[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.
D. 
Nothing in this Subsection 8 shall prohibit or prevent more than one high tunnel on an owner's total contiguous land area, so long each high tunnel meets the criteria of Subsection 8B, and all high tunnels combined meet the criteria of Subsection 8A.
E. 
Any structure that does not meet the above requirements must comply with all sections of the Stormwater Management Ordinance.
F. 
Nothing in this Subsection 8 shall be construed to exempt high tunnels from other requirements applicable under federal, state, or municipal laws or ordinances.
[1]
Editor's Note: This ordinance also renumbered former Subsections 8 through 11 as Subsections 9 through 12, respectively.
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.