For purposes of stormwater management, the Municipality of Murrysville
is located in the Turtle Creek watershed(s), which includes the stormwater
management performance district(s) shown on the map entitled "Turtle
Creek Watershed Performance District Map," which is hereby adopted
as a portion of this chapter. For areas not covered by a stormwater
performance district, the release rate shall be 80%* of the predevelopment
peak flow as set by the Municipality. For more information refer to
www.westmorelandstormwater.org.
*In areas not covered by a stormwater performance district,
an 80% release rate or less is recommended as a standard. This is
to apply a "factor of safety" to stormwater calculations; to account
for the many variables in site design and stormwater management; and
to avoid a land development project inadvertently increasing runoff
and causing harm downstream.
A.
Preparation and implementation of a stormwater management site plan
is required for all regulated activities, unless preparation of an
SWM site plan is specifically exempted.
B.
Projects that propose greater than one acre of earth disturbance
are subject to NPDES permit requirements and will require a stormwater
management plan.
C.
No regulated activities, unless exempted, shall commence until the
Municipality issues written approval of an SWM site plan, which demonstrates
compliance with the requirements of this chapter.
D.
Regulated development activities shall be as follows:
|
Regulated Development Activity Table
| |||
|---|---|---|---|
|
SWM Plan Requirement
|
New Impervious Area for New and Redevelopment
|
Disturbed Area*
|
Next Steps
|
|
Exempt
|
0
|
Less than 1 acre
|
Comply with exemption section of this chapter (§ 198-303)
|
|
No-harm
|
Up to 1,000 square feet for urban OR 3,000 square feet for suburban/rural
areas
|
Less than 3,000 square feet for urban OR 5,000 square feet for
suburban/rural areas
|
Comply with no-harm section of this chapter (§ 198-304)
|
|
Waiver/modification/demonstrated equivalency
|
Less than 1 acre, subject to municipal approval
|
Less than 1 acre
|
Comply with waiver/modification/demonstrated equivalency section of this chapter (§ 198-305)
|
|
Small project (per definition); refer to Appendix C[1]
|
3,000 square feet to 10,000 square feet
|
5,000 square feet to 20,000 square feet
|
Submit small project site plan complete with all attachments
|
|
Stormwater management plan meeting the chapter requirements
|
Greater than 10,000 square feet if exempt and small project
criteria are not met, or if improvements do not meet no-harm criteria
|
Greater than 20,000 square feet
|
Consult a qualified professional
|
|
*
|
The above table is only applicable for projects with earth disturbance
less than one acre and that have not had cumulative impacts, within
five years preceding the permit application date, that are in excess
of the square-foot limits.
|
[1]
Editor's Note: Appendix C is on file in the municipal offices.
A.
The following regulated activities are specifically exempt from the
stormwater management plan preparation and submission requirements
articulated in this chapter:
(1)
Agricultural activity limited to plowing or tilling activities, for animal concentrated (heavy) use areas provided the activities are performed according to the requirements of Chapter 102, or conservation practices being installed as part of the implementation of a conservation plan written by an NRCS- or SCS-certified planner. This exemption does not include any other type of earth disturbance subject to NPDES permit requirements, such as earth disturbance equal to or greater than one acre.
(2)
A high tunnel, if proof is provided that the high tunnel is
exempt pursuant to the provisions of Act 15 of 2018. Such an exemption
does not exempt high tunnels from other requirements applicable under
federal, state or municipal laws.
(3)
Forest management and timber operations, provided the activities are performed according to the requirements of Chapter 102.
(4)
Resource extraction activities, provided they are done in accordance
with applicable PA DEP regulations.
(5)
Roadway resurfacing and maintenance projects, which do not increase
impervious area, and underground infrastructure projects are exempt
from the provisions of this chapter, provided the activities meet
the requirements of all other municipal, state and federal requirements.
(6)
Domestic landscaping and/or vegetable gardening.
(7)
Voluntary green infrastructure (GI) or the retrofit of stormwater
management infrastructure as conversion to green infrastructure BMPs
to correct existing problems, that are solely intended to better manage
runoff from existing development, are not part of new development
or redevelopment, and that do not fall under the requirements of this
chapter or other development ordinances.
B.
The Municipality of Murrysville may deny or revoke any exemption
pursuant to this section at any time for any project that the Municipality
of Murrysville believes may pose a threat to public health, safety,
property or the environment.
