A.
All land development within the municipality shall
be designed, implemented, operated and maintained to meet the purposes
of this chapter through these two elements:
B.
No approval of any subdivision or land development plans, or issuance of any zoning permit or occupancy permit, or the commencement of any earth disturbance at a project site within the municipality, shall proceed until the requirements of this chapter are met, including approval of a project plan under § 164-23 and a permit under PADEP regulations, where applicable.
[Added 7-7-2004 by Ord. No. 514]
G.
The fee for review of any land development application
shall be based on the amount of land to be disturbed at the site,
and the fee schedule shall be established by the Township of Rostraver.
All of the monetary contributions shall be credited to a local budgetary
category to support local plan review, inspection and program administration,
and shall be made prior to the issuance of any zoning permit for the
development.
[Added 7-7-2004 by Ord. No. 514]
H.
Projects are subject to the MS4 regulations and 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).
[Added 12-2-2020 by Ord. No. 733]
[Amended 7-7-2004 by Ord. No. 514]
The following permit requirements apply to certain
land development activities and must be met prior to municipal approval
of subdivision approval or land development plans, or issuance of
zoning or occupancy permits, where applicable:
A.
All earth disturbance activities subject to standards
and possible permit requirements by PADEP under regulations at 25
Pa. Code Chapter 102.
B.
Work within natural drainageways subject to permit
by PADEP under 25 Pa. Code Chapter 105.
C.
Any stormwater management facility that would be located
in or adjacent to surface waters of the commonwealth, including wetlands,
subject to permit by PADEP under 25 Pa. Code Chapter 105.
D.
Any stormwater management facility that would be located
on a state highway right-of-way subject to approval by the Pennsylvania
Department of Transportation (PennDOT).
E.
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 subject to permit by DEP under 25 Pa. Code
Chapter 105.
A.
Any person conducting any new land development activities
or redevelopment activities creating an impervious area of 1,000 square
feet or greater in the municipality or involving earth disturbance
of 5,000 square feet or greater, shall submit and obtain approval
from the municipality of a project plan meeting the requirements of
this chapter, prior to commencing the activity.
B.
The project plan shall describe the BMPs for erosion
and sediment control, and the postconstruction BMPs for water quality
protection.
D.
The requirements in this section apply to the total
land development project, even if it is to take place in stages.
E.
All redevelopment projects over 1,000 square feet
shall evaluate the feasibility of reducing site impervious area by
at least 20%. Where project site conditions prevent the reduction
of impervious area, then stormwater BMPs shall be evaluated to provide
qualitative controls for at least 20% of the site’s impervious
area.
[Added 12-2-2020 by Ord.
No. 733]
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 Rostraver Township
and in compliance with all commonwealth laws and regulations:
A.
Project located near or adjacent to the Monongahela River or Youghiogheny
River.
B.
Project able to discharge directly into existing flood control feature.
C.
Project will generate less than 0.5 cubic feet per second for the
ten-year storm peak rate increase as compared to predevelopment peak
rate.
D.
Project is not part of a larger development being piecemealed in
order to avoid stormwater management regulations.
E.
Project is not part of a larger development which has grown piecemeal
over the past five years without SWM.
F.
Project is a small percentage <5% of a much larger site and is
incidental to the much larger site.
G.
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.
H.
Project does not discharge to a combined sewer.
I.
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.
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 the above criteria. 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.
To be approved, no-harm requests must be reviewed and approved
by the municipality engineer and by the WCD, but final approval rests
with the municipality.
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.
[Amended 12-2-2020 by Ord. No. 733]
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.
[Amended 12-2-2020 by Ord. No. 733]
C.
In addition, under 25 Pa. Code Chapter 92, a DEP NPDES
construction activities permit is required for regulated development
activities.
[Amended 12-2-2020 by Ord. No. 733]
D.
A copy of the erosion and sediment control plan and
any required permit, under 25 Pa. Code Chapter 102, shall be available
at the project site at all times.
E.
Projects that propose greater than one acre of earth disturbance
are subject to NPDES permit requirements.
[Added 12-2-2020 by Ord. No. 733]
F.
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 and approval
by the municipality.
