A.
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 323-15:
B.
SWM site plans approved by the municipality, in accordance with § 323-24, shall be on site throughout the duration of the regulated activity.
C.
These standards apply to the landowner and any person engaged in
regulated activities.
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.[1] Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual[2]), No. 363-2134-008, as amended and updated.
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 § 323-16 and the peak rate controls of § 323-17 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 or downstream property shall not be
created, increased, decreased, relocated, impeded, or otherwise altered
without written notification of the affected property owner(s). Notification
shall include a description of the proposed development and the stormwater
flows that are being created, increased, decreased, relocated, impeded,
or otherwise altered. Adjacent property shall at a minimum include
any property having a shared boundary with the subject property of
the SWM site plan, however, if in the judgment of the designated plan
reviewer additional properties are being affected, additional notifications
may be required. Proof of notification (signed postal receipt for
example) shall be included as part of the SWM plan submission to the
municipality. 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.
(3)
Incorporate methods described in the Pennsylvania Stormwater Best
Management Practices Manual (BMP Manual[3]). If methods other than green infrastructure and LID methods
are proposed to achieve the volume and rate controls required under
this chapter, the SWM site plan must include a detailed justification,
acceptable to the designated plan reviewer, demonstrating that the
use of LID and green infrastructure is not practicable.
H.
Infiltration BMPs should be dispersed throughout the project site
at strategic locations, 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.
I.
Normally dry, open-top, storage facilities should completely drain
both the volume control and rate control capacities over a period
of time not less than 24 hours and not more than 72 hours from the
end of the design storm.
J.
The design storm precipitation depths to be used in the analysis
of peak rates of discharge shall be as obtained in PennDOT's
Drainage Manual, Publication 584, Appendix 7A; or 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[4] can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
K.
M.
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.[8]
[8]
Editor's Note: See 35 P.S. § 691.1 et seq.
B.
Earth disturbances between 0.25 acre (10,890 square feet) and one acre of earth disturbance must submit a SWM site plan to the municipality which shall consist of the following items and related supportive material needed to determine compliance with §§ 323-16 through 323-18. The applicant can use the protocols in the Small Project Stormwater Management Site Plan if municipality has adopted Appendix C.[1]
(1)
General description of proposed stormwater management techniques,
including construction specifications of the materials to be used
for stormwater management facilities.
(2)
An erosion and sediment control plan, including all reviews and letters
of adequacy from the Conservation District where appropriate.
(3)
Limits of earth disturbance, including the type and amount of impervious
area that is proposed; proposed structures, roads, paved areas, and
buildings; and a statement, signed by the applicant, acknowledging
that any revision to the approved drainage plan must be approved by
the municipality, and that a revised erosion and sediment control
plan must be submitted to the municipality or Conservation District
for approval.
(4)
All stormwater management facilities must be located on a plan and
described in detail; and all calculations, assumptions, and criteria
used in the design of the stormwater management facilities must be
shown.
[1]
Editor's Note: Appendix C is included as an attachment to this chapter.
C.
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.
D.
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.
E.
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.
G.
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.
H.
Voluntary green stormwater infrastructure (GSI) retrofit projects
that are solely intended to better manage runoff from existing development
and are not part of new development or redevelopment are exempt from
the stormwater management provisions of this chapter. This does not
exempt such projects from any other municipal, state, or federal regulation.
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. Water volume controls shall be implemented using the Design
Storm Method in Subsection A or the Simplified Method in Subsection
B below, or alternative design criteria as allowed by Pa. Code Title
25, Chapter 102.
A.
The Design Storm Method (CG-1 in the BMP Manual[2]) is applicable as a method to any size of regulated activity.
This method requires detailed modeling based on site conditions. The
following shall be incorporated into the CG-1 Method:
(1)
Do not increase the postdevelopment total runoff volume for all storms
equal to or less than the two-year twenty-four-hour duration precipitation.
(2)
At least the first one inch of runoff from the net increase in impervious
surfaces shall be permanently removed from the runoff flow, i.e.,
it shall not be released into the surface waters of this commonwealth.
Removal options include reuse, evaporation, transpiration, and infiltration.