A.
Applicants may request approval of a "no-harm option" regarding stormwater
management for their project. "No-harm option" requests must meet
the following criteria deemed appropriate by Municipality and in compliance
with all commonwealth laws and regulations:
(1)
Project located near or adjacent to a significantly larger body
of water.
(2)
Project able to discharge directly into an existing flood-control
feature.
(3)
(4)
Project will generate less than 0.5 cubic foot per second for
the ten-year storm peak rate increase as compared to predevelopment
peak rate.
(5)
Project is not part of a larger development being "piecemealed"
in order to avoid stormwater management regulations.
(6)
Project is not part of a larger development which has grown
"piecemeal" over the past five years without SWM.
(7)
Project is a small percentage <5% of a much larger site and
is incidental to the much larger site.
(8)
Project is not located in a neighborhood, watershed, or location
where known stormwater problems exist, such as overland flooding like
flooding of structures or roadways.
(9)
Project does not discharge to a combined sewer.
(10)
Project will not degrade water quality of the receiving stream.
Refer to the Westmoreland County Integrated Water Resources Plan,
www.westmorelandstormwater.org, for maps of impaired streams to determine
if the project area is not within an impaired stream corridor or provide
documentation that further degradation will not occur.
B.
To qualify for the "no-harm" option, the applicant may, at the request
of the Municipality, submit calculations, drawings, and details showing
that the project meets all of the applicable criteria.
C.
Projects approved for the "no-harm" option may be exempted from constructing
all or some of the usual stormwater management practices regularly
required for similar projects.
D.
To be approved, "no-harm" requests must be reviewed and approved
by the Municipality of Murrysville Engineer and by the WCD, but final
approval rests with the Municipality of Murrysville.
A.
If the Municipality of Murrysville, in conjunction with the Municipal Engineer, WCD, or DEP, as applicable, determines that any requirement under this chapter cannot be achieved for a particular regulated activity, the Municipality may, after an evaluation of alternatives, approve measures other than those in this chapter, subject to this Subsections B, C and D of this chapter and in compliance with all commonwealth laws and regulations. The request for a waiver, modification, or demonstrated equivalency shall originate with the landowner, shall be in writing, shall include a study of downstream effects, and shall accompany the stormwater management plan submission to the Municipality. The request shall provide the facts on which the request is based, the provision(s) of this chapter involved and the proposed modification or demonstrated equivalency. The Municipality shall review the request to determine if it meets the requirements of this chapter, including Subsections B, C and D of this section. If acceptable to the Municipality and the regulated stormwater activity involving earth disturbance is less than one acre, the Municipality may grant the waiver or modification. If the regulated stormwater activity involving earth disturbance is equal to or greater than one acre, the plan will be subject to the NPDES requirements of DEP.
B.
Waivers, modifications, or demonstrated equivalency of the requirements
of this chapter may be approved by the Municipality if enforcement
will exact undue hardship because of unique physical circumstances
or preexisting site conditions peculiar to the land in question, provided
that the modifications or demonstrated equivalency will not be contrary
or detrimental to the public interest and shall achieve the intended
outcome, and that the purpose of this chapter is preserved. Hardship
must be due to such unique physical circumstances or preexisting site
conditions and not the circumstances or conditions generally created
by the provisions of this chapter; and there is no possibility that
the property can be developed in strict conformity with the provisions
of this chapter. Cost or financial burden shall not be considered
a hardship. Hardship cannot have been created by the landowner or
developer. Modification or demonstrated equivalency shall not substantially
or permanently impair the appropriate use or development of adjacent
property(s) not under the landowner's control. Modification or
demonstrated equivalency may be considered if an alternative standard
or approach will provide equal or better achievement of the purpose
of this chapter.
C.
No waiver, modification or demonstrated equivalency of any regulated
stormwater activity involving earth disturbance greater than or equal
to one acre may be granted by the Municipality unless that action
is approved in advance by the Department of Environmental Protection
(DEP) or the Westmoreland Conservation District (WCD).
D.
Applicants may request approval of a demonstrated equivalent stormwater
activity for their project in lieu of performing traditional stormwater
management. Demonstrated equivalent stormwater activity requests will
be evaluated by the Municipal Engineer on a case-by-case basis. Prior
approval of a demonstrated equivalent stormwater activity on a site
does not set a precedent for future approval of the same or other
alternative activities on any site. The approval of a demonstrated
equivalent stormwater activity does not excuse the applicant from
following standard E&S and SWM practices as applicable on the
original site.
