[Ord. 432, 10/1/2008]
In order to protect the health, safety, and general welfare
of the residents of the municipality, as well as to protect, sustain,
and enhance the surface water and groundwater resources of the municipality,
drainage and stormwater management practices shall be utilized as
directed herein to achieve the following goals and objectives:
A.
Accommodate site development and redevelopment in a manner that protects
public safety and that is consistent with (or reestablishes) the natural
hydrologic characteristics of each watershed and sustains groundwater
recharge, stream base flows, stable stream channel (geomorphology)
conditions, the carrying capacity of streams and their floodplains,
groundwater and surface water quality, and aquatic living resources
and their habitats.
B.
Reduce and minimize the volume of stormwater generated.
C.
Protect natural infiltration and groundwater recharge rates in order
to sustain groundwater supplies and stream base flows.
D.
Maintain runoff characteristics of the site after completion of development
that are consistent with the carrying capacity and stable channel
conditions of the receiving streams.
E.
Protect water quality by removing and/or treating pollutants prior
to discharge to groundwaters and surface waters throughout the municipality
and to protect, restore, and maintain the chemical, physical, and
biological quality of groundwaters and surface waters.
F.
Protect in-stream channels and geomorphology conditions of the receiving
streams, protect their flood-carrying capacity and aquatic habitats,
and reduce in-stream erosion and sedimentation.
G.
Reduce flooding impacts and prevent a significant increase in surface
runoff rates and volumes, predevelopment to post-development, which
could worsen flooding downstream in the watershed, enlarge floodplains,
erode stream banks and create other flood-related health-welfare-property
losses; in general, to preserve and restore the natural flood-carrying
capacity of streams and their floodplains.
H.
Protect adjacent lands from adverse impacts of direct stormwater
discharges.
I.
Ensure effective long-term operation and maintenance of all permanent
stormwater management facilities.
J.
Maintain natural drainage patterns and encourage the use of natural
drainage systems.
K.
Treat and release stormwater as close to the source of runoff as
possible using a minimum of structures and maximizing reliance on
natural processes.
L.
Maintain the existing water balance in all watersheds, subwatersheds,
and streams in the municipality and protect and/or restore natural
hydrologic characteristics and habitats wherever possible throughout
the watershed systems.
M.
Address certain requirements of the Municipal Separate Storm Sewer
System (MS4) National Pollution Discharge Elimination System (NPDES)
Phase II Stormwater Regulations.
N.
Reduce the impacts of runoff from existing developed sites undergoing
redevelopment while encouraging development and redevelopment in urban
areas and areas designated for growth.
O.
Meet legal water quality requirements under state law, including
regulations at 25 Pa. Code, Chapter 93.4a, to protect and maintain
"existing uses" and maintain the level of water quality to support
those uses in all streams and to protect and maintain water quality
in special-protection streams.
P.
Prevent scour and erosion of stream banks and streambeds.
[Added by Ord. 497, 11/19/2018]
[Ord. 432, 10/1/2008]
1.
Primary Authority. The municipality is empowered to regulate these
activities by the authority of the Act of October 4, 1978, P.L. 864
(Act 167), 32 P.S. § 680.1 et seq., as amended, the Storm
Water Management Act, and the (appropriate municipal code).
[Ord. 432, 10/1/2008]
The standards contained herein shall apply to all regulated
activities within the municipality. In addition, all local, county
and state erosion and sedimentation control approvals must be in place
to proceed with any regulated activity.
A.
Activities regulated by this chapter include but are not limited
to the following:
(1)
Land development and redevelopment.
(2)
Subdivision.
(3)
Construction of new or additional impervious or semipervious
surfaces (driveways, parking lots, etc.).
(4)
Construction of new buildings or additions to existing buildings.
(5)
Diversion or piping of any natural or man-made stream channel.
(6)
Installation of stormwater management facilities or appurtenances
thereto.
(7)
Any earth disturbances or any activities that involve the alteration
or development of land or removal of trees and vegetation in a manner
that may affect postconstruction stormwater runoff.
B.
Redevelopments shall conform to the requirements contained in § 26-114, Subsection 3C, when more than a two-thousand-square-foot area of an existing facility is reconstructed, following the demolition or partial demolition of the existing facility. The area determination shall be made using the foot-print of the area being reconstructed, including all impervious surfaces proposed in the reconstructed area and the area of the parking lot required to support the reconstructed facility. The area of the parking lot required to support the reconstructed facility shall be determined using the requirements for parking in Chapter 27, Zoning.
[Ord. 432, 10/1/2008]
1.
The following activities are exempted from on-site stormwater runoff
control. An exemption shall apply only to the requirement for on-site
stormwater facilities and the preparation of a stormwater management
plan. All other stormwater management design elements, such as a storm
sewer system, road culverts, erosion and sedimentation control, and
runoff quality, shall be required.
A.
Regulated activities smaller than 800 square feet are exempt from
the requirements of this chapter to implement stormwater BMPs, unless
the activity is found to be a significant contributor to pollution
of the waters of this commonwealth.
[Amended by Ord. 497, 11/19/2018]
B.
Small Project Exemption. Activities having a disturbed area of less than 5,000 square feet are exempt from the peak rate control requirements of this chapter. These projects shall comply with the water quality volume standards contained in § 26-114, Subsection 3A, and the extended detention requirement contained in § 26-114, Subsection 3A. The "Small project Standardized SWM Guidance" document provided in Appendix F was prepared to assist applicants in meeting this requirement for individual lots only.[1] The reduced site plan requirements contained in the "Small
Project Standardized SWM Guidance" document shall apply.
[1]
Editor's Note: Appendix F is on file in the Township offices.
C.
Emergency Exemption. Emergency maintenance work performed for the
protection of public health, safety and welfare may be exempted from
the requirements in this chapter to obtain approval for a stormwater
management plan before commencement of the activity; however, a written
description of the scope and extent of any emergency work performed
shall be submitted to the municipality within two calendar days of
the commencement of the activity. If the municipality finds that the
work is not an emergency, then the work shall cease immediately and
may not resume until a written stormwater management plan is submitted
and approved.
D.
Maintenance Exemption. Any maintenance to an existing stormwater
management system made in accordance with plans and specifications
approved by the Municipal Engineer or municipality.
E.
Gardening: use of land for gardening for home consumption.
F.
Agricultural Activities: agriculture, when operated in accordance
with a conservation plan, nutrient management plan or erosion and
sedimentation control plan approved by the Allegheny County Conservation
District, including activities such as growing crops, rotating crops,
tilling of soil and grazing animals. Installation of new or expansion
of existing farmsteads, animal housing, waste storage and production
areas having impervious surfaces that result in a net increase in
impervious surface of less than 1,000 square feet are exempt from
the requirement to submit a written stormwater management plan.
G.
Forest Management: forest management operations which are consistent
with a sound forest management plan as filed with the Municipal Zoning
Officer and which follow the Pennsylvania Department of Environmental
Protection's management practices contained in its publication "Soil
Erosion and Sedimentation Control Guidelines for Forestry." Such operations
are required to have an erosion and sedimentation control plan.
2.
Waivers.
[Amended by Ord. 497, 11/19/2018]
A.
If the Township Board of Supervisors determines that any requirement under these regulations cannot be achieved for a particular regulated activity, the Township Board of Supervisors may, after an evaluation of alternatives, approve measures other than those in these regulations, subject to Subsection 2B below. The proposed area of disturbance shall be less than one acre. The request for a modification or waiver shall originate with the landowner, shall be in writing, and shall accompany the stormwater management site plan submitted to the Township. The request shall provide the facts on which the request is based, the provisions of the regulations involved, and the proposed modification. The Township shall review the request to determine if it meets the requirements of the regulations, including Subsection 2B below. If acceptable to the Township, the Township Board of Supervisors may grant the waiver or modification.
B.
Waivers or modifications of the requirements of these regulations may be approved by the Township Board of Supervisors if enforcement will exact undue hardship because of unique physical circumstances or conditions peculiar to the land in question, provided that the modifications will not be contrary or detrimental to the public interest and will achieve the intended outcome, and that the purpose of the regulations is preserved. Hardship must be due to such unique physical circumstances or conditions and not to circumstances or conditions generally created by the provisions of the stormwater management regulations. Cost or financial burden shall not be considered a hardship. Modifications shall not substantially or permanently impair the appropriate use or development of adjacent property. A request for modifications shall be in writing and accompany the stormwater management site plan submission, as directed in Subsection 2A above.
C.
No waiver or modification of any regulated stormwater activity involving
earth disturbance greater than or equal to one acre may be granted
by the Township Board of Supervisors.
D.
The Township shall keep a written record of all action on waiver
requests.
[Ord. 432, 10/1/2008]
1.
The management of stormwater on site, both during and upon completion of the disturbances associated with activities permitted under § 26-103, shall be accomplished in accordance with the standards and criteria of this chapter. The design of any temporary or permanent facilities and structures and the utilization of any natural drainage systems shall be in full compliance with this chapter.
2.
The intent of these design standards is to encourage environmentally
sound stormwater management practices that provide necessary drainage
facilities while protecting the hydrologic characteristics and water
quality of the site and watershed. Developments shall be required
to incorporate stormwater management controls. Stormwater management
design shall blend into the natural environment and be aesthetically
integrated into the site design.
3.
Applicants shall refer to the Pennsylvania Stormwater Best Management
Practices Manual, as amended, Pennsylvania Handbook of Best Management
Practices for Developing Areas (PACD, 1998), the 2000 Maryland Stormwater
Design Manual (MDE, 2000), or other appropriate references for guidance
in the design of stormwater management facilities most appropriate
to individual site conditions. Objectives for design are to reduce
the volume of stormwater generated, infiltrate runoff at its source
to the maximum extent possible, achieve water quality improvement
at the source or during conveyance, and provide for peak flow attenuation.
Applicants shall examine design alternatives by viewing them in a
series. In addition, applicants are strongly encouraged to use structural
and nonstructural stormwater management practices that reduce or eliminate
the need for detention basins.
4.
All SWM design work must be completed by a qualified design professional.
All designs proposing the use of an SWM retention or detention facility
with outlet structure(s) shall be completed by a professional engineer
licensed in the State of Pennsylvania.
5.
All development activity within a special flood hazard area designated by the Federal Emergency Management Agency (FEMA) shall comply with Chapter 27, Zoning, and this subsection. All development shall be designed to maintain the flood-carrying capacity of the floodway such that the base flood elevations are not increased, either upstream or downstream, unless an approval is received from PA DEP. The natural conveyance characteristics of the site and the receiving floodplain shall be incorporated into the stormwater management practices proposed for the site.
6.
The stormwater management system shall not create an adverse impact
on stormwater quantity or quality in either upstream or downstream
areas. Off-site areas which discharge to or across a site proposed
for development shall be addressed in the stormwater management plan
prepared for the development. No stormwater management plan shall
be approved until it is demonstrated that the runoff from the project
shall not adversely impact downstream areas.
7.
Wetlands shall not be used to meet the minimum design requirements
for stormwater management or stormwater runoff quality treatment,
except when used as part of a treatment train that incorporates a
portion of the outer zone (filter strip) of the wetland's riparian
buffer as a stormwater outfall.
8.
All proposed stormwater management systems shall be designed to prevent
the pollution of groundwater resources by stormwater, promote safety,
minimize health hazards, preserve natural features and provide infiltration
and groundwater recharge where appropriate. Neither submission of
a plan under the provisions herein nor compliance with the provisions
of these regulations shall relieve any person from responsibility
for damage to any person or property otherwise imposed by law.
9.
Where deemed necessary by the Municipal Engineer or as addressed
in an approved Act 167 stormwater management plan, the applicant shall
construct storm drains to handle on-site runoff; to the maximum extent
permitted under the Municipalities Planning Code and Act 167, or any
amendments thereto, provide on-site/off-site drainage easements; and
provide for the conveyance of off-site runoff to an acceptable outlet
in the same watershed.
10.
Where watercourses traverse a development site, drainage easements
shall be provided conforming to the line of such watercourses. The
terms of the easements shall prohibit excavation, the placing of fill
or structures, except as needed for roadways, driveways and walkways,
or any alterations that may adversely affect the flow of stormwater
within any portions of the easement, and require the establishment
and protection of riparian buffers.
11.
12.
Any regulated activity that may affect the stormwater flows toward
or onto a state or county highway right-of-way or facility shall be
designed, implemented, operated, and maintained in accordance with
the regulations of the Pennsylvania Department of Transportation (PennDOT)
or Allegheny County, as the case may be.
13.
At the time of application for a building permit for any approved
lot created by a subdivision and/or improved as a land development
project, issuance of the permit shall be conditioned upon adherence
to the terms of this chapter.
14.
Stormwater discharges to critical areas with sensitive resources
(e.g., special-protection waters, cold-water fisheries, recharge areas,
water supply reservoirs, etc.) may be subject to additional performance
criteria or may need to utilize or restrict certain stormwater management
practices.
15.
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 Pennsylvania Code Title 25 and the Clean Streams
Law. Various BMPs and their design standards are listed in the Erosion
and Sediment Pollution Control Program Manual (B & S Manual),
Commonwealth of Pennsylvania, Department of Environmental Protection,
No. 363-2134-008, as amended and updated.
16.
No regulated earth-disturbance activities within the municipality
shall commence until the requirements of this chapter are met.
17.
Postconstruction water quality protection shall be addressed as required
by the stormwater management requirements contained in this chapter.
19.
All best management practices (BMPs) used to meet the requirements
of this chapter shall conform to the state water quality requirements
and any more-stringent requirements as required by the municipality.
20.
Techniques described in Appendix B (Nonstructural Stormwater Management
Practices)[3] of this chapter are encouraged, because they reduce the
costs of complying with the requirements of this chapter and the state
water quality requirements.
[3]
Editor's Note: Appendix B is on file in the Township offices.
21.
In selecting the appropriate BMPs or combinations thereof, the applicant
shall consider the following:
A.
Total contributing area.
B.
Permeability and infiltration rate of the site soils.
C.
Slope and depth to bedrock.
D.
Seasonal high water table.
E.
Proximity to building foundations and wellheads.
F.
Erodibility of soils.
G.
Land availability and configuration of the topography.
H.
Peak discharge and required volume control.
I.
Stream bank erosion.
J.
Efficiency of the BMPs to mitigate potential water quality problems.
K.
The volume of runoff that will be effectively treated.
L.
The nature of the pollutant being removed.
M.
Maintenance requirements.
N.
Creation/protection of aquatic and wildlife habitats.
22.
Transference of runoff from one DEP-designated Act 167 watershed
to another shall be prohibited unless approved by the municipality.
23.
Any permit or authorization issued or approved based on false, misleading
or erroneous information provided by an applicant is void without
the necessity of any proceedings for revocation. Any work undertaken
or use established pursuant to such permit or other authorization
is unlawful. No action may be taken by a board, agency or employee
of the Township purporting to validate such a violation.
[Added by Ord. 497, 11/19/2018]
[Ord. 432, 10/1/2008]
Any ordinance or ordinance provision of the municipality inconsistent
with any of the provisions of this chapter is hereby repealed to the
extent of the inconsistency only; provided, however, that this repeal
shall in no manner be construed as a waiver, release or relinquishment
of the right to initiate, pursue or prosecute, as the case may be,
any proceeding at law or in equity pertaining to any act done which
would have constituted a violation of such prior ordinance or ordinance
provision. All of said ordinance or ordinance provisions shall remain
in full force and effect and are not repealed hereby as they pertain
to such acts and to the processing of such plans filed prior to the
effective date of this chapter, which are protected from the effect
of intervening ordinances by Section 508(4) of the Pennsylvania Municipalities
Planning Code.[1]
[1]
Editor's Note: See 53 P.S. § 10508(4).
[Ord. 432, 10/1/2008]
Should any section or provision of this chapter be declared
invalid by a court of competent jurisdiction, such determination of
invalidity shall not affect the validity of the remaining provisions
of this chapter.
