[Ord. 2011-8, 11/3/2011, § 301]
1.
No proposed regulated activity shall commence until the Township issues written approval of a SWM site plan in compliance with the provisions of this chapter. If the regulated activity is exempted from any requirements of this chapter pursuant to § 23-302, then the activity shall not commence until the Township issues written confirmation of the specific exemption(s).
2.
The Township may approve measures for meeting the state water quality
requirements other than those in this chapter subject to consultation
with DEP. Such measures shall meet the minimum requirements of, and
not conflict with, state law including but not limited to the Clean
Streams Law, 35 P.S. § 691.1 et seq.
3.
For all regulated activities, stormwater management facilities shall
be designed, implemented, operated and maintained to meet the purposes
and requirements of this chapter and to meet all requirements under
Title 25, Pa. Code, the Clean Streams Law, 35 P.S. § 691.1
et seq., and the Storm Water Management Act, 32 P.S. § 680.1
et seq.
4.
For all regulated earth disturbance activities, erosion and sediment
control BMPs shall be designed, implemented, operated and maintained
as required in accordance with 25 Pa. Code, Chapter 102, as amended,
the Clean Streams Law, 35 P.S. § 691.1 et seq., and the
applicable standards set forth in the Erosion and Sediment Pollution
Control Program Manual (E&S Manual),2 Commonwealth of Pennsylvania, Department of Environmental Protection,
No. 363-2134-008 (2000), as amended and updated.
5.
For all regulated activities, the measurement of impervious or semi-pervious
coverage shall include all impervious coverage for the total proposed
development, even if development is to take place in phases.
6.
The SWM site plan approved by the Township shall be on file at the
project site throughout the duration of the construction activity.
7.
Design Standards. The design of all stormwater management facilities
shall incorporate sound engineering judgment, principles and practices.
The Township reserves the right to disapprove any design that would
result in the creation or continuation adverse hydrologic or hydraulic
conditions. The following general requirements shall apply to all
regulated activities within the Township.
A.
All calculations, assumptions, criteria and references used in the
design of the SWM site plan shall be provided.
B.
Computations for determining stormwater runoff, and for the design
of stormwater management facilities, shall be based upon the NRCS
Soil-Cover-Complex Method (Technical Release 554 or Technical Release 20, as amended), or the Modified Rational Method. NRCS methods shall be acceptable for watershed analyses of all sizes. The Modified Rational Method shall be acceptable for watersheds up to 25 acres in size. Refer to § 23-303 for specific requirements when computing the change in the runoff volume for the two-year design storm.
C.
All pre-development stormwater runoff calculations shall be based upon existing land uses except existing agricultural uses, which shall be based on cultivated land with conservation treatment, pasture in good condition, meadow in good condition and farmstead, unless the actual ground cover generates a lower Curve Number or Rational "C" value. Refer to § 23-303 for specific requirements when computing the change in the runoff volume for the two-year design storm.
D.
Precipitation intensities utilized for Rational Method runoff computations
shall be based on mean precipitation frequency estimates (Duration=60
minutes) published in the Precipitation-Frequency Atlas of the United
States, Atlas 14, Volume 2, U.S. Department of Commerce, National
Oceanic and Atmospheric Administration (NOAA), National Weather Service,
Hydrometeorological Design Studies Center, Silver Spring, Maryland
20910, for the New Park, PA, Monitoring Station (36-6289), or the
Glen Rock, PA, Monitoring Station (36-3330). NOAA's Atlas 145 can be accessed at http://hdsc.nws.noaa.gov/hdsc/pfds/.
E.
Precipitation depths utilized for NRCS Method runoff computations
shall be based on mean precipitation frequency estimates (Duration=24
hours) published in the Precipitation-Frequency Atlas of the United
States, Atlas 14, Volume 2, U.S. Department of Commerce, National
Oceanic and Atmospheric Administration (NOAA), National Weather Service,
Hydrometeorological Design Studies Center, Silver Spring, Maryland,
20910 for the New Park, PA, Monitoring Station (36-6289), or the Glen
Rock, PA, Monitoring Station (36-3330). NOAA's Atlas 145 can be accessed at http://hdsc.nws.noaa.gov/hdsc/pfds/.