[Added 12-2-2020 by Ord. No. 733]
[Added 12-2-2020 by Ord.
No. 733]
A.
No regulated development activities which require a Chapter 105 (Water
Obstructions and Encroachment) permit from either PA DEP or 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 Board
of Commissioners of Rostraver Township.
E.
Any proposed stormwater management plan should be consistent with
the provisions of the Pennsylvania Flood Plain Management Act 166
of 1978 and applicable municipal floodplain ordinances.
A.
The project plan shall specify permanent stormwater
BMPs to be implemented, operated and maintained to meet legal water
quality requirements. Because water quality requirements vary depending
on the uses of the water bodies in the watershed, a framework methodology
is provided here.
B.
In order to protect and maintain water quality, additional
stormwater runoff created by the development project must be captured,
stored and treated. In addition, postconstruction stormwater infiltration
of runoff must replicate preconstruction infiltration of runoff to
the maximum extent possible, in high quality and exceptional value
watersheds, special requirements may apply.
C.
The volume of additional stormwater runoff to be captured,
stored and treated is called the “water quality volume”
(WQv).
(1)
The formula for determining WQv is:
|
WQv = [(P) (Rv) (A)]/12], where:
| |
|
P = Rainfall depth in inches, using the ninety-percent-storm,
the volume of rainfall for 90% of the storm events which produce runoff
in the watershed annually (e.g., 1.0 inches). (See Appendix A.[1])
| |
|
A = Project area in acres
| |
|
Rv = Volumetric runoff coefficient [0.05 + 0.009(I)],
where I is the impervious surface percentage (impervious area ÷
total project area) x 100%
|
[1]
Editor’s Note: Appendix A is on file
in the Township offices.
(2)
In special protection watersheds, as described in 25 Pa. Code Chapter 93, this volume may be required to remain on site through infiltration and other methods, to protect water quality. Guidance can be obtained from PADEP.
(3)
Runoff treatment BMPs must be employed where necessary
to ensure the water quality requirements are met.
(4)
Design systems that are capable of removing 80% TSS
and 40% TP removal.
D.
Water temperature is a particular concern in high
quality and exceptional value watersheds. Temperature sensitive BMPs
and stormwater conveyance systems are to be used and designed with
storage pool areas and supply outflow channels, and should be shaded
with trees. Vegetation shall be planted within the facilities, provided
that capacity for volumes and rate control as required by this chapter
is maintained.
(1)
At a minimum, the southern half on pond shorelines
shall be planted with shade or canopy trees within 10 feet of the
pond shoreline.
(2)
In conjunction with this requirement, the maximum
slope allowed on the berm area to be planted is 10 to one. This will
lessen the destabilization of berm soils due to root growth.
(3)
A long-term maintenance schedule and management plan
for the thermal control BMPs is to be established and recorded for
all development project sites.
E.
The applicant may, subject to approval of the municipality,
use any of the following stormwater credits, described in the following
table, in computing the required water quality volume:
|
Stormwater Credit
|
Description
| |
|---|---|---|
|
Natural area conservation
|
Conservation of natural areas, such as forest,
wetlands, or other sensitive areas in a protected easement, thereby
retaining their predevelopment hydrologic and water quality characteristics.
Using this credit, a designer may subtract conservation areas from
total site area when computing the required water quality volume.
| |
|
Disconnection of rooftop runoff
|
Credit is given when rooftop runoff is disconnected
and then directed over a pervious area where it may either infiltrate
into the soil or filter over it. Credit is typically obtained by grading
the site to promote overland flow or by providing bioretention on
single-family residential lots. If a rooftop area is adequately disconnected,
the impervious area may be deducted from the total impervious cover.
| |
|
Disconnection of non-rooftop runoff
|
Credit is given for practices that disconnect
surface impervious cover by directing it to pervious areas where it
is either infiltrated or filtered through the soil. As with rooftop
runoff, the impervious area may be deducted from the total impervious
cover thereby reducing the required water quality volume.
| |
|
Stream buffer credit
|
Credit is given when a stream buffer effectively
treats stormwater runoff. Effective treatment constitutes capturing
runoff from pervious and impervious areas adjacent to the buffer and
treating the runoff through overland flow across a grass or forested
area. Areas treated in this manner may be deducted from total site
area.
| |
|
Grass channel (open section roads)
|
Credit may be given when open grass channels
are used to reduce the volume of runoff and pollutants during smaller
storms. If designed according to appropriate criteria, these channels
may meet water quality criteria for certain types of residential development.
| |
|
Environmentally sensitive rural development
|
Credit is given when a group of environmental
site design techniques are applied to low-density or rural residential
development. This credit eliminates the need for structural practices
to address water quality volume. See Appendix C.[2]
|
[2]
Editor’s Note: Appendix C is on file
in the Township offices.
