A.
For all regulated activities, unless preparation of a stormwater management site plan is specifically exempted in § 58-13:
B.
Stormwater management site plans approved by the Township shall be
on site throughout the duration of the regulated activity.
C.
The Township 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.
D.
For all regulated activities, erosion and sediment control BMPs shall
be designed, implemented, operated, and maintained during the regulated
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. Various BMPs and their
design standards are listed in DEP's Erosion and Sediment Pollution
Control Program Manual (E&S Manual), 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 § 58-14 and the peak rate controls of § 58-15 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 DEP's Pennsylvania Stormwater
Best Management Practices Manual (BMP Manual). If methods other than
green infrastructure and LID methods are proposed to achieve the volume
and rate controls required under this chapter, the stormwater management
site plan must include a detailed justification demonstrating that
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 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.
(1)
NOAA's Atlas 14 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
L.
For all regulated activities, stormwater management 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.
M.
Various BMPs and their design standards are listed in the BMP Manual.
A.
No person shall commence or perform any earth disturbance activity as herein defined without first having obtained a minor earth disturbance permit from the Township Engineer. A separate minor earth disturbance permit shall be required for each site. One permit may cover both an excavation and any fill made on the same site. Notwithstanding the exceptions from obtaining a minor earth disturbance permit, all provisions of Chapter 58 shall apply to any earth disturbance activity conducted in the Township. A minor earth disturbance permit will not be required in the following situations:
(1)
Any excavation which does not exceed 20 cubic yards, total, of material
removed.
(2)
A fill which does not exceed 20 cubic yards, total, of material deposited.
(3)
An excavation below finished grade for:
(a)
Basements and footings of buildings;
(b)
Swimming pools or underground structures authorized by a building
permit;
(c)
Driveways between a single-family residence building site and
the street which are less than 100 feet in length;
(d)
The grading of excavated materials into the site from which
excavated and including the provision of additional topsoil as may
be required for seed bed preparation, provided that such grading shall
not exceed 20 cubic yards, alter drainage patterns, accelerate erosion,
interfere with existing stormwater facilities, or adversely impact
adjoining properties.
(4)
Minor increases in impervious surfaces on existing developed properties
where the increase in impervious surfaces does not exceed 1,000 square
feet, provided that the changes will not alter drainage patterns,
accelerate erosion, interfere with existing stormwater facilities,
or adversely impact adjoining properties.
(5)
Earthmoving on existing developed properties not exceeding 1,200
square feet, provided that the changes will not alter drainage patterns,
accelerate erosion, interfere with existing stormwater facilities,
or adversely impact adjoining properties.
(6)
Plowing, tilling, irrigation and drainage for agricultural purposes;
nursery operations such as removal of cultivated sod, shrubs, and
trees for transplantation; and the addition of topsoil with a change
in natural contours of one foot or less, provided that the activity
will not alter drainage patterns, accelerate erosion, interfere with
existing stormwater facilities, or adversely impact adjoining properties.
(7)
Wetland mitigation or other remedial environmental projects, as determined
by the Township, involving less than one acre of earth disturbance.
B.
Agricultural activity is exempt from the stormwater management site
plan preparation requirements of this chapter provided the activities
are performed according to the requirements of 25 Pa. Code Chapter
102 and provided that the activity will not alter drainage patterns,
accelerate erosion, interfere with existing stormwater facilities,
or adversely impact adjoining properties.
C.
Forest management and timber operations are exempt from the stormwater
management site plan preparation requirements of this chapter provided
the activities are performed according to the requirements of 25 Pa.
Code Chapter 102 provided that the activity will not alter drainage
patterns, accelerate erosion, interfere with existing stormwater facilities,
or adversely impact adjoining properties.
E.
The Township may deny or revoke any exemption pursuant to this section
at any time for any project that the Township 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 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.
A.
The Design Storm Method (CG-1 in the BMP Manual) is applicable to
any size of regulated activity. This method requires detailed modeling
based on site conditions.
B.
The Simplified Method (CG-2 in the BMP Manual) 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 10,000 square feet 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:
(1)
Post-development 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 post-development 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, including the Wissahickon Creek Watershed
Act 167 Plan:
(1)
For the one-, two-, five-, ten-, twenty-five-, fifty-, and 100-year,
twenty-four-hour storm events, the post-development peak discharge
rates will follow the applicable approved release rate maps. For any
areas not shown on the release rate maps, the post-development 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.
B.
Except as required by 25 Pa. Code Chapter 102, the riparian buffer
easement should be measured to the limit of the 100-year floodplain,
but no less than a minimum of 35 feet from the top of the streambank
(on each side).
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 Township
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 Township
Zoning Ordinance.
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.
G.
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.
