[Ord. 183-2013, 12/2/2013, § 2]
1.
All land disturbance activities listed in Table 23-301-1, whether
or not this chapter requires that a plan be prepared or a permit obtained,
shall comply with the standards contained in Subsection 1A through
L below:
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Table 23-301-1
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1.
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2.
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Temporary storage of impervious or pervious material (rock,
soil, etc.):
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A.
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Where the ground contact coverage exceeds 2,500 square feet
and where the material is placed on slopes exceeding 8%.
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B.
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Where the ground contact coverage exceed 5,000 square feet regardless
of slope.
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C.
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In an area of alluvial soils.
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A.
All persons engaged in land disturbance activities shall design,
implement and maintain control measures which prevent accelerated
erosion and sedimentation. This design shall be reviewed by the Township
for adequacy with this chapter.
B.
There shall be no increase in discharge of sediment or other solid
materials from the site into water resources of the Township as a
result of stormwater runoff than that which would have occurred due
to natural processes prior to the disturbance.
C.
All land disturbance shall be conducted to conserve natural features.
The features so protected by this include agriculturally suited soils,
woodlands and other vegetation, steep slopes and other sloping lands,
and certain water resources such as flood hazard districts and wetlands.
D.
Disturbances to other water resources, including natural streams, channels, drainage swales, and areas of surface water concentration, shall be minimized except where otherwise permitted in the Zoning Ordinance, Part 11, [Chapter 27, Part 11], or where changes can be justified on the basis of other design standards of this chapter.
Dumping of leaves, twigs, garden debris, etc., into streams,
drainage channels, swales, and other stormwater conveyances is strictly
prohibited. It is the responsibility of the property owner upon whose
property the stream, drainage channel or swale is located, to keep
the facility clear and functioning.
E.
Any permanent (final) vegetative and structural erosion control and
drainage measures shall be installed as soon as practical.
F.
All persons shall comply with the design requirements for controlling
erosion and sedimentation and managing stormwater runoff as set forth
herein.
G.
If, in the opinion of the Township Engineer, the nature of the land
disturbance is such as to create a hazard to life or property unless
adequately safeguarded, the applicant shall construct walls, fences,
guide rails or other structures to safeguard the street, sidewalk,
alley or other property and persons.
H.
Changing of existing grades of a property within five feet of a property
line shall be done so with the knowledge of the adjacent property
owner whose property the change may affect. Proof of notification
to the affected adjacent property owner must be submitted with the
application for a grading permit. The affected property owner shall
receive written notice. No person shall dump, move or place any soil,
bedrock or other material so as to cause the same to be deposited
upon or roll or wash upon or over the premises of another without
the express written consent of the owner of such premises so affected.
I.
No person shall, when hauling soil, bedrock or other material over
any public street, road, alley or public property, allow such materials
to blow or spill over and upon such street, road, alley or public
property or adjacent private property.
J.
If any soil, bedrock or other material or water or liquid is caused
to be deposited upon or to roll, flow or wash upon any public property
or right-of-way, the person responsible shall cause the same to be
removed immediately from such public property or way. In the event
it is not so removed, the Township shall cause such removal and the
cost of such removal shall be paid to the Township by the person who
failed to so remove the material and shall be a debt due the Township
enforceable by an action at law and/or by the imposition of a municipal
lien pursuant to the Municipal Lien Law, 53 P.S. § 7101
et seq. Said lien may include the Township's costs in collecting
the lien, including reasonable attorney's fees.
K.
The following activities are exempt from on-site stormwater facilities
and the preparation and submission of the stormwater management site
plan requirements. All other stormwater management design elements,
such as storm sewer system, road culverts, erosion and sedimentation
control, and runoff quality, shall be required. All exemption requests
must be filed with the Township.
(1)
Emergency.
(a)
Emergency maintenance work performed for the protection of public
health, safety and welfare. This exemption is limited to repair of
the existing facility; upgrades, additions or other improvements are
not permitted under this exemption.
(b)
A written description of the scope and extent of any emergency
work performed shall be submitted to the Township within two calendar
days of the commencement of the activity.
(c)
A detailed plan shall be submitted no later than 30 days following
commencement of the activity.
(d)
If the Township finds that the work is not an emergency, then
the work shall cease immediately and the requirements of this chapter
shall be addressed as applicable.
(2)
Maintenance. Any maintenance to an existing stormwater management
system made in accordance with plans and specifications approved by
the Township Engineer.
(3)
Landscaping for Existing Residential Properties. Use of land
for maintenance, replacement or enhancement of existing residential
landscaping by residential property owner.
(4)
Gardening. Use of land for gardening for home consumption.
(5)
Agricultural Activities. Agriculture activities, limited to
growing crops, rotating crops, tilling of soil and grazing animals,
when operated in accordance with a conservation plan, nutrient management
plan or erosion and sedimentation control plan approved by the Chester
County Conservation District. For agriculture with an approved conservation
plan, installation or expansion of existing farmsteads, animal housing,
waste storage, and production areas having impervious surfaces that
result in a net increase in impervious surface between 100 and 999
square feet shall apply the simplified SWM site plan approach, and
net increases in impervious surface of greater than or equal to 1,000
square feet shall be subject to the provisions of these standards.
(6)
Forest Management.
(a)
Forest management operations, which are consistent with a sound
forest management plan as filed with the Township Zoning Officer and
which follow the Pennsylvania Department of Environmental Protection's
management practices contained in its publication "Soil Erosion and
Sedimentation Control Guidelines for Forestry."
(b)
Such operations are required to have an erosion and sedimentation
control plan, which meets the requirements of 25 Pa. Code, Chapter
102, as per Table 23-302-1.
(8)
In Kind Replacement of Residential Impervious Surfaces. The
replacement of existing residential impervious surfaces in the exact
footprint of the existing impervious surface.
(9)
In Kind Repair, Maintenance of Patios, Decks and Sidewalks.
The replacement of existing residential patios, decks and/or sidewalks
in the exact footprint of the existing impervious surface.
(10)
Interior or Exterior Cosmetic Improvements to Existing Dwellings
and Other Residential Accessory Structures. Improvements and home
maintenance (such as replacing roofs, siding, etc.) to existing dwellings
and other residential accessory structures (such as garages, sheds,
etc.).
(11)
All exemption requests must be filed with the Township.
(12)
An exemption shall not relieve the applicant from the requirements
of this or other municipal ordinances or from implementing such measures
as are necessary to protect public health, safety, and property.
(13)
An exemption shall not relieve the applicant from complying
with any other current or future state or Township requirements or
regulations.
L.
The applicant shall have the burden of complying with each of the
following criteria in order to justify the grant of a waiver:
(1)
The site conditions of the property in question are such that
control of stormwater in compliance with this chapter is unreasonable
to achieve, such site conditions to include, but not be limited to,
extreme topography.
(2)
The applicant presents evidence including, but not limited to,
engineering data, geotechnical reports, soil and geological studies,
etc., which adequately documents that literal enforcement of the standards
of this chapter and its associated addenda are not achievable or would
result in undue hardship.
M.
Duty of persons engaged in a regulated activity: Notwithstanding
any provision(s) of this Part, including exemptions, any Landowner
or any person engaged in a regulated activity, including but not limited
to the alteration or development of land, which may affect stormwater
runoff characteristics, shall implement such measures as are reasonably
necessary to prevent injury to health, safety, or other property.
Such measures also shall include actions as are required to manage
the rate, volume, direction, and quality of resulting stormwater runoff
in a manner which otherwise adequately protects health, property,
and water quality of waters of the commonwealth.
N.
Any regulated activity (including but not limited to new development,
redevelopment, or earth disturbance) that is to take place incrementally
or in phases, or occurs in sequential projects on the same parcel
or property, shall be subject to regulation by this chapter if the
cumulative proposed impervious surface or earth disturbance exceeds
the corresponding threshold for exemption.
O.
The date of adoption of this chapter shall be the starting point
from which to consider tracts as parent tracts relative to future
subdivisions, and from which impervious surface and earth disturbance
computations shall be cumulatively considered.
[Ord. 183-2013, 12/2/2013, § 2]
1.
All land disturbances listed in Table 23-302-1, in addition to complying with § 23-301 above, also shall comply with Subsection 1A and B below.
