ORDINANCE NO. 157
AN ORDINANCE
OF
THE BOARD OF SUPERVISORS
OF
SECTION 1.
Amend Article V.
1.
Amend Sections 511 and 512 by deleting them in their entirety and
replacing with the following:
1.
It is the goal of
2.
The specific purposes of comprehensive stormwater management are:
a.
To foster an environment between the Township and applicant to consider
best management, stormwater alternatives and creative planning prior to project
development and during the sketch plan stage,
b.
To reward applicants who incorporate innovative best management practices
into overall project designs,
c.c.
To generally maintain the pre-development water balance in watersheds,
sub-watersheds and especially sensitive streams,
d.d.
To work to restore natural hydrologic regimes where these regimes have
been altered.
e.
To maintain or improve the volume of pre-development groundwater recharge
to protect the groundwater table, critical stream base flow, and discharges to
natural wetlands.
f.
To enhance and encourage aesthetic considerations in the design and
construction of stormwater management facilities, using landscaping, grading and
multipurpose concepts.
g.
To prevent increased post-development surface runoff volumes,
h.
To minimize nonpoint source pollutants, impacts on stream temperatures,
and aquatic habitats,
i.
To continually enhance the quality of surface and ground waters within
the Township in order to protect the health, safety, and welfare or the
community.
1.
Permanent management of stormwater runoff associated with any
proposed subdivision or land development shall be accomplished in accordance
with the standards and criteria of this section.
Design of any temporary or permanent facilities or structures and the
utilization of any natural drainage systems shall be in full compliance with
this ordinance, and Title 25, PA Code Chapter 102, and Title 25, PA Code Chapter
105.
A.
Scope
1.
No person shall develop
any land for residential, commercial, industrial or institutional uses without
having provided stormwater management consistent with the requirements of this
chapter.
2.
No person shall construct
or expand any structures or enlarge impervious coverage without complying with
this ordinance.
3.
The Township may exempt
specific projects or proposed improvements from this section as provided below.
B.
Exemptions
The following development
activities or improvements may be exempt from the stormwater management
provisions of this ordinance as determined by the Zoning Officer
except where the provisions of Subsection
511.B.2.D,
below, may apply:
1.
Agricultural uses,
excluding mushroom plants, including:
a.
Gravel areas or temporary (seasonal or storage) structures.
b.
Any structure requiring a
building permit on properties engaged in agricultural use is exempt up to a
maximum footprint of 100 square feet per acre or a maximum of 1000 square feet,
whichever is smaller, contained within the parcel.
2.
Additions or modifications to existing single family detached residential
structures of less than 1000 square feet.
3.
Reconstruction of existing structures or impervious areas where such
reconstruction does not expand current
coverages
and where current coverage has acceptable stormwater management in
place and
is not known
to cause or
significantly
contribute to
negative on or
off-site impacts
associated with stormwater runoff.
2.
Stormwater Management Criteria
A.
All construction activities subject to the regulations contained within
this section shall provide permanent stormwater management in accordance with
the following performance standards:
1.
Post development peak discharge from the site shall not exceed the before
construction peak discharge rate.
This analysis should be performed for the seven design storms and 24-hour
precipitation values:
Storm
Precipitation
1 yr.
-
2.6”
2 yr.
-
3.2”
5 yr.
-
4.2”
10 yr.
-
5.0”
25 yr.
-
5.6”
50 yr.
-
6.3”
100 yr.
-
8.4”
2.
After installation of impervious coverage, there shall be no increase in
the total volume of stormwater runoff over that which was discharged prior to
development as a result of a 5 year, 24 hour storm event.
3.
Best Management Practices (BMP) shall be employed to enhance water
quality and control of post development runoff for the “First
Flush” (first 1/2 inch of stormwater runoff).
B.
Potential
Modification to
Stormwater Management
Criteria where
Performance and
BMP
Employed
1.
The Township may permit modifications to the stormwater
management criteria outlined above in Paragraph 511.B.2.A.
Modifications will be considered where the applicants have made
substantial use of Best Management Practices in the project design, which result
in increases in groundwater recharge or water quality enhancement.
Any modifications will be permitted at the sole
discretion of the
The
Township’s Board of Supervisors
upon the
recommendation of
the Township Engineer.
In permitting modifications to the stormwater
management criteria the Township must be satisfied that the benefits of the
proposed BMPs clearly outweigh any negative impacts of relaxing controls on
volume or peak rate attenuation. In
no case can the volume control be reduced below the 2 year/24 hour event
anticipated
by
standards set
forth in Subsection
A
above.
2.
Acceptable
use of
These
BMPs
may
include, but are not limited to:
·
Constructed wetlands
·
Wetland forebays
·
Sediment forebays
·
Extended duration water quality basins
·
Filters (sand-peat, underground sand, perimeter sand filter, organic
sand, pocket sand filter, gravel)
·
Wet swales
·
Grass channels
·
Dry swales
·
Retention ponds/extended detention ponds
·
Filter strips
·
Other bioretention BMPs
B
3.
BMP selection, design and implementation shall
be based upon appropriate reference materials such as the
Pennsylvania Handbook of
Best Management Practices for Developing Areas, Design of Stormwater Filtering
Systems, and other generally accepted manuals or abstracts.
4.
All BMP designs must be accompanied with an operation and maintenance
manual which sets forth specific requirements for long term maintenance and
mosquito control.
5.
An easement over and around all stormwater BMPs shall be provided along
with a 15 feet wide access easement to provide ingress and egress from a public
right-of-way.
6.
The applicant shall be responsible for completing an “As-Built Survey” of
all stormwater BMPs included in the approved Project Plan.
The As-Built Survey, and an explanation of any discrepancies with the
Project Plan, shall be submitted to the Township Engineer at the time of
dedication.