[Ord. 432, 10/1/2008]
Permits and approvals issued pursuant to this chapter shall
not relieve the applicant of the responsibility to comply with or
to secure other required permits or approvals for activities regulated
by any other applicable code, rule, act, statute or ordinance. This
chapter shall not preclude the inclusion in such other permit of more-stringent
requirements concerning regulation of stormwater and erosion. Where
a conflict exists between a provision within this chapter and that
of the PA DEP Phase II NPDES regulations, as amended, or any other
ordinance of the municipality, the more-stringent requirements shall
govern.
[Ord. 432, 10/1/2008]
1.
All regulated earth-disturbance activities are subject to permit
requirements by the DEP under regulations at 25 Pa. Code, Chapter
102.
2.
Work within natural drainageways is subject to permit by the DEP
under 25 Pa. Code, Chapter 105.
3.
Any stormwater management facility that would be located in or adjacent
to surface waters of the commonwealth, including wetlands, is subject
to permit by the DEP under 25 Pa. Code, Chapter 105.
4.
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).
5.
Culverts, bridges, storm sewers or any other facilities which must
pass or convey flows from the tributary area and any facility which
may constitute a dam are subject to permit by the DEP under 25 Pa.
Code, Chapter 105.
[Ord. 432, 10/1/2008]
1.
No regulated earth-disturbance activities within the municipality
shall commence until the municipality receives a copy of any required
approvals from the Conservation District or DEP for an erosion and
sediment control plan.
2.
The 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).
3.
In addition, under 25 Pa. Code, Chapter 92, a DEP NPDES construction
activities permit is required for regulated earth-disturbance activities.
4.
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.
5.
A copy of the erosion and sediment control plan and any required
permits, as required by DEP regulations, shall be available at the
project site at all times.
6.
Additional erosion and sediment control design standards and criteria
are recommended to be applied where infiltration BMPs are proposed
and shall include the following:
A.
Areas proposed for infiltration BMPs shall be protected from sedimentation
and compaction during the construction phase to maintain maximum infiltration
capacity.
B.
Infiltration BMPs shall not be constructed nor receive runoff until
the entire contributory drainage area to the infiltration BMP has
achieved final stabilization.
[Ord. 432, 10/1/2008]
1.
No person in the municipality shall allow, or cause to allow, stormwater discharges into the municipality's separate storm sewer system and or waters of this commonwealth which are not composed entirely of stormwater, except as provided in Subsection 2 below, and except discharges allowed under a state or federal permit.
2.
The following discharges are authorized, unless they are determined
to be significant contributors to pollution to the waters of this
commonwealth:
A.
Discharges from fire-fighting activities.
B.
Potable water sources, including dechlorinated waterline and fire
hydrant flushings.
C.
Irrigation drainage.
D.
Routine external building washdown (which does not use detergents
or other compounds).
E.
Air-conditioning condensate.
F.
Water from individual residential car washing.
G.
Springwater from crawl space pumps.
H.
Uncontaminated water from foundations or from footing drains.
I.
Flows from riparian habitats and wetlands.
J.
Lawn watering.
K.
Pavement washwaters where spills or leaks of toxic or hazardous materials
have not occurred (unless all spill material has been removed) and
where detergents are not used.
L.
Dechlorinated swimming pool discharges.
M.
Uncontaminated groundwater.
3.
In the event that the municipality determines that any of the discharges identified in Subsection 2 of this section significantly contribute to pollution of waters of the commonwealth, or is so notified by DEP, the municipality or PA DEP will notify the responsible person to cease the discharge.
4.
Nothing in this section shall affect a discharger's responsibilities
under state law.
5.
Existing roof drain, underdrain and sump pump discharge should be
directed to lawn area or other pervious areas. If required by the
municipality, the discharge shall be directed to a stone sump or infiltration
BMP. If approved by the municipality, the discharge may also be directly
connected to the storm sewer system.
[Ord. 432, 10/1/2008]
1.
Right of Entry. Upon presentation of proper credentials, the municipality
may enter at reasonable times upon any property within the municipality
to inspect the condition of the stormwater structures and facilities
in regard to any aspect regulated by this chapter.
2.
Inspections. SWM BMPs should be inspected by the landowner/developer
(including the municipality for dedicated facilities) according to
the following list of frequencies:
3.
Enforcement.
A.
It shall be unlawful for a person to undertake any regulated activity
except as provided in an approved SWM site plan.
B.
It shall be unlawful to alter or remove any control structure required
by the SWM site plan.
C.
Inspections regarding compliance with the SWM site plan are a responsibility
of the municipality.
4.
Suspension and Revocation.
A.
Any approval for a regulated activity issued may be suspended or
revoked, in whole or in part, by the municipality for:
(1)
Noncompliance with or failure to implement any provision of
the approval.
(2)
A violation of any provision of this chapter or any other applicable
law, ordinance, rule or regulation relating to the regulated activity.
(3)
The creation of any condition or the commission of any act during
the regulated activity which constitutes or creates a hazard or nuisance,
pollution, or which endangers the life or property of others.
C.
An approval that has been revoked by the municipality cannot be reinstated.
The applicant may apply for a new approval under the provisions of
this chapter.
D.
Prior to revocation or suspension of a permit, if there is no immediate
danger to life, public health, or property, the municipality may notify
the landowner/developer to discuss the noncompliance.
5.
Penalties.
A.
Anyone violating the provisions of this chapter shall be guilty of
a summary offense and, upon conviction, shall be subject to a fine
of not more than $1,000 for each violation, recoverable with costs.
Each day that the violation continues shall be a separate offense,
and penalties shall be cumulative.
B.
In addition, the municipality may institute injunctive, mandamus
or any other appropriate action or proceeding at law or in equity
for the enforcement of this chapter. Any court of competent jurisdiction
shall have the right to issue restraining orders, temporary or permanent
injunctions, mandamus or other appropriate forms of remedy or relief.
6.
Appeals.
A.
Appeals to the Zoning Hearing Board. Any applicant or person aggrieved by any decision, notice or order issued under this chapter shall have the right to appeal to the Richland Township Zoning Hearing Board insofar as the same relates to development not involving subdivision and land development applications under Chapter 22, Subdivision and Land Development, or planned residential development applications under Chapter 27, Zoning, provided that a written application for an appeal is filed within 30 days as required by Section 914.1 of the Pennsylvania Municipalities Planning Code, 53 P.S. § 10914.1.
B.
Appeals to the Township Board of Supervisors. Any applicant or person aggrieved by a decision, notice or order issued under this chapter shall have the right to appeal to the Township Board of Supervisors insofar as the same relates to development involving subdivision and land development applications under Chapter 22, Subdivision and Land Development, or planned residential development applications under Chapter 27, Zoning, provided that a written application for an appeal is filed within 30 days as required by Section 914.1 of the Pennsylvania Municipalities Planning Code, 53 P.S. § 10914.1. The Board of Supervisors may hear and decide the appeal or may appoint a hearing tribunal or hearing officer to make a hearing record and/or to decide the appeal, at the option of the Board of Supervisors.
C.
Appeals to Court. Any applicant or person aggrieved by any decision of the Richland Township Zoning Hearing Board referenced in Subsection A above or the Township Board of Supervisors referenced in Subsection B above may appeal therefrom within 30 days after entry of the decision to the Court of Common Pleas of Allegheny County.
[Ord. 432, 10/1/2008]
For all regulated activities not eligible for exemptions pursuant to § 26-104 of this chapter, the applicant shall submit a stormwater management plan and report, prepared by a professional engineer licensed in the Commonwealth of Pennsylvania, which shall contain but not be limited to the following. Final copies of all plans, specifications and reports shall also be submitted to the municipality in Adobe PDF format.
A.
A suitable map of the watershed for any and all named streams within
which the project is proposed (a United States Geological Survey quadrangle
map is usually sufficient), with existing and proposed development
areas presented on the map.
B.
Suitable maps and drawings showing all existing natural and constructed
drainage facilities affecting the subject property.
C.
Hydrologic (watershed) and water feature boundaries, including all
areas flowing to the proposed project, existing streams (including
first-order and intermittent streams), springs, lakes, ponds, or other
bodies of water within the project area.
D.
Sufficient topographical information with elevations to verify the
location of all ridges, streams, etc. (two-foot contour intervals
within the project's boundaries and for proposed off-site improvements;
for slopes greater than 15%, five-foot contours are acceptable).
E.
Notes pertaining to and locations of existing standing water, areas
of heavy seepage, springs, wetlands, streams, and hydrologically sensitive
areas. The Chapter 93 Water Quality Standards use designation must
also be provided on the plan.
F.
General type of soils with hydrologic soil group noted, estimated
permeabilities in inches per hour, and location and results of all
soil tests and borings (if needed).
G.
One-hundred-year flood elevations for any special flood hazard areas
on or within 100 feet of the property. For redevelopment sites, also
show the ten- and twenty-five-year flood elevations for any special
flood hazard areas on or within 100 feet of the property. The source
of these elevations shall also be shown on the plans.
H.
A description of current and proposed ground cover and land use.
The total area and percent impervious cover shall be noted.
I.
A wetland delineation report for the project site, with a location
map identifying wetland areas if any were found.
J.
A plan of the proposed stormwater drainage system attributable to
the activity proposed, including runoff calculations, stormwater management
practices to be applied, both during and after development, and the
expected project time schedule.
K.
The design computations for all proposed stormwater drainage systems,
including storm drainpipes, inlets, runoff control measures and culverts,
drainage channels, and other features, facilities, and stormwater
management practices.
L.
A grading plan, including all areas of disturbance of the subject
activity. The total area of disturbance shall be noted in square feet
and acres. Topographic contours showing the existing and proposed
final contours shall be at an interval of two feet; in areas having
slope of greater than 15%, a five-foot contour interval may be used.
M.
A plan of the erosion and sedimentation procedures to be utilized
as required by local ordinance and state regulations.
N.
The effect of the project (in terms of runoff volumes and peak flows)
on adjacent properties and on any other stormwater collection system
that may receive runoff from the project site and specifics of how
erosion and flooding impacts to adjacent properties will be avoided
or otherwise mitigated.
P.
The name of the development, the name and address of the property
owner and applicant, and the name and address of the individual or
firm preparing the plan.
Q.
A North arrow, submission date, graphic scale and revision dates,
as applicable, shall be included on each page of all plans submitted.
R.
Complete delineation of the flow paths used for calculating the time
of concentration for the predeveloped and post-developed conditions.
S.
Construction details sufficient to completely express the intended
stormwater design components consistent with this chapter.
T.
A listing of all permits required for the site, providing the status
of the permit application(s) and approval(s).
U.
The following signature block shall appear on the stormwater site
plan:
[Added by Ord. 497, 11/19/2018]
|
"(Township Engineer), on this date (signature date), has reviewed and hereby certifies that the stormwater site plan meets all design standards and criteria of Chapter 26 of the Richland Township Code, except where waivers have been granted on the plan. The review is based on a survey and plan prepared by others and assumes that all information is correct and valid as submitted."
|
V.
The approved stormwater site plans must be on site throughout construction.
[Added by Ord. 497, 11/19/2018]
[Ord. 432, 10/1/2008]
1.
Design Goals. Applicants shall adhere to a holistic design process incorporating the goals listed below. The objective is to achieve post-development hydrologic conditions that are consistent with the predevelopment ground cover assumption for new development (refer to § 26-115B) and improve the runoff conditions for redevelopment (refer to § 26-114, Subsection 3C). The design goals are:
A.
Minimize the volume of runoff that must be collected, conveyed, treated and released by stormwater management facilities. NOTE: Minimization of runoff generated by a proposed site is directly related to the various land use and design standards for site improvements required under Chapter 27, Zoning, and Chapter 22, Subdivision and Land Development. The effect that these requirements have on generating stormwater should be taken into consideration. Site design should implement runoff reduction techniques such as those described in Appendix B.[1]
[1]
Editor's Note: Appendix B is on file in the Township offices.
B.
Maintain the natural infiltration process and rate and infiltrate
runoff at its source when appropriate.
C.
Remove and/or treat pollutants at the source or during conveyance.
D.
Provide for peak flow attenuation, as needed.
E.
Attenuate runoff to protect the in-stream channel of the receiving
stream.
2.
General Principles. The following general principles apply to all applicable activities pursuant to § 26-103:
A.
Incorporate conservation design practices to minimize the amount
of stormwater generated on a site, encourage the disconnection of
impervious land cover, and maximize the use of pervious areas for
stormwater treatment and on-site rainfall infiltration.
B.
Infiltration of surface water runoff at its source is to be a mechanism for stormwater management based on hydrologic soil group (or infiltration testing). Infiltration practices include but are not limited to those referenced in § 26-116, Subsection 2B(1), and as outlined in the publications listed in § 26-116. Infiltration practices shall adhere to the following criteria:
(1)
In choosing methods of infiltration, preference shall be given
to a combination of surface and subsurface infiltration methods.
(2)
Applicants shall first consider minimum disturbance/minimum
maintenance techniques combined with site grading that distributes
runoff to reduce concentration. Next, applicants shall consider depression
areas combined with subsurface infiltration practices, followed by
other subsurface measures, including but not limited to porous paving
and perforated pipe storage.
(3)
The use of multiple infiltration features and facilities that
provide for the following is encouraged:
(a)
Discourage concentration of flows;
(b)
Encourage disconnection of flows;
(c)
Infiltrate as close to the source of runoff as possible; and
(d)
Reduce visual impact.
|
NOTE: An example of promoting the concepts listed in § 26-114, Subsection 2B(3), is choosing a design method to address runoff collected from rooftops and conveyed to the surface by downspouts. The disconnection of flows can be accomplished by directing the downspouts over pervious surfaces rather than impervious surfaces. This can be taken one step further by directing the downspouts into infiltration facilities close to the source of the runoff. This promotes the idea of infiltrating as close to the source of runoff as possible and discourages the concentration of flows.
|
(4)
Where high water tables, subsurface contamination, slope stability concerns, or other site constraints preclude achieving the required infiltration volume, additional conservation design practices and alternative stormwater management practices should be implemented to reduce, to the maximum extent practicable, the total volume of stormwater released to streams. The applicant shall follow the stormwater runoff hierarchy of § 26-116, Subsection 1A.
(5)
Infiltration areas should be designed to maintain any broad
and even infiltration pattern which existed prior to development.
Such facilities should use the natural topography and vegetation in
order to blend in with the site. Infiltration designs which do not
provide this may be used if the applicant demonstrates to the municipality's
satisfaction that alternative approaches would be more effective,
more harmonious with their existing environment and as easily maintained.
(6)
Aboveground stormwater infiltration facilities should be as
shallow as possible while still achieving the requirements of this
chapter.
C.
Water quality improvement shall be achieved in conjunction with or
as part of infiltration practices. Water quality improvements shall
also be provided for drainage areas not otherwise addressed by infiltration
practices either at the source of runoff and/or during conveyance
away from the source of runoff.
D.
To reduce the need for large retention and/or detention basins designed
to satisfy the peak flow attenuation and extended detention requirements,
other innovative stormwater management practices located close to
the source of runoff generation shall be considered, including a combination
of practices (e.g., rooftop storage, open vegetated channels, bioretention,
pervious pavement systems and infiltration trenches).
E.
When designing stormwater management facilities to satisfy the peak flow attenuation and extended detention requirements [refer to § 26-114, Subsection 3B(2)], the effect of structural and nonstructural stormwater management practices implemented as part of the overall site design may be taken into consideration when calculating total storage volume and release rates.
F.
Site hydrology and natural infiltration patterns shall guide site
design, construction and vegetation decisions. All channels, drainageways,
swales, natural streams and other surface water concentrations shall
be considered and, where possible, incorporated into design decisions.
G.
Incorporate methods described in the Pennsylvania Stormwater BMP
Manual, as amended and updated. If methods other than green infrastructure
and low-impact development (LID) methods are proposed to achieve the
volume and rate controls required under these regulations, the stormwater
site plan must include a detailed justification, acceptable to the
Township Engineer, demonstrating that the use of LID and green infrastructure
is not practicable.