F.
The volume and rate of any stormwater discharges allowed
under this chapter must be managed to prevent the physical degradation
of receiving waters, such as by stream bank scour and erosion. If
a detention facility is proposed which is part of the BMPs approved
for the project, the facility (ies) must be designed to provide for
a twenty-four-hour extended detention of the one-year, twenty-four-hour
storm event (i.e., the stormwater runoff will be released over a minimum
24 hours for the one-year, twenty-four-hour storm event).
A.
Prevention of stormwater runoff is a key objective of Chapter 93 of the DEP regulations, because runoff can change the physical, chemical and biological integrity of water bodies thereby impacting water quality.
B.
The project plan shall describe how these 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 postconstruction 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 in § 164-15.
C.
Postconstruction stormwater infiltration of runoff
shall replicate preconstruction infiltration of runoff to the maximum
extent possible. In high quality and exceptional value watersheds,
special requirements may apply. Guidance is available from PADEP.
D.
In calculating the volume of runoff that can be infiltrated
at a site, the following methodology shall be used:
(1)
Methodology:
(a)
Recharge volume calculation.
|
Rev = [(S)(Rv)(A)]/12, where:
Rev = Recharge volume
(acre-feet)
S = Soil specific recharge factor (inches)
A = Site area contributing to the recharge facility
(acres)
Rv = Volumetric runoff
coefficient, Rv = 0.05 + 0.009 (I), where I
= percent impervious area; and
S shall be obtained based upon hydrologic soil
group based upon the table below:
|
|
Hydrologic Soil Group
|
Soil Specific Recharge Factor (S)
| |
|---|---|---|
|
A
|
0.38
| |
|
B
|
0.25
| |
|
C
|
0.13
| |
|
D
|
0.06
|
(b)
If more than one hydrologic soil group (HSG)
is present at a site, a composite recharge volume shall be computed
based upon the proportion of total site area within each HSG.
(2)
In selecting the appropriate infiltration BMPs, the
applicant shall consider the following:
(3)
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, susceptibility
to sinkhole formation, and subgrade 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 conductivity.
(c)
Design infiltration BMPs for required stormwater
volume based on field-determined capacity at the level of the proposed
infiltration surface.
(4)
Soil characteristics: subject to the specific considerations in Subsection D(7) below:
(a)
Infiltration BMPs are particularly appropriate
in hydrologic soil Groups A and B, as described in the Natural Resources
Conservation Service 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)
Infiltration BMPs shall be located a minimum
of 10 feet away from the foundation wall of any building.
(f)
The infiltration system shall have positive
overflow controls to prevent storage within one foot of the finished
surface or grade.
(g)
Infiltration rates shall not be used in computing
the storage volume of the infiltration system.
(h)
Surface inflows shall be designed to prevent
direct discharge of sediment into the infiltration system.
(5)
The recharge volume provided at the site shall be
directed to the most permeable HSG available, except where other considerations
apply, such as in limestone geology.
(6)
Any infiltration BMP shall be capable of completely
infiltrating the impounded water within 48 hours.
(7)
Extreme caution shall be exercised where infiltration
is proposed in geologically susceptible areas such as:
(a)
Strip mines;
(b)
Where salt or chloride may be applied in deicing
and other winter applications, causing groundwater pollution since
soils do little to filter this pollutant; and
(c)
Limestone areas:
[1]
Whenever a basin will be located in an area
underlain by limestone, geological evaluation of the proposed location
shall be conducted to determine susceptibility to sinkhole formations.
[2]
The design of all BMPs over limestone formations
shall include measures to prevent groundwater contamination and, where
necessary, sinkhole formation.