C.
Riparian buffer requirements, as set forth in Section 1414 of the Kennett
Township Zoning Ordinance, are required for all sites.
Additional Township requirements for other sensitive environmental
features are also applicable.
D.
Under certain conditionsWhere
appropriate, the Township,
at its sole discretion and
upon recommendation by the Township Engineer, may impose the
following additional
restrictions on
stormwater
discharges
management requirements:
1.
Peak discharge may be further restricted when it can be shown that a
probable risk to downstream structures or unique natural areas exists or that
existing severe flooding problems could be further aggravated.
Risk to downstream structures includes, but is not limited to, abnormal
alterations to geomorphologic characteristics of existing natural streams such
as potential increases in stream bank erosion, or changes in stream channel
entrenchment, width/depth ratio, or sinuosity.
2.
Additional
Mmeasures
shall be imposed to protect against ground or surface water pollution where the
type of land use activity may result in significant nonpoint source pollution or
the nature of the soils or bedrock underlying a stormwater management structure
constitutes substantial risk of contamination, such as might be the case in
limestone formationsareas
underlain by Cockeysville Marble.
Special provisions shall also be imposed where stormwater runoff is
likely to impact the biotic integrity of aquatic systems, for example, by
reducing diversity or abundance of benthic macro invertebrates, decreasing
available habitat for benthic-feeding fishes and fishes intolerant of
disturbance, or creating habitat conditions that promote hybridization or
deformities among aquatic species.
Special provisions to be followed in
these
such
cases
are will be
provided by the Township Engineer
and may include required filtration or pretreatment of stormwater prior to
discharge or other imposition of water quality BMP(s).
E.
Post-Construction Stormwater Runoff Controls for New Development and
Redevelopment, Including Operations and Maintenance of Stormwater BMPs
1.
Post-Construction Runoff Control Requirements
A.
No
Regulated Earth Disturbance activities within the Municipality shall commence
until approval by the Municipality of a plan which demonstrates compliance with
State Water Quality Requirements after construction is complete.
B.
The 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").
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
chemical and physical pollutants from the stormwater runoff, and
3.
Streambank 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).
D.
DEP has regulations that require municipalities to ensure design,
implementation and maintenance of Best Management Practices ("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.
E.
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 Municipality. The issuance of an NPDES Construction Permit
(or permit coverage under the statewide General Permit (PAG-2)) satisfies
the requirements subsection A.
3.
Facility Design
A.
All proposed stormwater management basins shall be designed in accordance
with United States Department of the Interior, Bureau of Reclamation’s “Design
of Small Dams”, Third or most current edition.
All designs should include, at a minimum:
1.
Cutoff trenches for embankment areas.
2.
Properly sized and
located anti-seep collars within the phreatic line. Alternatively properly
designed sand filter diaphragms may be used.
3.
Emergency spillways
sufficient to convey the peak 100 year unmanaged flows and downstream flow
paths.
B.
Standards for conventional basins shall meet requirements listed in this
section. In general, basins are to
be as shallow as possible, designed to conform to existing topography, and
replanted with native vegetation to the maximum extent possible.
1.
Basins shall be designed to provide for maximum groundwater recharge
wherever feasible.
2.
For basins located in
the
carbonate areas,
e.g., areas underlain by Cockeysville Marble, a detailed geologic
evaluation of the project site shall be performed to determine the suitability
for recharge, including both the potential for groundwater contamination and
potential for sinkhole formation. The
evaluation shall be performed by a qualified geologist and/or geotechnical
engineer, and at a minimum, address soil permeability, depth to bedrock,
susceptibility to sinkhole formation, and subgrade stability.
Based on such evaluation,
the Township, upon the recommendation of the Township Engineer,
may impose special design criteria for basins and related stormwater management
facilities in carbonate areas, including but not limited to the following:
a.
Soils used for the construction of basins shall have
low-erodibility factors ("K factors").;
b.
The Township may require aAn
impermeable liner
may be required
to be installed up to the one hundred (100) year design water surface
elevation.;
c.
Site
grading may be
required to be kept
to a minimum and alterations to existing surface and subsurface drainage
patterns minimized;
d.
Minimum
setbacks may be
imposed from
carbonate features for stormwater management facilities that result in
concentrations of stormwater; applicable carbonate features may include, but are
not limited to sinkholes, closed depressions, caverns, surface or subsurface
pinnacles, disappearing streams, fissures, faults, or fracture traces.
23.
The following slope restrictions shall apply to basins:
a.
Exterior slopes of compacted soil shall not exceed one (1) foot vertical
for four (4) feet horizontal, and may be further reduced if the soil has
unstable characteristics.
b.
Interior slopes of the basin shall not exceed one (1) foot vertical in
four (4) feet horizontal except with approval of the Township and:
i.
Where maximum water depth will not exceed two (2) feet; or
ii.
When a two (2) inch
rainfall in one (1) hour will not exceed the capacity of the basin in one (1)
hour; or,
iii.
Where concrete, stone or brick walls are used in conjunction with
Township-approved Best Management Practices and where a vertical drop exceeds 20
inches. The basin shall be fenced
by a permanent fence forty-two (42) inches in height.
A stable access for maintenance shall be provided.
c.
The maximum impoundment depth in a basin shall not exceed 6 feet from
basin outlet to the maximum stage of the routed 100-year event.
d.
The minimum bottom slope shall be one (1) percent for grass, and one-half
(0.50) percent for concrete paving.
A concrete low flow channel
may be required for basins where the distance from the inlet pipe to the
outlet structure exceeds one hundred (100) feet,
depending uponand
where warranted due to basin
design and/or site conditions,
including infiltration capacity.
