The following permit requirements may apply to certain regulated
earth disturbance activities and must be met prior to 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.
B. Work within natural drainage ways subject to permit by DEP under
25 Pa. Code Chapter 105.
C. Any stormwater management facility that would be located in or adjacent
to 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 PennDOT.
E. Culverts, bridges, storm sewers, or any other facilities which must
pass or convey flows from the tributary area and any facility which
may constitute a dam subject to permit by DEP under 25 Pa. Code Chapter
105.
Maximizing the groundwater recharge capacity of the area being developed is required. Design of the infiltration facilities shall consider groundwater recharge to compensate for the reduction in the recharge that occurs when the ground surface is disturbed or impervious surface is created. It is recommended that roof runoff be directed to infiltration BMPs that may be designed to compensate for the runoff from parking areas. These measures are required to be consistent with §
134-103 and to take advantage of utilizing any existing recharge areas. Infiltration may not be feasible on every site due to site-specific limitations such as soil type. If it cannot be physically accomplished, then the design professional shall be responsible to show that this cannot be physically accomplished. Appropriate soils testing and/or geotechnical evaluation shall be included as part of any documentation for infiltration BMPs. If it can be physically accomplished, then the volume of runoff to be infiltrated shall be determined from §
134-405A(2).
A. Infiltration BMPs shall meet the following minimum requirements:
(1)
Infiltration BMPs intended to receive runoff from developed
areas shall be selected based on suitability of soils and site conditions
and shall be constructed on soils that have the following characteristics:
(a)
A minimum depth of 24 inches, preferably 36 inches, between
the bottom of the BMP and the top of the limiting zone (e.g., SHWT,
groundwater, bedrock, etc.).
(b)
An infiltration rate sufficient to accept the additional stormwater
load and dewater completely as determined by field tests conducted
by the applicant's design professional.
(c)
The infiltration facility shall be capable of completely infiltrating
the recharge (infiltration) volume (Rev) within three days (72 hours)
or less.
(d)
Pretreatment shall be provided prior to infiltration.
(2)
The size of the infiltration facility shall be based upon the
Net Two Year Volume Approach, where the recharge (infiltration) volume
(Rev) to be captured and infiltrated shall
be the volume difference between the pre-development two-year, twenty-four-hour
storm event and post-development two-year, twenty-four-hour storm
event.
The recharge volume calculated using this section is the minimum
volume the applicant must control through an infiltration BMP facility.
However, if a site has areas of soils where additional volume of recharge
can be achieved, the applicant is encouraged to infiltrate as much
of the stormwater runoff from the site as possible.
(a)
Existing (pre-development) nonforested pervious areas must be
considered meadow (good condition) or its equivalent.
(b)
Twenty percent of existing impervious area, when present, shall
be considered meadow (good condition) in the model for existing use
conditions for redevelopment.
(3)
Simplified Volume Computation: Capture 1.56 inches of rainfall
for all impervious surfaces - for projects with less than 5,000 square
feet impervious surface and less than 5,000 square feet of earth disturbance.
A simpler method of volume computation is permitted for projects that
meet all of the following criteria:
(a)
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More than 1,000 square feet and less than 5,000 square feet
new impervious surface area is proposed;
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(b)
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Less than 5,000 square feet of total area is to be disturbed;
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(c)
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Soil and site conditions are suitable for infiltration as described in § 134-405A(1).
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For such projects, the required infiltration volume may be computed
by the following equation:
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Recharge Volume (cubic feet) = Area Impervious (square feet)
x 0.13
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B. Soils. A detailed soils evaluation of the project site shall be required
to determine the suitability of infiltration facilities. The evaluation
shall be performed by a qualified design professional and at a minimum
address soil permeability, depth to bedrock, and subgrade stability.
The general process for designing the infiltration BMP shall be:
(1)
Analyze hydrologic soil groups as well as natural and man-made
features within the site to determine general areas of suitability
for infiltration practices. In areas where development on fill material
is under consideration, conduct geotechnical investigations of subgrade
stability; infiltration may not be ruled out without conducting these
tests.
(2)
Provide field tests such as double ring infiltrometer or hydraulic
conductivity tests (at the level of the proposed infiltration surface)
to determine the appropriate hydraulic conductivity rate. Percolation
tests are not recommended for design purposes.
(3)
Design the infiltration structure for the required recharge
(Rev) volume based on field determined capacity
at the level of the proposed infiltration surface.
(4)
If on-lot infiltration structures are proposed by the applicant's
design professional, it must be demonstrated to the Township that
the soils are conducive to infiltrate on the lots identified.
C. Stormwater hotspots.
(1)
Below is a list of examples of designated hotspots. If a site
is designated as a hotspot, it has important implications for how
stormwater is managed. First and foremost, untreated stormwater runoff
from hotspots shall not be allowed to recharge into groundwater where
it may contaminate water supplies. Therefore, the Rev requirement shall NOT be applied to development sites that fit into
the hotspot category (the entire WQv must still
be treated). Second, a greater level of stormwater treatment shall
be considered at hotspot sites to prevent pollutant washoff after
construction. The Environmental Protection Agency's (EPA) NPDES
stormwater program requires some industrial sites to prepare and implement
a stormwater pollution prevention plan.