[Added by Ord. 497, 11/19/2018]
3.
Minimum Performance Criteria.
A.
The following minimum performance standards shall apply to all applicable activities, whether they are new development or redevelopment, pursuant to § 26-103A:
(1)
Water quality treatment of stormwater runoff shall be provided
for all discharges prior to release to a receiving water body. If
a stormwater management practice does not provide water quality treatment,
then water quality best management practices shall be utilized prior
to the runoff entering the stormwater management practice.
(2)
Water quality management shall be provided through the use of
structural and/or nonstructural stormwater management practices. Water
quality stormwater management practices shall be designed to reduce
or eliminate solids, sediment, nutrients, and other potential pollutants
from the site. It is presumed that a stormwater management practice
complies with this requirement if it is:
(3)
Stormwater discharges from land uses or activities with higher potential for pollutant loadings (hotspots) may require the use of specific structural stormwater management practices and pollution prevention practices. In addition, stormwater from a hotspot land use shall be provided with proper pretreatment prior to infiltration. For the purpose of this chapter, the sites/facilities listed in § 26-114, Subsection 3A(4), below are considered hotspots.
(4)
Certain industrial sites may be required to prepare and implement
a stormwater pollution prevention plan and file notice of intent as
required under the provision of the EPA Industrial Stormwater NPDES
Permit Requirements. Other industrial sites storing significant quantities
of chemicals/wastes should also prepare a prevention plan. Sites that
are required by the EPA to prepare a plan include but are not limited
to:
(5)
Conveyance structures/channels shall be designed and adequately
sized so as to protect the properties receiving runoff from impacts
of flooding and erosion. Where necessary, and to the maximum extent
permitted under the Municipalities Planning Code and Act 167, or any
amendments thereto, drainage easements from adjoining properties shall
be obtained to ensure the drainageway and the property and shall also
establish the operation and maintenance requirements for the drainageway.
(6)
All stormwater management practices shall have an operation and maintenance plan pursuant to § 26-122 of this chapter and, if to be privately owned, an enforceable operation and maintenance agreement per § 26-123 of this chapter to ensure the system functions as designed and to provide remedies for system failure.
(7)
Stormwater runoff generated from development and discharged
directly into a jurisdictional wetland or waters of the United States
and their adjacent wetlands shall be treated by an approved stormwater
management practice prior to release into a natural wetlands and shall
not be used to meet the minimum design requirements for stormwater
management or stormwater runoff quality treatment, except when used
as part of a treatment train that incorporates a portion of the outer
zone (filter strip) of the wetland's riparian buffer as a stormwater
outfall. In such instances, the discharge velocity from the terminal
end of a pipe or associated energy-dissipation practice shall not
exceed two feet per second for the two-year-frequency storm event.
Where such a management strategy is used, all feasible methods shall
be used to convert concentrated flow to uniform, shallow sheet flow
before entering the outer zone of the wetland's riparian buffer. In
addition, it shall be demonstrated that such an approach will not
cause erosion.
B.
The following minimum performance standards shall apply to all applicable new development activities, pursuant to § 26-103A:
(1)
Water quality improvement shall be achieved in conjunction with or as part of infiltration practices (if used). Water quality improvements shall also be provided for drainage areas not otherwise addressed by infiltration practices either at the source of runoff and/or during conveyance away from the source of runoff. Stormwater quality management practices shall be designed to capture and treat stormwater runoff generated by the one-inch rainfall event. Refer to § 26-116, Subsection 2A(4), for water quality volume design standards and assumptions. Stormwater quality management practice selection, design and implementation shall be based upon appropriate reference materials, as provided in § 26-105, Subsection 3.
(2)
The post-development peak rate discharge rate shall not exceed the predevelopment peak discharge rate multiplied by the subbasin release rate percentage (where determined in Act 167 watersheds) by the one-, two-, five-, ten-, twenty-five-, fifty- and 100-year, twenty-four-hour storm events pursuant to the predevelopment cover assumption described in § 26-115B. Refer to Appendix A for release rate percentages information.[2]
[Amended by Ord. 497, 11/19/2018]
[2]
Editor's Note: Appendix A is on file in the Township offices.
(3)
Facilities capable of attenuating rainfall runoff shall be provided
and be designed to attenuate the runoff volume from the one-year,
twenty-four-hour storm event for at least 24 hours.
(4)
Stormwater shall be infiltrated and/or discharged within the
same drainage area of the stream receiving the runoff from the development
site prior to development.
(5)
Structural and nonstructural stormwater management practices
that make the best possible use of infiltration on site shall be considered
in all site designs, when appropriate.
C.
The following minimum performance standards shall apply to all applicable redevelopment activities, pursuant to § 26-103B. The intent of § 26-114, Subsection 3C, is to accommodate redevelopment that is designed to provide improved stormwater management while recognizing that redevelopment sites have inherent physical constraints which may make the application of the new development stormwater design parameters difficult to achieve.
(1)
One of the following minimum performance standards shall be
accomplished. Selection of the performance standard shall be whichever
is most appropriate for the given site conditions:
(a)
Reduce the total impervious cover on the site (e.g., by using
pervious pavement, replacement of pavement with pervious planting
areas or green roof systems) by at least 25%, based on a comparison
of existing impervious cover to proposed impervious cover;
(b)
Provide facilities designed to attenuate the runoff volume from
the one-year, twenty-four-hour post-development storm event for at
least 24 hours; or
(c)
Provide facilities to ensure that the post-development peak
discharge rate shall not exceed the predevelopment peak discharge
rate multiplied by the subbasin release rate percentage (where determined
in Act 167 watersheds) for the two- and ten-year, twenty-four-hour
storm events. A predevelopment cover CN of 71 shall be assumed.
(2)
In addition to the minimum performance standards for redevelopment areas in § 26-114, Subsection 3C, above, water quality improvements shall be provided for drainage areas not otherwise addressed by infiltration practices either at the source of runoff and/or during conveyance away from the source of runoff. Stormwater quality management facilities shall be designed to capture and treat 0.25 inch of runoff from all pavement areas (i.e., parking lots, pavements and noncovered sidewalks). Roof area may be excluded from this calculation.
D.
The following minimum volume control performance standards shall apply to all applicable new development activities pursuant to § 26-103A.
[Added by Ord. 497, 11/19/2018]
(1)
The green infrastructure and low-impact development practices provided in the Pennsylvania Stormwater BMP Manual, as amended and updated (BMP Manual) shall be utilized for all regulated activities wherever possible. Water volume controls shall be implemented using the Design Storm Method in Subsection 3D(1)(a) or the Simplified Method in Subsection 3D(1)(b) below, or alternative design criteria as allowed by Pennsylvania Code Title 25, Chapter 102.
(a)
The Design Storm Method (CG-1 in the BMP Manual) 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 Township Engineer
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) 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 Township Engineer
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.
4)
This method is exempt from the requirements for peak rate control
of the one-, two-, five-, ten-, twenty-five-, fifty-, and 100-year,
twenty-four-hour storm events.
[Ord. 432, 10/1/2008]
In addition to the infiltration and water quality requirements
of this chapter, peak flow from those activities resulting in increases
in impervious surface and/or regrading and compaction shall be attenuated
consistent with the following stormwater calculation methods:
A.
The following design storms shall be used for analysis of the predevelopment
and post-development conditions. These values are applicable to the
Soil Cover Complex Method:
[Amended by Ord. 497, 11/19/2018]
|
Return Period
(years)
|
24-Hour Storm
(inches)
|
|---|---|
|
1
|
2.01
|
|
2
|
2.40
|
|
5
|
2.94
|
|
10
|
3.37
|
|
25
|
3.99
|
|
50
|
4.50
|
|
100
|
5.03
|
|
Note: The precipitation values above are derived from the precipitation
frequency estimates developed by NOAA Atlas 14 and can be accessed
from the NOAA website.
|
B.
The following assumptions shall be used for runoff calculations:
(1)
For new development sites, the ground cover used as the predevelopment
assumption for runoff calculations shall be as follows:
(a)
Wooded sites shall use a ground cover of woodland in good condition.
Portions of a site having more than one viable tree of a DBH [diameter
at breast height (DBH) is the diameter of the tree stem 4 1/2
feet above the ground] of six inches or greater per 1,500 square feet
shall be considered wooded where such trees existed within 10 years
of application. If there is evidence of logging within the ten-year
period, logged area shall be considered as woodland in good condition.
NOTE: The intent of this Subsection B(1)(a) is to recognize woodland
conditions and not inadvertently encourage tree harvesting.
(b)
Agricultural sites shall use a ground cover of pasture in good
condition.
(c)
All other portions of a site shall use a ground cover of meadow
in good condition.
(d)
All watershed area(s) contributing to the point of interest,
including off-site area, shall be considered.
(2)
The runoff curve numbers listed in the table below shall be used in developing the runoff calculations for the ground covers noted in § 26-115B(1). These values are referenced from the Urban Hydrology for Small Watersheds Technical Release No. 55 (USDA, 1986). Coefficients for equivalent ground cover conditions shall be used if a runoff method other than the Soil-Cover-Complex Method is used.
|
Hydrologic Soil Group Curve Numbers
| ||||
|---|---|---|---|---|
|
Ground Cover
|
A
|
B
|
C
|
D
|
|
Woodland
|
30
|
55
|
70
|
77
|
|
Meadow
|
30
|
58
|
71
|
78
|
|
Grass
|
39
|
61
|
74
|
80
|
(3)
Impervious cover shall have a curve number of 98.
(4)
Gravel pavement shall have a curve number of 89.
(5)
Average antecedent moisture conditions, or AMC II, shall be
used (for the Soil-Cover-Complex Method only for example, TR-55, TR-20).
(6)
A Type II distribution storm (for the Soil-Cover-Complex Method
only for example, TR-55, TR-20).
(7)
For time-of-concentration calculations, sheet flow lengths shall
not exceed 100 feet, and shallow concentrated flow lengths shall not
exceed 1,000 feet.
(8)
The kinematic "n" value in the sheet flow equation should be
applied as per the following table (values taken from TR-55):
|
Type
|
"n" Value
|
|---|---|
|
Impervious surfaces
|
0.011
|
|
Agricultural lands
|
0.17
|
|
Grass, lawn, or open space
|
0.24
|
|
Wooded areas
|
0.40
|
C.
In all plans and designs for stormwater management systems and facilities
submitted to the Municipal Engineer for approval, stormwater peak
discharge and runoff shall be determined through the use of the NRCS
Soil-Cover-Complex Method as set forth in Urban Hydrology for Small
Watersheds, Technical Release No. 55 (USDA, 1986), with specific attention
given to antecedent moisture conditions, flood routing, time of concentration,
and peak discharge specifications included therein and in Hydrology
National Engineering Handbook, Section 4 (USDA, 1985), both by the
United States Department of Agriculture, Natural Resources Conservation
Service. Note that when TR-55 is used for natural system-based approaches
and practices encouraged herein, calculations must be performed on
a detailed small subarea basis. Use of Technical Release No. 20 and
other methods listed in Table 1 are also acceptable. The design professional's
selection of a specific method shall be based on the suitability of
the method for the given project site conditions with due consideration
to the limitations of the method chosen. Table 1 herein summarizes
the computational methods available.
|
Table 1
| ||
|---|---|---|
|
Acceptable Computation Methodologies for Stormwater Management
Plans
| ||
|
Method
|
Source
|
Applicability
|
|
TR-20 or commercial package based on TR-20
|
USDA — NRCS
|
When use of full model is desirable or necessary
|
|
TR-55 or commercial package based on TR-55
|
USDA — NRCS
|
Applicable for plans within the model's limitations
|
|
HEC-HMS
|
U.S. Army Corps of Engineers
|
When full model is desirable or necessary
|
|
PSRM
|
Penn State University
|
When full model is desirable or necessary
|
|
VT/ PSUHM
|
Virginia Polytechnic Institute and Penn State University
|
When full model is desirable or necessary
|
|
Modified Rational Method or commercial package based on this
method
|
Emil Kuiching (1889)
|
For sites less than 20 acres
|
|
SWMM or commercial package based on SWMM
|
U.S.EPA
|
Most applicable in urban areas
|
|
Small Storm Hydrology Method (as included in SLAMM)
|
PV and Associates, or the website www.winslamm.com
|
Calculation of runoff volume from urban and suburban areas
|
D.
A Modified Rational Method analysis may be used for drainage areas
smaller than two acres when permitted by the Municipal Engineer. The
term "Modified Rational Method" used herein refers to a procedure
for manipulation of the basic Rational Method techniques to reflect
the fact that storms with a duration greater than the normal time
of concentration for a basin will result in a larger volume of runoff
even though the peak discharge is reduced. The methodology and model
chosen for use shall be well documented as being appropriate for use
in this region, and all relevant assumptions, methodologies, calculations
and data used shall be provided to the Municipal Engineer for review.
Information on the Modified Rational Method is presented in the Recommended
Hydrologic Procedures for Computing Urban Runoff from Small Watersheds
in Pennsylvania (PA DEP, 1982).
E.
Rainfall intensities used for the Modified Rational Method shall
be based on the precipitation frequency estimates developed by the
National Oceanic and Atmospheric Administration as set forth in NOAA
Atlas 14.
F.
The Rational Method (that is, Q = CIA) shall be used for calculations
of the peak rate of runoff for the design of storm sewers and drainage
swales but not for the design of stormwater management facilities
where a full hydrograph is needed. The equation representing the Rational
Method is comprised of the following (in English units):
|
Q
|
=
|
Peak flow rate, in cubic feet per second (cfs).
|
|
C
|
=
|
Runoff coefficient, dependent on land use/cover.
|
|
I
|
=
|
Design rainfall intensity, in inches per hour.
|
|
A
|
=
|
Drainage area, in acres.
|
G.
Runoff characteristics of off-site areas that drain through a proposed
development shall be considered and be based on the existing conditions
in the off-site area.
[Ord. 432, 10/1/2008]
1.
The Pennsylvania Stormwater Best Management Practices Manual shall
serve as a guide for the design of stormwater management practices.
Additional design guidance may also be obtained from other related
sources, including the 2000 Maryland Stormwater Design Manual, Volumes
I and II (MDE, 2000), Design of Stormwater Filtering Systems (CWP,
1996), and the American Society of Civil Engineers Manual and Report
on Engineering Practice, No. 87, Urban Runoff Quality Management (ASCE,
1998), for the design of stormwater runoff quality control features
for site development. A list of references is provided with this chapter.
The water quality volume design measures used herein are partially
based on the methodology expressed in the Maryland Manual referenced
above.
2.
Pursuant to the design options recommended in the above documents,
the following standards shall be adhered to:
A.
Extended Detention, Water Quality Volume, Infiltration and Nonstructural
BMP Credits Criteria. The following sizing criteria shall be followed
at all sites required to meet the standards of this chapter:
(1)
Extended Detention.
(a)
Detain the one-year, twenty-four-hour design storm using the
SCS Type II distribution. Provisions shall be made so that the one-year
storm takes a minimum of 24 hours to drain from the facility from
a point where the maximum volume of water from the one-year storm
is captured (i.e., the maximum water surface elevation is achieved
in the facility). Release of water can begin at the start of the storm
(i.e., the invert of the water quality orifice is at the invert of
the facility). The design of the facility shall consider and minimize
the chances of clogging and sedimentation potential.
(b)
Detention ponds shall detain the one-year storm event and allow
it to naturally infiltrate and recharge the groundwater table. All
subsequent orifices for the two-, ten-, twenty-five-, and one-hundred-year
storm events shall be placed above the maximum water surface elevation
of the one-year storm.
(c)
Flow from off-site areas must be considered as pass-through
flow if it is conveyed through the BMP and should be modeled as "present
condition" for the one-year storm event.
(d)
The length of overland flow used in time-of-concentration (tc)
calculations is limited to no more than 100 feet for post-development
conditions.