Where required,
Tthe
minimum channel width shall be four (4) feet.
The channel shall be constructed of six (6) inch thick concrete
(3,500 psi 28-day strength) over four (4)
inches of PADOT No. 2A stone.
34.
Basins shall also be designed to meet the following requirements:
a.
The minimum top of berm width shall be ten (10) feet.
b.
Outlet pipes shall have a minimum diameter of fifteen (15) inches.
All pipe materials are to be reinforced concrete pipe.
Trash racks/and vortex devises shall be permanently secured.
The Township may require structures to prevent access to large drainage
pipes.
c.
Properly spaced anti-seep collars shall be installed on all basin outlet
pipes. Design calculations shall be
provided. Sand filter diaphragms
shall be required for all wet ponds.
Diaphragms shall be designed in accordance with PaDEP standards.
d.
All basins, embankments and cut-off trenches shall be constructed of a
compacted relatively impervious (Unified Soil Classification CL-ML or CL) soils.
The cut-off trench shall extend at least four (4) feet into undisturbed
subsoil (below topsoil layer) and shall have a minimum width of eight (8) feet.
The side slopes of the cut-off trench shall not exceed one (1) horizontal
to one (1) vertical, and the top elevation of the core shall be set at or above
the twenty-five (25) year design water elevation.
45.
Basin outlet structures and emergency spillways:
a.
All outlet structures within basins which will control peak discharge
flows and distribute the flows by pipes to discharge areas shall be constructed
of concrete or masonry material and shall have child-proof, non-clogging trash
racks over all design openings, except those openings designed to carry
perennial stream flows. Trash rack
material should be epoxy coated
galvanized or stainless steel.
Other materials are subject to approval by the Township Engineer.
b.
Outlet structure shall be recessed into stormwater embankments so as to
be less noticeable.
c.
Six (6) inches of freeboard shall be
provided between the crest of the primary outlet structure and the invert of the
emergency spillway. The emergency spillway may be used as a principle outlet
structure for routed outflows from the basin for low frequency events beginning
with the 25 yr. return period.
d.
Emergency spillways shall be constructed in
undisturbed earth wherever possible.
When constructed in fill, emergency spillways and all adjacent embankment
slopes must be armored, based on calculated velocities, use of riprap will not
be permitted. Alternative armoring
design options shall include pegged sod, reinforced turf, pre-cast concrete
paving blocks, or cast-in-place concrete.
Emergency spillways shall be designed to safely convey the post
development one hundred (100) year basin inflow hydrograph assuming the
principal outlet is completely blocked and the basin water surface elevation is
equal to the spillway invert elevation.
A minimum of six (6) inches of freeboard should be provided between the
calculated 100-year storm elevation in the spillway and the top of the basin
berm elevation for dry basins and twelve (12) inches for wet basins.
56.
Basin inlet and outlet structures should be located at maximum distances
from one another. The Township may
require a rock filter berm or rock-filled gabions between inlet and outlet areas
when the distance is deemed insufficient for sediment trapping.
67.
Stabilization measures shall be established on the sides of all earthen
basins by hydroseeding within five (5) days of initial construction, or, if
applicable, from the conversion of a sediment basin or sediment trap.
Permanent re-vegetation shall be accomplished using native grass species.
The Township may require jute or erosion control matting to be installed inside
the basin or on the basin embankment.
78.
Stormwater basin shall discharge to a suitable
natural drainage course. Where not possible or not permitted, level spreading
devices or other suitable facilities shall be designed with sufficient capacity
to convey the 100-year storm event without creating any safety, flooding, or
property hazard. Securing of
necessary drainage easements for this purpose shall be the sole responsibility
of the developer.
The existing points of concentrated
drainage that discharge onto adjacent property shall not be altered without
permission of the adjacent property owner(s).
Point discharges from basins at downstream properties shall not be
permitted.
89.
The Township may require soil samples from the site be analyzed to
determine suitability for berm embankment
construction. If the soils are
found to be unsuitable, the developer shall import suitable soils for
constructing the basin.
C.
Water temperature is a particular concern in High Quality and exceptional
Value watersheds.
Temperature-sensitive BMP’s and stormwater conveyance systems are to be used and
designed with storage pool areas and supply outflow channels, and should be
shaded with trees. Vegetation shall
be planted within the facilities, provided that capacity for volumes and rate
control as required by this Ordinance is maintained.
1.
At a minimum, the southern half on pond shorelines shall be planted with
shade or canopy trees within ten (10) feet of the pond shoreline.
2.
When trees are planted along the berm of embankment the maximum slope
allowed on the berm area to be planted is 10 to 1.
This will lessen the destabilization of berm soils due to root growth.
3.
A long term maintenance schedule and management plan for the thermal
control BMP’s is to be established and recorded for all development project
sites.
D.
The Township may require geotechnical analysis, test borings or other
soils exploration necessary to demonstrate that the siting of the proposed
basins is appropriate.
E.
The
design of shallow flat
basins is preferable touse
of deep
and/or
steeply sloped basin berms and side slopes.
shall
be avoided in favor of
shallow berms
and
flat side slopes
to the maximum extent practicable.
F.
All proposed infiltration facilities shall be accompanied by soils
testing to confirm infiltration rates.
Design calculations of infiltration facilities shall include routing of
storm flows, positive discharge, overflow or bypass flow and drawdown time.
G.
A facility maintenance program is to be developed with each stormwater
management facility. Any
restrictions on the use of the property or specific maintenance requirements
must be incorporated in the deeds to the individual lots, and/or homeowner’s
documents. Maintenance and planting
should be incorporated into any required Open Space Management plans.
All plans must address mosquito control.
H.
Inspections
1.
