A.
For all regulated activities, unless preparation of a SWM site plan is specifically exempted in § 395-14:
B.
SWM site plans approved by the municipality, in accordance with § 395-25, shall be on site throughout the duration of the regulated activity.
C.
The municipality may, after consultation with DEP, approve measures
for meeting the state water quality requirements other than those
in this chapter, provided that they meet the minimum requirements
of, and do not conflict with, state law including, but not limited
to, the Clean Streams Law.[1]
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
D.
For all regulated earth disturbance activities, erosion and sediment
control BMPs shall be designed, implemented, operated, and maintained
during the regulated earth disturbance activities (e.g., during construction)
to meet the purposes and requirements of this chapter and to meet
all requirements under Title 25 of the Pennsylvania Code and the Clean
Streams Law,[2] Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual[3]), No. 363-2134-008, as amended and updated. Erosion and
sediment control during regulated earth disturbance activities shall
be addressed as required.
E.
Impervious areas:
(1)
The measurement of impervious areas shall include all of the impervious
areas in the total proposed development even if development is to
take place in stages.
(2)
For development taking place in stages, the entire development plan
must be used in determining conformance with this chapter.
(3)
For projects that add impervious area to a parcel, the total impervious area on the parcel is subject to the requirements of this chapter; except that the volume controls in § 395-15, and the peak rate controls of § 395-16 do not need to be retrofitted to existing impervious areas that are not being altered by the proposed regulated activity.
F.
Stormwater flows onto adjacent property shall not be created, increased,
decreased, relocated, or otherwise altered without written notification
to the adjacent property owner(s). Such stormwater flows shall be
subject to the requirements of this chapter.
G.
All regulated activities shall include such measures as necessary
to:
(1)
Protect health, safety, and property.
(2)
Meet the water quality goals of this chapter by implementing measures
to:
(a)
Minimize disturbance to floodplains, wetlands, and wooded areas.
(b)
Maintain or extend riparian buffers.
(c)
Avoid erosive flow conditions in natural flow pathways.
(d)
Minimize thermal impacts to waters of this commonwealth.
(e)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible.
H.
The design of all facilities over karst shall include an evaluation
of measures to minimize adverse effects.
I.
Infiltration BMPs should be spread out, made as shallow as practicable,
and located to maximize use of natural on-site infiltration features
while still meeting the other requirements of this chapter.
J.
Normally dry, open top, storage facilities should completely drain
both the volume control and rate control capacities over a period
of time of not less than 24 and not more than 72 hours from the end
of the design storm.
K.
The design storm values to be used in the analysis of peak rates
of discharge should be obtained from the latest version of the Precipitation-Frequency
Atlas of the United States, National Oceanic and Atmospheric Administration
(NOAA), National Weather Service, Hydrometeorological Design Studies
Center, Silver Spring, Maryland. NOAA's Atlas 14[5] can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
L.
For all regulated activities, SWM BMPs shall be designed, implemented,
operated, and maintained to meet the purposes and requirements of
this chapter and to meet all requirements under Title 25 of the Pennsylvania
Code, the Clean Streams Law, and the Storm Water Management Act.[6]
[6]
Editor's Note: See 35 P.S. § 691.1 et seq.
and 32 P.S. § 680.1 et seq., respectively.
Exemptions from any provisions of this chapter shall not relieve the applicant from the requirements in § 395-13D through K.
A.
Regulated activities that result in cumulative earth disturbances
of less than 6,000 square feet are exempt from the requirements.
B.
Agricultural activity is exempt from the SWM site plan preparation
requirements of this chapter provided the activities are performed
according to the requirements of 25 Pa. Code Chapter 102.
C.
Forest management and timber operations are exempt from the SWM site
plan preparation requirements of this chapter provided the activities
are performed according to the requirements of 25 Pa. Code Chapter
102.
D.
The municipality may deny or revoke any exemption pursuant to this
section at any time for any project that the municipality believes
may pose a threat to public health and safety or the environment.
