A.
For all regulated activities, unless specifically exempted in § 189-13:
(1)
Preparation and implementation of an approved SWM site plan is required.
(2)
No regulated activities shall commence until the municipality issues
written approval of a SWM site plan, which demonstrates compliance
with the requirements of this chapter.
(4)
The SWM site plan approved by the municipality shall be onsite throughout
the duration of the regulated activities.
B.
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 (including,
but not limited to Chapter 102 Erosion and Sediment Control) and the
Clean Streams Law.[1] Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual), No. 363-2134-008 (April 15, 2000), as amended and updated.
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
C.
For all regulated activities, stormwater BMPs shall be designed,
installed, 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 and the Clean Streams Law, conform
to the state water quality requirements, meet all requirements under
the Storm Water Management Act[2] and any more stringent requirements as determined by the
municipality.
[2]
Editor's Note: See 32 P.S. § 680.1 et seq.
D.
The municipality may, after consultation with PADEP, 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.
E.
All regulated activities shall include, to the maximum extent practicable,
measures 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, natural slopes,
existing native vegetation and woodlands.
(b)
Create, maintain, or extend riparian buffers and protect existing
forested buffers.
(c)
Provide trees and woodlands adjacent to impervious areas whenever
feasible.
(d)
Minimize the creation of impervious surfaces and the degradation
of waters of the commonwealth and promote groundwater recharge.
(e)
Protect natural systems and processes (drainageways, vegetation,
soils, and sensitive areas) and maintain, as much as possible, the
natural hydrologic regime.
(f)
Incorporate natural site elements (wetlands, stream corridors,
mature forests) as design elements.
(g)
Avoid erosive flow conditions in natural flow pathways.
(h)
Minimize soil disturbance and soil compaction.
(i)
Minimize thermal impacts to waters of the commonwealth.
(j)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible, and decentralize and manage stormwater at
its source.
F.
Impervious areas.
G.
If diffused flow is proposed to be concentrated and discharged onto
adjacent property, the applicant must document 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.
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 chapter.
I.
Where watercourses traverse a development site, drainage easements
(with a minimum width of 20 feet) shall be provided conforming to
the line of such watercourses. The terms of the easement 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, may be required, except as approved by the appropriate
governing authority.
J.
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 drainage ways
shall be subject to approval by PADEP under regulations at 25 Pa.
Code Chapter 105 through the joint permit application process, or,
where deemed appropriate by PADEP, through the general permit process.
K.
Any stormwater management facilities or any facilities that constitute
water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures,
etc.) that are regulated by this chapter, that will be located in
or adjacent to waters of the commonwealth (including wetlands), shall
be subject to approval by PADEP under regulations at 25 Pa. Code Chapter
105 through the Joint Permit Application process, or, where deemed
appropriate by PADEP, the General Permit process. When there is a
question whether wetlands may be involved, it is the responsibility
of the applicant or his agent to show that the land in question cannot
be classified as wetlands; otherwise, approval to work in the area
must be obtained from PADEP.
L.
Should any stormwater management facility require a dam safety permit
under PADEP Chapter 105, the facility shall be designed in accordance
with Chapter 105 and meet the regulations of Chapter 105 concerning
dam safety.
M.
Any stormwater management facilities regulated by this chapter that
will be located on, or discharged onto state highway rights-of-ways
shall be subject to approval by the Pennsylvania Department of Transportation
(PENNDOT).
N.
Minimization of impervious surfaces and infiltration of runoff through
seepage beds, infiltration trenches, etc., are encouraged, where soil
conditions and geology permit, to reduce the size or eliminate the
need for detention facilities.
O.
Infiltration BMPs should be dispersed throughout the site, 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.
P.
The design of facilities over karst and limestone shall include an
evaluation and implementation of measures to minimize adverse effects.
Q.
Roof drains shall not be connected to streets, sanitary or storm
sewers, or roadside ditches in order to promote overland flow and
infiltration/percolation of stormwater where it is advantageous to
do so. When it is more advantageous to connect directly to streets
or storm sewers, then the municipality shall permit it on a case-by-case
basis.
