A.
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 81-302:
B.
SWM site plans approved by the municipality, in accordance with § 81-406, 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.
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 § 81-303 and the peak rate controls of § 81-304 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.
(3)
Incorporate methods described in the Pennsylvania Stormwater Best
Management Practices Manual (BMP Manual[4]). 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
demonstrating the use of LID and green infrastructure is not practicable.
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 not less than 24 hours and not more than 72 hours from the
end of the design storm.
K.
The design storm volumes 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/.
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.
E.
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.
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 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 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.
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.
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.
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 as required by zoning, unless otherwise specified in the municipal
Zoning Ordinance.[2]
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.