[3]
It shall be the applicant’s responsibility
to verify whether the site is underlain by limestone.
[4]
The following note shall be attached to all
drainage plans and signed and sealed by the applicant’s licensed
engineer/surveyor or landscape/architect or geologist if a detention
facility is proposed: “I certify that the proposed facility
is/is not underlain by limestone.”
(8)
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.
(9)
Infiltration BMPs shall not be constructed nor receive
runoff until the entire contributory drainage area to the infiltration
BMP has received final stabilization.
A.
Applicants may select a combination of runoff control
techniques which are most suitable to control stormwater runoff from
the site. All controls shall 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 section.
B.
The applicant shall consider the effect of the proposed
stormwater management techniques on any special soil condition or
geological hazards which may exist on the development site. In the
event such conditions are identified on the site, the Municipal Engineer
may require in-depth studies by a competent geotechnical engineer.
C.
The stormwater management BMPs shall be selected according
to the following order of preference:
(1)
Site planning for locating proposed buildings, impervious
areas and grading which minimizes disruption of the natural site characteristics.
(2)
Minimization of impervious areas and promotion of
retentive grading.
(4)
Infiltration of runoff on site.
(5)
Flow attenuation by use of open vegetated swales and
natural depressions.
(6)
Stormwater detention/retention structures.
(7)
Implementation of innovative/green infrastructure structural measures
(refer to the PA DEP Stormwater BMP Manual, 2006, or current edition).
[Added 12-2-2020 by Ord. No. 733]
D.
Any BMP which is a dam, culvert, stream, enclosure
or outfall as defined in 25 Pa. Code Chapter 105 shall be designed
according to the requirement in those regulations.
E.
Any stormwater BMP, which does not constitute a dam
under 25 Pa. Code Chapter 105, and is designed to store runoff and
requiring a berm or earthen embankment (i.e., detention basin), shall
be designed to satisfy the following:
(1)
Berms and earthen embankments shall be designed to
provide an emergency spillway to handle flow up to and including the
one-hundred-year postdevelopment conditions.
(2)
Berms and earthen embankments shall be designed to
provide a minimum 1.0 foot of freeboard above the maximum pool elevation
computed when the facility functions for the one-hundred-year postdevelopment
inflow.
(3)
Water obstructions shall convey runoff from the twenty-five-year
design storm with a minimum of 1.0 foot of freeboard measured below
the lowest point along the top of the roadway, without damage to the
drainage structure or the roadway.
(4)
Roadway crossings located within designated floodplain
areas must be able to convey runoff from a one-hundred-year design
storm.
(5)
Drainage conveyances must be able to convey, without
damage to the drainage structure or roadway, runoff from the twenty-five-year
design storm without surcharging.
(6)
Adequate erosion and sediment control protection shall
be provided along all open channels, and at all points of discharge.
(7)
All BMP facilities will be sized for the two-, ten-
and twenty-five-year storm and release ratings.
F.
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.
[Added 12-2-2020 by Ord.
No. 733]
G.
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.
[Added 12-2-2020 by Ord.
No. 733]
H.
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.
[Added 12-2-2020 by Ord.
No. 733]
I.
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.
[Added 12-2-2020 by Ord.
No. 733]
J.
Persons engaged in land development activities shall provide the required financial security and stormwater best management practices maintenance and monitoring agreement to the municipality as outlined in Article VII of this chapter.
[Added 12-2-2020 by Ord.
No. 733]
K.
Criteria for riparian buffers.
[Added 12-2-2020 by Ord.
No. 733]
(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 25 Pa. Code Chapter 102, the riparian
buffer easement shall 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 the
continued private ownership and shall count toward the minimum lot
area required by zoning, unless otherwise specified in the municipal
Zoning Ordinance.[2]
(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.
L.
Criteria for stream restoration project.
[Added 12-2-2020 by Ord.
No. 733]
(1)
A stream restoration project may be eligible for stormwater management
and/or MS4 load reduction credits if it meets qualifying criteria
set by the municipality and as follows:
(a)
Existing conditions, such as channel or streambank erosion and
an actively enlarging or incising urban stream condition, shall be
documented prior to restoration.