All basin embankments are to be inspected and approved by the Township
Engineer. The Township Engineer may require or directly engage a Geotechnical
Engineer, experienced in the construction of dams to perform certain
inspections.
2.
All infiltration facilities are to be inspected and approved by the
Township Engineer. Annual or periodic inspections by the Township and/or its
assignees may be performed after 2-week notice to the property owner.
Such notice should not be required in an emergency situation.
Such restrictions shall be incorporated into the individual lot
deed or development homeowners documents.
3.
Inspection may take place by the Township or their assignees on an
emergency basis where the health, safety, and general welfare of the community
is in question or in jeopardy. In
emergency situations (such as West Nile or mosquito infestation), adequate and
reasonable notice may be shorter than the two weeks provided in the previous
paragraph.
I.
Permanent Maintenance of Facilities
1.
All stormwater management
facilities, either in private property or common open space, shall be described
with a permanent easement. These
easements shall be dedicated to the Township and shall be reflected on the deeds
of each property. All maintenance
responsibilities will be either the individual lot owner or homeowners
association. The following language
should be noted on the recorded plans:
“In the event the
homeowners association or homeowner fails to properly maintain stormwater
retention facilities, after notice to the association or lot owner of its intent
to do so, which notice shall not be required in emergency situations, the
Township may, but shall not be obligated to, perform said maintenance or repair
and charge the cost thereof, including any fees relating thereto, to the
homeowners association or facility owner. The Township may place a lien on any
property including homeowners associations members to recoup the costs and any
collection fees and interest”
2.
Where new residential or commercial lots have permanent storm drainage or
stormwater management facilities, the developer is to provide to the Township a
copy of the new parcel deed reflecting the appropriate easements before an
occupancy permit will be issued.
J.
Stormwater Management Calculation Methods
1.
Designs for stormwater management system and facilities shall be
determined using the Soil Cover Complex Method as set forth in Urban
Hydrology for Small Watersheds, Technical Release No. 55. Other equivalent
methods may be utilized if approved in advance by the Township Engineer. The
design shall pay specific attention to antecedent moisture conditions, flood
routing, and peak discharge specifications included therein and in Hydrology
National Engineering Handbook, Section 4, both by US Department of
Agriculture, Natural Resources Conservation Service (Soil Conservation Service).
Note that use of TR-55 with many of the natural system-based approaches
and practices recommended by this Ordinance requires that sites be subdivided
into multiple detailed small sub-areas as necessary for TR-55 modeling.
2.
The Township Engineer may permit the use of the Rational Method for
calculation of runoff on land developments of 10 acres or less and for the
design of storm drainage structures.
3.
In establishing the antecedent conditions for calculating runoff prior to
land disturbance, the following assumptions shall apply:
a.
Average antecedent moisture conditions;
b.
A Type II distribution storm;
c.
Woodland shall be used as the prior condition for those portions of the
site meeting the definition of woodland per this Ordinance.
d.
Meadow shall be used for all other areas including areas of impervious
surface which were installed prior to providing stormwater management.
e.
All areas to be disturbed during construction and subsequently returned
to open space will be assumed to be reduced one level on the Hydrologic Group
category for post-development runoff.
K.
Stormwater Management Standards During Land Disturbance
1.
During the period of land disturbance, when significant sediment can be
contained in runoff, this runoff shall be controlled prior to entering any
proposed infiltration area. No
runoff shall be permitted to enter the infiltrated locality until drainage area
is adequately stabilized.
2.
Peak discharges and discharge volumes from the site shall comply with the
appropriate sections above as well as with guidance provided by the Chester
County Conservation District. In
situations of special sensitivity, the Township Engineer may increase
requirements, such as requiring that the entire volume of all storms up to a
2‑year storm from the disturbed areas be retained on site and that special
sediment trapping facilities (such as check dams, etc.) be installed.
3.
Applicants, as part of the sedimentation and erosion control plan
required in Section 511.D. shall submit data, including dates where appropriate,
demonstrating that the proposed subdivision or development will be carried out
in accordance with the following principles:
a.
The smallest practicable land area shall be disturbed and exposed at any
one time during construction.
b.
Land exposure shall occur for the shortest practicable time period.
c.
Temporary ditches, dikes, vegetation, mulching and/or one of the new
erosion control products subject to the approval of the Township Engineer and
Chester County Conservation District should be used to protect critical areas
exposed during development or construction.
d.
Sedimentation basins (debris basins, desilting basins or sediment traps)
shall be installed and maintained to remove sediment from runoff from disturbed
areas prior to any earth disturbance.
e.
Where feasible, natural vegetation should be retained and protected,
natural grade alterations minimized, and total site disturbance minimized.
f.
Permanent vegetation and erosion control structures should be installed
as soon as practicable during construction activities.
g.
Increased runoff caused by altered soil and surface conditions during and
after construction shall be accommodated effectively.
4.
All activities involving land disturbance shall be consistent with
Section 511.D. unless specific modification(s) are granted as part of
subdivision or land development approval.
5.
All activities involving land disturbance shall comply with the current
National Pollution Elimination Discharge Systems permit requirements established
by the Pennsylvania Department of Environmental Protection Agency. Issuance of
an N.P.D.E.S. permit is required prior to Final Plan Approval.
L.
Special
Provisions for Stormwater Management Systems Incorporating Infiltration
1.
Infiltration devices shall be selected based on suitability of soils and
site conditions. Suitability of
soils shall be determined by soil infiltration testing, with suitability
typically defined as having minimum percolation rates of 0.5 inches per hour
at the elevation of the bottom of the facility.
Lower rates can be acceptable in special situations.
2.