(2)
Examples of hotspots:
(a)
Vehicle salvage yards and recycling facilities.
(b)
Vehicle fueling stations.
(c)
Vehicle service and maintenance facilities.
(d)
Vehicle and equipment cleaning facilities.
(e)
Fleet storage areas (bus, truck, etc.).
(f)
Industrial sites based on Standard Industrial Codes.
(g)
Marinas (service and maintenance).
(h)
Outdoor liquid container storage.
(i)
Outdoor loading/unloading facilities.
(j)
Public works storage areas.
(k)
Facilities that generate or store hazardous materials.
(l)
Commercial container nursery.
(m)
Other land uses and activities as designated by an appropriate
review authority.
(3)
The following land uses and activities are not normally considered
hotspots:
(a)
Residential streets and rural highways.
(c)
Institutional development.
(f)
Pervious areas, except golf courses and nurseries [which may
need an integrated pest management (IPM) plan].
(4)
While large highways (average daily traffic volume (ADT) greater
than 30,000) are not designated as stormwater hotspots, it is important
to ensure that highway stormwater management plans adequately protect
groundwater.
D. Extreme caution shall be exercised where infiltration is proposed
in SWPAs as defined by the Township or water authority.
E. Infiltration facilities shall be used in conjunction with other innovative
or traditional BMPs, stormwater control facilities, and nonstructural
stormwater management alternatives.
F. Extreme caution shall be exercised where salt or chloride (municipal
salt storage) would be a pollutant since soils do little to filter
this pollutant, and it may contaminate the groundwater. The qualified
design professional shall evaluate the possibility of groundwater
contamination from the proposed infiltration facility and perform
a hydrogeologic justification study if necessary. Specific consideration
should be given to the particular type of salt or de-icing material
to be used within this watershed in regards to its potential long-term
effects on the soils, especially in areas that contain clay soil.
G. The infiltration requirement in HQ or EV waters shall be subject
to the Department's Chapter 93 Anti-degradation Regulations.
H. An impermeable liner will be required in detention basins where the
possibility of groundwater contamination exists. A detailed hydrogeologic
investigation may be required by the Township.
I. The Township shall require the applicant to provide safeguards against
groundwater contamination for land uses that may cause groundwater
contamination should there be a mishap or spill.
The applicant shall comply with the following water quality
requirements of this article.
A. No regulated earth disturbance activities within the Township shall
commence until approval by the Township of a plan that demonstrates
compliance with post-construction state water quality requirements.
B. The BMPs shall be designed, implemented, and maintained to meet state
water quality requirements and any other more stringent requirements
as determined by the Township.
C. To control post-construction stormwater impacts from regulated earth
disturbance activities, state water quality requirements can be met
by BMPs, including site design, which provide for replication of pre-construction
stormwater infiltration and runoff conditions so that post-construction
stormwater discharges do not degrade the physical, chemical, or biological
characteristics of the receiving waters. As described in the DEP Comprehensive
Stormwater Management Policy (#392-0300-002, September 28, 2002),
this may be achieved by the following:
(1)
Infiltration: replication of pre-construction stormwater infiltration
conditions;
(2)
Treatment: use of water quality treatment BMPs to ensure filtering
out of the chemical and physical pollutants from the stormwater runoff;
and
(3)
Stream bank and stream bed protection: management of volume
and rate of post-construction stormwater discharges to prevent physical
degradation of receiving waters (e.g., from scouring).
D. Developed areas shall provide adequate storage and treatment facilities necessary to capture and treat stormwater runoff. If site conditions allow for infiltration, the water quality volume and the recharge volume are the same volume and may be managed in a single facility. If infiltration can not be physically accomplished, the water quality volume should be calculated using the Net Two Year Volume Approach described in §
134-405A(2). In this case, the water quality volume may be captured and treated by methods other than infiltration BMPs.
This volume requirement can be accomplished by the permanent volume of a wet basin or the detained volume from other BMPs. Where appropriate, wet basins shall be utilized for water quality control and shall follow the guidelines of the BMP manuals referenced in Chapter
134, Appendix F.
The water quality volume shall take a minimum of 24 hours to
be discharged from a BMP facility. Release of the water quality volume
can begin at the start of the storm (i.e., the invert of the water
quality orifice is at the invert of the facility). The design of the
facility shall provide for protection from clogging and unwanted sedimentation.
E. For areas within defined special protection subwatersheds that include
EV and HQ waters, the temperature and quality of water and streams
shall be maintained through the use of temperature sensitive BMPs
and stormwater conveyance systems.
F. To accomplish the above, the applicant shall submit original and
innovative designs to the Township Engineer for review and approval.
Such designs may achieve the water quality objectives through a combination
of different BMPs.
G. If a perennial or intermittent stream passes through the site, the
applicant shall create a stream buffer extending a minimum of 35 feet
to either side of the top-of-bank of the channel. The buffer area
shall be maintained with and encouraged to use appropriate native
vegetation (refer to Appendix B of the Pennsylvania Stormwater Best
Management Practices Manual, latest version, for plant lists). If
an existing buffer is legally prescribed (i.e., deed, covenant, easement,
etc.) and it exceeds the requirements of this chapter, the existing
buffer shall be maintained. This does not include lakes or wetlands.
H. Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP regional office must be provided
to the Township.