(1)
Demonstrated equivalent stormwater activities shall only be
approved when the following criteria are met:
(a)
Traditional stormwater management activities on the site are
precluded by a particular site limitation, such as contaminated soil,
steep slopes, existing buildings/infrastructure, or combined sewer;
(b)
Construction of traditional stormwater management activities
on the site would require extra permits or lead to excessive permitting
activities and delays;
(c)
The site in question does not already have a stormwater management
problem; and
(d)
The site in question is not already contributing to water quality
problems in the receiving stream.
(2)
Approvable demonstrated equivalent stormwater activities may
include the following:
(a)
Restoration of an existing degraded wetland, stream channel,
floodplain, or riparian buffer, including daylighting of a stream.
(b)
Restoration, retrofit or upgrade an existing stormwater management
feature (inadequate detention pond, for example).
(c)
Creation of new stormwater management features, especially green
infrastructure, for a previously unmanaged site
(d)
Provide a water-based benefit to the public other than stormwater
management (for example, extend a public sewer to an area not already
served).
(e)
Treatment of abandoned mine drainage.
(3)
The proposal for demonstrated equivalency shall be accompanied
by documentation or methodology quantifying the equivalency of the
proposed project to what would have been originally required. Acceptable
documentation or methodology may include use of the worksheets and
checklist found in the PA DEP NPDES permit application Appendix D
or an approved method showing the proposed equivalency:
(a)
Controls approximately the same amount of runoff volume as what
would originally have been proposed.
(b)
Improves approximately the same amount of runoff quality as
would have been originally proposed.
(c)
Is located within an impaired watershed or stream segment which
will benefit from the proposed project. Impairment may include stream
impairment, reduced stream buffer, and pollutant loading. Refer to
the Westmoreland County Integrated Water Resources Plan at www.westmorelandstormwater.org.
(4)
The demonstrated equivalent stormwater activity shall:
(a)
Be constructed concurrently with the project for which it is
being applied;
(b)
Be constructed according to plans approved by the Municipality,
including any erosion control and stormwater management practices
as applicable;
(c)
Obtain all necessary permits;
(d)
Be located on land owned by or controlled by the applicant or
by a cooperating public or private entity(ies) (school, church, club,
municipality, etc.);
(e)
Be protected by a perpetual easement or deed restriction, or
landowner agreement;
(f)
Be located in the same general watershed as the project for
which it is being applied; and
(g)
Have an operation and maintenance plan (O&M) specifying
who is responsible for what tasks.
A.
When a regulated development activity (refer to Table in § 198-302 of this chapter) creates impervious area between 3,000 and 10,000 square feet, or total earth disturbance between 5,000 and 20,000 square feet, the stormwater management requirements are as follows. Refer also to Appendix C.[1]
[1]
Editor's Note: Appendix C is on file in the municipal offices.
B.
For new impervious surfaces, the first one inch of runoff shall be
permanently removed from the runoff flow and shall not be released
to waters of the commonwealth. Removal options include reuse, evaporation,
transpiration and infiltration.
C.
Facilities, to the greatest extent possible and subject to municipal
approval, shall be designed to drain the permanently removed runoff
volume in a period no greater than 72 hours. Runoff volumes in excess
of one inch shall be safely conveyed to a stable vegetated area, natural
watercourse, the curb or gutter line of roadway or an existing storm
collection/conveyance/control system, as applicable.
E.
A small project stormwater management plan must be submitted to the Municipality and shall consist of the following items and related support material needed to determine compliance with §§ 198-307 to 198-311 of this chapter. The applicant can also use protocols listed in Appendix C.[2]
(1)
Narrative: a general description of proposed stormwater management
techniques, including calculations, assumptions and criteria used
in the design of the stormwater management facilities and BMPs, and
construction specifications of the materials to be used for stormwater
management facilities and BMPs;
(2)
Stormwater management plan: showing locations of all stormwater
management facilities and BMPs, especially green infrastructure, limits
of disturbance, including the type and amount of proposed impervious
area, structures, roads, paved areas and buildings;
(3)
Small project stormwater management worksheet;
(5)
Erosion and sediment control plan: including all reviews and
letters of adequacy from the Conservation District.
[2]
Editor's Note: Appendix C is on file in the municipal offices.