Soil infiltration testing shall be performed for all proposed
infiltration areas; soil testing shall include evaluation of appropriate soil
horizons with deep pits and percolation measurements, making sure to assess
percolation rates at the proposed infiltration device bed bottom.
Soil testing, including the frequency and locations of the tests, should
be reviewed and approved by the Township.
The design soil percolation rate shall be the average rate measured at
each proposed area.
3.
The lowest elevation of the infiltration area shall be at least two (2)
feet above the seasonal high water table and bedrock, except in the case of
limestone formations, in which case the distance shall be four (4) feet.
4.
All roof drains which discharge to infiltration systems shall have
appropriate measures
to prevent clogging by vegetation and prevent sinkhole
formation; roof drains should be connected directly
to these infiltration systems.
5.
All infiltration systems shall have appropriate positive overflow
control.
6.
All infiltration systems shall be isolated a minimum of fifteen (15) feet
from all structures and property lines.
Seepage into sub-surface structures shall be prevented.
All infiltration systems must be isolated from septic systems a minimum
of 50 feet or as prescribed by State regulation, whichever is greater.
7.
All infiltration systems shall be designed to infiltrate the stored
volume within forty-eight (48) hours.
8.
All surface inflows shall be designed with baffles, debris pits or other
devices to minimize the discharge of sediment into the infiltration system and
to prevent sediment accumulation.
9.
Special provisions are required when using infiltration BMPs in carbonate
areas in order to avoid groundwater contamination and solution channel/sinkhole
formation.
a.
Because potential for these problems to develop increases as soil
thickness decreases, the soil mantle should be determined to be a minimum of
four feet in thickness, in order to both remove pollutants and uniformly
disperse groundwater movement, which is important to avoid solution channel
formation.
b.
Stormwater runoff from significant pollutant producing sources (so called
"hot spots" such as industrial uses, gas stations, fast food and other
commercial uses generating large numbers of vehicle trips, and other uses as
determined by the Township) shall be filtered and/or
pretreated using a water quality BMP
before being discharged in carbonate areas.
In these cases, the
Township may require that a detailed geologic evaluation of the project site be
performed to determine the suitability for recharge, including both the
potential for groundwater contamination and potential for sinkhole formation.
The evaluation shall be performed by a qualified geologist and/or soil
scientist, and at a minimum, address soil permeability, depth to bedrock,
susceptibility to sinkhole formation, and subgrade stability.
M.
Related Site Development Requirements
1.
Procedures shall be established in conjunction with the Township, for
protecting soils or areas of potential water supply contamination from surface
runoff. All streams and tributaries
within Kennett Township are source waters for public water supply intake in
northern New Castle Co., Delaware. Accordingly, the Township may require
pollution control facilities be provided on existing or proposed storm water
management systems near or adjacent to these tributaries or other sensitive
areas,
2.
Provisions for protecting existing wells or other water supplies shall be
established and noted on the plan.
3.
Finished graded slopes shall not be steeper than three (3) horizontal
units to one (1) vertical unit.
4.
Any approvals required by
the Steep Slope Conservation DistrictCompliance
with the Natural Resource Protection Standards of Section 1414 in
the
Kennett Township's
Zoning Ordinance
(Article XIII)
shall be
secured
demonstrated prior to earthmoving or stripping of vegetation.
5.
A minimum of six (6) inches of topsoil shall be provided on all disturbed
areas prior to final seeding and mulching.
6.
Mature healthy trees of at least six (6) inches DBH and other significant
existing vegetation within the limits of earth disturbance shall be located in
the field and on the storm drainage plan and shall be retained and protected.
Such trees shall not be removed except as provided on the approved
subdivision or land development plan.
Equipment traffic, or filling of soil over roots within the drip line is
prohibited (roots are presumed to extend out from the tree as far as the tree's
branches extend outward.)
A.
Public Nuisance
1.
The violation of any provision of this ordinance is hereby deemed a
Public Nuisance.
2.
Each day that a violation continues shall constitute a separate
violation.
B.
Enforcement
1.
Whenever the Municipality finds that a person has violated a prohibition
or failed to meet a requirement of this Ordinance, the Municipality may order
compliance by written notice to the responsible person. Such notice may require
without limitation:
a.
The performance of monitoring, analyses, and reporting;
b.
The elimination of prohibited discharges;
c.
Cessation of any violating discharges, practices, or operations;
d.
The abatement or remediation of storm water pollution or contamination
hazards and the restoration of any
affected property;
e.
Payment of a fine to cover administrative and remediation costs;
f.
The implementation of stormwater BMPs; and
g.
Operation and maintenance of stormwater BMPs.
2.
Failure to comply within the time specified shall also subject such
person to the penalty provisions of this Ordinance. All such penalties shall be
deemed cumulative and shall not prevent the Municipality from pursuing any and
all other remedies available in law or equity.
C.
Suspension and Revocation of Permits and Approvals
Any building, land development or other permit or approval for Regulated Earth
Disturbance Activities issued by the Municipality may be suspended or revoked by
the governing body for:
1.
Non-compliance with or failure to implement any provision of the permit,
2.
A violation of any provision of this Ordinance, or
3.
The creation of any condition or the commission of any act during
construction or development which constitutes or creates a hazard or nuisance,
pollution or which endangers the life or property of others.
D.
Penalties
1.
Any person violating the provisions of this ordinance shall be guilty of
a misdemeanor, and upon conviction shall be subject to a fine to be determined
by resolution of the Board of Supervisors for each violation, recoverable with
costs. Each day that the violation continues shall be a separate offense.
2.
In addition, the Municipality, through its solicitor, may institute in
junctive, mandamus or any other appropriate action or proceeding at law or in
equity for the enforcement of this Ordinance. Any court of competent
jurisdiction shall have the right to issue restraining orders, temporary or
permanent injunctions, mandamus or other appropriate forms of remedy or relief.