The green infrastructure and low-impact development practices
provided in the BMP Manual[1] shall be utilized for all regulated activities wherever
possible. Water volume controls shall be implemented using the Design
Storm Method in Subsection A or the Simplified Method in Subsection
B below. For regulated activity areas equal or less than one acre
that do not require hydrologic routing to design the stormwater facilities,
this chapter establishes no preference for either methodology; therefore,
the applicant may select either methodology on the basis of economic
considerations, the intrinsic limitations on applicability of the
analytical procedures associated with each methodology and other factors.
A.
The Design Storm Method (CG-1 in the BMP Manual[2]) is applicable to any size of regulated activity. This
method requires detailed modeling based on site conditions.
(1)
Do not increase the postdevelopment total runoff volume for all storms
equal to or less than the two-year twenty-four-hour-duration precipitation.
(2)
For modeling purposes:
(a)
Existing (predevelopment) nonforested pervious areas must be
considered meadow in good condition.
(b)
Twenty percent of existing impervious area, when present, shall
be considered meadow in good condition in the model for existing conditions.
If constructing facilities to accommodate the resulting volume requirement
is believed by the developer to be unfeasible on site, the developer
may submit a modification request along with technical support documentation
for review by the Borough. The Borough may grant a modification to
alternatively construct off-site volume controls providing that the
alternative site is located within the same subwatershed as the project
site and the peak discharge rates downstream of the project site are
not increased above predevelopment magnitudes.
[1]
Design and construction of the off-site controls shall be subject
to review and approval by the Borough. Costs shall be the responsibility
of the developer. Design documentation shall demonstrate that the
proposed facilities are effective in removing an amount equal to the
project's increase in the two-year storm volume from the overall
runoff where the facility is to be located.
[2]
In lieu of construction of off-site controls, the developer
may request, and the Borough may accept, the payment into a stormwater
fund. The cost shall be based upon the Borough's current fee
schedule (adjusted annually) based upon an established cost per cubic
foot of storage.
B.
The Simplified Method (CG-2 in the BMP Manual[3]) provided below is independent of site conditions and
should be used if the Design Storm Method is not followed. This method
is not applicable to regulated activities greater than one acre or
for projects that require design of stormwater storage facilities.
Twenty percent of existing impervious area, when present, shall be
considered meadow in good condition. Then, for new (additional) impervious
surfaces:
(1)
Stormwater facilities shall capture at least the first two inches
of runoff from all new impervious surfaces.
(2)
At least the first one inch of runoff from new impervious surfaces
shall be permanently removed from the runoff flow, i.e., it shall
not be released into the surface waters of this commonwealth. Removal
options include reuse, evaporation, transpiration, and infiltration.
(3)
Wherever possible, infiltration facilities should be designed to
accommodate infiltration of the entire "permanently removed" (first
one inch, minimum) runoff; however, in all cases, at least the first
0.5 inch of the permanently removed runoff should be infiltrated.
A.
For areas not covered by a release rate map from an approved Act
167 stormwater management plan: Postdevelopment discharge rates shall
not exceed the predevelopment discharge rates for the one-, two-,
five-, ten-, twenty-five-, fifty-, and 100-year twenty-four-hour storm
events. If it is shown that the peak rates of discharge indicated
by the postdevelopment analysis are less than or equal to the peak
rates of discharge indicated by the predevelopment analysis for one-,
two-, five-, ten-, twenty-five-, fifty-, and 100-year, twenty-four-hour
storms, then the requirements of this section have been met. Otherwise,
the applicant shall provide additional controls as necessary to satisfy
the peak rate of discharge requirement.
B.
For areas covered by a release rate map from an approved Act 167
stormwater management plan: For the one-, two-, five-, ten-, twenty-five-,
fifty-, and 100-year, twenty-four-hour storm events, the postdevelopment
peak discharge rates will follow the applicable approved release rate
maps. For any areas not shown on the release rate maps, the postdevelopment
discharge rates shall not exceed the predevelopment discharge rates.
C.
Calculation methods for development sites: For the purpose of computing
peak flow rates and runoff hydrographs from development sites, calculations
shall be performed using one of the following: USDA NRCS publications,
Technical Release (TR) 55 or 20, HEC1 or Penn State Runoff Model (PSRM)
or Modified Rational Method. Under special circumstances other computation
methods may be used subject to the approval of the Borough. No times
of concentrations less than five minutes shall be accepted.