A.
Proposed land development must consider avoiding, minimizing, and
mitigating impacts to the site that may increase stormwater runoff
from the proposed project. Applied sequentially, these three low-impact
development strategies should be an overall guide as a project is
planned and carried out.
B.
The Westmoreland County Integrated Water Resources Plan provides
an online decision-making tool to assist developers, designers, and
property owners in addressing all water resources during development
and redevelopment and should be consulted. Refer to www.paiwrp.com
and www.westmorelandstormwater.org.
C.
The following provisions shall be considered the overriding performance
standards against which all proposed stormwater control measures shall
be evaluated and shall apply throughout the Municipality of Murrysville:
(1)
Any landowner and any person engaged in the alteration or development
of land which may affect stormwater runoff characteristics shall implement
such measures as are reasonably necessary to prevent injury to health,
safety or other property. For alteration or development taking place
in stages, the cumulative development must be used in determining
conformance with this chapter. Such measures shall include such actions
as are required:
(a)
To assure that the maximum rate of stormwater runoff is no greater
after development than prior to development activities for the two-,
ten-, fifty-, and 100-year storms. Rainfall data shall be obtained
from NOAA Atlas 14 or other source approved by the Municipality.
(b)
To manage the water quality, rate and volume and direction of
resulting stormwater runoff in a manner which otherwise adequately
protects health and property from possible injury.
(c)
To notify adjacent property owners or owners of affected properties
of any alteration or increase of stormwater flows.
(2)
Runoff treatment BMPs must be employed where necessary to ensure
the water quality, rate and volume requirements are met.
(3)
Volume control BMPs shall be used to maintain existing hydrologic
conditions for small storm events by promoting groundwater recharge
and/or evapotranspiration. Runoff volume controls shall be implemented
using the PA DEP Stormwater BMP Manual 2006 or other approved method
such as those listed in the following chart:
|
Acceptable Computation Methodologies for Stormwater Management
Plans
| ||
|---|---|---|
|
Method
|
Developed By
|
Applicability
|
|
Win TR-20 (or commercial computer package based on TR-20)
|
USDA NRCS
|
Applicable where use of full hydrologic computer model is desirable
or necessary
|
|
Win TR-55 (or commercial computer package based on TR-55, i.e.,
VT/PSUHM)
|
USDA NRCS
|
Applicable for land development plans within limitations described
in TR-55
|
|
HEC-1, HEC-HMS
|
US Army Corps of Engineers
|
Applicable where use of full hydrologic computer model is desirable
or necessary
|
|
PennDOT 584 (based on Rational Method)
|
PennDOT
|
Applicable under standards established by PennDOT
|
|
EFH2
|
USDA NRCS
|
Applicable in agricultural areas subject to the program limits
|
|
SWMM
|
EPA
|
Applicable in urban and suburban areas subject to limits established
by EPA
|
|
PA DEP BMP Manual 2006
|
PA DEP
|
Applicable under standards established by PA DEP
|
|
Other methods
|
Varies
|
Other methodologies approved by the Municipality
|
D.
The project plan shall specify permanent stormwater BMPs to be implemented,
operated and maintained to meet legal water quality, rate and volume
requirements. If methods other than low-impact development (LID) and
green infrastructure methods are proposed to achieve the volume and
rate controls required under this chapter, the SWM site plan must
include a detailed justification demonstrating that the use of LID
and green infrastructure is not practicable.
E.
In order to protect and maintain water quality, additional stormwater
runoff created by the development project must be captured, stored
and treated. In addition, post-construction stormwater infiltration
of runoff must replicate preconstruction infiltration of runoff to
the maximum extent possible with the exception of hotspots. As a minimum,
this shall be a volume of additional runoff generated by a two-year,
twenty-four-hour storm. Preferred BMPs for a hotspot include storm
inlet filters, proprietary stormwater quality devices, underground
detention tanks, detention ponds with forebays, tree planting, and
green roof. Permeable pavement, infiltration BMPs, and rain gardens
are not recommended for hotspots.
F.
G.
No regulated development activities within the Municipality shall
commence until the requirements of this chapter are met.
H.
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 determined by the Municipality
of Murrysville.
I.
LID and green infrastructure techniques described in the PA DEP Stormwater
BMP Manual 2006, or most current edition, are encouraged.
J.