1.
Stormwater drainage shall be provided to:
A.
Permit unimpeded flow of natural watercourses; in general every effort
shall be made to avoid any disturbance of the existing natural system of site
drainage;
B.
Ensure adequate drainage of all low points along the line of streets or
any other locations where stormwater concentration would cause problems;
C.
Intercept stormwater runoff along streets at intervals related to the
extent and grade of the area drained;
D.
Provide positive drainage away from onsite sewage disposal facilities.
2.
If existing storm sewers are reasonably accessible, proposed subdivisions
may connect therewith, provided that no other alternatives exist for managing
stormwater at the sites themselves.
3.
In the design of stormwater facilities, special consideration will be
given to avoidance of situations which may arise from concentration of
stormwater runoff, and to the solution of existing problems.
The concentration of stormwater runoff onto adjacent properties shall
not
be
permittedprohibited,
unless waived by the Township due to special site conditions.
4.
Storm collection and conveyance facilities shall be designed to meet the
following criteria:
A.
Stormwater piping and inlet systems shall be designed for the 25-year
frequency storm.
The design of storm sewer
systems within the drainage area of detention or retention facilities must be
analyzed for adequacy during the 100-year storm, including the effects of the
control facility tailwater. This
may require a hydraulic grade line analysis.
When approved by the Township, overflow swales may be provided at low
points in streets to safely convey the full one hundred (100) year peak flow
to the control facility, in lieu of providing the full capacity in the
storm sewer.
B.
Culverts across roadways shall be designed for the 50-year frequency
storm. Provisions shall be made to
accommodate the 100-year storm across the roadway.
C.
Those facilities at site low points shall be designed to accommodate the
100-year storm.
5.
Where a subdivision or land development is traversed by a watercourse,
drainage way, channel, or stream, there shall be provided a drainage easement
conforming substantially to the high water line of such watercourse attributable
to the 100-year flood, in order to preserve the unimpeded flow of natural
drainage and protect these critical natural functions.
Changes to and impacts on the existing natural system of site drainage
shall be avoided and shall be the option of last resort, subject to the approval
of the Township Engineer and the Pennsylvania Department of Environmental
Protection.
6.
The developer shall employ available measures for the control of erosion
and sedimentation and shall meet, as a minimum, the standards and specifications
of the USDA Soil Conservation Service as then adopted for use by the Chester
County Conservation District, and the guidelines under Chapter 102 of the
Pennsylvania Department of Environmental Protection.
7.
Storm Sewer Design
A.
Storm sewers shall have a minimum diameter of fifteen (15) inches and
only PA DOT class III reinforced cement concrete pipe shall be used where the
Township will have ultimate maintenance responsibility.
All storm sewers beneath a paved surface shall be bedded and backfilled
with fine grained or densely graded soils free of stone fragments greater than 6
inches in diameter. This backfill shall be placed in six (6) inch lifts and
solidly compacted to the satisfaction of the Township. The minimum grade of the
pipe shall be one-half of one percent (0.50%).
B.
For storm sewers not to be maintained by the Township, smooth bore
high-density polyethylene pipe up to a maximum diameter of thirty-six (36)
inches may be used in lieu of concrete.
The minimum diameter shall be fifteen (15) inches and the minimum grade
shall be one-half of one percent (0.50%).
C.
Headwalls, endwalls, or end sections shall be required on all open pipes,
shall be of concrete construction and shall be set on a minimum of twelve (12)
inches of AASHTO No. 57 (PADOT 2B) coarse aggregate.
Flared end sections, when allowed by the Township, shall be concrete.
D.
All storm sewers shall be constructed per PADOT specifications as
outlined in Publication 408
Design Manual, Part 2, Highway Design and Standards for Roadway
Construction, RC-Series unless otherwise dictated by Township ordinance.
E.
Any changes in alignment shall be made using inlets or manholes.
F.
When there is a change in pipe size through an inlet, the top inside
elevation of the outlet pipe shall be at or below the
top inside
elevations of all incoming pipes.
There should be a minimum of 0.2 tenths of
a foot difference in inlet and outlet inverts.
G.
Inlet efficiency and bypass flow shall be determined for all inlets, and
the gutter flow spread shall not exceed one-half (1/2) the travel lane width or
to a maximum of eight (8) feet where parking is permitted.
The Township
may require that a hydraulic grade line analysis be performed on storm sewer
systems.
H.
Culverts shall be evaluated for inlet
and outlet control restrictions.
1.
Rainfall intensity curves and other hydraulic design data, provided by
the Pennsylvania Department of Transportation and/or manufacturers of storm
drainage structures shall be used for design purposes.
2.
Manholes and/or inlets shall not be more than three hundred (300) feet
apart on pipe sizes up to twenty-four (24) inches, and not more than four
hundred (400) feet apart on larger sizes.
3.
Inlets, manholes, covers and frames shall conform to Pennsylvania
Department of Transportation RC standards and Form 408 specifications. At street
intersections, every attempt should be made to place inlets at the points of
tangency or curvature sections and not in the curved portion of the curbing.
4.
When precast concrete inlets or manholes are used
within a street, a minimum of two (2) 4-inch
leveling courses of brick masonry or precast grade ring shall be placed to bring
the grate or cover to proper elevation.
No more than 18 inches of masonry or grade rings will be permitted.
8.
Swale Design
A.
Grass swales not specifically designed as BMP devices shall have a
minimum bottom slope of two (2) percent.
Swales lining shall be designed based on the 10-year velocity.
Swales shall have sufficient freeboard to convey the 100-year storm
discharge without creating any safety or property hazard.
B.