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Table 23-302-1
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1.
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All new impervious surfaces comprising more than 2,000 square feet shall incorporate a stormwater management plan in accordance with § 23-302, Subsection 1B. New impervious surfaces less than 2,000 square feet and greater than 100 square feet shall comply with Subsection 1C below.
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2.
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All subdivisions, land developments and redevelopments proposing
any increase in impervious surface.
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3.
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All land disturbances in excess of 1,000 square feet, either
of slopes exceeding 15% grade or which have a predictable or apparent
impact on an existing watercourse.
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A.
Erosion and Sedimentation Control During Land Disturbances.
(1)
For all regulated activities, erosion and sediment control BMPs
shall be designed, implemented, operated, and maintained during the
Regulated Activities (i.e., during construction) as required to meet
the purposes and requirements of this Part, to meet the erosion and
sediment control requirements of the Municipality, if applicable,
and to meet all requirements under 25 Pa. Code and the Clean Streams
Law.
(2)
For all regulated activities, permanent BMPs and conveyances
shall be designed, implemented, operated, and maintained to meet the
purposes and requirements of this Part and to meet all requirements
under 25 Pa. Code, the Clean Streams Law, and the Storm Water Management
Act.
(3)
During the period of land disturbance, site runoff and soil
erosion control shall be managed in accordance with the following
standards:
(a)
No impervious surface shall be created until adequate stormwater
management facilities for the watershed into which the impervious
surface drains have been completed and are fully functional.
(b)
The area of site in which vegetation may be disturbed may not
exceed the area of the stormwater management facilities under construction,
plus 10% of the intended total site grading/excavation area, until
such time as all stormwater management facilities are complete which
shall include, but not be limited to:
(c)
Upon installation and completion of the stormwater management
facilities, ground disturbance and removal of vegetation may not exceed
the surface area which, in an unvegetated state, generates stormwater
runoff equal to the capacity of the stormwater management facilities
proposed for the project, unless interim additional stormwater management
facilities are indicated on the plan and are so installed.
(d)
Where multiple stormwater management systems are designed for
multiple discharge points, these provisions shall apply individually
to each discharge and its originating watershed(s).
(e)
Unless attached to and made a part of the approved site plans,
detailed ground disturbance and stormwater management construction
phasing plans shall be submitted and approved by the Township Engineer
prior to any ground disturbance.
(f)
Between the completion of the stormwater management facility
and completion of paving, structures and complete vegetation growth
on all surfaces, all outflow points on the stormwater management system
shall be provided with additional silt arresting features such as,
but not limited to, wrapping of perforated outflow stand pipes with
geotextile (filter fabric), siltation basins, straw bales around all
inlets to the completed system where silt might enter, etc.
(g)
Maintenance of sedimentation and erosion control facilities:
All silt arresting devices such as straw bales and silt retention
fences shall be inspected after each rain and accumulated silt shall
be removed to ensure continued effectiveness.
(h)
Sedimentation and erosion control measures: All control measures,
materials and installation shall be in accordance with the latest
revision of DEP 25 Pa. Code, Chapter 102, Erosion and Sediment Pollution
Control Program Manual.
(i)
Conduit outlet protection, riprap, and channel lining:
1)
Provide stabilization at the outlet of a conduit in which the
exit velocity from the conduit is reduced, to prevent soil erosion
and the downstream channel banks are stabilized/protected to handle
the stream velocities and resultant soil erosion.
2)
All conduit outlet protection, rip rap, and channel lining shall
be designed in accordance with 25 Pa. Code, Chapter 102, PA DEP Erosion
and Sediment Pollution Control Program Manual.
(4)
Wherever erosive soils (as identified in the Soil Survey, Chester
and Delaware Counties, Pennsylvania), slopes equal to or greater than
15%, unique topographical features, or other conditions, suggest substantial
soil erosion potential during land disturbance, the Township may require
that special sediment trapping facilities and additional measures
be installed, as recommended by the Township Engineer.
(5)
Procedures shall be established for protecting soils and geologic
structures with water supply potential from contamination by surface
water or other disruption by construction activity.
B.
Permanent Stormwater Management. The stormwater management and runoff
control criteria and standards in this Part shall apply to the total
proposed regulated activity, even if it is to take place in stages.
The measurement of impervious surfaces shall include all of the impervious
surfaces in the total proposed regulated activity even if the development
is to take place in stages.
(1)
Runoff Discharge Standards, Volume Standards, and Calculation
Methodology.
(a)
The post-construction total runoff volume shall not exceed the
predevelopment total runoff volume for all storms equal to or less
than the two-year, twenty-four-hour duration precipitation (design
storm). The water quality and runoff volume to be managed shall consist
of any runoff volume generated by the proposed regulated activity
over and above the Predevelopment total runoff volume and shall be
captured and permanently retained or infiltrated on the site. Permanent
retention options may include, but are not limited to, reuse, evaporation,
transpiration, and infiltration.
(b)
For modeling purposes, the predevelopment ground cover conditions
shall be determined using the corresponding ground cover assumptions
presented in Subsection 1B(1)(l)(3) of this Part.
(c)
Water quality improvement shall be achieved in conjunction with achieving the infiltration requirements of Subsection 1B(1)(g) through (i). The infiltration volume required under § 23-306 may be included as a component of the water quality volume. If the calculated water quality and runoff volume is greater than the volume infiltrated, then the difference between the two volumes shall be managed for water quality and runoff volume control through other techniques or practices but shall not be discharged from the site.
(d)
When the regulated activity contains or is divided by multiple
drainage areas, the water quality and runoff volume shall be separately
addressed for each drainage area.
(e)
Weighted averaging of runoff coefficients shall not be used
for manual computations or input data for water quality and runoff
volume calculations.
(f)
Areas located outside of the site (i.e., areas outside of the
regulated activity) may be excluded from the calculation of the water
quality and runoff volume requirements.
(g)
Where, based on soils testing data, the infiltration requirements cannot be fully achieved, the applicant shall infiltrate to the maximum extent possible and employ best management practices (BMPs) to improve water quality. Acceptable practices include those described in Chapter 6, "Structural BMPs," and Chapter 5, "Non-Structural BMPs," in accordance with Chapter 8, "Stormwater Calculations and Methodology," in the Pennsylvania Stormwater Best Management Manual.
The soils testing for infiltration feasibility shall take into
account site geology, groundwater conditions, soil conditions, and
minimize the potential of sinkhole formation.
(h)
A minimum of one-inch of runoff from all areas disturbed shall
be infiltrated to protect groundwater recharge and stream base flows.
(i)
The one-year, twenty-four-hour storm event shall be attenuated
for at least 24 hours (i.e., the stormwater runoff will be released
over a minimum of 24 hours).
(j)
Table 23-302-2 (Peak Flow Rate of the Post-construction Design
Storm Shall be Reduced to the Peak Flow Rate of the Corresponding
Predevelopment Design Storm Shown in the Table)
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Table 23-302-2
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Post-Construction Design Storm Frequency (24 Hour Duration)
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Predevelopment Design Storm (New Development Regulated
Activities)
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Predevelopment Design Storm (Redevelopment Regulated Activities)
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2-Year
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1-Year
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1-Year
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5-Year
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2-Year
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2-Year
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10-Year
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2-Year
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2-Year
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25-Year
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25-Year
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25-Year
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50-Year
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50-Year
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50-Year
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100-Year
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100-Year
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100-Year
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(k)
Rainfall values to be utilized in the SCS Method shall be based
upon the most current NOAA Atlas 14 values. These values can be found
at NOAA's website (http://hdsc.nws.noaa.gov/hdse/pfds).
(l)
In establishing the antecedent conditions for calculating runoff
prior to land disturbance, the following assumptions shall apply:
1)
Average antecedent moisture conditions as utilized in the latest
edition of Urban Hydrology for Small Watersheds (Technical Release
No. 55).
2)
A Type II distribution storm as identified in the latest edition
of Urban Hydrology for Small Watersheds (Technical Release No. 55).
3)
For regulated activities involving new development, the following
around cover assumptions shall be used:
4)
For regulated activities involving redevelopment, the following
ground cover assumptions shall be used:
a)
For areas that are woods (as defined in Part 2 of this chapter), predevelopment calculations shall assume ground cover of "woods in good condition."
b)
For areas that are not woods or not impervious surfaces, predevelopment
calculations shall assume ground cover of "meadow."
c)
For areas that are impervious surfaces, predevelopment calculations
shall assume "meadow" ground cover.