(e)
The models TR-55 and TR-20 (or approved equivalent) can be used
for determining peak discharge rates.
(2)
Water Quality Volume.
(a)
Treatment of the water quality volume (WQv) of stormwater prior
to its release to receiving waters or water bodies shall be provided
at all developments where stormwater management is required. The WQv
equals the storage volume needed to capture and treat the runoff from
storms of one inch or less. Runoff from the first one inch of rainfall
transports most of the total pollutant load.
(b)
The WQv is based on the following equation:
|
WQv = [(P)(Rv)(A)]/12 (acre-feet)
| |||
|
Where:
| |||
|
P
|
=
|
Rainfall depth, in inches (set to one inch).
| |
|
Rv
|
=
|
Volumetric runoff coefficient, 0.05 plus 0.009(I), where I is
the percent of impervious cover.
| |
|
A
|
=
|
Site area (acres).
| |
(c)
The formula assumes approximately 5% runoff from pervious surfaces
and 90% runoff from impervious surfaces. A minimum of 0.2 inch per
acre of runoff volume shall be met at sites or in drainage areas that
have less than 15% impervious cover.
(d)
Drainage areas having no impervious cover and no proposed disturbance
during development may be excluded from the WQv calculations. However,
designers are encouraged to incorporate water quality treatment practices
for these areas.
(e)
Stormwater Quality Treatment. The final WQv shall be treated
by an acceptable stormwater management practice(s) from those described
in this section or as approved by the municipality.
(f)
For new developments and redevelopments, infiltration is considered
an acceptable method of satisfying part or all of the water quality
volume.
(h)
As a basis for design, the following
assumptions may be made:
[1]
Multiple Drainage Areas. When a project contains
or is divided by multiple drainage areas, the WQv volume shall be
addressed for each drainage area.
[2]
Off-Site Drainage Areas. The WQv shall be based
on the impervious cover of the proposed site. Off-site existing impervious
areas may be excluded from the calculation of the water quality volume
requirements.
(3)
Infiltration Volume. Where possible, all of the water quality
volume should be treated using infiltration BMPs. The following calculation
shall be used to determine the minimum recharge goal for the site.
|
Recharge Volume (Rev) (acre-feet)
|
|
Fraction of WQv, depending on soil hydrologic
group
|
|
Rev = (S)(Ai)
| |||
|
Where:
| |||
|
S
|
=
|
Soil-specific recharge factor, in inches.
| |
|
AI
|
=
|
The measured impervious cover.
| |
|
Hydrologic Soil
Group
|
Soil Specific Recharge Factor (S)
|
|---|---|
|
A
|
0.40 inch
|
|
B
| |
|
C
| |
|
D
|
(a)
Infiltrated volume may be subtracted from the total site WQv.
(b)
Infiltration should not be considered for sites or areas of
sites that have activities that may allow pollution to be infiltrated.
For example, the use of infiltration for the runoff of a service station's
paved lot would not be appropriate, although roof water from the service
station may be infiltrated.
(c)
Infiltration should only be used when, in the opinion of a professional
engineer, it will not contribute to slope instability or cause seepage
problems into basements or developed downgradient areas.
(d)
If more than one hydrologic soil group is present at a site,
a composite recharge volume shall be computed based upon the proportion
of total site area within each hydrologic soil group.
(e)
All infiltration facilities shall be set back at least 15 feet
from all structures with subgrade elements (e.g., basements, foundation
walls).
(4)
Credits for Use of Nonstructural BMPs. The developer may obtain
credits for the use of nonstructural BMPs using the procedures outlined
below. Examples of nonstructural credit calculations are provided
in Appendix E.[1]
(a)
Volume Reduction Method No. 1: Natural Area Conservation. A
water quality volume reduction can be taken when undisturbed natural
areas are conserved on a site, thereby retaining their predevelopment
hydrologic and water quality characteristics. Under this method, a
designer would be able to subtract the conservation areas from the
total site area when computing the water quality protection volume.
An added benefit is that the post-development peak discharges will
be smaller, and hence, water quantity control volumes will be reduced
due to lower post-development curve numbers or Rational Formula "C"
values.
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Rule: Subtract conservation areas from total site area
when computing water quality protection volume requirements.
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|
Criteria:
| |
|
•
|
Conservation area cannot be disturbed during project construction
and must be protected from sediment deposition. The conservation area
shall be protected with a safety fence until construction has been
completed. After construction, the area shall be posted with signage
indicating that it is a conservation area.
|
|
•
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Shall be protected by limits of disturbance clearly shown on
all construction drawings.
|
|
•
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Shall be located within an acceptable conservation easement
instrument that ensures perpetual protection of the proposed area.
The easement must clearly specify how the natural area vegetation
shall be managed and boundaries will be marked [Note: managed turf
(e.g., playgrounds, regularly maintained open areas) is not an acceptable
form of vegetation management].
|
|
•
|
Shall have a minimum contiguous area requirement of 10,000 square
feet.
|
|
•
|
Rv is kept constant when calculating WQv.
|
|
•
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Must be forested or have a stable, natural ground cover.
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(b)
Volume Reduction Method No. 2: Stream Buffers. This reduction
can be taken when a stream buffer effectively treats stormwater runoff.
Effective treatment constitutes treating runoff through overland flow
in a naturally vegetated or forested buffer. Under the proposed method,
a designer would be able to subtract areas draining via overland flow
to the buffer from total site area when computing water quality protection
volume requirements. The design of the stream buffer treatment system
must use appropriate methods for conveying flows above the annual
recurrence (one-year storm) event.
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Rule: Subtract areas draining via overland flow to the
buffer from total site area when computing water quality protection
volume requirements.
| |
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Criteria:
| |
|
•
|
The minimum undisturbed buffer width shall be 50 feet from the
top of bank.
|
|
•
|
The maximum contributing length shall be 150 feet for pervious
surfaces and 75 feet for impervious surfaces.
|
|
•
|
The average contributing slope shall be 3% maximum, unless a
flow spreader is used. In no case shall the average contributing slope
be greater than 10%.
|
|
•
|
Runoff shall enter the buffer as overland sheet flow. A flow
spreader can be installed to ensure this.
|
|
•
|
Buffers shall remain as naturally vegetated or forested areas
and will require only routine debris removal or erosion repairs.
|
|
•
|
Rv is kept constant when calculating WQv.
|
|
•
|
Not applicable if overland flow filtration/groundwater recharge
reduction is already being taken.
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(c)
Volume Reduction Method No. 3: Enhanced Swales. This reduction
may be taken when enhanced swales are used for water quality protection.
Under the proposed method, a designer would be able to subtract the
areas draining to an enhanced swale from total site area when computing
water quality protection volume requirements. An enhanced swale can
fully meet the water quality protection volume requirements for certain
kinds of low-density residential development (see Volume Reduction
Method No. 5). An added benefit is the post-development peak discharges
will likely be lower due to a longer time of concentration for the
site.
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Rule: Subtract the areas draining to an enhanced swale
from total site area when computing water quality protection volume
requirements.
| |
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Criteria:
| |
|
•
|
This method is typically only applicable to moderate- or low-density
residential land uses (three dwelling units per acre maximum).
|
|
•
|
The maximum flow velocity for a water quality design storm shall
be less than or equal to 1.0 feet per second.
|
|
•
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The minimum residence time for the water quality storm shall
be five minutes.
|
|
•
|
The bottom width shall be a maximum of six feet. If a larger
channel is needed, use of a compound cross-section is required.
|
|
•
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The side slopes shall be 3:1 (horizontal:vertical) or flatter.
|
|
•
|
The channel slope shall be 3% or less.
|
|
•
|
Rv is kept constant when calculating WQv.
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(d)
Volume Reduction Method No. 4: Overland Flow Filtration/Groundwater
Recharge Zones. This reduction can be taken when overland flow filtration/infiltration
zones are incorporated into the site design to receive runoff from
rooftops or other small impervious areas (e.g., driveways, small parking
lots, etc). This can be achieved by grading the site to promote overland
vegetative filtering or by providing infiltration or "rain garden"
areas. If impervious areas are adequately disconnected, they can be
deducted from total site area when computing the water quality protection
volume requirements. An added benefit will be that the post-development
peak discharges will likely be lower due to a longer time of concentration
for the site.
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Rule: If impervious areas are adequately disconnected,
they can be deducted from total site area when computing the water
quality protection volume requirements.
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|
Criteria:
| |
|
•
|
Relatively permeable soils (Hydrologic Soil Groups A and B)
should be present.
|
|
•
|
Runoff shall not come from a designated hotspot.
|
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•
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The maximum contributing impervious flow path length shall be
75 feet.
|
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•
|
Downspouts shall be at least 10 feet away from the nearest impervious
surface to discourage reconnections.
|
|
•
|
The disconnection shall drain continuously through a vegetated
channel, swale, or filter strip to the property line or structural
stormwater control.
|
|
•
|
The length of the disconnection shall be equal to or greater
than the contributing length.
|
|
•
|
The entire vegetative disconnection shall be on a slope less
than or equal to 3%.
|
|
•
|
The surface impervious area tributary to any one discharge location
shall not exceed 5,000 square feet.
|
|
•
|
For those areas draining directly to a buffer, reduction can
be obtained from either overland flow filtration or stream buffers
(see Method No. 2).
|
|
•
|
Rv is kept constant when calculating WQv.
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(e)
Volume Reduction Method No. 5: Environmentally Sensitive Large-Lot
Subdivisions. This reduction can be taken when a group of environmental
site design techniques is applied to low- and very-low-density residential
development [e.g., one dwelling unit per two acres (du/ac) or lower].
The use of this method can eliminate the need for structural stormwater
controls to treat water quality protection volume requirements. This
method is targeted towards large-lot subdivisions and will likely
have limited application.
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Rule: Targeted towards large-lot subdivisions (e.g., two-acre
lots and greater). The requirement for structural facilities to treat
the water quality protection volume may be waived.
| |
|
Criteria:
| |
|
For Single Lot Development:
| |
|
•
|
Total site impervious cover is less than 15%.
|
|
•
|
Lot size shall be at least two acres.
|
|
•
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Rooftop runoff is disconnected in accordance with the criteria
in Method No. 4.
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•
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Grass channels are used to convey runoff versus curb and gutter.
|
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For Multiple Lots:
| |
|
•
|
Total impervious cover footprint shall be less than 15% of the
area.
|
|
•
|
Lot areas should be at least two acres, unless clustering is
implemented. Open space developments should have a minimum of 25%
of the site protected as natural conservation areas and shall be at
least a half-acre average individual lot size.
|
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•
|
Grass channels should be used to convey runoff versus curb and
gutter (see Method No. 3).
|
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•
|
Overland flow filtration/infiltration zones should be established
(see Method No. 4).
|
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NOTE: The following sections provide minimum design standards
for stormwater management facilities.
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[1]
Editor's Note: Appendix E is on file in the Township offices.
B.
Stormwater Infiltration Practices.
(1)
In selecting the appropriate infiltration BMPs, the applicant
shall consider the following:
(a)
Permeability and infiltration rate of the site soils.
(b)
Slope and depth to bedrock.
(c)
Seasonal high water table.
(d)
Proximity to building foundations and wellheads.
(e)
Erodibility of soils.
(f)
Land availability and topography.
(g)
Slope stability.
(h)
Effects on nearby properties and structures.
(2)
A detailed soils evaluation of the project site shall be performed
to determine the suitability of infiltration BMPs. The evaluation
shall be performed by a qualified professional and, at a minimum,
address soil permeability, depth to bedrock and slope stability. The
general process for designing the infiltration BMP shall be:
(a)
Analyze hydrologic soil groups as well as natural and man-made
features within the watershed to determine general areas of suitability
for infiltration BMPs.
(b)
Provide field-testing data to determine appropriate percolation
rate and/or hydraulic connectivity.
(c)
Design infiltration BMPs for required stormwater volume based
on field-determined capacity at the level of the proposed infiltration
surface.
(3)
Soil characteristics, as subject to the specific considerations
below:
(a)
Infiltration BMPs are particularly appropriate in Hydrologic
Soil Groups A and B, as described in the Natural Resources Conservation
Manual TR-55.
(b)
Low-erodibility factors ("K" factors) are preferred for the
construction of basins.
(c)
There must be a minimum depth of 48 inches between the bottom
of any facility and the seasonal high water table and/or bedrock (limiting
zones), except for infiltration BMPs receiving only roof runoff, which
shall be placed in soils having a minimum depth of 24 inches between
the bottom of the facility and the limiting zone.
(d)
There must be an infiltration and/or percolation rate sufficient
to accept the additional stormwater load and to drain completely,
as determined by field tests.
(e)
The infiltration system shall have positive overflow controls
to prevent storage within one foot of the finished surface or grade.
(f)
Infiltration rates shall not be used in computing the storage
volume of the infiltration system.
(g)
Surface inflows shall be designed to prevent direct discharge
of sediment into the infiltration system.
(4)
The recharge volume provided at the site shall be directed to
the most-permeable hydrologic soil group available, except where other
considerations apply, such as in limestone geology.
(5)
Any infiltration BMP shall be capable of completely infiltrating
the impounded water within 48 hours. The forty-eight-hour period is
to be measured from the end of the twenty-four-hour design storm.
(7)
During the period of land disturbance, runoff shall be controlled
prior to entering any proposed infiltration area. Areas proposed for
infiltration BMPs shall be protected from sedimentation and compaction
during the construction phase so as to maintain their maximum infiltration
capacity.
(8)
Infiltration BMPs shall not be constructed nor receive runoff
until the entire contributory drainage area to the infiltration BMP
has received final stabilization.
(9)
Infiltration facilities shall be selected based on suitability
of soils and site conditions. Acceptable infiltration facilities include
but are not limited to filter strips or stormwater filtering systems
(for example, bioretention facilities, sand filters), open vegetated
channels (that is, dry swales and wet swales), infiltration trenches,
dry wells, infiltration basins, porous paving systems, retention basins,
wet extended detention ponds, riparian corridor management, riparian
forested buffers, rooftop runoff management systems, and sand filters
(closed or open).
(10)
Where sediment transport in the stormwater runoff is anticipated
to reach the infiltration system, appropriate permanent measures to
prevent or collect sediment shall be installed prior to discharge
to the infiltration system.
(11)
All infiltration facilities shall be set back at least 15 feet
from all structures with subgrade elements (e.g., basements, foundation
walls).
(12)
All infiltration facilities that serve more than one lot and
are considered a common facility shall have a drainage easement. The
easement shall provide to the municipality the right of access.
(13)
If detailed infiltration study is required, the following guidance
shall be followed:
(a)
Soil evaluations shall be performed to determine the feasibility
and extent to which infiltration systems can be used. The evaluation
shall be performed by a qualified, licensed geologist, geotechnical/civil
engineer or soil scientist and, at a minimum, address soil types,
soil permeability, depth to bedrock, limitations of soils, presence/absence
of carbonate geology, susceptibility to subsidence and/or sinkhole
formation and subgrade stability. The testing and evaluation should
be completed at the preliminary design stage.
(b)
Infiltration requirements shall be based on the portions of
the site that are permeable prior to disturbance and the degree to
which development will reduce the permeability of the site. Permeability
of the site shall be determined based on the detailed evaluations
described herein. Use of stormwater management facilities to retain
stormwater for infiltration should be applied to all areas where the
soils evaluation indicates favorable conditions. Areas generally not
favorable for infiltration shall still be provided with an appropriate
water quality practice.
(c)
Soil infiltration tests shall be performed to an equivalent
depth or elevation of the bottom of the proposed infiltration areas.
These tests shall follow the procedures of percolation test holes
as established by the Allegheny County Health Department (ACHD) for
on-lot septic systems. The testing shall include a test pit and percolation
test holes. The test hole shall be excavated to a depth so that the
presence or absence of bedrock and/or seasonal high water table can
be determined. A soil log describing the soils present in each test
pit shall be performed. All test holes used for evaluating the percolation
rate shall be presoaked in accordance with the procedures established
by the ACHD. The location and number of test pits and percolation
holes shall be determined based on the type(s) of stormwater management
facilities being designed. Acceptability of infiltration rates shall
be based on sound engineering judgment and recommended design considerations
described in the design manuals listed in the references or other
source material acceptable to the Municipal Engineer.