D.
Routing of hydrographs through detention/retention facilities for
the purpose of designing those facilities shall be accomplished using
the Modified-Puls Method or other recognized reservoir routing method
subject to the approval of the Borough.
E.
Design criteria for stormwater management controls.
(1)
General criteria.
(a)
Applicants may select runoff control techniques, or a combination
of techniques, which are most suitable to control stormwater runoff
from the development site. All controls shall be subject to approval
of the Borough Engineer. The Borough Engineer may request specific
information on design and/or operating features of the proposed stormwater
controls in order to determine their suitability and adequacy in terms
of the standards of this section.
(b)
The applicant should consider the effect of the proposed stormwater
management techniques on any special soil conditions or geological
hazards which may exist on the development site. In the event such
conditions are identified on the site, the Borough Engineer may require
in-depth studies by a competent geotechnical engineer.
(c)
Not all stormwater control methods may be advisable or allowable
at a particular development site. In developing a stormwater management
plan for a particular site, stormwater controls shall be selected
according to the following order of preference:
(d)
Infiltration practices shall be used to the extent practicable
to reduce volume increases and promote groundwater recharge. A combination
of successive practices may be used to achieve the applicable minimum
control requirements. Justification shall be provided by the applicant
for rejecting each of the preferred practices based on actual site
conditions.
(e)
Open detention/retention facilities shall be permitted within
residential areas. However, ponding depths, slope rates, structure
types, fencing, etc., shall be considered by the Borough prior to
approval.
(2)
Criteria for infiltration systems.
(a)
Infiltration systems shall be sized and designed based on local
soil and groundwater conditions. Design rates shall be justified by
the designer, including field tests if required.
(b)
Infiltration systems greater than three feet deep shall be located
at least 10 feet from basement walls.
(c)
Infiltration systems may not be approved for handling runoff
from commercial or industrial working areas. Drainage areas shall
be suitably protected from the effects of the commercial/industrial
activities.
(d)
Infiltration systems may not receive runoff until the entire
drainage area to the system has received final stabilization.
(e)
The stormwater infiltration facility design shall provide an
overflow system with measures to provide a nonerosive velocity of
flow along its length and at the outfall.
(3)
Criteria for flow attenuation facilities.
(a)
If flow attenuation facilities are employed to assist in the
control of peak rates of discharge, their effects must be quantified
using the SCS Technical Release (TR) 55 Urban Hydrology for Small
Watersheds or other approved method. The effects of the flow attenuation
facilities on travel time should be reflected in the calculations.
(b)
Flow attenuation facilities, such as swales and natural depressions,
should be properly graded to ensure positive drainage and avoid prolonged
ponding of water.
(c)
Swales shall be properly stabilized with vegetation or otherwise
lined to prevent erosion. The applicability of swales shall be in
accordance with this section.
(d)
Swales shall be designed according to the recommendations contained
in the commonwealth of Pennsylvania Erosion and Sediment Pollution
Control Program Manual, latest edition.
(4)
Criteria for stormwater detention facilities.
(a)
All detention facilities shall be equipped with outlet structures to provide discharge control for the seven designated storm frequencies. Provisions shall also be made to safely pass the postdevelopment 100-year storm runoff without damaging (i.e., impairing the continued function of) the facilities. Should any stormwater management facilities qualify as a dam under PA DEP Chapter 105, a dam permit shall be obtained from the DEP. A minimum of one foot of freeboard shall be provided between the top of the 100-year storm elevation and the top of the berm.
(b)
Shared-storage facilities which provide detention of runoff
for more than one development site within a single subarea are encouraged
wherever feasible and provided such facilities meet the criteria contained
in this section. In addition, runoff from the development sites involved
shall be conveyed to the facility in a manner that avoids adverse
impacts (such as flooding or erosion) to channels and properties located
between the development site and the shared-storage facilities.