5)
The applicant shall determine which stormwater standards apply
to the proposed regulated activity as follows:
a)
Stormwater standards for new development shall apply to all proposed
regulated activities that involve only new development activities
as defined in this Part.
b)
Stormwater standards for redevelopment shall apply to all proposed
regulated activities that involve only redevelopment activities as
defined in this Part.
c)
At the discretion of the Municipal Engineer, regulated activities
that involve a combination of both new development and redevelopment
activities, as defined in this chapter, may either:
i.
Apply the stormwater standards (redevelopment or new development)
that are associated with the activity that involves the greatest amount
of land area.
ii.
Apply the redevelopment and new development stormwater standards
to the corresponding redevelopment and new development portions of
the proposed regulated activity.
(m)
All plans and designs for stormwater management systems and
facilities submitted to the Township Engineer for approval shall determine
stormwater peak discharge and runoff by the use of the soil cover
complex method as set forth in Urban Hydrology for Small Watersheds,
Technical Release No. 55, with specific attention given to antecedent
moisture conditions, flood routing, and peak discharge specifications
included therein and in Hydrology National Engineering Handbook, § 4,
both by United States Department of Agriculture, Soil Conservation
Service.
1)
The Township Engineer, however, may permit the use of the rational
method for calculation of runoff on land developments of five acres
or less and for the design of storm sewers.
2)
All calculations using the rational method shall use rainfall
intensities consistent with appropriate times-of-concentration (duration)
and storm events with rainfall intensities obtained from NOAA Atlas
14 partial duration series estimates, or the latest version of the
PennDOT Drainage Manual (PDM Publication 584). Times of concentration
shall be calculated based on the methodology recommended in the respective
model used. Times of concentration for channel and pipe flow shall
be computed using Manning's equation.
(n)
If site conditions preclude capture of runoff from limited portions
of the disturbed area for achieving water quality volume control standards,
stream channel protection standards, and the two-, five-, and ten-year
storm event peak runoff rate reduction standards for new development
required by this Part, the applicant shall propose alternate methods
to mitigate the bypass of the BMPs, subject to the approval of the
Municipal Engineer. In no case shall resulting peak rate be greater
than the pre-development peak rate for the equivalent design storm.
(o)
Only the area of the proposed regulated activity shall be subject
to the peak flow rate control standards of this Part. Undisturbed
areas for which the discharge point has not changed are not subject
to the peak flow rate control standards.
(p)
Areas located outside of the site (i.e., areas outside of the
regulated activity) that drain through a proposed site are not subject
to peak flow rate control requirements. Drainage facilities located
on the site shall be designed to safely convey flows from outside
of the site through the site.
(q)
When a regulated activity contains or is divided by multiple
drainage areas, the peak flow rate controls shall be separately addressed
for each drainage area.
(r)
The effect of structural and non-structural stormwater management
practices implemented as part of the overall site design may be taken
into consideration when calculating total storage volume and peak
flow rates.
(s)
Weighted averaging of runoff coefficients shall not be used
for manual computations or input data for water quality and runoff
volume calculations.
C.
All new impervious surfaces including drives, patios, and buildings
less than 2,000 square feet but more than 100 square feet shall provide
stormwater management in accordance with the following design standards:
(1)
Design of Seepage Pits and Seepage Trenches for Infiltration
of Roof Drainage. These structures shall be designed to assimilate,
in 24 hours, a volume of water equal to .365 cubic feet per square
foot of impervious coverage (i.e., length by width of building space
or other impervious covered).
(a)
Runoff control capacity may be distributed among several seepage
pits or trenches so long as total assimilated capacity of all structures
equals the amount required above.
(b)
Seepage pits connected to roof drains should be located at least
10 feet from basement walls and downhill from the building in the
direction of groundwater flow. A location uphill from wells is considered
advantageous.
(c)
The bottom of a seepage pit should be at least two feet above
seasonal high-water table and bedrock, except in case of limestone
formations in which case the distance shall be four feet, or be shown
to be otherwise capable of handling required design volumes.
(d)
The assimilative capacity of an infiltration structure is computed
as the sum of storage plus infiltration, both measured in cubic feet.
Storage is equal to the volume of the structure (length by width by
depth of the area filled with stones) by the porosity of the material
used to fill the structure. Infiltration is equal to the area of the
bottom surface of the structure (in square feet) by the soil infiltration
rate in inches per hour by the duration of the design storm in hours
(24 or two), divided by 12. Soil infiltration rate shall be determined
by actual field test by a licensed professional surveyor or engineer
in accordance with established standards.
(e)
The porosity of the gravel or rock to be used in seepage pits
must be specified in the plan. The rock or gravel shall be totally
wrapped with a ground stabilization fabric.
(f)
Where adequate seepage pit capacity is difficult to achieve
with a rock-filled pit, a concrete (or equivalent material) culvert
pipe with a lid may be placed vertically over a stone bed to provide
storage capacity; alternatively, a septic tank-type structure operating
as a cistern with discharge to the seepage pit may be used.
(g)
The longer dimension of seepage pits or seepage trenches should
parallel the slope where slopes exceed 5%.
(h)
Seepage pits or seepage trenches shall be kept away from steep
human-made grades.
(i)
The use of a drip strip or porous pipe leading to the seepage
pit is encouraged.
(j)
In all cases, an overflow system should be provided to accommodate
heavy rains in excess of the design criteria.
(k)
Seepage pits or the drains to them must contain a sediment trap
which can be maintained regularly. All downspouts should have leaf
strains to prevent leaves from clogging the seepage pit.
(l)
If concrete lattice block is placed on top of an infiltration
structure, the infiltration structure must be shown to be capable
of handling both the roof drainage and the expected seepage from the
concrete lattice blocks.
(2)
Design of Seepage Pits and Seepage Trenches, Other than Roof
Drainage. Where seepage pits or trenches will be used for infiltration
of flows from grassed areas or street runoff in excess of ten-year
storm, their design generally shall follow the guidelines above. It
is also suggested that seepage trenches for such flows be located
in diversion channels where feasible, and seepage pits be installed
in drainage swales uphill of check dams or small detention facilities.
D.
Post-construction Runoff Control Requirements.
(1)
No regulated activity within the Municipality shall commence
until:
(a)
The Municipality receives documentation that the applicant has
received:
1)
A "letter of adequacy" from the Conservation District or other
approval from PADEP in compliance with 25 Pa. Code, Chapter 102, of
an erosion and sediment control plan for construction activities,
if applicable.
2)
A PADEP NPDES Construction Activities Permit as required under
25 Pa. Code, Chapter 92, if applicable.
3)
Evidence of any other permit(s) or approvals required for the
regulated activities; and
(b)
An erosion and sediment control plan has been approved by the
Municipality, if required.
(2)
A copy of the erosion and sediment control plan and any required
permit(s), as required by PADEP regulations, shall be available on
the site at all times.
(3)
Additional erosion and sediment control measures shall be applied
where infiltration BMPs are proposed.
(4)
All BMPs must be designed to protect and maintain existing uses
(e.g., drinking water use; cold water fishery use) and maintain the
level of water quality necessary to protect those uses in all streams,
and to protect and maintain water quality in "special protection"
streams, as required by statewide regulations at 25 Pa. Code, Chapter
93 (collectively referred to herein as "State Water Quality Requirements").
(5)
To control post-construction stormwater impacts from regulated
earth disturbance activities, state water quality requirements may
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:
(a)
Infiltration. Replication of pre-construction stormwater infiltration
conditions.
(b)
Treatment. Use of water quality treatment BMPs to ensure filtering
out of chemical and physical pollutants from the stormwater runoff.
(c)
Stream Bank and Streambed Protection. Management of volume and
rate of post-construction stormwater discharges to prevent physical
degradation of receiving waters (e.g., from scouring and erosion).
(6)
DEP has regulations that require municipalities to ensure design,
implementation and maintenance of BMPs that control runoff from new
development and redevelopment (hereinafter "development") after regulated
earth disturbance activities are complete. These requirements include
the need to implement post-construction stormwater BMPs with assurance
of long-term operations and maintenance of those BMPs.