R.
Applicants are encouraged to use low-impact development practices
to reduce the costs of complying with the requirements of this chapter
and the state water quality requirements.
S.
When stormwater management facilities are proposed within 1,000 feet
of a downstream municipality, the developer shall notify the downstream
municipality and provide a copy of the SWM plan, upon request, for
review and comment.
B.
The applicant must utilize the following BMPs to the maximum extent
practicable to receive consideration for the exemptions:
(1)
Design around and limit disturbance of floodplains, wetlands, natural
slopes over 15%, existing native vegetation, and other sensitive and
special value features.
(2)
Maintain riparian and forested buffers.
(3)
Limit grading and maintain nonerosive flow conditions in natural
flow paths.
(4)
Maintain existing tree canopies near impervious areas.
(5)
Minimize soil disturbance and reclaim disturbed areas with topsoil
and vegetation.
(6)
Direct runoff to pervious areas.
C.
The applicant's proposed development/additional impervious area
may not adversely impact the following:
D.
An applicant proposing regulated activities, after demonstrating compliance with § 189-13A, B and C, may be exempted from various requirements of this chapter according to the following table:
|
New Impervious Area1, 2
(square footage)
|
Applicant Must Provide
| |
|---|---|---|
|
0 to 1,000
|
—
| |
|
1,000 to 2,500
|
Documentation of impervious area3
| |
|
2,500 to 5,000
|
Volume controls and small project SWM application3
| |
|
Greater than 5,000
|
Rate controls, volume controls and SWM site plan
|
|
NOTES:
| ||
|---|---|---|
|
1
|
New impervious area since the date of adoption of this chapter.
| |
|
2
|
Gravel in existing condition shall be considered pervious and
gravel in proposed condition shall be considered impervious.
| |
|
3
|
The small project stormwater management application included
in Appendix E[1] may be used for projects under 5,000 square feet of new
impervious surface. The small project SWM application allows documentation
of new impervious surface, credits through disconnection of impervious
surfaces and tree planting, and sizing of volume control BMPs that
may be required.
| |
[1]
Editor's Note: Appendix E is included at the end of this chapter.
E.
Single-family residential activities are exempt from these requirements,
provided the construction:
F.
An applicant proposing regulated activities, after demonstrating compliance with §§ 189-13A, B and C, may be exempted from various requirements of this chapter if documentation can be provided that a downstream man-made water body (i.e., reservoir, lake, or man-made wetlands) has been designed or modified to address the potential stormwater flooding impacts of the proposed development.
G.
The purpose this section is to ensure consistency of stormwater management
planning between local ordinances and NPDES permitting (when required)
and to ensure that the applicant has a single and clear set of stormwater
management standards to which the applicant is subject. The municipality
may accept alternative stormwater management controls under this section,
provided that:
(1)
The municipality, in consultation with the PADEP, determines that meeting the volume control requirements (see § 189-15) is not possible or places an undue hardship on the applicant.
(2)
The alternative controls are documented to be acceptable to PADEP,
for NPDES requirements pertaining to post-construction stormwater
management requirements.
H.
Agricultural activities are exempt from requirements of this chapter,
provided the activities are performed according to the requirements
of 25 Pa. Code Chapter 102.
I.
Forest management and timber operations are exempt from the rate
and volume control requirement and SWM site plan preparation requirement
of this chapter, provided the activities are performed according to
the requirements of 25 Pa. Code Chapter 102. It should be noted that
temporary roadways are not exempt.
A.
The provisions of this chapter are the minimum standards for the
protection of the public welfare.
B.
C.
If an applicant demonstrates to the satisfaction of the governing body of the municipality that any mandatory provision of this chapter is unreasonable or causes unique or undue unreasonableness or hardship as it applies to the proposed project, or that an alternate design may result in a superior result within the context of §§ 189-2 and 189-3 of this chapter, the governing body of the municipality upon obtaining the comments and recommendations of the Municipal Engineer and Conservation District may grant a waiver or relief so that substantial justice may be done and the public interest is secured; provided that such waiver will not have the effect of nullifying the intent and purpose of this chapter.