If the developer provides justification that the listed removal options
are not feasible, and the designated plan reviewer agrees, runoff
shall be detained in a facility designed for a twenty-four-to-seventy-two-hour
dewatering time in an area with a dedicated stormwater system (not
contributory to a combined sewer system) and shall be detained in
a facility designed for a seventy-two-hour dewatering time in an area
contributory to a combined sewer system before discharge to local
stormwater systems or the environment.
B.
The Simplified Method (CG-2 in the BMP Manual[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.
For new impervious surfaces:
(1)
Stormwater facilities shall capture at least the first two inches
of runoff from the net increase in impervious surfaces.
(2)
At least the first one inch of runoff from the net increase in impervious
surfaces shall be permanently removed from the runoff flow, i.e.,
it shall not be released into the surface waters of this commonwealth.
Removal options include reuse, evaporation, transpiration, and infiltration.
If the developer provides justification that the listed removal options
are not feasible, and the designated plan reviewer agrees, runoff
shall be detained in a facility designed for a twenty-four-hour dewatering
time in an area with a dedicated stormwater system (not contributory
to a combined sewer system) and shall be detained in a facility designed
for a seventy-two-hour dewatering time in an area contributory to
a combined sewer system before discharge to local stormwater systems
or the environment.
(3)
Wherever possible, infiltration facilities should be designed to
accommodate infiltration of the entire permanently removed runoff;
however, in all cases at least the first 0.5 inch of the permanently
removed runoff should be infiltrated.
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. This is the equivalent to a 100% release rate area when
compared to those rates shown in the maps contained in Appendix A
(New and Existing Release Rate Management Districts).[1] This predevelopment-to-postdevelopment control is not
to be misconstrued as the same as the "Conditional Direct Discharge"
areas on the release rate maps. 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. Peak
flows should be computed using the methods included in the chapter
titled "Stormwater Calculations and Methodology" of the PADEP Stormwater
Management BMP Manual.
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
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. These maps are contained in Appendix A (New and Existing Release
Rate Management Districts)[2] of this model ordinance. For any areas not shown on the
release rate maps, the postdevelopment discharge rates shall not exceed
the predevelopment discharge rates for the specified design events.
Peak flows should be computed using the methods included in Chapter
8 of the PADEP Stormwater Management BMP Manual.
[2]
Editor's Note: Appendix A is included as an attachment to this chapter.
A.
In order to protect and improve water quality, a riparian buffer
easement shall be created and recorded as part of any subdivision
or land development that encompasses a riparian buffer. The intent
of this chapter in establishing a riparian buffer is to protect and
improve stream water quality. The riparian buffer is intended to slow
overland flow to the stream through the presence of native grasses,
trees and shrubs, allowing infiltration/groundwater recharge; causing
deposition of sediment, nutrients, pesticides, and other pollutants
in the buffer rather than in the stream; and reducing erosion by providing
stream bank stabilization. The trees provide shade for streams; keeping
waters cooler and reducing evaporation.
B.
Except as required by Pa. Code Title 25 Chapter 102, the riparian buffer easement shall be required for all streams (as defined in Article II) with a contributing watershed area of greater than 10 acres. The riparian buffer easement shall be measured to be a minimum of 35 feet from the top of the stream bank (on each side).
C.
Minimum management requirements for riparian buffers.
(1)
No use or construction within the riparian buffer shall be permitted that is inconsistent with the intent of the riparian buffer as described in § 323-18A.
(2)
Existing native vegetation shall be protected and maintained within
the riparian buffer easement.
(3)
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.
D.
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.[1]
E.
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.
F.
Stormwater drainage pipes shall be permitted within the riparian
buffer easement, but they shall cross the easement in the shortest
practical distance. Other structural stormwater management facilities
are not permitted within the riparian buffer easement.
G.
The following conditions shall apply when public and/or private recreation
trails are permitted by the municipality within riparian buffers:
H.
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.
I.
Underground utilities shall be permitted within the riparian buffer
easement; however, work shall be performed to minimize disturbance
area and removal of trees. Restoration within the riparian buffer
easement shall be with native species of trees, grasses, and other
plantings. One tree shall be planted for each tree removed and the
restoration shall be designed by a registered professional with the
requisite experience. Aboveground utilities shall only be permitted
to cross the easement perpendicular to the easement or in the shortest
practical distance. Existing utilities may remain and be maintained
as required.