F.
Runoff Curve Numbers (CN) utilized for runoff computations based
on The Soil Cover Complex Method shall be obtained from the NRCS TR-55
Manual4.
G.
Runoff coefficients (c) utilized for runoff computations based on
the Modified Rational Method shall be obtained from Table 23-D-1 in
Appendix 23-D of this chapter.
H.
The stormwater management plan shall consider and provide provisions
for management of all stormwater runoff affecting the development
site, including safe conveyance of the one-hundred-year design storm
runoff from off-site watersheds, if any.
I.
Storm sewers, swales and other stormwater conveyance structures shall
be designed to convey post-development runoff from a twenty-five-year
design storm with adequate freeboard. Storm sewers shall not surcharge
above inlet grates. Six inches of freeboard shall be provided in swales
carrying less than 15 cfs. One foot of freeboard shall be provided
for in drainageways designed to carry flows of 15 cfs or greater.
J.
The minimum pipe diameter permitted for use in storm sewer systems
and/or stormwater carrying culverts dedicated to the Township shall
be 15 inches.
K.
Stormwater drainage systems shall be provided in order to permit
unimpeded flow along natural watercourses.
L.
Stormwater flows onto adjacent property shall not be created, increased,
concentrated or relocated without written consent by the adjacent
property owner(s). Such stormwater flows shall be subject to the requirements
of this chapter.
M.
If existing diffused drainage discharge will be concentrated in the
post development condition and discharged onto an adjacent property,
the applicant must document that adequate downstream conveyance facilities
exist to safely transport the concentrated discharge, or otherwise
prove that no erosion, sedimentation, flooding or other harm will
result from the concentrated discharge.
N.
Any stormwater management facilities regulated by this chapter that
would be located in or adjacent to waters of this commonwealth or
wetlands shall be subject to approval by DEP and, if applicable, the
U.S. Army Corps of Engineers. When there is a question whether wetlands
or other regulated resources may exist, it is the responsibility of
the applicant or his agent to demonstrate to the applicable regulatory
agencies that the lands or features in question cannot be classified
as wetlands or other regulated resources.
O.
Any stormwater management facilities regulated by this chapter that
would be located in state highway rights-of-way shall be subject to
approval by the Pennsylvania Department of Transportation.
P.
A manhole, inlet or cleanout structure shall be provided at all horizontal
and vertical directional changes in storm sewer piping. They shall
install intermediate cleanout structures as required at spacing intervals
that will ease adequate maintenance of all storm sewer runs.
Q.
The stormwater management plan shall include calculations indicating
velocities of flow, grades, sizes and capacities of water carrying
structures, and retention and detention structures, as well as sufficient
design information to construct such facilities.
R.
Proposed lots or buildings adjacent to stormwater management basins
and channels designed to convey a one-hundred-year design storm shall
have a finished grade elevation or first floor elevation two feet
above the calculated one-hundred-year storm event water surface elevation.
First floor and finished grade elevations shall be specified on the
plan.
S.
For all regulated activities, SWM BMPs shall be designed, implemented,
operated and maintained to meet the purposes and requirements of this
chapter and to meet all requirements under Title 25, Pa. Code, the
Clean Streams Law, 35 P.S. § 691.1 et seq., and the Storm
Water Management Act, 32 P.S. § 680.1 et seq. Special provisions
may be required for projects draining to, or located in, special protection
waters, which are High Quality (HQ) or Exceptional Value (EV) by designation
in 25 Pa. Code, Chapter 93, or by statewide existing use as dictated
by DEP.
[Ord. 2011-8, 11/3/2011, § 302]
1.