(14)
The following design and construction standards shall be followed
when planning and constructing infiltration BMPs:
(a)
The lowest elevation of the infiltration area shall be at least
two feet above the seasonal high water table and bedrock.
(b)
Where roof drains are designed to discharge to infiltration
facilities, they shall have appropriate measures to prevent clogging
by unwanted debris (for example, silt, leaves and vegetation). Such
measures shall include but are not limited to leaf traps, gutter guards
and cleanouts.
(c)
All infiltration facilities shall have appropriate positive
overflow controls to prevent storage within one foot of the finished
surface or grade, unless a specific amount of surface storage away
from pedestrian and vehicular traffic is provided and such areas infiltrate
the stored volume within 48 hours after the end of the twenty-four-hour
design storm.
(d)
All infiltration facilities shall be designed to infiltrate
the stored volume within 48 hours after the end of the twenty-four-hour
design storm.
(e)
All surface inflows shall be treated to prevent the direct discharge
of sediment into the infiltration practice; accumulated sediment reduces
stormwater storage capacity and ultimately clogs the infiltration
mechanism. No sand, salt or other particulate matter may be applied
to a porous (pervious) surface for winter ice conditions.
(f)
During site construction, all infiltration practice components
shall be protected from compaction due to heavy equipment operation
or storage of fill or construction material. Infiltration areas shall
also be protected from sedimentation. Areas that are accidentally
compacted or graded shall be remediated to restore soil composition
and porosity. Adequate documentation to this effect shall be submitted
for review by the Municipal Engineer. All areas designated for infiltration
shall not receive runoff until the contributory drainage area has
achieved final stabilization.
(g)
The following procedures and materials
shall be required during the construction of all subsurface facilities:
[1]
Excavation for the infiltration facility shall
be performed with equipment that will not compact the bottom of the
seepage bed/trench or like facility.
[2]
The bottom of the bed and/or trench shall be scarified
prior to the placement of aggregate.
[3]
Only clean aggregate with documented porosity,
free of fines, shall be allowed.
[4]
The tops and sides of all seepage beds, trenches,
or like facilities shall be covered with drainage fabric. Fabric shall
meet the specifications of PennDOT Publication 408, Section 735, Construction
Class 1.
[5]
Perforated distribution pipes connected to centralized
catch basins and/or manholes with the provision for the collection
of debris shall be provided in all facilities. Where perforated pipes
are used to distribute stormwater to the infiltration practice, stormwater
shall be distributed uniformly throughout the entire seepage bed/trench
or like facility.
C.
Open Vegetated Channels.
(1)
Open vegetated channels are conveyance systems that are engineered
to also perform as water quality and infiltration facilities. Such
systems can be used for the conveyance, retention, infiltration and
filtration of stormwater runoff.
(2)
Open vegetated channels primarily serve a water quality function
(WQv); they also have the potential to augment infiltration. Examples
of such systems include but are not limited to dry swales, wet swales,
grass channels, and biofilters. Open vegetated channels are primarily
applicable for land uses such as roads, highways, residential developments
(dry swales only) and pervious areas.
(3)
Open vegetated channels shall be designed to meet the following
minimum standards:
(a)
The channel shall be designed to safely convey the ten-year-frequency
storm event with a freeboard of at least 12 inches. Freeboard is the
difference between the elevation of the design flow in the channel
and the top elevation of the channel.
(b)
The peak velocity of the runoff from the ten-year storm shall
be nonerosive for the soil and ground cover provided in the channel.
(c)
The longitudinal slope shall be no greater than 4%.
(d)
Channels shall be trapezoidal in cross-section.
(e)
Channels shall be designed with moderate side slopes of four
horizontal to one vertical. Flatter side slopes may be necessary under
certain circumstances.
(f)
The maximum allowable ponding time in the channel shall be less
than 48 hours.
(g)
Channels (for example, dry swales) may require an underdrain
in order to function and dewater.
(h)
Channels shall be designed to temporarily store the WQv within
the system for a maximum period of 48 hours and a minimum period of
one hour.
(i)
Landscape specifications shall address the grass species, wetland
plantings (if applicable), soil amendment and hydric conditions present
along the channel.
(j)
Accumulated sediment within the channel bottom shall be removed
when 25% of the original WQv volume has been exceeded. The channel
shall be provided with a permanent concrete cleanout marker that indicates
the 25% loss level.
(k)
Check dams along the channel length may be warranted.
(l)
The bottom of dry swales shall be situated at least two feet
above the seasonal high water table.
(4)
Additional design information for open vegetated channels is
available in Design of Roadside Channels with Flexible Linings, HEC
15, FHWA, September 2005.
D.
Retention Basins.
(1)
Retention basins shall be designed to create a healthy ecological community with sufficient circulation of water to prevent the growth of unwanted vegetation and mosquitoes or other vectors. If circulation cannot be provided via natural means, then artificial aeration and circulation shall be provided. Care shall be taken to landscape retention basins in accordance with § 26-117.
(2)
The retention basin shall be of sufficient size to allow the
appropriate aquatic community needed to maintain healthy pond ecology
and avoid mosquitoes capable of carrying West Nile Virus and other
diseases. The Allegheny County Health Department, Pennsylvania Fish
and Boat Commission, the Natural Resource Conservation Service, the
Pennsylvania Extension Service, or other qualified professional consultant
shall be consulted during the design of these facilities in order
to ensure the health of aquatic communities and minimize the risk
of creating mosquito-breeding areas.
(3)
An outlet structure shall be designed to allow complete drainage
of the pond for maintenance.
(4)
The design of a retention basin shall include the determination
of the proposed site's ability to support a viable permanent pool.
The design shall take into account such factors as the available and
required rate and quality of dry-weather inflow, the stormwater inflow,
seasonal and longer-term variations in groundwater table, and impacts
of potential pollutant loadings.
(5)
Sediment storage volume equal to at least 20% of the volume
of the permanent pool shall be provided.
(6)
A sediment forebay with a hardened bottom shall be provided
at each inlet into the retention basin. The forebay storage capacity
shall at minimum be 10% of the permanent pool storage. The forebay
shall be designed to allow for access by maintenance equipment for
periodic cleaning. A permanent concrete cleanout maker shall be installed
in the forebay to indicate the level where 25% of the forebay storage
has been used.
(7)
Emergency spillways shall be sized and located to permit the
safe passage of stormwater flows from an unattenuated one-hundred-year
post-development storm with one foot of freeboard. The maximum velocities
in vegetated spillways excavated in otherwise undisturbed soil shall
be analyzed based upon the velocity of peak flow in the emergency
spillway during an assumed clogged primary outlet condition. Where
maximum velocities exceed design standards contained in the Engineering
Field Manual for Conservation Practices (USDA, SCS, July 1984), suitable
lining shall be provided. All emergency spillways placed on fill materials
shall be lined. Lining for emergency spillways shall incorporate native
colors and materials where possible, including mono-slab revetments,
grass pavers, rip rap and native stone.
(8)
Basin and pond embankments must be designed by a professional
engineer registered in the State of Pennsylvania. The design must
include an investigation of the subsurface conditions at the proposed
embankment location to evaluate settlement potential, groundwater
impacts, and the need for seepage controls. The submittal of a geotechnical
report from a geotechnical engineer for any embankment over 10 feet
in effective height or posing a significant hazard to downstream property
or life is required. The selection of fill materials must be subject
to approval of the design engineer. Fill must be free of frozen soil,
rocks over six inches, sod, brush, stumps, tree roots, wood, or other
perishable materials. Embankment fills less than 10 feet in fill height
must be compacted using compaction methods that would reasonably guarantee
that the fill density is at least 90% of the maximum density as determined
by standard proctor (ASTM-698). All embankment fills more than 10
feet in fill height must be compacted to at least 90% of the maximum
density as determined by standard proctor (ASTM-698) and must have
their density verified by field density testing. A PA DEP dam permit
is required for embankments having a maximum depth of water, measured
from the upstream toe of the dam to the top of the dam at maximum
storage elevation, of greater than 15 feet, and/or for ponds having
contributory drainage area of greater than 100 acres, and/or for impoundments
of greater than 50 acre-feet.
(9)
The embankment's interior slope may not be steeper than 3:1
(three horizontal to one vertical). The exterior slope of the embankment
may not exceed 2:1 (two horizontal to one vertical).
(10)
The minimum embankment width shall be four feet for embankments
less than six feet in height, six feet if the embankment is between
6.1 feet and 9.9 feet in height, and eight feet if the embankment
is between 10 feet and 15 feet in height.
(11)
Existing ponds or permanent pool basins can be used for stormwater
management, provided that it can be demonstrated that the ponds are
structurally sound and meet the design requirements herein.
(12)
Inlet structures and outlet structures shall be separated to
the greatest extent possible in order to maximize the flow path through
the retention basin.
(13)
Retention basins shall be designed to provide a length-to-width
ratio of at least 3L:1W, as measured in plan view (for example, a
ratio of 4L:1W is too narrow).
(14)
The retention basin depth shall average three to six feet.
(15)
Fencing of the facility is not required if the interior slope
of the pond is 4H:1V or flatter and the design also includes a five-foot-wide
bench around the pond perimeter at an elevation one foot below the
permanent water surface elevation.
(16)
Any side slopes below the permanent water surface level shall
not exceed 3H:1V. Interior side slopes above the permanent water surface
level shall not exceed 3H:1V.
(17)
Stabilization. Proper stabilization structures, including stilling
basins, energy dissipators, and channel lining, shall be constructed
at the outlets of all retention basins and emergency spillways. The
stabilization structures shall control water to avoid erosion, reduce
velocities of released water, and direct water so that it does not
interfere with downstream activities.
(18)
Energy dissipators and/or level spreaders shall be installed
to prevent erosion and/or initiate sheet flow at points where pipes
or drainageways discharge to or from basins. Level spreaders shall
be used only where the maximum slope between the discharge point and
the waterway does not exceed 5%. Energy dissipators shall comply with
criteria in Hydraulic Design of Energy Dissipators for Culverts and
Channels, HEC 14, FHWA, July 2006. Such facilities shall be both functional
and harmonious with the surrounding environment; for example, native
rock shall be used in constructing dissipators where practical.
(19)
Discharge Points. The minimum distance between a proposed basin
discharge point (including the energy dissipator, etc.) and a downstream
property boundary shall in no case be less than 15 feet. Where there
is discharge onto or through adjacent properties prior to release
to a stream, designers shall demonstrate how downstream properties
are to be protected. The Municipal Engineer may require that the setback
distance be increased based upon factors such as topography, soil
conditions, the size of structures, the location of structures, and
discharge rates. A drainage easement may also be required.
(20)
Outlet Structures. Outlet structures shall meet the following
specifications:
(a)
To minimize clogging and to facilitate cleaning and inspecting,
outlet pipes shall have an internal diameter of at least 15 inches
and a minimum grade of 1%.
(b)
Bentonite plugs shall be provided on all outlet pipes within
a constructed berm.
(c)
All principal outlet structures shall be built using reinforced
concrete with watertight construction joints.
(d)
The use of architecturally treated concrete, stucco, painted
surface or stone facade treatment shall be considered for enhancing
the outlet structure. Such facilities shall be both functional and
harmonious in design with the surrounding environment.
(e)
Outlet pipes shall be constructed of reinforced concrete with
rubber gaskets in conformance with AASHTO M170, M198 and M207, or
smooth interior HDPE pipe in conformance with AASHTO M252 or M294.
(f)
Basin outlet structures shall have childproof nonclogging trash
racks over all design openings exceeding 12 inches in diameter, except
those openings designed to carry perennial stream flows. Periodic
cleaning of debris from trash racks shall be included in the operation
and maintenance plan.
(g)
Antivortex devices, consisting of a thin vertical plate normal
to the basin berm, shall be provided at the top of all circular risers
or standpipes.
E.
Detention Basins.
(2)
The maximum inside side slopes shall not exceed three horizontal to one vertical (3H:1V). The minimum required slope for the basin bottom is 2%. A level bottom is acceptable, provided that the designer demonstrates to the municipality's satisfaction that the basin bottom will be landscaped with appropriate wetland vegetation pursuant to § 26-117. In addition, detention basins of sufficient size and slope may serve other functions as well, including recreational uses which do not hinder or conflict with the function of the detention basin.
(3)
Inlet Structures. The inlet pipe invert into a basin shall be
six inches above the basin floor or lining so that the pipe can adequately
drain after rainstorms. Inlets shall discharge into areas of the basin
that slope toward the outlet structure.
(4)
Inlet structures and outlet structures shall be separated to
the greatest extent possible in order to maximize the flow path through
the retention basin.
(5)
Low Flow Channels. Low flow channels constructed of concrete
or asphalt are not permitted. Where low flow channels are necessary,
they shall be composed of a natural or bioengineered material. Low
flow channels shall be designed to promote water quality and slow
the rate of flow through the basin. Low flow channels may also be
designed to infiltrate where practical.
(6)
Outlet Structures. Outlet structures shall meet the following
specifications:
(a)
To minimize clogging and to facilitate cleaning and inspection,
outlet pipes shall have an internal diameter of at least 15 inches
and a minimum grade of 1%.
(b)
Bentonite plugs shall be provided on all outlet pipes within
a constructed berm.
(c)
All principal outlet structures shall be built using reinforced
concrete with watertight construction joints.
(d)
The use of architecturally treated concrete, stucco, painted
surface or stone facade treatment shall be considered for enhancing
the outlet structure. Such facilities shall be both functional and
harmonious in design with the surrounding environment.
(e)
Outlet pipes shall be constructed of reinforced concrete with
rubber gaskets in conformance with AASHTO M170, M198 and M207, or
smooth interior HDPE pipe in conformance with AASHTO M252 or M294.
(f)
Energy-dissipation facilities that convert concentrated flow
to uniform shallow sheet flow shall be used where appropriate.
(g)
Basin outlet structures shall have childproof nonclogging trash
racks over all design openings exceeding 12 inches in diameter, except
those openings designed to carry perennial stream flows.
(h)
Antivortex devices, consisting of a thin vertical plate normal
to the basin berm, shall be provided at the top of all circular risers
or standpipes.
(7)
Emergency spillways shall be sized and located to permit the
safe passage of stormwater flows from an unattenuated one-hundred-year
post-development storm with one foot of freeboard. The maximum velocities
in vegetated spillways excavated in otherwise undisturbed soil shall
be analyzed based upon the velocity of peak flow in the emergency
spillway during an assumed clogged primary outlet condition. Where
maximum velocities exceed design standards contained in the Engineering
Field Manual for Conservation Practices (USDA, SCS, July 1984), suitable
lining shall be provided. In general, emergency spillways should not
be located in fill areas; all such facilities placed on fill materials
shall be lined. Lining for emergency spillways shall incorporate native
colors and materials where possible, including mono-slab revetments,
grass pavers, rip rap and native stone.
(8)
Basin and pond embankments must be designed by a professional
engineer registered in the State of Pennsylvania. The design must
include an investigation of the subsurface conditions at the proposed
embankment location to evaluate settlement potential, groundwater
impacts, and the need for seepage controls. The submittal of a geotechnical
report from a geotechnical engineer for any embankment over 10 feet
in effective height or posing a significant hazard to downstream property
or life is required. The selection of fill materials must be subject
to approval of the design engineer. Fill must be free of frozen soil,
rocks over six inches, sod, brush, stumps, tree roots, wood, or other
perishable materials. Embankment fills less than 10 feet in fill height
must be compacted using compaction methods that would reasonably guarantee
that the fill density is at least 90% of the maximum density as determined
by standard proctor (ASTM-698). All embankment fills more than 10
feet in fill height must be compacted to at least 90% of the maximum
density as determined by standard proctor (ASTM-698) and must have
their density verified by field density testing. A PA DEP dam permit
is required for embankments having a maximum depth of water, measured
from the upstream toe of the dam to the top of the dam at maximum
storage elevation, of greater than 15 feet, and/or for ponds having
contributory drainage area of greater than 100 acres, and/or for impoundments
of greater than 50 acre-feet.