(b)
Projects should be located on first- to third-order (small)
streams to be effective.
(c)
Project should address a minimum of 100 linear feet of stream
channel and both sides where need to do so is evident.
(d)
Upstream impervious area should be sufficiently treated to address
peak flows that may exceed engineering design thresholds or compromise
channel form and function.
(e)
Utilize a comprehensive approach employing a mix of techniques
appropriate to the site, creating long-term stability of the streambed,
streambanks, and floodplain.
(f)
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.
(g)
Project shall maximize floodplain reconnection, with minimal
channel invert elevation increase (i.e., bank height ratio = 1.0 or
less) to achieve the objective.
(h)
Project shall include a minimum thirty-five-foot permanent riparian
buffer.
(i)
Project shall include an O&M plan identifying O&M activities,
frequencies, and responsible parties.
A.
Stormwater runoff from all development and postdevelopment
sites shall be calculated using either the Rational Method or a Soil
Cover Complex methodology.
B.
Any stormwater runoff calculations involving areas
greater than 200 acres, including on- and off-site areas, shall use
a generally accepted calculation technique that is based on the NRSC
Soil Cover Complex Method. Table III-1[1] summarizes acceptable computation methods. All methods
will be selected by the design professional based on the individual
limitations and suitability of each method for a particular site.
These assumptions shall be used in runoff calculations:
(1)
Average antecedent moisture conditions.
(2)
Type II distribution storm.
(3)
Meadow in good condition shall be used in predevelopment
runoff calculations for all areas of existing cultivation.
(4)
All areas other than cultivation shall use the land
cover condition which existed during the past 10 consecutive years.
(5)
All areas to be disturbed during construction and
subsequently returned to open space will be assumed to be reduced
one hydrologic group category level for postdevelopment runoff.
(6)
If the initial condition of the site is undeveloped
land, the land use shall be considered as “meadow” unless
the natural land cover is proven to generate lower curve numbers or
Rational C value, such as forested lands.
[1]
Editor’s Note: Table III-1 is included
at the end of this section.
C.
All calculations consistent with this chapter using
the Soil Cover Complex Method shall use the appropriate design rainfall
depths for the various return period storms presented in Table D-1
in Appendix D of this chapter.[2] If a hydrologic computer model such as TR-20, PSRM or
HEC-HMS is used for stormwater runoff calculations, then the duration
of rainfall shall be 24 hours. The NRCS S-curve shown in Figure D-1,
Appendix B,[3] shall be used for the rainfall distribution.
D.
All calculations using the Rational Method shall use
rainfall intensities consistent with appropriate times of concentration
for overland flow and return periods from the design storm curves
from PA Department of Transportation Design Rainfall Curves (1986)
(Figure B-2). Times of concentration for overland flow shall be calculated
using the methodology presented in Chapter 3 of Urban Hydrology for
Small Watersheds, NRCS, TR-55 (as amended or replaced from time to
time by NRCS). Times of concentration for channel and pipe flow shall
be computed using Manning’s equation.
F.
Runoff coefficient (c) for both existing and proposed
conditions for use in the Rational Method shall be obtained from Appendix
A.
G.
Where uniform flow is anticipated, the Manning equation
shall be used for hydraulic computations, and to determine the capacity
of open channels, pipes, and storm sewers. Values for Manning’s
roughness coefficient (n) shall be consistent with those in Appendix
A.
H.
Outlet structures for stormwater management facilities
shall be designed to meet the performance standards of this chapter
using any generally accepted hydraulic analysis technique or method.
I.
The design of any stormwater detention facilities
intended to meet the performance standards of this chapter shall be
verified by routing the design storm hydrograph through these facilities
using the Storage-Indication Method. For drainage areas greater than
20 acres in size, the design storm hydrograph shall be computed using
a calculation method that produces a full hydrograph. The municipality
may approve the use of any generally accepted full hydrograph approximation
technique, which shall use a total runoff volume that is consistent
with the volume from a method that produces a full hydrograph.
J.
The municipality may require that computed existing
runoff rates be reconciled with field observations and conditions.
If the design professional can substantiate through actual physical
calibration that more appropriate runoff and time-of-concentration
values should be utilized at a particular site, then appropriate variations
may be made upon review and recommendations of the Municipal Engineer.