D.
The applicant shall submit all requests for waivers in writing and
shall include such requests as a part of the plan review and approval
process. The applicant shall state in full the facts of unreasonableness
or hardship on which the request is based, the provision or provisions
of this chapter that are involved, and the minimum waiver or relief
that is necessary. The applicant shall state how the requested waiver
and how the applicant's proposal shall result in an equal or
better means of complying with the intent or purpose and general principles
of this chapter.
E.
The municipality shall keep a written record of all actions on waiver
requests.
F.
The municipality may charge a fee for each waiver request, which
shall be used to offset the administrative costs of reviewing the
waiver request. The applicant shall also agree to reimburse the municipality
for reasonable and necessary fees that may be incurred by the Municipal
Engineer in any review of a waiver request.
G.
In granting waivers, the municipality may impose reasonable conditions
that will, in its judgment, secure substantially the objectives of
the standards or requirements that are to be modified.
H.
The municipality may grant applications for waivers when the following
findings are made, as relevant:
(1)
That the waiver shall result in an equal or better means of complying
with the intent of this chapter.
(2)
That the waiver is the minimum necessary to provide relief.
(3)
That the applicant is not requesting a waiver based on cost considerations.
(4)
That existing down-gradient stormwater problems will not be exacerbated.
(5)
That runoff is not being diverted to a different drainage area.
(6)
That increased flooding or ponding on off-site properties or roadways
will not occur.
(7)
That potential icing conditions will not occur.
(8)
That increase of peak flow or volume from the site will not occur.
(9)
That erosive conditions due to increased peak flows or volume will
not occur.
(10)
That adverse impact to water quality will not result.
(11)
That increased one-hundred-year floodplain levels will not result.
(12)
That increased or unusual municipal maintenance expenses will
not result from the waiver.
(13)
That the amount of stormwater generated has been minimized to
the greatest extent allowed.
(14)
That infiltration of runoff throughout the proposed site has
been provided where practicable and predevelopment groundwater recharge
protected.
(15)
That peak flow attenuation of runoff has been provided.
(16)
That long-term operation and maintenance activities are established.
(17)
That the receiving streams and/or water bodies will not be adversely
impacted in flood-carrying capacity, aquatic habitat, channel stability
and erosion and sedimentation.
B.
Stormwater runoff volume controls shall be implemented using the
Design Storm Method or the Simplified Method as defined 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 method; therefore, the applicant
may select either method on the basis of economic considerations,
the intrinsic limitations on applicability of the analytical procedures
associated with each methodology, and other factors.
(1)
The Design Storm Method (CG-1 in the BMP Manual) is applicable to
any sized regulated activity. This method requires detailed modeling
based on site conditions.
(a)
Do not increase the post-development total runoff volume when
compared to the predevelopment total runoff volume for the two-year/twenty-four-hour
storm event.
(b)
For hydrologic modeling purposes:
[1]
Existing nonforested pervious areas must be considered meadow
(good condition) for predevelopment hydrologic calculations.
[2]
Twenty percent of existing impervious area, when present within
the proposed project site, shall be considered meadow (good condition)
for predevelopment hydrologic calculations for redevelopment.
(2)
The Simplified Method (CG-2 in the BMP Manual) 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 detailed design of stormwater
storage facilities. For new impervious surfaces:
(a)
Stormwater facilities shall capture at least the first two inches
of runoff from all new impervious surfaces.
(b)
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 surface waters of the commonwealth. Removal options
include reuse, evaporation, transpiration, and infiltration.
(c)
Wherever possible, infiltration facilities should be designed
to accommodate infiltration of the entire permanently removed runoff;
however, in all cases at least the first 0.5 inch of the permanently
removed runoff should be infiltrated.
(d)
Actual field infiltration tests at the location of the proposed
elevation of the stormwater BMPs are required. Infiltration tests
shall be conducted in accordance with the BMP Manual. Notification
of the municipality shall be provided to allow witnessing of the testing.