Regulated activities that meet the following criteria shall be eligible
for an exemption from the specified provisions of this chapter. Exemption
requests shall be submitted to the Township in writing and shall identify
the justification and basis for the request pursuant to the criteria
in this. Exemption requests shall be reviewed by the Township Engineer
and evaluated by the Township on an individual site basis using the
criteria set forth in this section. The Township has the ability to
grant or deny exemptions at its discretion. An exemption shall not
relieve the applicant from the responsibility to implement measures
that are necessary to protect the public health, safety, welfare,
property and the resources of the people and the environment.
2.
Exemption criteria shall apply to all regulated activities proposing
to construct impervious or semi-pervious surfaces after the effective
date of this chapter. The impervious surface measured for the purpose
of exemption eligibility shall include new impervious surfaces only.
The new impervious surface shall include the impervious area proposed
for the total proposed development, even if the development is to
take place in phases. The effective date of the chapter shall be the
date after which impervious coverage shall be cumulatively measured.
Proposed gravel, shale and crushed stone areas shall be included in
the impervious surface measurement. Existing impervious and semi-pervious
surfaces constructed prior to the effective date of this chapter shall
not be included in the impervious surface measurement.
3.
Regulated activities that create DIAs equal to or less than 1,000 square feet shall be exempt from the requirements of § 23-304, Rate Controls, and SWM site plan requirements of this chapter.
4.
Regulated activities that create DIAs greater than 1,000 square feet and equal to or less than 5,000 square feet shall be exempt from the requirements of § 23-304, "Rate Controls." All other requirements of this chapter shall remain applicable.
5.
Agricultural activity is exempt from the rate control and SWM site
plan preparation requirements of this chapter provided the activities
are performed according to the requirements of 25 Pa. Code, Chapter
102.
6.
Forest management and timber operations are exempt from the rate
control and SWM site plan preparation requirements of this chapter
provided the activities are performed according to the requirements
of 25 Pa. Code, Chapter 102.
7.
Domestic gardening and landscaping are exempt from specific approval
and permitting under this chapter so long as those activities are
associated with one, and only one, dwelling unit and the activities
comply with all other applicable ordinances and statutes.
8.
A high tunnel under the following conditions:
[Added by Ord. No. 6-2023, 8/10/2023[1]]
A.
The high tunnel or its flooring must not result in an impervious area exceeding 25% of all structures located on the owner's total contiguous land area, regardless of whether existing on, or placed or constructed after, the effective date of this Subsection 8; and
B.
The high tunnel must meet at least one of the following criteria:
(1)
The high tunnel must be located at least 100 feet from any perennial
stream or other watercourse, public road, or neighboring property
line.
(2)
The high tunnel must be located at least 35 feet from any perennial
stream or other watercourse, public road or neighboring property line,
and located on land with a slope not greater than 7%.
(3)
There is a diversion system or buffer built and managed consistent
with the ordinance that ensures that runoff from the high tunnel does
not directly drain into a stream or other watercourse.
C.
An operations and maintenance agreement must be submitted to the
Township.
E.
Any structure that does not meet the above requirements must comply
with all sections of the Stormwater Management Ordinance.
9.
Emergency maintenance work performed for the protection of public
health, safety and welfare. A written description of the scope and
extent of any emergency work performed shall be submitted to the Township
within 24 hours of the commencement of the activity. If the Township
determines that work is not an emergency, then the work shall cease
immediately and the requirements of this chapter shall be addressed
as applicable.
10.
Any maintenance to an existing stormwater management system made
in accordance with plans and specifications approved as part of an
O&M plan or by the Township Engineer.
11.
Regulated activities exempted from SWM site plan requirements are
not subject to review and approval for the volume control requirements
of this chapter. It shall be the landowner's responsibility to assure
compliance with the volume control requirements. The Township may
at its discretion require drawings and calculations in sufficient
detail to show proposed volume controls of this chapter are met.
12.
The Township may deny or revoke any exemption pursuant to this section
at any time for any project that the Township determines poses a threat
to public health, safety, welfare, property or the environment.