(c)
Where open detention facilities will be utilized, multiple use facilities, such as wetlands, lakes, ball fields or similar recreational/open space uses are encouraged wherever feasible, subject to the approval of the Borough and PA DEP's Chapter 105 regulations.
(d)
Other considerations which should be incorporated into the design
of open detention facilities include:
[1]
Inflow and outflow structures shall be designed and installed
to prevent erosion, and bottoms of impoundment type structures should
be protected from soil erosion.
[2]
Control and removal of debris both in the storage structure
and in all inlet or outlet devices shall be a design consideration.
Provisions shall be made for trapping sediment and grit upstream of
storage facilities.
[3]
Inflow and outflow structures, pumping stations, and other structures
shall be designed and protected to minimize safety hazards.
[4]
The facility shall be located to facilitate maintenance, considering
the frequency and type of equipment that will be required.
[5]
Where an open detention facility is installed, the design configuration
should be based on public health and safety; the water depth at the
perimeter of a storage pond shall be limited to that which is safe
for children. All open detention facilities shall be surrounded by
a secure fence not less than five feet high. All fences must have
at least one lockable gate, minimum twelve-foot-wide opening, to facilitate
maintenance operations.
[6]
Side slopes of storage ponds shall not exceed a ratio of 2.5:1
horizontal to the vertical dimension.
[7]
Landscaping which is compatible with the surrounding area shall
be provided for the facility.
[8]
Bottoms of detention basins should be graded with a minimum
slope of 1.5% to provide positive surface drainage. A subdrainage
system may be required depending on the location of the pond bottom
relative to groundwater levels.
A.
Calculation methods for stormwater collection/conveyance facilities:
For the purposes of designing storm sewers, open swales and other
stormwater runoff collection and conveyance facilities, the Rational
Method or other method as approved by the Borough shall applied. Rainfall
intensities for design should be obtained from the appropriate PennDOT
region rainfall chart.
B.
Criteria for collection/conveyance facilities:
(1)
All stormwater runoff collection or conveyance facilities, whether
storm sewers or other open or closed channels, shall be designed in
accordance with the following basic standards:
(a)
All sites shall be graded to provide drainage away from and
around the structure in order to prevent any potential flooding damage.
(b)
Collection/conveyance facilities should not be installed parallel
and close to the top or bottom of a major embankment to avoid the
possibility of failing or causing the embankment to fail.
(c)
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
without damage to the drainage structure or roadway, with runoff from
the twenty-five-year design storm at a minimum one foot of freeboard
measured below the lowest point along the top of the roadway. Roadway
crossings located within designated floodplain areas must be able
to convey runoff from a 100-year design storm while providing a minimum
finished roadway grade 1.0 foot above the 100-year flood elevation.
When it can be shown that, due to topographic conditions, natural
drainageways on the site cannot adequately provide for drainage, open
channels may be constructed conforming substantially to the line and
grade of such natural drainageways. Work within natural drainageways
shall be subject to approval by PA DEP through the Joint Permit Application
process, or, where appropriate by PA DEP, through the General Permit
process.
(d)
Where drainage swales or open channels are used, they shall
be suitably lined to prevent erosion and designed to avoid excessive
velocities. For drainage facilities to be conveyed to the Borough,
grass-lined facilities shall be provided. If grass lining is not stable
at the design velocity(ies), storm sewers shall be provided.
(e)
Stormwater drainage systems shall be provided in order to permit
unimpeded flow along natural watercourses, except as modified by stormwater
management facilities or open channels consistent with this section.
(f)
Existing points of concentrated drainage that discharge onto
adjacent property shall not be adversely impacted and shall be subject
to any applicable discharge criteria specified in this section.
(g)
Areas of existing diffused drainage discharge shall be subject
to any applicable discharge criteria in the general direction of existing
discharge, whether proposed to be concentrated or maintained as diffused
drainage areas, except as otherwise provided by this section. If diffused
flow is proposed to be concentrated and discharged onto adjacent property,
the developer must document that easements, satisfactory to the Borough,
have been obtained and that adequate downstream conveyance facilities
exist to safely transport the concentrated discharge, or otherwise
prove that no erosion, sedimentation, flooding, or other harm will
result from the concentrated discharge.