(7)
Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP regional office or County Conservation
District must be provided to the Township.
(8)
PA Turnpike Commission projects are required to comply with
the requirements of this chapter; however, the specific technical
standards that apply to these projects are presented in Chapter 8
of the Valley Creek Watershed Stormwater Management Plan (2010), including
applicability thresholds, and these projects are not required to comply
with the land development standards of this chapter.
Neither the Valley Creek Watershed Stormwater Management Plan
(2010) nor its mandatory minimum standards applies to any PA Turnpike
Commission project for which preliminary design has been completed
and has received internal approval by the Commission prior to the
date of PADEP approval of the Valley Creek Plan.
(9)
PA Turnpike Commission projects that do not require municipal
review and approval, but that do require a permit or approval from
PADEP (i.e., NPDES, 25 Pa. Code, Chapter 102, Chapter 105, joint permit,
etc.) must be submitted to and reviewed by PADEP for consistency with
all applicable standards of this plan.
(10)
Projects that do not require either municipal approval or a
permit or approval from PADEP must be reviewed by the Commission for
consistency with the applicable standards of this plan.
[Ord. 183-2013, 12/2/2013, § 2]
1.
In order to improve the quality and general utility of permanent
stormwater management facilities, they shall be planned, designed
and constructed in conformance with the latest edition of the BMP
Manual and the following principles.
A.
Site Design Process. The applicant shall design the site to minimize
the disturbances to land, site hydrology, and natural resources, and
to maintain the natural hydrologic regime, drainage patterns and flow
conditions. The applicant shall demonstrate in its SWM site plan that
the design sequence, objectives and techniques described below were
applied to the maximum extent practicable in the Site design of the
regulated activity while complying with all other requirements of
this Part. The site design shall:
(1)
First, identify and delineate all existing natural resources
and natural and man-made hydrologic features that are located within
the site, or receive discharge from, or may be impacted by the proposed
regulated activity.
(2)
Second, provide a prioritized listing of these resources and
features to identify:
(a)
Those to be incorporated into the site design in a manner that
provides protection from any disturbance or impact from the proposed
regulated activity,
(b)
Those to be protected from further disturbance or impact but
for which the proposed regulated activity will provide improvement
to existing conditions.
(c)
Those that can be incorporated into and utilized as components
of the overall site design in a manner that protects or improves their
existing conditions while utilizing their hydrologic function within
the limits of their available capacity (e.g., for infiltration, evapotranspiration,
or reducing pollutant loads, runoff volume or peak discharge rates,
etc.) to reduce the need for or size of constructed BMPs.
(d)
Those that may be considered for alteration, disturbance or
removal.
(3)
Third, develop the site design to achieve the following:
(a)
Recognize and incorporate the priorities identified in Subsection 1A(2) as the basis for the proposed site layout, grading, construction, and permanent ground cover design.
(b)
Minimize earth disturbance (both surface and subsurface).
(c)
Maximize protection of or improvement to natural resources and
special management areas.
(d)
Minimize the disturbance of natural site hydrology, in particular
natural drainage features and patterns, discharge points and flow
characteristics, natural infiltration patterns and characteristics,
and natural channel and floodplain conveyance capacity.
(e)
Incorporate natural hydrologic features and functions identified in Subsection 1A(2) into the site design to protect and utilize those features and their hydrologic functions to reduce the need for or size of constructed BMPs.
(f)
Maximize infiltration and the use of natural site infiltration
features, patterns and conditions, and evapotranspiration features.
(g)
Apply selective grading design methods to provide final grading
patterns or preserve existing topography in order to evenly distribute
runoff and minimize concentrated flows.
(h)
Minimize the cumulative area to be covered by impervious surfaces,
and:
(i)
Minimize the volume and peak discharge rates of stormwater generated.
(j)
Avoid or minimize stormwater runoff pollutant loads and receiving
stream channel erosion.
(m)
For flow volumes requiring conveyance from the source of generation
to a BMP for management, give preference to open channel conveyance
techniques that provide infiltration and water quality benefits, and
landscaped-based management in common open space areas, where practicable.
(4)
The procedures set forth above shall be utilized to the maximum
extent practicable for the overall site design and selection, location
and design of features and BMPs.
B.
For regulated activities with one acre or more of proposed earth
disturbance, existing drainage peak rate discharges up to and including
the one-hundred-year storm onto or through adjacent property(ies)
or downgradient property(ies), including diffuse drainage discharge,
shall not be altered in any manner without written permission from,
and, where applicable as determined by the Municipality an easement
and agreement with, the affected landowner(s) for conveyance of discharges
onto or through their property(ies). Such discharge shall be subject
to any applicable discharge criteria specified in this Part.
C.
For regulated activities with one acre or less proposed earth disturbance,
the applicant shall provide written notification to the affected landowner(s)
describing the proposed regulated activity and proposed discharge(s),
unless otherwise required by the Municipality.
D.
Stormwater infiltration practices shall conform to the following:
(1)
All systems shall be underground and shall be designed to minimize
disturbance of natural features and contours.
(2)
Infiltration practices shall be selected based on suitability
of soils and site conditions. Acceptable infiltration practices are
described in § 6.4, "Volume/Peak Rate Reduction by Infiltration
BMPs," in the Pennsylvania Stormwater Best Management Practices Manual
(PA BMP Manual).
Where sediment transport into the stormwater runoff is anticipated
to reach the infiltration system, appropriate permanent measures to
prevent or collect sediment shall be installed prior to discharge
to the infiltration system.
(3)
Soil infiltration tests shall be performed to determine the
feasibility and extent to which infiltration systems can be used.
Such evaluations shall be performed by a licensed and qualified geologist,
geotechnical/civil engineer, or soil scientist and shall at a minimum
address soil types, permeability, depth to bedrock, soil limitations,
carbonate geology, susceptibility to subsidence or sinkholes, and
subgrade stability. Testing and evaluation shall be completed at the
preliminary design stage.
Infiltration requirements shall be based within portions of
the site that are permeable prior to site disturbance and the degree
to which development will reduce permeability. Infiltration practices
should be applied to all areas where the soils evaluation reveals
favorable conditions. Appropriate water quality practices shall be
applied in areas not generally favorable for infiltration.
Soil infiltration tests shall be performed in accordance with
the methods described in Appendix C, "Site Evaluation and Soils Testing,"
in the PA BMP Manual.
(4)
All infiltration practices shall be set back at least 15 feet
from any structure with subgrade elements (e.g., basements, foundation
walls).
(5)
The lowest elevation of the infiltration area shall be at least
two feet above seasonal high water table and bedrock, except in areas
underlain by karst and/or carbonate geology, in which case the distance
shall be determined by the Township Engineer on a site specific basis.
(6)
Where roof drains discharge into infiltration practices, they
shall have measures to prevent clogging by debris (e.g., silt, leaves,
and vegetation). Such measures shall include without limitation leaf
traps, gutter guards, and cleanouts.
(7)
Infiltration practices shall have positive overflow controls
to prevent storage within one foot of the finished surface, unless
a specific amount of surface storage away from pedestrian and vehicular
traffic is provided and such areas infiltrate the stored volume within
48 hours.
(8)
Infiltration practices shall be designed to infiltrate the stored
volume within 48 hours.
(9)
All surface flow shall be treated to prevent direct discharge
of sediment into the infiltration practice. No sand, silt, or other
particulate matter may be applied to a pervious paved surface for
winter ice conditions.
(10)
During site construction, all infiltration practice components
shall be protected from sedimentation and from compaction due to equipment
operation, material storage, or any other construction related activity.
Areas that are accidentally impacted shall be remediated to restore
soil composition and porosity. Adequate documentation to this effect
shall be submitted to the Township Engineer for review. Any area designated
for infiltration shall not receive runoff until the contributory drainage
area has been finally stabilized.
(11)
The following procedures and materials shall be required during
construction of all subsurface facilities:
(a)
Excavation for the infiltration facility shall be performed
with equipment and in a manner that does not compact the bottom of
the facility.
(b)
The bottom of the bed and/or trench shall be scarified prior
to placement of aggregate.
(c)
Only clean aggregate with documented porosity and free of fines
shall be allowed.