(9)
The embankment's interior slope may not be steeper than 3:1
(three horizontal to one vertical). The exterior slope of the embankment
may not exceed 2:1 (two horizontal to one vertical).
(10)
The minimum embankment width shall be four feet for embankments
less than six feet in height, six feet if the embankment is between
6.1 feet and 9.9 feet in height, and eight feet if the embankment
is between 10 feet and 15 feet in height.
(11)
Fencing of the facility is not required if the interior slope
of the pond is 4:1 or flatter.
(12)
Freeboard. Freeboard is the difference between the elevation
of the design flow in the emergency spillway (usually the one-hundred-year
peak elevation) and the top elevation of the settled basin embankment
(that is, top of berm). The minimum freeboard shall be one foot.
(13)
Energy dissipators and/or level spreaders shall be installed
to prevent erosion and/or initiate sheet flow at points where pipes
or drainageways discharge to or from basins. Level spreaders shall
be used only where the maximum slope between the discharge point and
the waterway does not exceed 5%. Energy dissipators shall comply with
criteria in Hydraulic Design of Energy Dissipators for Culverts and
Channels, HEC 14, FHWA, July 2006. Such facilities shall be both functional
and attractive; for example, native rock shall be used in constructing
dissipators where practical.
(14)
Stabilization. Proper stabilization structures, including stilling
basins, energy dissipators, and channel lining, shall be constructed
at the outlets of all basins and emergency spillways. The stabilization
structures shall control water to avoid erosion, reduce velocities
of released water and direct water so that it does not interfere with
downstream activities.
(15)
Discharge Points. The minimum distance between a proposed basin
discharge point (including the energy dissipator, etc.) and a downstream
property boundary shall in no case be less than 15 feet. Where there
is discharge onto or through adjacent properties prior to release
to a stream, designers shall demonstrate how downstream properties
are to be protected. The Municipal Engineer may require that the setback
distance be increased based upon factors such as topography, soil
conditions, the size of structures, the location of structures, and
discharge rates. A drainage easement may also be required.
(16)
A sediment forebay with a hardened bottom shall be provided
at each inlet into the detention basin. The forebay storage capacity
shall at minimum be 10% of the permanent pool storage. The forebay
shall be designed to allow for access by maintenance equipment for
periodic cleaning.
(17)
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 hours and not more than 72 hours from the
end of the design storm.
[Added by Ord. 497, 11/19/2018]
F.
Conveyance Systems (Open Channels, Drainageways, and Storm Sewers).
(1)
Applicants are encouraged to design conveyance systems that
encourage infiltration and improve water quality wherever practicable.
(2)
Wherever conveyance channels are necessary, drainage shall be
maintained by an open channel with landscaped banks designed to carry
the ten-year, twenty-four-hour stormwater runoff from upstream contributory
areas. The Municipal Engineer may increase the design storm as conditions
require. All open channels shall be designed with one foot of freeboard
above the design water surface elevation of the design runoff condition.
(3)
Flood-relief channels shall be provided and designed to convey
the runoff from the one-hundred-year, twenty-four-hour storm, such
that a positive discharge of this runoff to an adequate receiving
stream or conveyance system occurs without allowing this runoff to
encroach upon other properties.
(4)
Manholes and/or inlets shall not be spaced more than 300 feet
apart for pipe sizes up to 24 inches in diameter and not more than
450 feet apart for larger pipe sizes.
(5)
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 2% but shall not exceed a grade of 9%. Drainage swales used strictly for conveyance are not the same as open vegetated channels. Design standards for open vegetated channels are provided under § 26-116, Subsection 2C, of this chapter.
(6)
On streets that must contain curbing, storm sewers shall be
placed in front of the curbing. To the greatest extent possible, storm
sewers shall not be placed directly under curbing. At curbed street
intersections, storm inlets shall be placed in the tangent section
of the road.
(7)
Use of grassed swales or open vegetated swales in lieu of curbing
to convey, infiltrate and/or treat stormwater runoff from roadways
is encouraged. Inlets shall be placed at the center of the shoulder
swale draining the street and shall be located no closer than four
feet from the edge of the cartway.
(8)
When requested by the municipality, 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.
(9)
No property owner shall obstruct or alter the flow, location
or carrying capacity of a stream, channel or drainage swale to the
detriment of any other property owner, whether upstream or downstream.
All subdivision and/or land development plans containing streams,
channels, drainage swales, storm sewers or other conveyance systems
that cross property boundaries, existing or proposed, or whose discharge
crosses such boundaries shall contain a note stating the above.
(10)
Water Quality Inlets. Storm drainage systems that collect runoff
from parking areas and/or loading areas exceeding 10,000 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
municipality'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
municipality.
(11)
Roof drains and sump pumps shall discharge to infiltration or
vegetative BMPs wherever feasible.
[Added by Ord. 497, 11/19/2018]
[Ord. 432, 10/1/2008]
Stormwater management facilities shall be landscaped in accordance
with the following standards:
A.
Landscaping shall be required in and around all constructed stormwater
management facilities with a minimum surface area of 1,000 square
feet for the purposes of:
B.
A planting plan and planting schedule shall be submitted in accordance
with the following:
(1)
Wet Meadows, Including Floors of Stormwater Management Facilities.
(a)
Wet meadows and floors of stormwater management facilities shall
be planted with noninvasive plants native to western Pennsylvania,
such as wildflowers and noninvasive grasses, the intent being to create
a mixed meadow of such plantings, where appropriate. Selection of
plantings shall be based on whether the area in question is usually
well drained or permanently wet and whether the area will be used
for recreation purposes. No woody plants shall be planted within the
saturated zone (phreatic line) of a stormwater management practice
or on a berm constructed for impounded water.
(b)
Seeding by drills, corrugated rollers, cyclone or drop seeders
or hand seeding of such areas is preferred; however, hydroseeding
followed by hydromulching can be used on wet ground and steep slopes.
(c)
Fertilizers, as a nutrient supplement, shall not be used unless
it is documented that soil conditions warrant such use and the nutrient
applied does not exceed plant uptake. Soil for planting of wildflowers
shall contain not less than 3% nor more than 10% organic matter, as
determined by an agricultural chemist, with certification of the test
before planting.
(d)
Seeding shall take place either between April 1 and May 15 or
between September 1 and October 15. Planting areas shall be soaked
to maintain a consistent level of moisture for at least four to six
weeks after planting. For seeding recommendations, reference the DEP's
E&S Pollution Control Program Manual.
(e)
Once established, a single annual mowing when plants are dormant
should be sufficient to maintain a wet meadow and/or floor of a stormwater
management facility.
(2)
Wet edges that remain wet all or most of the year shall be planted
with wildflowers, grasses and shrubs. Plants to be located on rims
or banks, which remain dry most of the year, shall be planted with
species tolerant of dry soil conditions.
(3)
Wooded Areas.
(a)
Where stormwater management facilities adjoin wooded areas,
trees and shrubs shall be selected and planted outside the practice
so as to blend with existing surroundings.
(b)
Plantings in such areas shall be of sufficient density to eliminate
the need for mowing.
(c)
It is recommended that clusters of trees and shrubs be planted
around stormwater management facilities but well away from outfalls
and any constructed berms, where applicable, to provide for wildlife
habitat, wind control and buffering and screening.
(d)
Vegetation shall be planted during appropriate times of the
year, predominantly between late March and mid May or from early October
until evidence of ground freezing, depending upon the species selected.
Most deciduous trees and shrubs can be planted in either spring or
fall. Evergreens are best planted in late summer or early fall.
(4)
Slopes.
(a)
Where slopes are gentle, a mixture of meadow grasses and wildflowers
(for wet meadows) shall be planted.
(b)
On steep slopes, as defined by the municipality's Code of Ordinances,
dense spreading shrubs (shrubs tolerant of dry soils) shall be planted.
Heavy mat mulch shall be used during the period of establishment.
(c)
No woody plant materials or trees shall be located on a constructed
or natural berm acting as the impoundment structure of a stormwater
management practice. Trees shall be located downstream of an impoundment
berm a sufficient distance from the toe of the constructed slope to
assure that the toe of the slope is outside the dripline of the species
planted at maturity, but in no case less than 15 feet.
(5)
In cases where stormwater management facilities are to be located
in proximity to wetlands or waterways, the applicant's planting plan
and schedule shall consider the sensitive conditions existing therein
and be modified accordingly to reflect existing flora.
(6)
Stormwater management facilities shall be screened in a manner
which complements the existing landscape and provides sufficient access
for maintenance.
[Ord. 497, 11/19/2018[1]]
1.
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 these regulations 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
water cooler and reducing evaporation.
2.
Except as required by Pennsylvania Code Title 25, Chapter 102, the
riparian buffer easement shall be required for all streams (as defined)
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).
3.
Minimum Management Requirements for Riparian Buffers.
A.
No use or construction within the riparian buffer shall be permitted that is inconsistent with the intent of the riparian buffer as described in Subsection 1 above.
B.
Existing native vegetation shall be protected and maintained with
the riparian buffer easement.
C.
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 plan community
appropriate to the intended ecological context of the site.
4.
The riparian buffer easement shall be enforceable by the Township
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 the
continued private ownership and shall count toward the minimum lot
area required by zoning, unless otherwise specified in the Township
Zoning Ordinance.[2]
5.
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.
6.
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.
7.
The following conditions shall apply when public and/or private recreation
trails are permitted by the Township with riparian buffers:
A.
It is preferred that trails be designed to be permeable and for nonmotorized
use only; however, impermeable trails are permitted, provided they
have adequate drainage.
B.
Trails shall be designed to have the least impact on native plant
species and other sensitive environmental features.
C.
Septic drain fields and sewage disposal systems shall not be permitted
within the riparian buffer easement and shall comply with setback
requirements established under Pennsylvania Code Title 25, Chapter
73.
D.
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.
[1]
Editor's Note: This ordinance also repealed former § 26-118,
Stream Buffer Requirements (Ord. 432, 10/1/2008).
[Ord. 432, 10/1/2008]
1.
The owner of stormwater management facilities, and any other persons or entities named in the operation and maintenance agreement as having operation and maintenance obligations, shall be responsible for the proper operation and maintenance of those facilities during and after construction. An operation and maintenance plan consistent with the requirements of § 26-121 shall be prepared for review and approval by the Municipal Engineer and shall be executed and signed by the Municipal Engineer and the applicant.
2.
The owner of the stormwater management facilities for a tract shall
be responsible for the proper installation and function of those facilities
in accordance with the approved stormwater management plan. All temporary
soil erosion and sedimentation control measures shall be removed or
converted to their permanent configuration in accordance with an approved
erosion control plan. This requirement in no way precludes the authority
of the Allegheny County Conservation District to determine when sufficient
stabilization has occurred on a site in order to convert to the permanent
stormwater management facilities.
3.
Dedication and Acceptance of Stormwater Management Facilities.
A.
Upon completion of construction of stormwater management facilities
shown on an approved subdivision or land development plan as being
dedicated to the Township and within 90 days after approval of such
construction, the applicant shall submit a written offer of such stormwater
management facilities for dedication to the municipality. Said offer
shall include a deed of dedication covering said facilities, together
with satisfactory proof establishing an applicant's clear title to
said property. Such documents are to be filed with the Municipal Secretary
for review by the Municipal Solicitor. Deeds of dedication for stormwater
management facilities may be accepted by resolution of the municipality
at a regular meeting thereof.
B.
The municipality may require that stormwater management facilities
remain undedicated, with operation and maintenance the responsibility
of individual lot owners, or a homeowners' association or similar
entity, or an organization capable of carrying out maintenance responsibilities.
C.
Regardless of ownership, the applicant shall submit a written offer deeding an access and/or drainage easement to the municipality pursuant to § 26-120. Such easement shall cover the stormwater management facilities and any drainage to and from such facilities and shall clearly permit municipal entry for inspection and/or maintenance purposes.
D.
Regardless of ownership, the applicant shall submit an actual as-built
plan to the municipality for the stormwater management facilities
required per the approved stormwater management plan. The as-built
plan shall show all final design specifications for all permanent
stormwater management facilities, including but not limited to pipe
material and diameter, inlet, outlet and overflow elevations, two-foot
contours for all detention/retention basins and drainage swales and
a comparison of as-built capacities compared to the capacities of
the approved design facilities and shall be prepared and certified
by a licensed professional engineer. The as-built plan shall be based
on an actual field survey performed by a licensed professional land
surveyor. The surveyor shall certify as to the accuracy of the plan.
The as-built plan shall be submitted to the municipality for review
by the Municipal Engineer. Any performance and/or financial securities
established for the project shall include requirements for submittal
of as-built plans.
E.
The as-built plan(s) shall be submitted to the municipality in a
digital format or formats approved by the municipality.
[Ord. 432, 10/1/2008]
All stormwater management facilities identified within an approved
stormwater management plan shall be owned and maintained by one or
a combination of the following entities, as may be directed by the
Township:
A.
Private Ownership.
(1)
Where individual on-lot stormwater management facilities are
proposed, the subdivision and/or land development plan shall contain
a note in a form satisfactory to the Municipal Solicitor designating
the entity responsible for operation and maintenance of the on-lot
facilities consistent with an approved operation and maintenance plan
and, in the event that the responsible person or entity fails to do
so, granting to the municipality the right but not the duty to enter
upon the premises to repair or restore said facilities, to charge
and assess the costs thereof to the owner, including a reasonable
allowance for overhead, and to enforce said charges and assessments
by lien upon the property. In addition, the deed for each lot shall
contain a perpetual covenant binding the grantee and all successors
in interest designating the responsibility for operation and maintenance
of the on-lot facilities essentially in the following form:
|
"UNDER AND SUBJECT, nevertheless, to the following conditions
and restrictions: Prior to any Earth Disturbance for which stormwater
management facilities are required by the Municipality, Grantee shall
construct the permanent stormwater management facilities as shown
on the stormwater management plan (the "Plan") prepared by <NAME>,
P.E., dated <DATE> and last revised <DATE> and approved by Municipality;
thereafter, the Grantee, his heirs, executors, administrators, successors
and assigns ("Owner"), at his sole cost and expense, shall operate,
maintain and repair said stormwater management facilities on the lot
in accordance with said Plan, so that the facilities shall at all
times continue to operate and function in the same manner and capacity
as they were designed. In the event of the failure of the Owner to
comply with these conditions and restrictions, Municipality shall
have said stormwater management facilities repaired or restored as
required, and the costs thereof plus a reasonable allowance for overhead
shall be assessed to the Owner; said assessment shall be a charge
and a continuing lien upon the property herein. The Municipality,
before it may exercise this right, shall notify the Owner by certified
mail of its intention to take the aforesaid action. The notice shall
set forth in what manner the Owner has neglected the operation and
maintenance of or repair to the stormwater management facilities,
and if the Owner fails, within a period of 90 calendar days, to correct
or repair the items listed in the notice from the Municipality, then
and only then, may the Municipality exercise this right."
|
(2)
In addition to the above, developers of parcels with more than
one dwelling unit shall record in the office of Recorder of Deeds
for Allegheny County a declaration of covenants and restrictions,
in a form satisfactory to the Municipal Solicitor, describing the
responsibility for operation and maintenance of the on-lot facilities,
consistent with an approved operation and maintenance plan, prior
to the sale of any individual lots. The terms of this covenant and
restriction shall run with the land and be binding upon the initial
grantees of each lot within the subdivision, his, her or their heirs,
administrators, successors or assigns.
B.