Projects proposed in municipalities which are subject to the MS4
regulations must comply with that municipality's approved MS4
permit, including compliance with the six minimum control measures
(MCMs), and with the Municipality's Pollutant Reduction Plan
(PRP).
A.
The stormwater management performance standards in this chapter are
intended to implement the provisions, standards and criteria contained
in the Pennsylvania Stormwater Management Act (Act 167), 32 P.S. § 680.1
et seq. If there is any discrepancy between the provisions of this
chapter and the provisions, standards and criteria of the Act, or
if a stormwater management plan is subsequently approved and adopted
by the appropriate governmental agency or body, then the provisions,
standards and criteria of the current watershed plan shall govern.
B.
Management of stormwater runoff is a key objective of 25 Pa. Code,
Chapter 93, of the DEP Regulations, because runoff can change the
physical, chemical and biological integrity of water bodies thereby
impacting rate, volume and water quality.
C.
The project plan shall describe how these rate, volume and water
quality protection requirements will be met. Infiltration BMPs shall
be evaluated and utilized to the maximum extent possible to manage
the net change in stormwater runoff generated so that post-construction
discharges do not degrade the physical, chemical or biological characteristics
of the receiving waters. These BMPs may be used to satisfy all or
part of the requirements found within this chapter.
D.
Refer to the Stormwater Performance Districts outlined in Appendix
A,[1] and the Westmoreland County Integrated Water Resources
Plan (IWRP) at www.westmorelandstormwater.org. The project plan shall
describe how the proposed project will address performance standards,
impairments, and pollutant loading found in the IWRP. For areas not
covered by a stormwater performance district, the release rate shall
be 80% of the predevelopment peak flow as set by the Municipality.
[1]
Editor's Note: Appendix A is on file in the municipal offices.
A.
General criteria.
(1)
Applicants may select runoff control techniques, or a combination
of techniques, which are most suitable to control stormwater runoff
from the development site. Refer to the Acceptable Computation Methodologies
Table of this chapter.[1] All controls must be subject to approval of the Municipal
Engineer. The Municipal Engineer may request specific information
on design and/or operating features of the proposed stormwater controls
in order to determine their suitability and adequacy in terms of the
standards of this chapter.
[1]
Editor's Note: See § 198-307C(3).
(2)
If the proposed development site is located in an impaired watershed
according to Category 4 of the PA Integrated Water Quality Monitoring
and Assessment Report, or in a watershed with a TMDL according to
Category 5 of the same Report, the applicant shall identify the source
and cause of impairment and shall propose, if required or applicable,
the use of BMPs to mitigate any impacts to the waters.
(3)
The applicant should consider the effect of the proposed stormwater
management techniques on any special soil conditions or geological
hazards which may exist on the development site. In the event such
conditions are identified on the site, the Municipality of Murrysville
Engineer may require in-depth studies by a competent geotechnical
engineer. Not all stormwater control methods may be advisable or allowable
at a particular development site.
(4)
The applicant shall consider the effect of the proposed stormwater
management techniques on existing stream impairments and pollutant
loading. Refer to the Westmoreland County Integrated Water Resources
Plan (IWRP) at www.westmorelandstormwater.org.
(5)
The applicant shall consider existing conditions on the site
for the prior five years to determine prevailing land use and impervious
cover and shall consider 20% of existing impervious cover as meadow
for preexisting conditions on redevelopment sites.
(6)
The stormwater management practices to be used in developing
a stormwater management plan for a particular site shall be selected
according to the following order of preference:
(a)
Site planning for locating proposed buildings, impervious areas
and grading which minimizes disruption of the natural site characteristics,
especially utilizing low-impact development techniques.
(b)
Minimization of impervious areas and promotion of retentive
grading.
(c)
Implementation of nonstructural measures (refer to the PA DEP
Stormwater BMP Manual 2006, or current edition).
(d)
Implementation of innovative/green infrastructure structural
measures (refer to the PA DEP Stormwater BMP Manual 2006, or current
edition).
(e)
Stormwater detention/retention structures.
(7)
Any BMP which is a dam, culvert, stream obstruction or encroachment
or outfall as defined in 25 Pa. Code, Chapter 105, shall be designed
according to the requirements in those regulations.
(8)
Drainage easements shall be provided for all stormwater conveyance
and BMPs serving multiple properties and not located within a public
right-of-way. Easements shall include ingress and egress to a public
right-of-way and shall be recorded at the county with the final plan.