(d)
The tops and sides of all seepage beds, trenches, and similar
systems shall be covered with drainage fabric meeting the specifications
of PennDOT Publication 408, § 735, Construction Class 1.
(e)
Perforated distribution pipes connected to centralized catch
basins and/or manholes with provisions for the collection of debris
shall be provided in all facilities unless the Township Engineer agrees
that site soils provide superior infiltration (A Soils or highly porous
B Soils). Where perforated pipes are used to distribute stormwater
to the infiltration practices, stormwater shall be distributed throughout
the entire infiltration area.
(12)
Infiltration practices serving more than one lot are considered
common facilities and shall have drainage easements that provide the
Township a right of access.
(13)
In areas underlain by karst and/or carbonate geology, the viability
and design standards if infiltration BMP's shall be determined
on a site-specific basis to avoid groundwater contamination, solution
channels, sinkholes, and other potential dangers. Site evaluation
shall be conducted by a licensed and qualified geologist, geotechnical
engineer, or other qualified professional, or ascertain subsurface
conditions of soil, rock, and groundwater. Such evaluation shall include
without limitation:
(a)
Soil thickness, gradation, anisotropy, and permeability (from
existing soils data and borings) to determining the capacity and rate
of infiltration of the soil, and relative depth of soil necessary
to protect against sinkhole formation.
(b)
Karst characteristics of geologic units underlying the site
as identified in sources such as US Geological Survey, PA Geological
Survey, PA Department of Transportation, etc.
(c)
Inventory of existing karst landforms, visual indications, and/or
surface manifestations of subsurface features, or other karst features.
Inventory shall be based on site reconnaissance, review of aerial
photography, and interviews with municipal and other officials familiar
with known problem areas.
(d)
Geophysical survey of the site to identify locations and extent
of subsurface karst features.
(e)
Effectiveness of soil mantle to remove pollutants from infiltration
water to determine the need for pollutant removal prior to infiltration
(e.g., soil thickness and cation exchange capacity, etc.).
(f)
Depth to groundwater and vertical location of water table relative
to carbonate geologic unit.
(g)
Other appropriate site specific parameters affecting infiltration.
Location of infiltration BMP's is critical and shall be
considered early in the site planning process. Where karst conditions
exist, infiltration BMP's shall be located and designed to avoid
formation of new karst features and to protect existing karst features
from accelerated development. Infiltration BMP's shall be located
at least 100 feet away from existing karst features and sited away
from buildings, roads, or other structures where subsidence could
damage the structure and/or create an unsafe condition. Where underlying
geologic units are prone to formation of karst features, but no karst
features are identified on the site, infiltration BMP's shall
be designed to avoid formation of new karst features.
Groundwater quality of a carbonate aquifer shall be protected
from infiltration of pollutants. At a minimum, stormwater runoff from
pollutant sources shall first be discharged through stormwater quality
BMP's to remove pollutants prior to infiltration. Wherever soil
characteristics are insufficient to provide removal of pollutants,
runoff shall be discharged through water quality BMP prior to infiltration.
(14)
Where infiltration practices are determined by the Township
Engineer to be unfeasible or detrimental to subsurface hydrology and/or
geology, applicants shall employ alternative practices that best manage
stormwater flows and maximize protection of water quality.
E.
Design of retention, detention, and groundwater recharge systems
shall be in accordance with the following:
In order to maximize compatibility with surroundings, minimize
the potential for negative aesthetic impacts, and to avoid creation
of mosquito breeding areas, all stormwater management facilities shall
be subsurface.
(1)
If proposing a surface stormwater management facility for a property, the applicant shall request a waiver from the Board of Supervisors, and shall document that the type of facility proposed is designed to meet the objectives of § 23-103 to the greatest extent practicable and shall optimize the following:
(a)
The quality of discharged water.
(b)
The quantity of recharged water.
(c)
The availability of safe, additional uses on or within the facility
in addition to the handling of stormwater. Creation of natural habitat
and passive recreation area would be one of the acceptable additional
uses.
(d)
Visual and environmental compatibility with the adjacent natural
and built land uses remaining after development of the property.
Requests for waivers from the subsurface stormwater management
requirements shall be subject to prior review and recommendation by
the Township Engineer and planning commission for any subdivision
or land development. Waiver requests for projects not related to subdivision
or land development shall be subject to review by the Township Engineer.
(2)
Any stormwater management facility must demonstrate stability of performance over time and the ability to be maintained, and the design shall include a maintenance protocol to ensure that the facility functions permanently at the level of design parameters consistent with § 23-103.
(3)
Any surface basin must utilize best management practices for low impact stormwater detention as shall be promulgated from time to time by the Chester County Conservation District and other jurisdictional agencies which shall include design parameters to control flooding, promote water quality, provide habitat and create a neighborhood amenity compatible with surrounding areas in accordance with § 23-103. Surface basins shall be designed in accordance with the Charlestown Design Manual for Surface Basins and shall include detailed plans for plantings designed to create natural habitat areas consistent with the guidelines in Appendices 23-A and 23-B.
(4)
The following slope restrictions shall be applied to surface
basins:
(a)
Permanent surface basins shall have interior and exterior side
slopes not exceeding one foot vertical in four feet horizontal.
(b)
Temporary surface basins associated with construction activities
shall have interior and exterior slopes not exceeding one-foot vertical
in three feet horizontal or as deemed appropriate by the Township
Engineer.
(c)
Maximum basin side slopes may be further reduced if the soil
has unstable characteristics as noted in the Soil Survey of Chester
and Delaware Counties, as prepared by the U.S. Department of Agriculture.
(5)
In addition to any plans, specifications, and details otherwise required for submission, the applicant shall include a narrative statement that addresses compliance with Subsection 1E(1) above.
(6)
Retention and/or detention basis shall be designed in accordance
with the following:
(a)
Basins shall be installed prior to any earthmoving or land disturbances
which they will serve. The phasing of their construction shall be
noted in the narrative and on the plan.
(b)
Soil Requirements.
1)
Basins shall be located only on soils acceptable for such use
and may not be located in areas identified as having underlying solution
cavities or voids.
2)
Soils used for the construction of basins should be suitable
soils.
3)
Detention basins designed to hold the excess volume of runoff
from a two-year storm should be located on soils with a high percolation
rate (see Soil Use Guide: Infiltration Rate) in order to encourage
rapid recharge and reduce potential for stagnant water conditions.
Where soils with high percolation rates are found at higher elevations
of a site, such detention facilities may require incorporation into
building lot layout. Drainage easements and deed restrictions against
the alteration of such detention areas shall be provided.
(c)
Energy dissipaters and/or level spreaders shall be installed
at points where pipes and drainage ways discharge to or from basins.
Outlet pipes designed to carry the predevelopment two-year storm discharge
will be permitted to discharge to a stream with only an energy dissipater.
Storm discharges from a ten year or greater intensity storm should
be spread across floodplains by level spreaders wherever possible,
so that post development flow leaves the property with the same distribution
as predevelopment flow. Whenever possible, rock material found on
the site is suggested for the construction of energy dissipaters.
(d)
The following slope restriction shall be applied to basins:
1)
Exterior slopes of compacted soil shall not exceed one-foot
vertical for three feet horizontal and may be further reduced if the
soil has unstable characteristics as noted in the Soil Survey of Chester
and Delaware Counties, as prepared by U.S. Department of Agriculture.
2)
Interior slopes of the basin shall not exceed one-foot vertical
in three feet horizontal.
(e)
Retention Basin Restrictions.
1)
Maximum water depth for basins that do not maintain a permanent
water elevation (i.e., detention basins) shall be five feet. For basins
with a permanent pool, the minimum pool depth shall be three feet.
The maximum total water depth shall be eight feet for permanently
wet basins.
Permanently wet basins deeper than four feet shall have two
safety benches, totaling 15 feet in width. One bench should start
at the normal pool elevation and extend up to the pond side slopes,
and the other should extend from the water surface into the pond to
a maximum depth of 18 inches. Maximum bench slope is 10%.
Permanently wet basins shall be designed in accordance with
§ 6.6.2, "Wet Pond/Retention Basin," in the PA BMP Manual.
2)
Retention basins shall be provided with a valve for draining
the permanent ponds.