Calibration shall require detailed gauge and rainfall data for the
particular site in question.
|
Table III-1
| |||
|---|---|---|---|
|
Acceptable Computation Methodologies for
Stormwater Management Plans
| |||
|
Method
|
Method Developed By
|
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 models limitations
| |
|
HEC - 1
|
U.S. Army Corps of Engineers
|
When full model is desirable or necessary
| |
|
PSRM
|
Penn State University
|
When full model is desirable or necessary
| |
|
Rational Method or commercial package based
on Rational Method
|
Emil Kuiching (1889)
|
For sites less than 200 acres
| |
|
Other methods
|
Various
|
As approved by the Municipal Engineer
| |
A.
A “stormwater hotspot” is defined as a
land use or activity that generates higher concentrations of hydrocarbons,
trace metals or toxicants than are found in typical stormwater runoff,
based on monitoring studies. If a site is designated as a “hotspot,”
it has important implications for how stormwater is managed. First
and foremost, stormwater runoff from hotspots cannot be allowed to
infiltrate into groundwater, where it may contaminate water supplies.
Second, a greater level of stormwater treatment is needed at hotspot
sites to prevent pollutant washoff after construction. This treatment
plan typically involves preparing and implementing a stormwater pollution
prevention plan that involves a series of operational practices at
the site that reduces the generation of pollutants from a site or
prevent contact of rainfall with the pollutants. Table 3.2 provides
a list of designated hotspots for the Commonwealth of Pennsylvania.
B.
Under EPA’s stormwater NPDES program, some industrial
sites are required to prepare and implement a stormwater pollution
prevention plan. A list of industrial categories that are subject
to the pollution prevention requirement can be found in the commonwealth.
In addition, Pennsylvania requirements for preparing and implementing
a stormwater pollution prevention plan are described in the NPDES
general discharge permit. The stormwater pollution prevention plan
requirement applies to both existing and new industrial sites.
|
Table 3.2 Classification of Stormwater
Hotspots
| |
|---|---|
|
The following land uses and activities are deemed
stormwater hotspots:
| |
|
Vehicle salvage yards and recycling facilities
| |
|
Vehicle fueling stations
| |
|
Vehicle service and maintenance facilities
| |
|
Vehicle and equipment cleaning facilities
| |
|
Fleet storage areas (bus, truck, etc.)
| |
|
Industrial sites (based on SIC codes)
| |
|
Marinas (service and maintenance)
| |
|
Outdoor liquid container storage
| |
|
Outdoor loading/unloading facilities
| |
|
Public works storage areas
| |
|
Facilities that generate or store hazardous
materials
| |
|
Commercial container nursery
| |
|
Other land uses and activities as designated
by an appropriate review authority
|
C.
The following land uses and activities are not normally
considered hotspots:
D.
While large highways [average daily traffic volume
(ADT) greater than 30,000] are not designated as a stormwater hotspot,
it is important to ensure that highway stormwater management plans
adequately protect groundwater.
A.
Method of computation. Peak discharge and runoff shall be computed using those methods listed in § 164-18.
C.
Maintenance of natural drainageways. All natural streams, channels, swales, drainage systems and/or areas of surface water concentration shall be maintained in their existing condition unless an alteration is approved by the municipality. All encroachment activities shall comply with the requirements of Chapter 105 (Water Obstructions and Encroachments) of Title 25, Rules and Regulations of the Pennsylvania Department of Environmental Resources. The applicant must refer to Rostraver Township Zoning Ordinance, § 195-70, in regard to any disturbance within 50 feet of a stream.
D.
Methods of stormwater runoff detention and control.
The following is a listing of detention and control methods which
may be utilized in stormwater management systems, if appropriate.
The choice of control techniques is not limited to the ones appearing
on this list.
(1)
Detention basins (extended dry ponds for all Township-owned
facilities).
(2)
Rooftop storage.
(3)
Parking lots and street ponding.
(4)
Seepage pits, seepage trenches or other infiltration
structures.
(5)
Porous pavement and concrete lattice block surfaces.
(6)
Grassed channels and vegetated strips.
