicable as a method to any size of regulated activity.
This method requires detailed modeling based on site conditions. The
following shall be incorporated into the CG-1 Method:
(1)
Do not increase the post-development total runoff volume for all
storms equal to or less than the two-year, twenty-four-hour duration
precipitation.
(2)
At least the first one inch of runoff from the net increase in 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.
If the developer provides justification that the listed removal options
are not feasible, and the designated plan reviewer agrees, runoff
shall be detained in a facility designed for a twenty-four- to seventy-two-hour
dewatering time in an area with a dedicated stormwater system (not
contributory to a combined sewer system) and shall be detained in
a facility designed for a seventy-two-hour dewatering time in an area
contributory to a combined sewer system before discharge to local
stormwater systems or the environment.
B.
The Simplified Method (CG-2 in the BMP Manual)[3] 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 the net increase in impervious surfaces.
(2)
At least the first one inch of runoff from the net increase in 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.
If the developer provides justification that the listed removal options
are not feasible, and the designated plan reviewer agrees, runoff
shall be detained in a facility designed for a twenty-four-hour dewatering
time in an area with a dedicated stormwater system (not contributory
to a combined sewer system) and shall be detained in a facility designed
for a seventy-two-hour dewatering time in an area contributory to
a combined sewer system before discharge to local stormwater systems
or the environment.
(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.
A.
For areas not covered by a release rate map from an approved Act
167 Stormwater Management Plan: Post-development discharge rates shall
not exceed the predevelopment discharge rates for the one-, two-,
five-, ten-, twenty-five-, fifty-, and 100-year, twenty-four-hour
storm events. This is equivalent to a 100% release rate area when
compared to those rates shown in the maps contained in Appendix A
(new and existing release rate management districts).[1] This predevelopment to post-development control is not
to be misconstrued as the same as the "conditional direct discharge"
areas on the Release Rate Maps. If it is shown that the peak rates
of discharge indicated by the post-development 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 100-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. Peak
flows should be computed using the methods included in the chapter
titled "Stormwater Calculations and Methodology" of the PADEP Stormwater
Management BMP Manual.
[1]
Editor's Note: Appendix A is included as an attachment to
this chapter.
B.
For areas covered by a release rate map from the approved Monongahela
Act 167 Stormwater Management Plan: For the one-, two-, five-, ten-,
twenty-five-, fifty-, and 100-year, twenty-four-hour storm events,
the post-development peak discharge rates will follow the applicable
approved release rate maps. These maps are contained in Appendix A
— Monongahela River Stormwater Management Plan Assigned Release
Rate Percentages.[2] For any areas not shown on the release rate maps, the
post-development discharge rates shall not exceed the predevelopment
discharge rates for the specified design events. Peak flows should
be computed using the methods included in Chapter 8 of the PADEP Stormwater
Management BMP Manual.
[2]
Editor's Note: Appendix A is included as an attachment to
this chapter.
A.
In order to protect and improve water quality, a riparian buffer
easement shall be created and recorded as part of any subdivision
or land development that encompasses a riparian buffer. The intent
of this chapter in establishing a riparian buffer is to protect and
improve stream water quality. The riparian buffer is intended to slow
overland flow to the stream through the presence of native grasses,
trees and shrubs, allowing infiltration/groundwater recharge; causing
deposition of sediment, nutrients, pesticides, and other pollutants
in the buffer rather than in the stream; and reducing erosion by providing
stream bank stabilization. The trees provide shade for streams, keeping
waters cooler and reducing evaporation.
B.
Except as required by 25 Pa. Code, Chapter 102, the riparian buffer easement shall be required for all streams (as defined in Article II) with a contributing watershed area of greater than 10 acres. The riparian buffer easement shall be measured to be a minimum of 35 feet from the top of the stream bank (on each side).
C.
Minimum management requirements for riparian buffers.
(1)
No use or construction within the riparian buffer shall be permitted that is inconsistent with the intent of the riparian buffer as described in § 212-17A.
(2)
Existing native vegetation shall be protected and maintained within
the riparian buffer easement.
(3)
Whenever practicable, invasive vegetation shall be actively removed
and the riparian buffer easement shall be planted with native trees,
shrubs and other vegetation to create a diverse, native plant community
appropriate to the intended ecological context of the site.
D.
The riparian buffer easement shall be enforceable by the municipality
and shall be recorded in the appropriate County Recorder of Deeds'
office, so that it shall run with the land and shall limit the use
of the property located therein. The easement shall allow for continued
private ownership and shall count toward the minimum lot area required
by zoning, unless otherwise specified in the municipal Zoning Ordinance.
E.
Any permitted use within the riparian buffer easement shall be conducted
in a manner that will maintain the extent of the existing 100-year
floodplain, improve or maintain the stream stability, and preserve
and protect the ecological function of the floodplain.
F.
Stormwater drainage pipes shall be permitted within the riparian
buffer easement, but they shall cross the easement in the shortest
practical distance. Other structural stormwater management facilities
are not permitted within the riparian buffer easement.
G.
The following conditions shall apply when public and/or private recreation
trails are permitted by the municipality within riparian buffers:
H.