(h)
Where a development site is traversed by watercourses, drainage
easements shall be provided conforming to the line of such watercourses.
The terms of the easements shall prohibit excavation, the placing
of fill or structures, and any alterations that may adversely affect
the flow of stormwater within any portion of the easement. Also, maintenance,
including mowing of vegetation within the easement shall be required,
except as approved by the appropriate governing authority.
(i)
In order to promote overland flow and infiltration/percolation
of runoff where it is advantageous to do so, roof drains must not
be connected to streets, storm sewers, or roadside ditches. When it
is more advantageous to connect directly to streets or storm sewers,
then it shall be permitted on a case-by-case basis by the Borough.
(2)
Wherever storm sewers are proposed to be utilized, they shall comply
with the following criteria:
(a)
If constructed within 10 feet of road paving, walks or other
surfaced areas, drains shall have a narrow trench and maximum compaction
of backfill to prevent settlement of the superimposed surface or development.
(b)
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 cover and/or adequate protection during
the fill construction.
(c)
Designed with cradle when traversing fill areas of indeterminate
stability, anchors when gradient exceeds 20%, and encasement or special
backfill provisions when traversing under a paved area.
(d)
Designed to adequately handle the anticipated peak discharge
and be economical to maintain. The minimum pipe size shall be 15 inches
in diameter. The capacity shall, at a minimum, convey a ten-year,
five-minute-duration peak discharge (without surcharging the system)
unless the storm sewer is part of a stormwater facility with a more
severe design frequency in which case, the capacity shall adequately
convey the peak discharge associated with the more severe design frequency.
(e)
Specifications for materials and construction methods for drain
pipe, trenching, bedding and backfilling requirements shall conform
to the requirements of the Borough and/or applicable PennDOT Specifications,
Publication 408, the Standards for Roadway Construction, Publication
72, and the Borough details available at the Planning/Zoning Office.
(f)
Design criteria, including acceptable pipe types, shall conform
to PennDOT Design Manual Part 2.
(g)
Storm inlets and structures shall be designed to be adequate,
safe, unobtrusive and consistent with Borough standards. Inlets and
structures within a Borough right-of-way shall comply with the PennDOT
Standards for Roadway Construction, Publication 72. Inlets and manholes
shall be sumped at least six inches and shall be easily entered for
cleaning and inspection.
(h)
Appropriate grates shall be designed for all catch basins, stormwater
inlets, and other entrance appurtenances. Bicycle-safe grates shall
be provided.
(i)
Manholes shall be designed so that the top shall be at finished
grade and sloped to conform to the slope of the finished grade. Top
castings of structures located in roads or parking areas shall be
machined or installed to preclude "rattling."
(j)
Where proposed storm sewer connects with an existing storm sewer
system, the applicant shall demonstrate that discharge rates and volumes
are not being increased.
A.
No regulated earth disturbance activities within the municipality
shall commence until approved by the municipality or its designee
of an erosion and sediment control plan for construction activities.
B.
DEP has regulations that require preparation of a written erosion
and sediment control plan for any earth disturbance activity of 5,000
square feet or more, under 25 Pa. Code § 102.4(b).
C.
In addition, under 25 Pa. Code Chapter 92a, a DEP NPDES construction
activities permit is required for regulated earth disturbance activities.
D.
Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP regional office or County Conservation
District must be provided to the municipality.
E.
A copy of erosion and sediment control plan and any required permit,
as required by DEP regulations, shall be available at the project
site at all times.
The following permit requirements may apply to certain regulated
earth disturbance activities, and must be met prior to the commencement
of regulated earth disturbance activities, as applicable:
A.
All regulated earth disturbance activities subject to permit requirements
by DEP under regulations at 25 Pa. Code Chapter 102.
C.
Any stormwater management facility that would be located in or adjacent to regulated surface waters of the commonwealth, including wetlands, subject to permit by DEP under 25 Pa. Code Chapter 105.
D.
Any stormwater management facility that would be located on a state
highway right-of-way, or require access from a state highway, shall
be subject to approval by the Pennsylvania Department of Transportation
(PennDOT).