Homeowners' or Condominium Association Ownership. Where a homeowners'
association is created to own and manage common facilities, the subdivision
and/or land development plan shall contain a note, in a form satisfactory
to the Municipal Solicitor, designating the entity responsible for
construction and/or maintenance of the stormwater management facilities
consistent with an approved operation and maintenance plan and, in
the event that the responsible entity fails to do so, granting to
the municipality the right but not the duty to enter upon the premises
to repair or restore said facilities, to charge and assess the costs
thereof plus a reasonable allowance for overhead to each owner of
property within the development and to enforce said charges and assessments
by lien upon each property within the development. In addition, the
developer shall record in the office of the Recorder of Deeds for
Allegheny County a declaration of covenants, in a form satisfactory
to the Municipal Solicitor, setting forth the rights and responsibilities
of the homeowners' association for operation and maintenance of the
stormwater management facilities, prior to the sale of individual
lots. The terms of this covenant and restriction shall run with the
land and be binding upon the initial grantees of each lot within the
subdivision, his, her or their heirs, administrators, successors and
assigns.
C.
Municipal Ownership. Where the municipality has accepted an offer
of dedication of the permanent stormwater management facilities, the
municipality shall be responsible for operation and maintenance. Municipal
ownership notwithstanding, the applicant is required to prepare a
stormwater management plan and an operation and maintenance plan,
as defined herein. Upon approval of the stormwater management facilities
by the municipality, the applicant shall provide a lump-sum long-term
maintenance payment to the municipality, to be reserved and used at
all times by the municipality only for costs of operation and maintenance
of the dedicated facilities, as follows:
(1)
Long-Term Maintenance Payment. The long-term maintenance payment
shall be in an amount equal to the present value of operation and
maintenance costs for the facilities for a ten-year period. The long-term
maintenance payment shall be based on a ten-year cost estimate prepared
by the applicant's engineer and reviewed and approved by the Municipal
Engineer. The amount of the payment shall include all costs of operation
and maintenance, which shall include but not be limited to typical
operation and maintenance costs as well as costs such as landscaping
and planting, tax payments required and construction of any kind associated
with the use, benefit and enjoyment of the facilities by the owners.
In particular, a description of routine facility operation and day-to-day
management requirements and a description of projected maintenance
actions and schedules necessary to ensure proper operation of stormwater
management facilities shall be submitted for review and approval to
the Municipal Engineer.
(2)
Documentation. The terms of the long-term maintenance payment
shall be documented as part of the stormwater management plan and
the operation and maintenance plan.
[Ord. 432, 10/1/2008]
An operation and maintenance plan shall be prepared by an engineer
licensed to practice in the Commonwealth of Pennsylvania that identifies
the ownership, operation and maintenance responsibilities and as-built
conditions for all stormwater management facilities. At a minimum,
the operation and maintenance plan shall include the following:
A.
Any obligations concerning perpetuation and/or maintenance of natural
drainage or infiltration facilities and other facilities identified
within the stormwater management plan. Ownership of and responsibility
for operation and maintenance of stormwater management facilities,
including names and contact information, shall be required.
B.
A description of the permanent stormwater management facilities on
the site, explaining how each facility is intended to function and
operate over time. All drainage and access easements shall be depicted,
and any site restrictions to be recorded against the property shall
be identified on the recorded plan. All such easements and restrictions
shall be perfected to run with the land and be binding upon the landowner
and any successors in interest.
C.
A description of the actions, budget and schedule for operating and
maintaining the stormwater management facilities. This description
should be written in a clear manner, consistent with the knowledge
and understanding of the intended user.
D.
A general description of operation and maintenance activities and
responsibilities for facilities held in common or on lot, including
but not limited to lawn care, vegetation maintenance, cleanout of
accumulated debris and sediment (including from grates, trash racks,
inlets, etc.), liability insurance, maintenance and repair of stormwater
management facilities, landscaping and planting, payment of taxes
and construction of any kind associated with the use, benefit and
enjoyment of the facilities by the owners. In particular, a description
of routine facility operation and day-to-day management requirements
(as needed) and a description of routine maintenance actions and schedules
necessary to ensure proper operation of stormwater management facilities
shall be submitted.
E.
Assurances that no action will be taken by any lot owner to disrupt
or in any way impair the effectiveness of any stormwater management
system, setting forth in deed restrictions the ability of the municipality
to take corrective measures if it is determined at any time that stipulated
permanent stormwater management facilities have been eliminated, altered,
or improperly maintained, including the ability of the municipality
to cause the work to be done and lien all costs plus a reasonable
overhead allowance against the property should the required corrective
measures not be taken by the lot owner, following written notification,
within a period of time set by the Municipal Engineer.
F.
Parties responsible for the long-term operation and maintenance of
stormwater management facilities shall make records of the installation
and of all maintenance and repairs and shall retain the records for
at least 10 years. These records shall be submitted to the municipality
as established by the operation and maintenance plan or if otherwise
required by the municipality.
[Ord. 432, 10/1/2008]
1.
The owner of any land upon which permanent stormwater management
facilities and/or BMPs will be placed, constructed or implemented,
as described in an approved stormwater management plan and the operation
and maintenance plan, shall record the following documents in the
office of the Recorder of Deeds for Allegheny County within 15 days
of approval of the operation and maintenance plan by the municipality:
2.
The operation and maintenance agreement shall be substantially the
same as the sample agreement in Appendix C of this chapter,[1] provided that the municipality may require other parties,
such as the developer, a homeowners' association, and other third
parties, to become a party to and execute the operation and maintenance
agreement where the addition of such parties will help to promote
the proper operation and maintenance of any permanent stormwater facilities
or BMPs.
[1]
Editor's Note: Appendix C is on file in the Township offices.
3.
Other items or conditions may be included in the operation and maintenance
agreement where determined necessary to guarantee the satisfactory
operation and maintenance of all permanent stormwater facilities and
BMPs. The agreement shall be subject to the review and approval of
the municipality.
[Ord. 432, 10/1/2008]
1.
Persons installing stormwater storage facilities will be required
to pay a specified amount to the Municipal Stormwater Facility Maintenance
Fund, if one is authorized by resolution of the Board of Supervisors,
to help defray costs of periodic inspections and annual maintenance
expenses. The amount of the deposit shall be determined as follows:
A.
If the storage facilities are to be privately owned and maintained,
the deposit shall cover the cost of periodic inspections performed
by the municipality for a period of 10 years, as estimated by the
Municipal Engineer. After that period of time, inspections will be
performed at the expense of the municipality.
B.
If the storage facilities are to be owned and maintained by the municipality,
the deposit shall cover the estimated annual costs for maintenance
and inspections for 10 years. The Municipal Engineer will establish
the estimated annual maintenance costs utilizing information submitted
by the applicant.
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 Municipal Engineer or Manager shall
determine the present-worth equivalents, which shall be subject to
the final approval of the governing body.
D.
If a storage facility is proposed which also serves as a recreation
facility, such as a lake or ballfield, the municipality may reduce
or waive the amount of the maintenance fund deposit based on the value
of the land for public recreational purposes.
2.
If any storage facility (whether publicly or privately owned) is
subsequently eliminated due to the installation of storm sewers or
another storage facility (e.g., a distributed storage facility), the
unused portion of the Maintenance Fund may 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 depositor.
[Ord. 432, 10/1/2008]
1.
Plan Submission. The municipality shall require receipt of a complete
plan, as specified in this chapter.
A.
Six copies of the stormwater management plan shall be submitted and
distributed as follows:
(1)
Two copies to the municipality accompanied by the requisite
municipal review fee as established by the municipality.
(2)
One copy to the Allegheny County Conservation District (when
required by the District).
[Amended by Ord. 497, 11/19/2018]
(3)
One copy to the Municipal Engineer.
(4)
One copy to the County Planning Commission/Department.
2.
Review.
A.
The Municipal Engineer shall review the stormwater management plan
for consistency with this chapter. Any stormwater management plan
found incomplete shall not be accepted for review and shall be returned
to the applicant.
B.
The Municipal Engineer shall review the stormwater management plan for any subdivision or land development against the provisions of Chapter 22, Subdivision and Land Development, not superseded by this chapter.
C.
When required by regulation, the County Conservation District shall
review and approve the erosion and sedimentation control plan for
consistency with PA DEP's Chapter 102 regulations.
D.
For activities regulated by this chapter, the Municipal Engineer
shall notify the applicant and the municipality whether the stormwater
management plan is consistent with this chapter.
(1)
Should the stormwater management plan be determined to be consistent
with the approved Act 167 Plan, the Municipal Engineer shall forward
an approval letter to the Municipal Secretary, who will then forward
a copy to the applicant.
(2)
Should the stormwater management plan be determined to be inconsistent
with the approved Act 167 Plan, the Municipal Engineer shall forward
a disapproval letter to the Municipal Secretary, who will then forward
a copy to the applicant. The disapproval letter shall cite the reason(s)
and specific ordinance sections for the disapproval. Disapproval may
be due to inadequate information to make a reasonable judgment as
to compliance with the stormwater management plan. Any disapproved
stormwater management plans may be revised by the applicant and resubmitted
consistent with this chapter.
E.
For regulated activities specified in §§ 26-102 through 26-112 of this chapter, which require a building permit, the Municipal Engineer shall notify the Municipal Building Permit Officer, in writing, within a time frame consistent with the Municipal Building Code[1] and/or Chapter 22, Subdivision and Land Development, whether the stormwater management plan is consistent with the approved Act 167 Plan and forward a copy of the approval/disapproval letter to the applicant. Any disapproved stormwater management plan may be revised by the applicant and resubmitted consistent with this chapter.
F.
For regulated activities under this chapter that require an NPDES
permit application, the applicant shall forward a copy of the Municipal
Engineer's letter stating that the stormwater management plan is consistent
with the approved Act 167 Plan to the County Conservation District.
PA DEP and the County Conservation District may consider the Municipal
Engineer's review comments in determining whether to issue a permit.
G.
The municipality shall not grant preliminary or final approval to any subdivision or land development for regulated activities specified in §§ 26-102 through 26-112 of this chapter if the stormwater management plan has been found to be inconsistent with the approved Act 167 Plan, as determined by the Municipal Engineer. All required permits from PA DEP must be obtained prior to approval of any subdivision or land development.
H.
No building permits shall be issued for any regulated activity specified in §§ 26-102 through 26-112 of this chapter if the stormwater management plan has been found to be inconsistent with the approved Act 167 Plan, as determined by the Municipal Engineer, or without considering the comments of the Municipal Engineer. All required permits from PA DEP must be obtained prior to issuance of a building permit.
I.
The developer shall be responsible for providing record drawings
of all stormwater BMPs included in the approved stormwater site plan.
The record drawings and an explanation of any discrepancies with the
construction plans shall be submitted to the Township.
[Amended by Ord. 497, 11/19/2018]
(1)
The record drawing submission shall include a certification
of completion signed by a qualified professional verifying that all
permanent stormwater BMPs have been constructed according to the approved
plans and specifications. The latitude and longitude coordinates for
all permanent stormwater BMPs must also be submitted at the central
location of the BMPs. If any licensed qualified professionals contributed
to the construction plans, then a licensed qualified professional
must sign the completion certificate.
(2)
The Township may conduct inspections during construction as
it deems appropriate. If inspections performed by the Township reveal
deficiencies from the submitted and approved stormwater site plan,
the Township may request corrective actions. Any corrective action
shall be at the cost of the stormwater facility owner.
(3)
After receipt of the completion certificate by the Township,
the Township may conduct a final inspection.
J.
The Township's approval of a stormwater site plan authorizes the regulated activities contained in the stormwater site plan for a maximum term of validity of five years following the date of approval. The Township may specify a term of validity shorter than five years in the approval for any specific stormwater site plan. Terms of validity shall commence on the date the Township signs the approval for a stormwater site plan. If an approved stormwater site plan is not completed according to § 26-124, Subsection 2I, within the term of validity, then the Township may consider the stormwater site plan disapproved and may revoke any and all permits. Stormwater site plans that are considered disapproved by the Township shall be resubmitted in accordance with § 26-124, Subsection 4.
[Amended by Ord. 497, 11/19/2018]
3.
Modification of Plans. A modification to a stormwater management plan under review by the municipality for a development site that involves a change in stormwater management facilities or techniques, or that involves the relocation or redesign of stormwater management facilities, or that is necessary because soil or other conditions are not as stated on the stormwater management plan as determined by the Municipal Engineer, shall require a resubmission of a modified stormwater management plan consistent with this chapter and shall be subject to review as specified in § 26-124 of this chapter.
4.
Resubmission of Disapproved Stormwater Plans. A disapproved stormwater management plan may be resubmitted, with the revisions addressing the Municipal Engineer's concerns documented in writing, and addressed to the Municipal Secretary in accordance with § 26-124 of this chapter and distributed accordingly, and shall be subject to review as specified in § 26-124 of this chapter. Any applicable municipal review and inspection fee must accompany a resubmission of a disapproved stormwater management plan.
5.
Municipal Stormwater Plan Review and Inspection Fees.
A.
Fees may be established from time to time by the municipality by
resolution in accordance with applicable laws to defray plan review
and construction inspection costs incurred by the municipality. All
fees shall be paid by the applicant at the time of stormwater management
plan submission.
B.
Any fees established pursuant to this chapter may include but not
necessarily be limited to any of the following:
(1)
Administrative costs.
(2)
The review of the stormwater management plan by the municipality,
the county (if applicable), the Allegheny County Conservation District
(if applicable) and the Municipal Engineer.
(3)
The site inspections.
(4)
The inspection of stormwater management facilities and stormwater
management improvements during construction.
(5)
The final inspection upon completion of the stormwater management
facilities.
(6)
Any additional work required to enforce any permit provisions
regulated by this chapter, correct violations and assure proper completion
of stipulated remedial actions, such additional work to include legal,
engineering or other professional consultant fees incurred by the
Township.
[Amended by Ord. 497, 11/19/2018]
(7)
Costs for engineering or legal review and for preparation of
the operations and maintenance agreement for stormwater BMPs.
[Added by Ord. 497, 11/19/2018]
[Ord. 432, 10/1/2008]
As used in this chapter, the following terms shall have the
meanings indicated:
The American Association of State Highway and Transportation
Officials. The web site home page for ASHTO is http://transportation1.org/aashtonew/.
The Allegheny County Conservation District.
The Allegheny County Health Department.
The Storm Water Management Act (Act of October 4, 1978, P.L.
864, No. 167; 32 P.S. § 680.1-680.17, as amended).
The plan for managing stormwater runoff throughout a designated
watershed adopted by Allegheny County as required by the Pennsylvania
Storm Water Management Act.
The work of producing crops, including tillage, land clearing,
plowing, disking, harrowing, planting, harvesting crops, or pasturing
and raising of livestock and installation of conservation measures.
Construction of new buildings or impervious area is not considered
an agricultural activity.
A landowner, developer or other person who has filed an application
for approval to engage in any regulated earth-disturbance activity
at a project site in the municipality.
A geologic formation, group of formations, or part of a formation
that contains sufficient saturated, permeable material to yield useful
quantities of groundwater to wells and springs.
To reduce the magnitude of the flow rate by increasing the
time it takes to release a specified volume of runoff (for example,
the one-year, twenty-four-hour storm event). Attenuation is a method
of reducing the peak flow rates for post-development compared to the
peak flow rates in predevelopment.
The portion of stream discharge derived from groundwater;
the sustained discharge that does not result from direct runoff or
from water diversions, reservoir releases, piped discharges, or other
human activities.
Activities, facilities, designs, measures, or procedures
used to manage stormwater impacts from regulated activities, to meet
state water quality requirements, to promote groundwater recharge,
and to otherwise meet the purposes these regulations. Stormwater BMPs
are commonly grouped into one of two broad categories or measures:
structural or nonstructural. In these regulations, nonstructural BMPs
or measures refer to operational and/or behavior-related practices
that attempt to minimize the contact of pollutants with stormwater
runoff, whereas structural BMPs or measures are those that consist
of a physical device or practice that is installed to capture and
treat stormwater runoff. Structural BMPs include, but are not limited
to, a wide variety of practices and devices, from large-scale retention
ponds and constructed wetlands, to small-scale underground treatment
systems, infiltration facilities, filter strips, low-impact design,
bioretention, wet ponds, permeable paving, grassed swales, riparian
or forested buffers, sand filters, detention basins, and manufactured
devices. Structural stormwater BMPs are permanent appurtenances to
the project site.