Septic drainfields and sewage disposal systems shall not be permitted
within the riparian buffer easement and shall comply with setback
requirements established under 25 Pa. Code, Chapter 73.
I.
Underground utilities shall be permitted within the riparian buffer
easement; however, work shall be performed to minimize disturbance
area and removal of trees. Restoration within the riparian buffer
easement shall be with native species of trees, grasses, and other
plantings. One tree shall be planted for each tree removed, and the
restoration shall be designed by a registered professional with the
requisite experience. Aboveground utilities shall only be permitted
to cross the easement perpendicular to the easement or in the shortest
practical distance. Existing utilities may remain and be maintained
as required.
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 shall 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 that
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)
In developing a stormwater management plan for a particular site,
stormwater controls 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.
Infiltration systems.
(1)
Infiltration systems shall be sized and designed based upon local
soil and groundwater conditions.
(2)
Infiltration systems greater than three feet deep 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. This prohibition does not
extend to roof areas which are demonstrated to be suitably protected
from the effects of the commercial/industrial activities.
(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.
Flow attenuation facilities.
(1)
If flow attenuation facilities are employed to assist in the control
of peak rates of discharge, their effects must be quantified using
the NRCS Technical Release (TR) 55, Urban Hydrology for Small Watersheds,
or other approved method. The effects of the flow attenuation facilities
on travel time should be reflected in the calculations.
(2)
Flow attenuation facilities such as swales and natural depressions
should be properly graded to ensure positive drainage and avoid prolonged
ponding of water.
(3)
Swales shall be properly vegetatively stabilized or otherwise lined
to prevent erosion.
(4)
Swales shall be designed according to the recommendations contained
in the Commonwealth of Pennsylvania Erosion and Sediment Pollution
Control Program Manual.
D.
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 in existence
prior to development for the two-, ten-, twenty-five- and 100-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 the post-development
100-year-storm runoff without damaging (i.e., impairing the continued
function of) the facilities. Should any stormwater management facilities
qualify as a dam under PADER Chapter 105, the facility shall be designed
in accordance with those regulations and meet the regulations concerning
dam safety.
(3)
Shared-storage facilities which provide detention of runoff for more
than one development site within a single watershed are encouraged
wherever feasible and provided that such facilities 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 recreational/open
space uses, are encouraged wherever feasible, subject to the approval
of the Borough and Pennsylvania Department of Environmental Resources'
Chapter 105 regulations.
(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 hazards.
(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)
The facility shall be located to facilitate maintenance, considering
the frequency and type of equipment that will be required.
(h)
Storage facilities should completely drain both the volume control
and rate control capacities over a period of time not less than 24
and not more than 72 hours from the end of the design storm.
E.
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 stormwater collection/conveyance/control
system or natural watercourse in accordance with the approved stormwater
management plan for the development site.
(c)
Collection/conveyance facilities should 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 drainage
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 sewer are proposed to be utilized, they shall comply
with the following criteria:
(a)
Where practical, they shall be 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, they shall be 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.
(c)
They shall be designed with cradle when traversing fill areas
of indeterminate stability; with anchors when the gradient exceeds
20%; and with encasement or special backfill requirements when traversing
under a paved area.
(d)
They shall be 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 municipality and/or applicable
PennDOT Specifications, Form 408.
(f)
Storm inlets and structures shall be designed to be adequate,
safe, self-cleaning and unobtrusive and consistent with municipal
standards.
(g)
Appropriate grates shall be designed for all catch basins, stormwater
inlets and other entrance appurtenances.
(h)
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
castings of structures located in roads or parking areas shall be
machined or installed to preclude rattling.
(i)
Where the 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.
(j)
Storm sewer outfalls shall be equipped with energy-dissipation
devices to prevent erosion and to conform with applicable requirements
of the Pennsylvania DEP for stream encroachments (Chapter 105 of the
Pennsylvania DEP Rules and Regulations).
A.
An erosion/sedimentation plan shall be prepared for each development
site in accordance with the Pennsylvania Erosion/Sedimentation Regulations
(25 Pa. Code, Chapter 102) and the standards and guidelines of the
Allegheny County Conservation District.
B.
Proposed erosion/sedimentation measures shall be submitted with the
stormwater management plan.
C.
No regulated earth disturbance activities within the Borough shall
commence until approval by the Borough of an erosion and sediment
control plan for construction activities.
D.
The Pennsylvania Department of Environmental Protection (PADEP) 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).
E.
In addition, under 25 Pa. Code, Chapter 92, a PADEP NPDES construction activities permit is required for any earth disturbance of one acre or more with a point-source discharge to surface waters or the Borough's storm sewer system, or five acres or more regardless of the planned runoff (hereinafter collectively referred to as "regulated earth disturbance activities"). This includes earth disturbance on any portion of, part of, or during any stage of a larger common plan of development.
F.
Copies of any necessary permit applications for regulated earth disturbance activities from the appropriate PADEP regional office or the Allegheny County Conservation District must be provided to the Borough. Copies of any permits will be required prior to the start of construction. The issuance of an NPDES construction permit [or permit coverage under the statewide general permit (PAG-2)] satisfies the requirements of Subsection C.
G.
A copy of the erosion and sediment control plan and any required
permits, as required by PADEP regulations, shall be available at the
project site at all times.