Terms of easement shall prohibit excavation or placement of fill or
structures and any alteration that may adversely affect the flow of
stormwater within any portion of the easement.
(9)
No person shall install, create, modify, remove, fill, landscape
or otherwise alter or place any structure, soil, rock, material or
vegetation in or on, or otherwise adversely affect, any stormwater
management facility or any area within a stormwater easement without
the written approval of the Municipality and/or approval of the WCD.
B.
Criteria for stormwater management facilities and BMPs.
(1)
If stormwater management facilities and BMPs are utilized for
the development site, the facility(ies) shall be designed such that
post-development peak runoff rates from the developed site are controlled
to those rates defined by a Stormwater Management Performance District
for the two-, ten-, fifty-, and 100-year storm frequencies. Rainfall
data shall be obtained from NOAA Atlas 14 or other source as approved
by the Municipality.
(2)
All stormwater management facilities and BMPs shall be equipped
with outlet/overflow structures to provide rate discharge control
for the designated storm frequencies. Provision shall also be made
to safely pass the entire post-development 100-year storm without
breaching or otherwise damaging the facilities or downstream or neighboring
properties.
(3)
Release of stormwater flow from a development site must be to
an existing stormwater conveyance or easement, whether natural or
man-made. Calculations and information shall be presented as to the
ownership, responsible party, capacity, and stability of such conveyance.
Release of "sheet flow," as from a level spreader, will be permitted
on a case-by-case basis as approved by the Municipality.
(5)
Shared stormwater management facilities and BMPs, which provide
control of runoff for more than one development site within a single
subarea, may be considered and are encouraged. Such facilities shall
meet the criteria contained in this section. In addition, runoff from
the development sites involved shall be conveyed to the facility in
a manner that avoids adverse impacts (such as flooding or erosion)
to channels and properties located between the development site and
the shared storage facilities.
(6)
Where stormwater management facilities and BMPs will be utilized,
multiple-use facilities, such as wetlands, lakes, ballfields or similar
recreational/open space uses, are encouraged wherever feasible, subject
to the approval of the Municipality of Murrysville.
(7)
Other considerations which shall be incorporated into the design
of the stormwater management facilities and BMPs include:
(a)
Inflow and outflow structures shall be designed and installed
to prevent erosion, and embankments, cuts, fills and bottoms of impoundment-type
structures should be protected from soil erosion.
(b)
Control and removal of debris, both in the storage structure
and in inlet or outlet devices, shall be a design consideration.
(c)
Inflow and outflow structures, pumping stations and other structures
shall be designed and protected, using safety benches, trash racks,
energy dissipaters and other means to minimize safety hazards.
(d)
Access may be restricted as specified by the provisions for
fencing swimming pools as found in the Zoning Ordinance, and in appropriate
instances such restriction of access may include fencing in a minimum
height of six feet.
(e)
Interior slopes of storage ponds shall not exceed a ratio of
three to one horizontal to vertical dimension with a combination of
interior and exterior slopes not exceeding five. Steeper slopes may
be approved by the Municipal Engineer if documented to be stable by
a geotechnical analysis.
(f)
Landscaping shall be provided for the facility which stabilizes
disturbed areas and preserves the natural and beneficial values of
the surrounding area.
(g)
The facility shall be located to facilitate maintenance, considering
the frequency and type of equipment that will be required.
(h)
Underground detention/retention/infiltration facilities shall
be equipped with open-grate inlet or manhole access to facilitate
visual inspections.
C.
Criteria for collection/conveyance facilities.
(1)
All stormwater runoff collection or conveyance facilities, whether
storm sewers or other open or closed channels, shall be designed in
accordance with the following basic standards:
(a)
All building sites shall use measures to provide drainage away
from and around the structure in order to prevent any potential flooding
damage as much as practical. Such measures shall include grading the
surrounding lawn or pavement area so that it slopes away from the
structure by a minimum of 2% slope over a minimum distance of 10 feet;
raising the floor of the structure so that it is a minimum of six
inches above the predominant surrounding land elevation and above
the designated floodplain elevation for those located within a floodplain;
eliminating or waterproofing penetrations through the structure's
walls or foundation; constructing berms, curbs, or swales to divert
surface water around the structure; and arranging roof and area drains
to carry water away from the structure.