(7)
Cisterns and underground reservoirs.
(8)
Routed flow over grass.
(9)
Decreased impervious area coverage.
E.
The use of other control methods which meet the criteria
in this section will be permitted when approved by the Township Engineer.
Various combinations of methods should be tailored to suit the particular
requirements of the type of development and the topographic features
of the project area.
A.
In order to implement the provisions of the Rostraver
Township Stormwater Management Plan, the municipality is hereby divided
into stormwater management districts which shall be designated as
follows:
(1)
Water districts.
(a)
Speers Run Watershed.
(b)
Tyrol Boulevard Watershed.
(c)
Unnamed tributary to Monongahela River No. 1
and No. 2 Watershed.
(d)
Turkey Hollow Watershed.
(e)
Webster Hollow Watershed.
(f)
Wilko Hill Watershed.
(g)
Beckets Run Watershed.
(h)
Long Hollow Run Watershed.
(i)
Pollock Run Water.
(j)
West Newton Cemetery.
(k)
Cedar Creek Watershed.
(l)
Concord Watershed.
(m)
Port Royal Watershed.
(n)
Flack Hollow Watershed.
(o)
Darr Road Watershed.
(p)
Browneller Run Watershed.
(q)
Lutz Run Watershed.
(r)
All other watersheds within the Township.
(2)
The location and boundaries of the stormwater management
districts are shown on an official map which is on file in the Township
office.
B.
When a project or land disturbance activity is located
in more than one stormwater management district, stormwater may not
be transferred from a district with stricter stormwater management
criteria to a district with less strict criteria, unless the need
for such a transfer is identified in the county stormwater management
plan, the regional water quality management plan, or the state water
plan.
A.
Speers Run Watershed. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
90% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
B.
Tyrol Boulevard Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
95% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
C.
Unnamed tributary to Monongahela No. 1 and No. 2 Watersheds.
There shall be no increase in the rate of stormwater discharge from
any activity covered by this chapter than would have occurred from
the land prior to the activity, using the predevelopment as the prior
condition. The peak postdevelopment release rate of the stormwater
from detention facilities shall be 100% of the predevelopment rate.
The water quality discharge standards shall be the removal of 80%
of the total suspended solids load (TSS) for all storage structures
that have a volume greater than 1,000 cubic feet (for the twenty-five-year
storm).
D.
Turkey Hollow Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
E.
Webster Hollow Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
95% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
F.
Wilko Hill Watershed. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
G.
Beckets Run Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
H.
Long Hollow Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
95% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
I.
Pollack Run Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
90% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for twenty-five-year storm).
J.
West Newton Cemetery Watershed. There shall be no
increase in the rate of stormwater discharge from any activity covered
by this chapter than would have occurred from the land prior to the
activity, using the predevelopment as the prior condition. The peak
postdevelopment release rate of the stormwater from detention facilities
shall be 95% of the predevelopment rate. The water quality discharge
standards shall be the removal of 80% of the total suspended solids
load (TSS) for all storage structures that have a volume greater than
1,000 cubic feet (for the twenty-five-year storm).
K.
Cedar Creek Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
95% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
L.
Concord Watershed. There shall be no increase in the
rate of stormwater discharge from any activity covered by this chapter
than would have occurred from the land prior to the activity, using
the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
M.
Port Royal Watershed. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
N.
Flack Hollow Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
O.
Darr Road Watershed. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
P.
Browneller Run Watershed. There shall be no increase
in the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
Q.
Lutz Run Watershed. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak post development
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
R.
All other watersheds. There shall be no increase in
the rate of stormwater discharge from any activity covered by this
chapter than would have occurred from the land prior to the activity,
using the predevelopment as the prior condition. The peak postdevelopment
release rate of the stormwater from detention facilities shall be
100% of the predevelopment rate. The water quality discharge standards
shall be the removal of 80% of the total suspended solids load (TSS)
for all storage structures that have a volume greater than 1,000 cubic
feet (for the twenty-five-year storm).
[Added 12-2-2020 by Ord.
No. 733]
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
or other development ordinances.
B.
The municipality may deny or revoke any exemption pursuant to this
section at any time for any project that the municipality believes
may pose a threat to public health, safety, property, or the environment.