3)
A fence and suitable vegetative screen shall be provided around
all permanently wet retention basins in form approved by the Township
Engineer. All fencing shall be at least four feet in height and shall
be either decorative or visually inconspicuous.
Decorative fencing shall be wood post and rail, wood post and
board, iron, aluminum, or other material as approved by the Township.
When necessary to prevent entry by small children, wire mesh shall
be incorporated in the fencing. Vinyl shall not be utilized.
Inconspicuous fencing shall consist of metal posts and wire
mesh with a black surface treatment to minimize visibility. Galvanized
metal shall not be utilized.
(f)
Outlet structures within basins which will control peak discharge
flows and distribute the flows by pipes to discharge areas shall be
constructed of concrete, steel or aluminum and shall have childproof,
non-clogging trash racks overall design openings exceeding 12 inches
in diameter except those openings designed to carry perennial stream
flows. Where spillways will be used to control peak discharges in
excess of the ten-year storm, the control weirs shall be constructed
of concrete, grass pavers or be of sufficient mass and structural
stability to withstand the pressures of impounded waters and outlet
velocities. Concrete outlet aprons shall be designed as level spreaders
and shall extend at a minimum to the toe of the basin slope. Decorative
surface treatments such as textured concrete or masonry veneer shall
be used on inlet and outlet structures where visually prominent from
streets, buildings, parking, pedestrian areas, or adjacent properties.
The incorporation of large stones found on the site into the concrete
apron to provide a more natural appearance is suggested. Construction
shall comply with PennDOT Publication Form 408 specifications.
(g)
Inlet and outlet structures shall be located at maximum distance
from one another. The Township Engineer may require a rock filter
berm between inlet and outlet areas when the distance is deemed insufficient
for sediment trapping. All inlets shall either be located above the
bottom of the basin or shall discharge to areas of the basin which
slope downward to lower elevations of the basin.
(h)
Emergency spillways shall be provided and shall be designed
to, at a minimum, pass the one-hundred-year storm and provide maximum
protection against erosion due to overtopping. Certain site conditions
may require a larger spillway depending upon downstream conditions.
The Township Engineer may require the use of concrete lattice blocks,
stone rip rap or concrete spillways when slopes will exceed one to
four or spillway velocities might exceed soil conservation service
standards for the particular soils involved. (Standards shall be those
contained in the Soil and Water Conservation District Environmental
Protection Handbook.)
(i)
The minimum distance between a building or structure and the
stormwater management basin shall be 30 feet measured from the outside
face of the building or structure to the outermost elevation of the
top of the berm of the basin.
(j)
The minimum distance between any grading or structure (including
endwalls, but exclusive of energy dissipating structures) related
to a stormwater management basin and the property line or street right-of-way
shall be 20 feet.
(k)
Temporary and permanent grasses or stabilization measures shall
be established on the sides of all earthen basins within 72 hours
of construction.
(l)
Detention Basin and Berm Construction.
1)
The minimum berm width at the top shall be 10 feet.
2)
A cutoff trench (keyway) of substantially impervious material
shall be provided beneath all embankments requiring fill material.
The keyway shall be four feet wide for maximum water depths less than
three feet and eight feet wide for maximum water depths greater than
three feet. The keyway shall be one foot deep and have one to one
side slopes.
3)
Anti-seep collars shall be installed around the pipe barrel
within the normal saturation zone of the detention basin berms. The
collar connections to the barrel shall be watertight and extend two
feet beyond the outside of the barrel.
4)
Outlet pipes shall have watertight joints.
5)
The minimum slope within the basin shall be 2% and the low flow
channel shall have a minimum slope of 1/2%.
6)
All basin embankments shall be placed in eight-inch lifts to
a minimum 95% dry density. Compaction tests shall be performed using
the modified Proctor method in accordance with ASTM-D-1557.
7)
The top of the basin riser shall be two feet below the top of
the berm and one foot below the emergency spillway.
8)
An "as built" plan of a detention basin (above or below ground)
shall be prepared by a professional engineer or surveyor to verify
that the basin has been constructed according to the plans and specifications
and submitted to the Township Engineer. The verification shall take
place after cleanout (if sedimentation basin) and placement of topsoil,
but prior to seeding, landscaping, and sale of the property.
(m)
Landscaping for Surface Basins. All surface basins shall be
landscaped with 100% native vegetation, consisting of a variety of
herbaceous or woody and herbaceous species to create an attractive
natural habitat area and visually screened only when necessary to
mitigate an unavoidable negative visual impact.
1)
If basins are screened, thickets of noninvasive plantings such
as Witch Hazel, Shrub Dogwood, Inkberry, Bayberry, Winterberry, Viburnum,
Red Cedar, Spicebush, Alder, Chokeberry or Sumac shall be used as
approved by the Township.
2)
All vegetation shall be appropriate to hydrologic and soil conditions
based on location within the basin. Recommended basin vegetation species
are included in Appendix 23-B.
3)
Surface basins shall be subject to conservation easements with
provisions for a maintenance protocol to ensure proper functioning
of the basin, to perpetuate native plant systems, to control invasive
species, and to specifically prohibit managing the basins vegetation
as a lawn area.
4)
Planting plans for surface basins shall be prepared and sealed
by a Pennsylvania registered landscape architect and shall include
species, quantities, and sizes of all plant materials, as well as
details and notations to specific methods of planting and establishment.
F.
Stormwater piping and open channels shall be designed in accordance with § 23-302, Subsection 1A(1)(i), and the following design standards:
(1)
General Design.
(a)
Storm sewer systems for conveyance of stormwater shall be designed
to carry a twenty-five-year peak flow rate and a fifty-year peak flow
rate at the sump area. The design of the twenty-five-year peak flow
rate into each inlet shall be indicated on the stormwater drainage
plans. The twenty-five-year flow rate with five-minute times of concentration
shall be determined by the rational formula.
(b)
Overflow System. An overflow system shall be provided to carry
flow to the detention or retention basin as designed, when the capacity
of the stormwater drainage pipe system is exceeded. The overflow system
shall be of sufficient capacity to carry the difference between the
one-hundred-year and the twenty-five-year peak flow rate.
(c)
Open ditches per se shall be avoided, but properly designed,
graded and turfed drainage swales shall be permitted in lieu of storm
sewers in residential areas and, where approved by the Township Engineer,
in commercial and industrial areas.
(d)
All storm sewers or drainage swales shall discharge to a detention,
retention or infiltration system for the control of peak runoff flows,
except as otherwise provided in the plan.
(e)
Adequate erosion protection and energy dissipation shall be
provided along all open channels and at all points of discharge. Design
methods shall be consistent with the Federal Highway Administration
Hydraulic Engineering Circular Number 11 (Publication No. FHWA-IP-89-016,
as amended) and the PADEP Erosion and Sediment Pollution Control Program
Manual (Publication No. 363-2134-008, as amended), or other design
guidance acceptable to the Municipal Engineer.
(2)
Specific Design Criteria for Storm Sewers.
(a)
Storm sewers, as required, shall be placed immediately in front
of the curb, when parallel to a public street and within the right-of-way.
When located in undedicated land, they shall be placed within an easement
not less than 20 feet wide as approved by the Township Engineer.
(b)
Storm sewers shall have a minimum diameter of 15 inches and
shall be reinforced concrete pipe or helical aluminum corrugated pipe
or corrugated steel pipe (metallic or polymer coated) in accordance
with PennDOT specifications. PennDOT approved plastic pipe may be
utilized in certain situations with the approval of the Township Engineer.
Minimum grade shall be 0.5%. Changes in alignment shall be by straight
sections connected by inlets or manholes. (Rainfall intensity curves
and other hydrologic design data, provided by PennDOT and/or the Soil
Conservation Service, shall be used for design purposes.)
(c)
Manholes shall be not more than 300 feet apart for diameters
up to, and including, 24 inches and not more than 350 feet apart for
greater diameters. Inlets may be substituted for manholes on approval
by the Township Engineer.
(d)
Inlets, manholes, covers, and frames shall conform to Pennsylvania
Department of Transportation specifications except as noted below.
At street intersections, inlets shall be placed in the tangent and
not in the curved portion of the curbing. All inlets shall be constructed
with inverts at least one foot below the out-flow pipe invert to provide
a sediment trap.