(3)
In cases where it is not possible or desirable to use infiltration-based best management practices to partially fulfill the requirements in either § 189-15B(1) or (2), the following procedure shall be used:
(a)
At a minimum, the following documentation shall be provided
to justify the decision to not use infiltration BMPs:
[1]
Description of and justification for field infiltration/permeability
testing with respect to the type of test and test locations.
[2]
An interpretive narrative describing existing site soils and
their structure as these relate to the interaction between soils and
water occurring on the site. In addition to providing soil and soil
profile descriptions, this narrative shall identify depth to seasonal
high-water tables and depth to bedrock, and provide a description
of all subsurface elements (fragipans and other restrictive layers,
geology, etc.) that influence the direction and rate of subsurface
water movement.
[3]
A qualitative assessment of the site's contribution to
annual aquifer recharge shall be made, along with identification of
any restrictions or limitations associated with the use of engineered
infiltration facilities.
[4]
The provided documentation must be signed and sealed by a professional
engineer or geologist.
(b)
The following water quality pollutant load reductions will be
required for all disturbed areas within the proposed development:
|
Pollutant Load
|
Units
|
Required reduction
| |
|---|---|---|---|
|
Total suspended solids (TSS)
|
Pounds
|
85%
| |
|
Total phosphorous (TP)
|
Pounds
|
85%
| |
|
Total nitrate (NO3)
|
Pounds
|
50%
|
(c)
The performance criteria for water quality best management practices
shall be determined from the Pennsylvania Stormwater Best Management
Practices Manual, most current version.
C.
The applicable worksheets from the BMP Manual must be used in calculations
to establish volume control.
A.
For lands contained within Jefferson County that have not had release
rates established under an approved Act 167 stormwater management
plan:
(1)
Post-development discharge rates shall not exceed the predevelopment
discharge rates for the one-, two-, ten-, twenty-five-, fifty-, and
one-hundred-year storms.
B.
For lands contained within Jefferson County that have had release
rates established under an approved Act 167 stormwater management
plan:
(1)
The post-development peak discharge rates shall be in accordance
with the approved release rate map for the individual watershed. See
Appendix F for the release rates.
A.
Sensitive areas, as defined below, and stormwater hotspots which
require special consideration with regard to stormwater management.
(1)
"Sensitive areas" are defined as those areas that, if developed,
have the potential to endanger a water supply. These areas consist
of the delineated one-year zone of contribution and direct upslope
areas tributary to the water supply wells. Municipalities may update
the sensitive area boundaries based on new research or studies as
required.
(2)
Stormwater hotspots are land development projects that have a high
potential to endanger local water quality and could potentially threaten
groundwater reservoirs. The Municipal Engineer will determine what
constitutes these classifications on a case-by-case basis. The PADEP
wellhead protection contaminant source list shall be used as a guide
in these determinations. Industrial manufacturing site and hazardous
material storage areas must provide NPDES SIC codes.
B.
Performance standards.
(1)
The location of the boundaries of sensitive areas is set by drainage
areas tributary to any public water supply. The exact location of
these boundaries as they apply to a given development site shall be
determined using mapping at a scale which accurately defines the limits
of the sensitive area. If the project site is within the sensitive
area (in whole or in part), two-foot contour interval mapping shall
be provided to define the limits of the sensitive area. If the project
site is adjacent to but within 500 linear feet of a defined sensitive
area, a five-foot contour interval map defining the limits of the
sensitive area shall be included in the stormwater management plan
to document the site's location relative to the sensitive area.
(2)
Stormwater hotspot developments may be required to prepare and implement
a stormwater pollution prevention plan and file notice of intent as
required under the provision of the EPA industrial stormwater NPDES
permit requirements.
(3)
Stormwater hotspot developments must use an acceptable pretreatment
BMP prior to volume control and/or rate control BMPs. Acceptable pretreatment
BMPs for these developments include those based on filtering, settling,
or chemical reaction processes such as coagulation.