Swales, when located outside of the Township right-of-way, shall be
located within an easement not less than twenty (20) feet wide, but of
sufficient width to allow access for maintenance and
to convey the 100-year storm. A
note on the plan shall indicate that the easement allows the Township the right,
though not the responsibility, to perform needed maintenance and/or repairs.
C.
Particular
care shall be given to points of discharge from gutter lines at the end of a cut
section in the road construction where water will discharge over banks with the
possibility of creating erosion channels.
Velocity checks, riprapping or if justified by the quantity of flow,
inlets and piping shall be provided to protect slopes against erosion.
D.
Where swales are used to convey storm water flows, they shall be broad
and flat in cross-section. No deep
ditches will be permitted and if the terrain prevents the construction of broad
swale, storm water shall be contained in piping.
9.
Building or Roof Drainage
A.
Storm water roof drains shall not discharge water directly over a
sidewalk or into any sanitary sewer line.
B.
Except for single-family homes, proposed roof drains and collector
locations shall be shown on the storm drainage plans. Roof drains and collectors
shall meet all BOCA codes and Township ordinances.
10.
Design of bridges and culverts
A.
Bridges and culverts shall have ample waterway to carry the design flows,
based on a minimum storm frequency of fifty (50) years, unless a larger design
flow is required by PADEP. One
hundred (100) year water depths shall not exceed six (6) inches above the
roadway edge of cartway. Bridge
and/or culvert construction shall be in accordance with the PADOT specifications
and shall meet the requirements of the PADEP.
The appropriate permits and approvals must be acquired by the applicant
prior to final plan approval.
B.
Culverts shall be provided with wing walls and constructed for the full
width of the right of way. If the
character of the road is expected to change for future planning, the cartway of
the bridge shall be made to anticipate this condition.
On each side of the bridge cartway, the bridge railing must be set back
from the edge of the cartway and this area may be used to place sidewalks,
present or future.
11.
The discharge of storm water from streets, pipes and swales shall, to the
maximum extent possible, be directed on to level areas in the rear of lots where
storm water will be dispersed and the concentration of storm water minimized at
property lines. Where storm water
must be discharged directly into streamways, energy dissipaters shall be
constructed to limit the velocity of discharge to prevent erosion of stream
banks and channels.
1.
All activities involving land disturbance shall be in accordance with
this ordinance. Erosion and
sediment control measures shall be designed in accordance with the standards and
specifications of the Pennsylvania Department of Environmental Protection and
the guidelines established under Title 25, PA Code Chapter 102 and the National
Pollution Discharge Elimination System Permit (NPDES) for non-point source
discharges, as determined in Title 25, PA Code Chapters 92 and 93.
1.A.
Exemptions
a.1.
All land disturbance activities shall be subject to this ordinance except
as specifically exempted below.
a.
Agricultural uses so long as the following conditions apply:
i.
Contour plowing, crop rotation and other generally accepted conservation
practices for agricultural uses.
ii.ii.
Drainage swales and areas of highly erosive soils shall be maintained
with a permanent vegetative cover.
iii.iii.
Permanent vegetative cover will be maintained within 75 feet of a stream.
iv.iv.
Runoff from impervious surfaces shall be diverted away from areas of
spent mushroom compost, manure storage,
nursery areas, and tilled areas
v.v.
Permanent vegetative cover shall be maintained a minimum of 20 feet from
the edge of any public road surface or property line.
vi.
Agricultural activities shall be conducted with conservation and
erosion/sediment control plans approved by the Chester County Conservation
District.
b.
Logging and wood cutting operations:
All logging or wood cutting operations conducted independently of any
property not under application for a building permit for land development or
subdivision shall be permitted only in accordance with an erosion and sediment
control plan approved by the Chester County Conservation District and the
Township Engineer. Any
property proposed for logging or clearing operations under an application for a
building permit, land development or subdivision approval (including sketch
plan) shall be subject to this ordinance.
B.
Earth Disturbance Requirements
1.
Under 25 Pa. Code Chapter 92, a DEP "NPDES Construction Activities"
permit is required for any earth disturbance one acre or more with a point
source discharge to surface waters or the Municipality's storm sewer system, or
five acres or more regardless of the planned runoff (hereinafter collectively
referred to as "Regulated Earth Disturbance Activities"). This includes earth
disturbance on any portion of, part of, or during any stage of, a larger common
plan of development.
2.
The Pennsylvania Department of Environmental Protection (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).
3.
No Regulated Earth Disturbance activities within the Municipality shall
commence until approval by the Municipality of an Erosion and Sediment Control
Plan for construction activities.
4.
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 Municipality.
2.
Land developments or subdivision of three or more lots shall be
accompanied by a conservation plan and program which shall incorporate temporary
and permanent measures designed to prevent accelerated erosion and sediment
discharges from the property. The
design criteria shall be in accordance with the Department of Environmental
Protection “Erosion and Sediment Pollution Control Manual”, dated March 2000 and
any subsequent revisions.
A.
Projects subject to the NPDES criteria for a general or individual
permits must receive permit approval from the Chester County Conservation
District before final land development or subdivision plan approval can be
granted.
B.
Projects not subject to an NPDES permit must be reviewed and approved by
the Township Engineer or, at the Township’s discretion, must be approved by the
Chester County Conservation District before final land development or
subdivision plan approval can be granted.
1.3.
Activities requiring a building permit must submit a plot plan with the
building permit. The plot plan
shall indicate the proposed lot improvements including existing and proposed
building driveways, accessories buildings, septic facilities, proposed grading
and limit of disturbance. This plan
shall also incorporate the following design information:
A.
On lot stormwater management if required under Section 511.B.1
individual building permits within subdivisions or land developments
where overall project stormwater management was approved pursuant to the
provisions of Section 511 is exempt from on lot stormwater management except as
required by the specific project plan approval.