(e)
The Township shall be granted a twenty-five-foot wide drainage
easement over drivable ground for the distance from the right-of-way
of any dedicated road to all detention and retention basins to provide
unobstructed access.
(f)
A minimum cover of two feet from finished grade to the outside
diameter of the pipe at the crown shall be provided.
(3)
Specific Design Criteria and Deed Restrictions for Drainage
Swales and Perennial Streams.
(a)
Where drainage swales are used in lieu of or in addition to
storm sewers, they shall be designed to carry the required discharge
without excessive erosion and also to increase the time-of-concentration
(reduce the peak discharge and velocity and permit the water to percolate
into the soil).
(b)
Deed restrictions shall be required on property(ies) containing
drainage swales and/or perennial streams. These deed restrictions
shall specify that no property owner may obstruct or alter any drainage
swale or perennial stream identified in the stormwater management
plan if such action would alter the natural course of runoff and/or
negatively impact abutting landowners.
G.
Stormwater Quality.
(1)
To improve water quality, sustain water quality (including groundwater
recharge and stream base flow), the Township requires a BMP approach
to stormwater control and encourages, and sometimes requires, infiltration
of stormwater flows.
(2)
This approach is to reduce pollutant loading to streams, recharge
ground water tables, enhance stream base flows during time of drought,
and reduce the threat of flooding and stream-bank erosion resulting
from storm events.
(3)
The Pennsylvania Stormwater Best Management Practices Manual,
or latest edition thereof, is the guide that contains the methods
for utilization of structural BMP's.
H.
Stormwater Hotspots. Stormwater runoff from hotspots shall be pretreated
prior to surface or groundwater infiltration to prevent pollutant
runoff. The applicant shall identify and show all hotspots on the
stormwater plan and include appropriate BMPs to pretreat runoff to
remove pollutants to the maximum extent practicable and to the satisfaction
of the Township Engineer.
Below is a list of examples of hotspots:
|
(1)
|
Vehicle salvage yards and recycling facilities.
| |
|
(2)
|
Vehicle fueling stations.
| |
|
(3)
|
Vehicle service and maintenance facilities.
| |
|
(4)
|
Vehicle and equipment cleaning facilities.
| |
|
(5)
|
Fleet storage areas (bus, truck, etc.).
| |
|
(6)
|
Industrial sites based on standard industrial codes.
| |
|
(7)
|
Marinas (service and maintenance areas).
| |
|
(8)
|
Outdoor liquid container storage.
| |
|
(9)
|
Outdoor loading/unloading facilities.
| |
|
(10)
|
Public works storage areas.
| |
|
(11)
|
Facilities that generate or store hazardous materials.
| |
|
(12)
|
Commercial container nursery.
| |
|
(13)
|
Contaminated sites/brownfields.
| |
|
(14)
|
Other land uses and activities as designated by an appropriate
review authority.
| |
|
The following land uses and activities are not normally considered
hotspots:
| ||
|
(1)
|
Residential streets and rural highways.
| |
|
(2)
|
Residential development.
| |
|
(3)
|
Institutional development.
| |
|
(4)
|
Office developments.
| |
|
(5)
|
Nonindustrial rooftops.
| |
|
(6)
|
Pervious areas, except golf courses and nurseries (which may
need an integrated pest management (DM) plan).
| |
|
While streets and highways (average daily traffic volume (ADT)
greater than 30,000 are not considered stormwater hotspots, it is
important to ensure that highway stormwater management facilities
are designed to adequately protect receiving streams and/or groundwater.
| ||
|
The Environmental Protection Agency's (EPA) NPDES stormwater
program requires some industrial sites to prepare and implement a
stormwater pollution prevention plan.
| ||
[Ord. 183-2013, 12/2/2013, § 2]
1.
Agricultural Operations. All agricultural operations shall conform
to the following principles and standards:
A.
Farming operations shall be performed to minimize erosion of tilled
areas where damage to streams or adjacent properties will result.
B.
Drainage swales shall be maintained with permanent cover of grasses,
plants, trees or other treatment approved by the Township Engineer.
C.
Permanent cover shall be maintained within a minimum of 50 feet of
a stream and for 10 feet up slope from property lines unless a written
waiver is received from the abutting landowner(s).
D.
Runoff from buildings and other impervious surfaces shall be directed
around areas where compost is stored, where sod or plants are regularly
removed, where livestock is confined or where tillage crops are planted
or shall be otherwise controlled to prevent direct transport of pollutants
(including sediments) to streams.
E.
A plan is to be developed by USDA, Soil Conservation Service, and
implemented to comply with the Federal Clean Water Act and PA Clean
Stream Law.
F.
A vegetative cover strip extending eight feet from the edge of the
right-of-way of any road shall be permanently maintained.
2.
Logging/Woodcutting Operations. All logging or woodcutting operations (conducted for profit or personal use or in conjunction with or prior to any land disturbance associated with a subdivision or land development) shall be conducted only in conformance with the following principles and the Township Zoning Ordinance [Chapter 27].
A.
On sites proposed for subdivision or land development, stumps, ground
cover, and root mass must be left intact until final plans are approved
and erosion and sedimentation control facilities are installed.
B.
Methods for removal of logs shall be specified in a plan, approved
by the Township Engineer, and shall not include traversing slopes
of 15% to 25% at more than the minimum gradient possible.
[Ord. 183-2013, 12/2/2013, § 2]
1.
Erosion and Sediment Control Plan.
A.
No regulated earth disturbance activities within the Township shall
commence until approval by the Township of an erosion and sediment
control plan for construction activities.
B.
The DEP has regulations that require an erosion and sediment control
plan for any earth disturbance activity of 5,000 square feet or more,
under 25 Pa. Code § 102.4(b).
C.
In addition, under 25 Pa. Code, Chapter 92, a DEP "NPDES Construction
Activities" permit is required for any earth disturbance of one acre
or more with a point source discharge to surface waters or the Township's
storm sewer system, or five acres or more regardless of the planned
runoff. This includes earth disturbance on any portion of, part of,
or during any stage of a larger common plan of development.
D.
Evidence of any necessary permit(s) for regulated earth disturbance
activities from the appropriate DEP regional office or County Conservation
District must be provided to the Township.
E.
A copy of the erosion and sediment control plan and any required
permit, as required by DEP regulations, shall be available at the
project site at all times.
F.
All applications for approval shall be on a form approved by the
Township by resolution from time to time.
2.
An erosion and sedimentation control (stormwater management) plan
is required for land disturbances listed in Table 23-301-1 which involve
more than 2,500 square feet and add no new impervious surface. Such
plan shall include the following information:
A.
Outbounds of property, adjacent streets, and north arrow at scale
no less than one inch equals 50 feet.
B.
Location of buildings and accessory uses.
C.
Other physical features including flood hazard boundaries, streams,
area of natural vegetation to be preserved.
D.
Topography of area to be disturbed (two-foot contours) and surrounding
area to indicate drainage patterns above and below site.
E.
Area to be disturbed clearly shown/delineated.
F.
Existing watercourses on site and adjacent (within 50 feet of the
property line).
G.
Existing utilities on site and within 50 feet of property lines.
H.
Proposed contours (two-foot interval).
I.
Copy of USGS map with site located.
J.
Soil type.
K.
Sedimentation and erosion control measures proposed with details.
L.
Description of how each permanent stormwater BMP will be operated
and maintained.
M.
Calculations for silt traps and diversion ditches.
N.
Seeding requirements-temporary and permanent.
O.
Proposed drainage patterns.
P.
Statement signed by the landowner acknowledging that the stormwater
BMPs are a fixture that can be altered or removed only after approval
by the Township.
Q.
Other information that may impact on the project or as required by
the Township Engineer to clarify existing or proposed conditions.
3.
An erosion or sedimentation control/stormwater management plan is
required for any land disturbances listed in Table 23-302-1, and shall
include the following information:
A.
All information enumerated in Subsection 1 above and subject to the provisions contained therein.
C.
A statement, signed by the applicant, acknowledging that any revision
to the approved SWM site plan shall be submitted to and approved by
the Township, and that a revised erosion and sediment control plan
shall be submitted to, and approved by, the Conservation District
or Township (as applicable) for a determination of adequacy prior
to construction of the revised features.
D.