[Ord. 2011-8, 11/3/2011, § 303]
1.
The post development two-year, twenty-four-hour design storm runoff
volume runoff discharged from the site shall not be increased compared
to pre-development conditions. The two-year, twenty-four-hour design
storm change in runoff volume shall be calculated for area of proposed
earth disturbance using worksheet in Appendix 23-B based on the following
assumptions:
A.
Existing (pre-development) non-forested pervious areas must be considered
meadow in good condition, or its equivalent.
B.
When the existing project site contains impervious coverage, 20%
of the existing impervious area to be disturbed must be considered
meadow in good condition or its equivalent.
2.
Guidance on the selection and design of volume control BMPs shall
be obtained from the most current version of the BMP Manual.1
[Ord. 2011-8, 11/3/2011, § 304]
Post development peak discharge rates shall not exceed pre-development
peak discharge rates for the one-, two-, five-, ten-, twenty-five-,
fifty-, and one-hundred-year design storm events. If the applicant
can mathematically demonstrate that post development peak discharge
rates are equal to or less than pre-development peak discharge rates
without stormwater management controls, then the requirements of this
have been met. Otherwise, the applicant shall provide stormwater management
controls as necessary to satisfy the requirements of this section.
[Ord. 2011-8, 11/3/2011, § 305]
All proposed regulated activities that involve an earth disturbance
of one acre or more shall provide water quality controls to address
nitrate pollution. Water quality compliance is achieved with a summary
"yes" rating on Worksheet 23-C-1 and Worksheet 23-C-2 in Appendix
23-C.
[Ord. 2011-8, 11/3/2011, § 306]
1.
The following requirements are minimum design standards. The qualified
professional shall exercise judgment in the design of all stormwater
storage facilities (e.g., detention and retention basins) and infiltration
facilities; and ensure that adequate safeguards are provided after
thorough consideration of the project site's physical, geological
and environmental characteristics, suitability, constraints and limitations.
A.
Stormwater Storage Facilities.
(1)
Embankment material used for basin construction shall be comprised
of either on-site or imported fill which meets the following criteria:
(a)
Free of organic material, ash, cinders and demolition debris.
(b)
Particle size distribution that is well graded.
(c)
Plasticity index less than 10, liquid limit less than 30.
(d)
Less than 15% by weight rock fragments larger than three inches,
less than 30% by weight larger than 3/4 inch and less than 30% smaller
than No. 200 sieve.
(2)
Embankment slopes shall not be steeper than one foot vertical
in three feet horizontal.
(3)
The top width of basin embankments shall not be less than six
feet.
(4)
Emergency spillways in berms or earthen embankments shall be
designed to convey the peak discharge from a one-hundred-year design
storm event while maintaining a minimum one foot of freeboard, assuming
that the principal outlet structure is completely blocked. Where possible,
emergency spillways shall be constructed in virgin material, not in
fill. Proper erosion control measures shall be provided to protect
the spillway and embankment against the erosive effects of accelerated
discharge. Calculations for erosion protection shall be provided.
(5)
All embankments shall incorporate a compacted clay core and
cutoff key trench meeting the criteria for embankment material as
well as the following additional criteria: soil shall be relatively
impermeable and meet the following USCS classification groups as determined
by ASTM D2487/D2488: CL and/or CL-ML. Top width of compacted clay
core shall be a minimum of two feet with a top elevation equal to
the twenty-five-year storm peak water storage elevation or higher.
The bottom width of clay key trench shall be a minimum of four feet
and the key shall extend a minimum of two feet into virgin, undisturbed
soil below the topsoil layer.
(6)
Anti-seep collars shall be installed on all basin outlet pipes.
The required size and spacing of the collars shall be confirmed through
calculations.
(7)
Basins designed to provide extended detention times as a water
quality control shall dewater in not less than 48 hours and not more
than 96 hours.
(8)
Basins shall be kept in a maintainable condition with a minimum
bottom slope of 1% toward the principal outlet. This requirement shall
not apply to basins that do not dewater the entire storage volume
through the principal outlet (i.e., infiltration basin, wet basin,
retention basin, etc.).