B.
Temporary erosion and sediment control measures for the individual lot
improvements. This design shall be
subject to the same design criteria as specified in the PaDEP Erosion and
Sediment Pollution Control Manual referenced above.
4.
Inspections
A.
The Township Engineer or designee shall inspect all phases of the
implementation of stormwater BMPs.
B.
Prior to the start of general earthmoving, all temporary erosion and
sediment control measures shall be in place in accordance with the approved
plan.
2.C.
Earthwork for temporary sediment basin embankments must be observed and
inspected by the Township. All
basin embankments are to be built of inorganic clayey soils (Soils
Classifications CL or ML) and compacted to a minimum density to be determined by
the Township Engineer. During the
approval process, the Township Engineer may require test borings or other soils
explorations to assure the suitability of the location and design for the basin.
D.
Any subdivision or land development shall be subject to periodic
inspections by the Township for compliance with erosion and sediment control
plan approval. During any stage of
the work, if the Township Engineer determines the BMPs are not being implemented
in accordance with this Ordinance, the Township shall revoke any existing
permits and approvals until work is brought into compliance with the approved
plans.
E.
Building permit inspections:
1.
Before building permit issuance, the applicant must provide a plot plan
for the lot. This plan shall be
approved by the Township Engineer prior to building permit issuance.
This plan shall incorporate proposed improvements, grading, erosion and
sediment control, and stormwater management as required.
Before the initial inspection by the Code Enforcement Officer is
performed, the Township Engineer must approve the in place temporary erosion and
sediment control measures.
b.2.
Before a final inspection for occupancy can occur, the Code Enforcement
Officer must receive from the Township Engineer a statement confirming that the
lot has received adequate permanent stabilization.
No occupancy permit can be issued unless permanent vegetative cover has
been established on the lots (Builders must be mindful of the coordination of
their occupancy permit with their ability to satisfy permanent lot
stabilization).
4.
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
5.
Right of Entry
A.
Upon presentation of proper credentials, duly authorized representatives
of the Township may enter at reasonable times upon any property with the
Township to inspect the implementation, condition, or operation and maintenance
of the stormwater BMPs in regard to any aspect governed by this Ordinance.
B.
BMP owners and operators shall allow persons working on behalf of the
Township ready access to all parts of the premises for the purposes of
determining compliance with this Ordinance.
C.
Persons working on behalf of the Township shall have the right to
temporarily locate on any BMP in the Township such devices as are necessary to
conduct monitoring and/or sampling of the facility’s storm water discharge.
D.
Unreasonable delays in allowing an authorized Township representative
access to a BMP is a violation of this Ordinance.
6.
Penalties
A.
Noncompliance by a builder, developer or landowner with the provisions of
this ordinance may result in a civil citation with the associated fines
established in the accordance with State laws.
Each day of noncompliance shall be considered a separate violation.
B.
Individual lots in previously approved developments where stormwater
management was not part of the subdivision design, or isolated unimproved
individual lots are subject to the stormwater management provisions of this
Ordinance.
C.
Noncompliance by a builder, developer or landowner with the provisions of
this ordinance may result in any of the following remedies:
1.
Issuance of a cease and desist order on all work on the property.
2.
Withholding of occupancy permits on any aspect of the project.
c.3.
Civil citation of each day of noncompliance will be considered a separate
violation.
d.4.
Criminal citation with the associated fines established in accordance
with the State laws. Each day of
noncompliance shall be considered a separate violation.
511.E
Prohibition Against Non-Stormwater Discharges
1.
Prohibited Discharges
A.
No person in the Municipality shall allow, or cause to allow, stormwater
discharges into the Municipality's separate storm sewer system which are not
composed entirely of stormwater, except (1) as provided in subsection B below,
and (2) discharges allowed under a state or federal permit.
B.
Discharges, which may be allowed, based on a finding by the Municipality
that the discharge(s) do not significantly contribute to pollution to surface
waters of the Commonwealth, are:
Discharges from fire fighting activities
Uncontaminated
water from foundation or from footing drains
Potable water sources including dechlorinated water line and fire hydrant
flushings
Flows from riparian habitats and wetlands
Lawn watering
Irrigation drainage
Pavement washwaters 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
Routine external building washdown (which does not use detergents or other
compounds)
Air conditioning condensate
Water from individual residential car washing
Dechlorinated swimming pool discharges
Springs
Uncontaminated
groundwater
Water from crawl space pumps
C.
In the event that the Municipality determines that any of the discharges
identified in Subsection B significantly contribute to pollution of waters of
the Commonwealth, or is so notified by DEP, the Municipality will notify the
responsible person to cease the discharge.
D.
Upon notice provided by the Municipality under subsection C, the
discharger will have a reasonable time, as determined by the Municipality, to
cease the discharge consistent with the degree of pollution caused by the
discharge.
E.
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 Section B above:
A.
Any drain or conveyance, whether on the surface or subsurface, which
allows any non-storm water discharge including sewage, process wastewater, and
wash water, to enter the separate storm sewer system, and any connections to the
storm drain system from indoor drains and sinks; and
B.
Any drain or conveyance connected from a commercial or industrial land
use to the separate storm sewer system, which has not been documented in, plans,
maps, or equivalent records, and approved by the Municipality.
ENACTED AND ORDAINED
this 16th
day of May, 2005.
KENNETT TOWNSHIP
BOARD OF SUPERVISORS
ATTEST:
_____________________________________
_________________________________
Thomas W. Nale, III, Chairman
Lisa M. Moore,
Secretary-Treasurer
_________________________________
Michael E. Elling,
Vice-Chair
_________________________________
Robert A. Hammaker