(b)
Developers proposing a land development or subdivision shall
arrange internal drainage within the subdivision so that surface water
is safely directed and channeled away from all structures within and
adjacent to the development site.
(c)
Developers shall provide to all persons constructing a structure
within a land development site standards, including drawings and specifications,
to ensure that those persons adhere to the general site plans and
stormwater management plans for the development. Persons constructing
a structure within a land development site shall submit to the Municipal
Engineer drawings, calculations, and other information to show how
they will meet the stormwater management requirements of the development
site.
(d)
Lots located on the high side or low side of streets shall extend
roof, trench and area drains to a stable vegetated area, natural watercourse,
the curb or gutter line of the roadway or a storm collection/conveyance/control
system (if applicable) in accordance with the approved stormwater
management plan for the development site.
(e)
For all building sites and lots, the inclusion of rain barrels,
rain gardens, drywells and other strategies for infiltration of roof
runoff close to its source is encouraged.
(f)
Collection/conveyance facilities should not be installed parallel
and less than 10 feet from the top or bottom of an embankment, greater
than or equal to 15 feet in height to avoid the possibility of failing
or causing the embankment to fail, unless documented to be stable
by a geotechnical analysis.
(g)
All collection/conveyance facilities shall be designed to convey
the twenty-five-year storm peak flow rate from the contributing drainage
area and to carry it to the nearest suitable outlet such as a stormwater
control facility, curbed street, storm sewer or natural watercourse.
(h)
Where drainage swales or open channels are used, they shall
be suitably lined to prevent erosion and designed to avoid erosive
velocities.
(2)
Wherever storm sewers are proposed to be utilized, they shall
comply with the following additional criteria:
(a)
Where practical, designed to traverse under seeded and planted
areas. If constructed within five feet of road paving, walks or other
surfaced areas, drains shall have a narrow trench and maximum compaction
of backfill to prevent settlement of the superimposed surface or development,
preferably installed after excavating and filling in the area to be
traversed is completed, unless the drain is installed in the original
ground with a minimum of three feet of cover and/or adequate protection
during the fill construction.
(c)
Designed to adequately handle the anticipated stormwater flow
and be economical to construct and maintain. The minimum pipe size
shall be 15 inches in diameter, with the exception of roof drains,
foundation drains or similar conveyances.
(d)
Drain pipe, trenching, bedding and backfilling requirements
and appropriate grates, catch basins, stormwater inlets, manholes
and other appurtenances shall conform to the requirements of the Municipality
and/or applicable PennDOT Specifications, Publication 408.
(e)
All corrugated metal pipe shall be polymer-coated, and with
paved inverts where prone to erode. Pipe within a Municipality roadway
shall be reinforced concrete pipe or high-performance polypropylene
pipe with a minimum diameter of 15 inches.
(f)
Storm inlets and structures shall be designed to be adequate,
safe, self-cleaning and unobtrusive and consistent with municipal
standards with sufficient capture and conveyance capacity and spacing
of inlets and cleanouts for maintenance.
(g)
Where a proposed sewer or conveyance connects with an existing
storm sewer or conveyance system, the applicant shall demonstrate
that sufficient capacity exists in the downstream system to handle
the additional flow.
(h)
Storm sewer outfalls shall be equipped with energy-dissipation
devices to prevent erosion and conform with applicable requirements
of the Pennsylvania DEP for stream encroachments (Section 7 of the
Dam Safety and Encroachments Act, 32 P.S. § 693.1 et seq.,
and the rules and regulations promulgated thereunder at 25 Pa. Code
§§ 105.441 to 105.449).
D.
Criteria for riparian buffers.
(1)
If a riparian buffer is required by PA DEP as part of an NPDES
permit, then DEP regulations will govern.
(2)
If a riparian buffer is used to meet stormwater management requirements
and/or MS4 pollutant load reduction credits, it shall meet the following
requirements:
(a)
In order to protect and improve water quality, a riparian buffer
easement may be created and recorded as part of any subdivision or
land development that encompasses a riparian buffer.
(b)
Except as required by Pa. Code, Title 25, Chapter 102, the riparian buffer easement shall may be measured to a minimum of 35 feet measured from the top of the nearest bank (on each side), or an average of 35 feet with no distance from top of bank less than 25 feet.
(c)
Minimum management requirements for riparian buffers:
[1]
Existing native vegetation shall be protected and maintained
within the riparian buffer easement.