B.
Infiltration Facilities.
(1)
A detailed soils evaluation of the project site shall be required
to decide the suitability of infiltration facilities. A qualified
design professional shall perform the evaluation, and at a minimum,
address soil permeability, depth to bedrock and normal or a seasonal
high water table, susceptibility to sinkhole formation, and subgrade
stability.
(2)
Provide field tests to determine the presence of appropriate
soil infiltration/percolation rates between 0.10 and 10.0 in/hr. Testing
shall be performed at the location of each proposed infiltration BMP
at the bottom elevation of the proposed facility. A plan including
the frequency and locations of soil tests shall be submitted to the
Township for review and approval.
(3)
Infiltration facilities shall be capable of completely dewatering
the infiltration volume within 72 hours from the end of the design
storm.
(4)
The bottom (infiltration surface) of infiltration facilities
shall be separated by a minimum 24 inches vertically from the static
or seasonal high water table and bedrock layer, as documented by soil
testing at the location of the facility.
(5)
Specific requirements shall be included on the plans to protect
infiltration facilities from compaction by equipment and to prevent
sediment from entering infiltration facilities during construction.
(6)
Infiltration facilities shall be at least 15 feet down-gradient,
or 50 feet up-gradient from on-site and/or off-site building foundations;
except that infiltration facilities that collect runoff from house
roof drains, having a roof area contributory to the infiltration facility
equal to 1,500 square feet or less, shall be at least 15 feet down-gradient,
or 15 feet up-gradient from on-site or off-site building foundations.
(7)
Infiltration facilities shall be a minimum of 100 feet from
any drinking water supply well.
(8)
Infiltration facilities shall not be located within 50 feet
of septic systems and/or septic system drain fields.
(9)
The bottom (infiltration surface) of infiltration facilities
shall not be constructed in a compacted fill layer.
(10)
The bottom (infiltration surface) of infiltration facilities
shall be constructed at a slope of 1% or flatter.
(11)
All infiltration facilities shall incorporate a conveyance and
control for overflow runoff.
(12)
In carbonate areas, infiltration facilities shall be designed
to disperse stormwater over the largest area feasible so as not to
significantly modify the natural hydrologic regime. The use of widely
distributed infiltration facilities (as opposed to centralized infiltration
facilities) is highly recommended.
[Ord. 2011-8, 11/3/2011, § 307; as amended by Ord.
2016-1, 1/4/2016]
1.
For the purposes of the Act 167 Stormwater Management Plan elements, contained within the York County Integrated Water Resources Plan, and this chapter, design policy pertaining to stormwater management facilities for Pennsylvania Department of Transportation (PennDOT) and Pennsylvania Turnpike Commission (PTC) roadways and associated facilities is provided in DM-2.13.7, "Antidegradation and Post Construction Stormwater Management Policy," of PennDOT Publication No. 13M, Design Manual Part 2 (August 2009), as developed, updated and amended in consultation with the Pennsylvania Department of Environmental Protection (DEP). As stated in DM-2.13.7.D (Act 167 and Township Ordinances), PennDOT and PTC roadways and associated facilities shall be consistent with Act 167 Plans. DM-2.13.7.B, "Policy on Antidegradation and Post Construction Stormwater Management," was developed as a cooperative effort between PennDOT and DEP. DM-2.13.7.C, "Project Categories," discusses the anticipated impact on the quality, volume, and rate of stormwater runoff.
2.
Where standards in the Act 167 elements of the IWRP and this chapter
are impractical, PennDOT or the PTC may request assistance from DEP,
in consultation with the county, to develop an alternative strategy
for meeting state water quality requirements and the goals and objectives
of the Act 167 elements within the IWRP.
3.
For the purposes of the Act 167 elements in the IWRP and this chapter,
road maintenance activities are regulated under 25 Pa. Code, Chapter
102.