The following signature block signed and sealed by the qualified
licensed professional responsible for the preparation of the SWM site
plan:
"I (name), on this date (date of signature), hereby certify to the best of my knowledge that the SWM site plan meets all design standards and criteria of the Charlestown Township Ordinance Chapter 23, Stormwater Management" [Note: include signature, name, discipline of professional license, and license stamp or seal here]
4.
Conditions of Issuance and Subsequent Requirement.
A.
In approving a stormwater management plan and granting a permit,
the Township Engineer may impose such conditions as he may deem necessary
to ensure the health, safety, and welfare of the community and its
property owners.
B.
No permit shall be issued until the applicant certifies in writing
that all site work shall be performed in accordance with the plan.
The plan shall be a condition of the permit, and no person shall violate
any such condition so imposed.
C.
Any of the activities regulated by this chapter, the preliminary
or final approval of subdivision and/or land development plans, or
the commencement of any regulated earth disturbance activity may not
proceed until the applicant or his/her agent has received written
approval from the Township and an adequate erosion and sediment control
plan review by the Township and the Chester County Conservation District
(if required).
D.
Neither submission of an SWM site plan under the provisions herein
nor compliance with the provisions of this Part shall relieve any
person from responsibility for damage to any person or property otherwise
imposed by law.
5.
Expiration and Renewal.
A.
Every permit issued hereunder by the Township Engineer shall expire
at the end of the period of time set out in the permit. The permittee
shall fully perform and complete all of the required work within the
time limit specified in the permit. If the permittee is unable to
complete the work within the specified time, he shall, within 30 days
prior to the expiration of the permit, present in writing to the Township
a request for an extension of time, setting forth therein the reasons
for the requested extension. If, in the discretion of the Township
Engineer, such an extension is warranted, additional time for the
completion of the work may be granted. Where the Township Engineer
determines that the stormwater management plan is inadequate to cover
the work remaining, any extension of a permit shall be subject to
approval of a revised stormwater management plan, as necessary, in
the same manner as an original plan and application.
B.
Permits for agriculture shall be valid for 10 years, provided that
the conditions of the plan and performance standards are followed
and there is no increase in impervious surfaces, intensification of
land use or changes in drainage.
6.
Modification of Plans.
A.
Major modifications of the approved application and plan, as determined
by the Township, shall be submitted to the Township Engineer and reprocessed
in the same manner as the original application and plans.
B.
All site work shall be suspended pending the approval of modified
plans. Field modifications of a minor nature may be authorized by
the Township Engineer in the form of written authorization given to
the person performing work pursuant to the permit.
7.
Revocation or Suspension. Any permit issued under this chapter may
be revoked or suspended by the Board of Supervisors, after notice,
for:
A.
Violation of any condition of the permit.
B.
Violation of any provision of this chapter or any other applicable
law, ordinance, rule or regulation relating to the permitted activities.
C.
Existence of any condition or the commission of any act constituting
or creating a nuisance or hazard or endangering human life or the
property of others.
D.
Falsification of any drawings, data or information pertaining to
the issuance of a permit.
E.
Any permit or authorization issued or approved based on false, misleading
or erroneous information provided by an applicant is void without
the necessity of any proceedings for revocation. Any work undertaken
or use established pursuant to such permit or other authorization
is unlawful.
8.
Performance Guaranties.
A.
Prior to the issuance of any permit hereunder, financial security
to cover the cost of the work shall be deposited with the Township.
9.
Liability Insurance.
A.
If, in the opinion of the Township Engineer, the nature of the work
to be performed is such that it may create a hazard to human life
or endanger adjoining property at a higher or lower elevation or any
street or street improvement or any other public property, then the
Township Engineer may, before issuing a permit, require that the applicant
file a certificate of insurance, showing that he or she is insured
against claims for damages for personal injury and property damage.
Said certificate shall also verify that the Township is named as an
additional insured party in the policy.
B.
Insurance shall include coverage for damage to the Township which
may be caused by deposit or washing of material onto Township streets
or other public improvements.
C.
Insurance shall cover damages resulting from work performed by the
applicant, or any subcontractor or any person directly or indirectly
employed by or for the applicant.
D.
The minimum amount for said insurance shall be $25,000; additional
amount of insurance shall be as determined by the Township Engineer;
based upon an assessment of the risks involved in the work covered
by the permit.
E.
Such insurance shall be written by a company licensed to do business
in the commonwealth of Pennsylvania and approved by the Township.
F.
Neither issuance of a permit nor compliance with the provisions hereof
or any condition imposed by the Township Engineer shall relieve any
person from any responsibility for damage to persons or property otherwise
imposed by law or impose any liability upon the Township or its officers
or employees for damages to persons or property.
10.
Penalties. Performing work regulated by this chapter and not in compliance with this chapter, whether or not a permit has been issued, or otherwise failing to comply with this chapter, shall also be subject to the provisions of § 22-906 of the Subdivision and Land Development Ordinance [Chapter 22].
[Ord. 183-2013, 12/2/2013, § 2]
1.
Prohibited Discharges.
A.
Any drain or conveyance, whether on the surface or subsurface, that
allows any non-stormwater discharge including sewage, process wastewater,
and wash water to enter the Municipality's separate storm sewer
system or the waters of the commonwealth is prohibited.
C.
The following discharges are authorized unless they are determined
by the Municipality to be significant contributors to pollution to
the Municipality's separate storm sewer system or to the waters
of the commonwealth:
(1)
Discharges from firefighting activities.
(2)
Potable water sources including water line and fire hydrant
flushings.
(3)
Irrigation drainage.
(4)
Air conditioning condensate.
(5)
Springs.
(6)
Water from crawl space pumps.
(7)
Pavement wash waters where spills or leaks of toxic or hazardous
materials have not occurred (unless all spill material has been removed)
and where detergents are not used.
(8)
Diverted stream flows.
(9)
Flows from riparian habitats and wetlands.
(10)
Uncontaminated water from foundations or from footing drains.
(11)
Lawn watering.
(12)
Dechlorinated swimming pool discharges.
(13)
Uncontaminated groundwater.
(14)
Water from individual residential car washing.
(15)
Routine external building washdown (which does not use detergents
or other compounds).
D.
In the event that the Municipality determines that any of the discharges
identified in Subsection 1C significantly contribute pollutants to
the Municipality's separate storm sewer system or to the waters
of the commonwealth, or is notified of such significant contribution
of pollution by PADEP, the Municipality will notify the responsible
person to cease the discharge.
E.
Upon notice provided by the Municipality under Subsection 1D, the
discharger shall, within a reasonable time period, as determined by
the Municipality consistent with the degree of pollution caused by
the discharge, cease the discharge.
F.
Nothing in this section shall affect a discharger's responsibilities
under state law.
2.
Prohibited Connections. The following connections are prohibited,
except as provided in Subsection 1C above:
A.
Any drain or conveyance, whether on the surface or subsurface, that
allows any non-stormwater discharge, including sewage, process wastewater,
and wash water to enter a separate storm sewer system, and any connections
to the separate storm sewer system from indoor drains and sinks.
B.
Any drain or conveyance connected from a commercial or industrial
land use to a separate storm sewer system, which has not been documented
in plans, maps, or equivalent records and approved by the Municipality.
3.
Roof Drains and Sump Pumps.
A.
Roof drains and sump pump discharges shall not be connected to sanitary
sewers.
B.
Roof drain, sump pump, foundation and footing drain discharges:
(1)
To the maximum extent practicable, shall discharge to infiltration
or vegetative BMPs, or to vegetated or other areas with adequate capacity.
(2)
May be connected to streets, storm sewers, or roadside ditches
only if determined necessary or acceptable by the Municipal Engineer.
(3)
Shall be considered in stormwater management calculations to
demonstrate that Conveyance and receiving facilities have adequate
capacity.
4.
Alteration of BMPs.
A.
No person shall modify, remove, fill, landscape, alter, or impair
the effectiveness of any stormwater BMPs, conveyances, facilities,
areas or structures unless the activity is part of an approved maintenance
program, without the written approval of the Municipality.
B.
No person shall place any structure, fill, landscaping, additional
vegetation, yard waste, brush cuttings, or other waste or debris into
a BMP or conveyance, or within a stormwater easement, that would limit
or alter the functioning of the stormwater BMP or conveyance, without
the written approval of the Municipality.