[2]
Whenever practicable, invasive vegetation shall be actively
removed, and the riparian buffer easement shall be planted with native
trees, shrubs and other vegetation to create a diverse native plant
community appropriate to the intended ecological context of the site.
[3]
There shall be no earth disturbance beyond which is necessary
to establish or maintain a planted buffer.
(3)
The riparian buffer easement shall be enforceable by the Municipality
and shall be recorded in the appropriate County Recorder of Deeds'
office, so that it shall run with the land and shall limit the use
of the property located therein. The easement shall allow for continued
private ownership and shall count toward the minimum lot area a required
by zoning, unless otherwise specified in the municipal Zoning Ordinance.[4]
(4)
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.
(5)
Stormwater drainage pipes and all other linear utility lines
as approved by the Municipality shall be permitted within the riparian
buffer easement, but they shall cross the easement in the shortest
practical distance. Other stormwater management facilities and BMPs
are not permitted within the riparian buffer easement.
(7)
Septic drainfields and sewage disposal systems shall not be
permitted within the riparian buffer easement and shall comply with
setback requirements established under 25 Pa. Code, Chapter 73.
E.
Criteria for stream restoration projects. A stream restoration project
may eligible for stormwater management and/or MS4 load reduction credits
if it meets qualifying criteria set by the Municipality and as follows:
(1)
Existing conditions, such as channel or stream bank erosion
and an actively enlarging or incising urban stream condition, shall
be documented prior to restoration.
(2)
Projects should be located on first- to third-order (small)
streams to be effective.
(3)
Project should address a minimum of 100 linear feet of stream
channel and both sides where need to do so is evident.
(4)
Upstream impervious area should be sufficiently treated to address
peak flows that may exceed engineering design thresholds or compromise
channel form and function.
(5)
Utilize a comprehensive approach employing a mix of techniques
appropriate to the site, creating long-term stability of the stream
bed, stream banks and floodplain.
(6)
Armored length of streams (i.e., using riprap or gabions) may
be used to maintain channel stability, but the same length shall not
be included in the load-reduction calculation.
(7)
Project shall maximize floodplain reconnection, with minimal
channel invert elevation increase (i.e., bank height ratio = 1.0 or
less) to achieve the objective.
(8)
Project shall include a minimum 35 feet of permanent riparian
buffer.
(9)
Project shall include an O&M plan identifying O&M activities,
frequencies and responsible parties.
A.
No regulated development activities within the Municipality shall
commence until approval by the Municipality and the WCD of an erosion
and sediment control plan for construction activities.
B.
Any earth disturbance activity of 5,000 square feet or more requires
an erosion and sedimentation control plan under 25 Pa. Code § 102.4(b).
Refer to the PA DEP Erosion and Sediment Pollution Control Manual
2012, or most-recent version.
C.
In addition, under 25 Pa. Code, Chapter 92, a DEP NPDES construction
activities permit is required for regulated development activities.
D.
Evidence of any necessary permit(s) for regulated development activities from the appropriate DEP regional office or Westmoreland Conservation District must be provided to the Municipality. The issuance of an NPDES construction permit [or permit coverage under the Statewide General Permit (PAG-2)] may satisfy the requirements under Subsection A upon review and approval by the Municipality.
E.
A copy of the erosion and sediment control plan and any permit required
by the DEP or the Municipality shall be available at the project site
at all times.
A.
No regulated development activities which require a Chapter 105 (Water
Obstructions and Encroachment) permit from either the PA DEP or the
Westmoreland Conservation District shall commence until all permits
have received PA DEP or WCD approval, and municipal approval.
B.
Evidence of any necessary Chapter 105 permit from PA DEP/WCD shall
be provided to the Municipality.
C.
Proposed development shall avoid the long- and short-term adverse
impacts associated with the occupancy and modification of floodplains
as designated by FEMA, to the extent possible wherever there is a
practicable alternative in order to reduce the risk of flood loss,
minimize the impacts of floods on human safety, health and welfare,
and restore and preserve the natural and beneficial values served
by floodplains.
D.
Any proposed development found to be within the base floodplain of
a waterway shall include the identification of impacts, an evaluation
of practicable alternatives outside the floodplain, and, when impacts
cannot be avoided, the development of measures to minimize the impacts
and restore and preserve the floodplain as appropriate. Findings shall
be presented at a public meeting and a determination made by the Council
of the Municipality of Murrysville.