[Amended by Ord. 497, 11/19/2018]
Cubic feet per second.
A natural or artificial watercourse that conveys, continuously
or periodically, flowing water.
Surface runoff from rainfall events, which converges and
flows primarily through water-conveyance features such as swales,
gullies, waterways, channels or storm sewers and which exceeds the
maximum specified flow rates of filters or perimeter controls intended
to control sheet flow.
A series of holistic land development design practices that
maximize protection of key land and environmental resources, preserve
significant concentrations of open space and greenways, evaluate and
maintain site hydrology, and ensure flexibility in development design
to meet community needs for complementary and aesthetically pleasing
development. Conservation design encompasses the following objectives:
conservation/enhancement of natural resources, wildlife habitats,
biodiversity corridors and greenways (interconnected open space);
minimization of environmental impact resulting from a change in land
use (minimum disturbance, minimum maintenance); maintenance of a balanced
water budget by making use of site characteristics and infiltration;
incorporation of unique natural, scenic and historic site features
into the configuration of the development; preservation of the integral
characteristics of the site as viewed from adjoining roads; and reduction
in maintenance required for stormwater management practices. Such
objectives can be met on a site through an integrated development
process that respects natural site conditions and attempts, to the
maximum extent possible, to replicate or improve the natural hydrology
of a site.
A conservation district, as defined in § 3(c) of
the Conservation District Law [3 P.S. § 851(c)], that has
the authority under a delegation agreement executed with PA DEP to
administer and enforce all or a portion of the regulations promulgated
under 25 Pa. Code Chapter 102.
[Amended by Ord. 497, 11/19/2018]
The Pennsylvania Department of Environmental Protection.
The magnitude and temporal distribution of precipitation
from a storm event measured in probability of occurrence (e.g., a
five-year storm) and duration (e.g., 24 hours), used in the design
and evaluation of stormwater management systems.
An impoundment designed to collect and retard stormwater
runoff by temporarily storing the runoff and releasing it at a predetermined
rate. Detention basins are designed to drain completely shortly after
any given rainfall event and are dry until the next rainfall event.
The prevention of, or to prevent, the discharge, directly
or indirectly, of a given volume of stormwater runoff into surface
waters by temporary storage.
See "project site."
To release water from a project, site, aquifer, drainage
basin or other point of interest (verb); the rate and volume of flow
of water, such as in a stream, generally expressed in cubic feet per
second (volume per unit of time) (noun).
An unstabilized land area where an earth disturbance is occurring
or has occurred.
An artificial waterway for irrigation or stormwater conveyance.
That land area contributing runoff to a single point and
that is enclosed by a ridge line.
All facilities and natural features used for the movement
of stormwater through and from a drainage area, including but not
limited to any and all of the following: conduits, pipes and appurtenant
features, channels, ditches, flumes, culverts, streets, swales, gutters,
as well as all watercourses, water bodies and wetlands.
A construction or other human activity which disturbs the
surface of the land, including but not limited to clearing and grubbing;
grading; excavations; embankments; road maintenance; building construction;
and the moving, depositing, stockpiling, or storing of soil, rock
or earth materials.
A right of use of a specified portion of land of another
for a specified purpose.
A professional engineer duly appointed as the Engineer for
the municipality.
The Environmental Protection Agency.
The wearing away of land surface by water or wind which occurs
naturally from weather or runoff but is often intensified by human
activity.
The dominant land cover during the five-year period immediately
preceding a proposed regulated activity.
The Federal Emergency Management Agency.
The uppermost perennial tributary in a watershed that has
not yet confluenced with another perennial stream. The confluence
of two first-order streams forms a second-order stream.
Any land area susceptible to inundation by water from any
natural source or delineated by applicable Federal Emergency Management
Agency (FEMA) maps and studies as being a special flood hazard area.
The channel of the watercourse and those portions of the
adjoining floodplains that are reasonably required to carry and discharge
the one-hundred-year flood. Unless otherwise specified, the boundary
of the floodway is as indicated on maps and flood insurance studies
provided by FEMA. In an area where no FEMA maps or studies have defined
the boundary of the one-hundred-year floodway, it is assumed, absent
evidence to the contrary, that the floodway extends from the stream
to 50 feet from the top of the bank of the stream.
Planning and activities necessary for the management of forestland.
These include timber inventory and preparation of forest management
plans, silvicultural treatment, cutting budgets, logging road design
and construction, timber harvesting, site preparation and reforestation.
The difference between the elevation of the design flow in
the emergency spillway (usually the one-hundred-year peak elevation)
and the top elevation of the settled basin embankment (that is, top
of berm). The minimum freeboard shall be one foot.
Water that occurs in the subsurface and fills or saturates
the porous openings, fractures and fissures of underground soils and
rock units.
An area where land use or activities generate highly contaminated
runoff, with concentrations of pollutants in excess of those typically
found in stormwater.
A graph of discharge versus time for a selected point in
the drainage system.
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into four HSG's (A, B, C, and D) according to their
minimum infiltration rate, which is obtained for bare soil after prolonged
wetting. The Natural Resources Conservation Service (NRCS) of the
United States Department of Agriculture defines the four groups and
provides a list of most of the soils in the United States and their
group classification. The soils in the area of the development site
may be identified from a soil survey report that can be obtained from
local NRCS offices or Conservation District offices. Soils become
less pervious as the HSG varies from A to D.
The study of the properties, distribution, circulation and
effects of water on the Earth's surface, soil and atmosphere.
See "impervious surface."
A surface (area) which has been compacted or covered with
a layer of material so that it is resistant to infiltration by water.
It includes semipervious surfaces such as compacted clayey soils,
as well as most conventionally surfaced streets, roofs, sidewalks,
parking lots, and other similar surfaces. "Net increase of impervious
surface" refers to the difference between the existing impervious
coverage and the total impervious surface proposed.
Movement of surface water into the soil, where it is absorbed
by plant roots, evaporated into the atmosphere, or percolates downward
to recharge groundwater.
The depth of accumulated rainfall per unit of time.
A defined channel in which surface water is absent during
a portion of the year, as groundwater levels drop below the channel
bottom.
A type of topography that is formed over limestone or other
carbonate rock formations by dissolving or solution of the rock by
water and that is characterized by closed depressions, sinkholes,
caves, a subsurface network of solution conduits and fissures through
which groundwater moves, and no perennial surface drainage features.
Inclusive of any or all of the following meanings:
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
buildings or the division or allocation of land or space 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.
Any subdivision of land.
Development in accordance with Section 503(1.1) of the Pennsylvania
Municipalities Planning Code.[1]
A low earthen berm constructed perpendicular to the direction
of slope and extending across the width of the slope for the purpose
of intercepting surface runoff and spreading it behind the berm to
enhance infiltration and reduce erosion and runoff from the slope.
The purpose of a level spreader is to prevent concentrated, erosive
flows from occurring and to spread out stormwater runoff uniformly
over the ground as sheet flow.
The total amount (generally measured in pounds or kilograms
per acre per year) of material (sediment, nutrients, oxygen-demanding
material, or other chemicals or compounds) brought into a lake, stream
or water body by in flowing streams, runoff, direct discharge through
pipes, groundwater, the air (aerial or atmospheric deposition) and
other sources over a specific period of time (often annually).
Site design approaches and small-scale stormwater management
practices that promote the use of natural systems for infiltration,
evapotranspiration, and reuse of rainwater. LID can be applied to
new development, urban retrofits, and revitalization projects. LID
utilizes design techniques that infiltrate, filter, evaporate, and
store runoff close to its source. Rather than rely on costly large-scale
conveyance and treatment systems, LID addresses stormwater through
a variety of small, cost-effective landscape features located on site.
[Added by Ord. 497, 11/19/2018]
The action taken to restore or preserve the as-built functional
design of any facility or system.
A natural groundcover with less than one viable tree of a
DBH of six inches or greater per 1,500 square feet within 10 years
of application; a cover condition for which SCS curve numbers have
been assigned or to which equivalent Rational Method runoff coefficients
have been assigned.
Municipal separate storm sewer system.
The local government that adopted this chapter.
created in 1972 under the Clean Water Act to authorize discharges
to local receiving waters only pursuant to governmental permits, in
an effort to reduce point-source and non-point-source pollutants.
Any activity regulated by this chapter that is not considered
a redevelopment as defined in this chapter.
The National Oceanic and Atmospheric Administration.
Passive site design approaches or regulatory approaches that
positively impact water quality and reduce or minimize the generation
of stormwater runoff without requiring the construction of specific
or discrete stormwater management control structures.
The Natural Resources Conservation Service.
Any natural or man-made watercourse or conduit in which water
flows with a free surface.
Also known as "swales," "grass channels," and "biofilters."
These systems are used for the conveyance, retention, infiltration
and filtration of stormwater runoff.
The Association of Conservation Districts.
The Pennsylvania Department of Environmental Protection.
A ground cover of grassland or range with continuous forage
for grazing and greater than 75% ground cover and lightly or only
occasionally grazed; a cover condition for which the Soil Conservation
Service curve numbers have been assigned or to which equivalent Rational
Method runoff coefficients have been assigned.
The maximum rate of stormwater runoff from a specific storm
event.
The Pennsylvania Department of Transportation.
The rate of movement of water under hydrostatic pressure
through interstices of rock or soil. For stormwater analysis, it is
typically measured as a distance per unit of time (e.g., inches per
hour).
Any area not defined as impervious.
The ground cover assumption used when analyzing the stormwater
runoff characteristics of a drainage area prior to the proposed development.
The specific area of land where any regulated activities
in the municipality are planned, conducted or maintained.
Any person licensed by the Pennsylvania Department of State
or otherwise qualified by law to perform the work required by this
chapter.
The depth of accumulated rainfall per unit of time.
Volume per unit of time.
Any water bodies, watercourses or wetlands into which surface
waters flow.
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
An existing, developed property and/or a graded, altered
and compacted site (as of or after the date of adoption of this chapter)
that is proposed for reconstruction involving the demolition or partial
demolition of the property.
Any earth disturbances or any activities that involve the
alteration or development of land in a manner that may affect postconstruction
stormwater runoff.
Activity involving earth disturbance subject to regulation
under 25 Pa. Code, Chapter 92, Chapter 102, or the Clean Streams Law.
The percentage of predevelopment peak rate of runoff from
a watershed subarea (as delineated in the Act 167 watershed plan),
which defines the allowable post-development peak discharge from any
development site in that subarea.
An impoundment designed to collect and retard stormwater
runoff by temporarily storing the runoff and releasing it at a predetermined
rate. Retention basins may also be designed to permanently retain
additional stormwater runoff. Retention basins are designed to retain
a permanent pool of water during dry weather.
The prevention of direct discharge of stormwater runoff into
receiving waters or water bodies by temporary or permanent containment
in a pond or depression; examples include systems which discharge
by percolation to groundwater, exfiltration, and/or evaporation processes
and which generally have residence times of less than three days.
The average interval, in years, within which a storm event
of a given magnitude can be expected to occur one time. For example,
the twenty-five-year return period rainfall would be expected to occur
on average once every 25 years.
Pertaining to anything connected with or immediately adjacent
to the banks of a stream or other body of water.
A permanent vegetated area of trees and shrubs located adjacent
to streams, lakes, ponds, and wetlands.
[Amended by Ord. 497, 11/19/2018]
See "stormwater."
The Soil Conservation Service.
Fragmented material that originated from weathering rocks
and decomposing organic material that are transported by, suspended
in, and eventually deposited in the stream bed.
Occurs when sediment particles that have been suspended within
flowing water are deposited on the stream bottom or floodplain.
A flow process associated with broad, shallow water movement
on sloping ground surfaces that is not channelized or concentrated.
Source Loading and Management Model. This model is based
on small storm hydrology and pollutant runoff from urban land uses.
Pollutant sources are identified, and both structural and nonstructural
stormwater practices can be accounted for in the model.
Those areas identified by the Federal Emergency Management
Agency (FEMA), Federal Insurance Administration (FIA), as floodway
area (FW), flood fringe area (FF), and general floodplain area (FA);
where determined by the municipality, identified alluvial soils may
be included as well.
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Pennsylvania Code Title 25 and the
Clean Streams Law.
The storm of a specific duration, intensity, and frequency.
Is abbreviated as "SWM BMPs" or "BMPs" throughout this chapter.
The approved detailed analysis, design, and drawings of the
stormwater management system required for all construction.
The designed and/or constructed features which infiltrate,
treat, collect, convey, channel, store, inhibit, or divert the movement
of stormwater; such practices include structural and nonstructural
practices.
The flow of water overland and/or in water bodies that results
from and occurs during and immediately following a rainfall event.
Any measures that require the design and construction of
a facility to help reduce or eliminate a non-point source of pollution
and control stormwater.
Anything constructed or installed with a fixed location on
the ground or attached to something having a fixed location on the
ground.
A portion of the watershed (basin) that has similar hydrological
characteristics and drains to a common point.
As defined in the Pennsylvania Municipalities Planning Code,
Act of July 31, 1968, P.L. 805, No. 247.[2]
The top elevation of graded and compacted earth underlying
roadway pavement.
An artificial or natural waterway which may contain contiguous
areas of standing or flowing water only following a rainfall event,
or is planted with or has stabilized vegetation suitable for soil
stabilization, stormwater treatment, and nutrient uptake, or is designed
to take into account the soil erodibility, soil percolation, slope,
slope length, and contributing drainage area so as to prevent erosion
and reduce the pollutant concentration of any discharge.
Stormwater Management Model. The EPA developed this model
for analyzing stormwater quantity and quality associated with runoff
from urban areas. Both single event and continuous simulation can
be performed on catchments having storm sewers, or combined sewers
and natural drainage, for prediction of flows, stages and pollutant
concentrations. Information on SWMM is available at http://www.epa.gov/ceampubl/swater/swmm/index.htm.
The total area of the parcel(s) being developed.
The United States Department of Agriculture.
The United States Department of Transportation, Federal Highway
Administration.
Any natural or artificial pond, lake, reservoir, or other
area which ordinarily or intermittently contains water and which has
a discernible shoreline and receives surface water flow.
A permanent or intermittent stream or other body of water,
whether natural or man-made, which gathers or carries surface water.
Region or land area drained by a river, watercourse, or other
surface water of this commonwealth to a downstream point.
[Amended by Ord. 497, 11/19/2018]
Any and all rivers, streams, creeks, rivulets, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs, and all other bodies or channels of conveyance of
surface and underground water, or parts thereof, whether natural or
artificial, within or on the boundaries of this commonwealth.
The uppermost level of saturation of pore space or fractures
by subsurface water in an aquifer. "Seasonal high water table" refers
to a water table that rises and falls with the seasons due either
to natural or man-made causes.
Those areas that are inundated or saturated by surface water
or groundwater at a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence of vegetation
typically adapted for life in saturated soil conditions, including
swamps, marshes, bogs, fens, and similar areas.
Land areas that are inundated or saturated by surface water
or groundwater with a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence of vegetation
typically adapted for life in saturated soil conditions (wetlands
generally include swamps, marshes, bogs, and similar areas); or areas
that are defined and delineated in accordance with the Federal Manual
for Identifying and Delineating Jurisdictional Wetlands, dated January
10, 1989, and as may be amended from time to time; or as further defined
and delineated by the United States Army Corps of Engineers, the United
States Environmental Protection Agency, or the Pennsylvania Department
of Environmental Protection.
A natural groundcover with more than one viable tree of a
DBH (diameter at breast height) of six inches or greater per 1,500
square feet which existed within 10 years of application; a cover
condition for which SCS curve numbers have been assigned or to which
equivalent rational method runoff coefficients have been assigned.
