Township of Susquehanna, PA Part 6 STORMWATER MANAGEMENT AND EROSION AND SEDIMENTATION CONTROL

§ 22-601 Statement of Findings.

The Township finds that:

A. Inadequate management of accelerated stormwater runoff resulting from development throughout a watershed increases flood flows and velocities contributes to erosion and sedimentation, overtaxes the carrying capacity of existing streams and storm sewers, greatly increases the cost of public facilities to convey and manage stormwater, undermines floodplain management and flood reduction efforts in upstream and downstream communities, reduces groundwater recharge, and threatens public health and safety.

B. A comprehensive program of stormwater management, including reasonable regulation of development and activities causing accelerated erosion, is fundamental to the public health, safety, welfare, and the protection of the people of the Township and all the people of the Commonwealth, their resources, and the environment.

C. Inadequate planning and management of stormwater runoff resulting from land development and redevelopment throughout a watershed can also harm surface water resources by changing the natural hydrologic patterns; accelerating stream flows (which increase scour and erosion of streambeds and stream banks thereby elevating sedimentation); destroying aquatic habitat; and elevating aquatic pollutant concentrations and loadings such as sediments, nutrients, heavy metals, and pathogens. Groundwater resources are also impacted through loss of recharge.

D. Stormwater can be an important water resource by providing groundwater recharge for water supplies and base flow of streams, which also protects and maintains surface water quality.

E. Public education on the control of pollution from stormwater is an essential component in successfully addressing stormwater issues.

F. Federal and state regulations require certain townships to implement a program of stormwater controls. These townships are required to obtain a permit for stormwater discharges from their separate storm sewer systems under the National Pollutant Discharge Elimination System (NPDES).

G. Nonstormwater discharges to municipal separate storm sewer systems can contribute to pollution of waters of the Commonwealth by the Township.

§ 22-602 Purpose.

The purpose of this Part is to promote health, safety, and welfare within the Township and its watersheds, by minimizing the harms and maximizing the benefits described in § 22-601 of this Chapter through provisions designed to:

A. Manage accelerated runoff and erosion and sedimentation problems at their source, by regulating activities that cause these problems.

B. Utilize and preserve the existing natural drainage systems as much as possible.

C. Encourage infiltration of stormwater, where appropriate, to maintain groundwater recharge, to prevent degradation of surface and groundwater quality, and to otherwise protect water resources.

D. Maintain existing flows and quality of streams and watercourses in the Township and the Commonwealth.

E. Preserve and restore the flood-carrying capacity of streams and prevent, scour and erosion of stream banks and streambeds.

F. Provide proper operations and maintenance of all temporary and permanent stormwater management facilities and BMPs that are constructed and implemented in the Township.

G. Provide performance standards and design criteria for watershed-wide stormwater management and planning.

H. Manage stormwater impacts close to the runoff source, with a minimum of structures and a maximum use of natural processes.

I. Meet legal water quality requirements under state law, including regulations at 25 Pennsylvania Code Chapter 93.4a to protect and maintain existing uses and maintain the level of water quality to support those uses in all streams and to protect and maintain water quality in special protection streams.

J. Provide a mechanism to identify controls necessary to meet the NPDES permit requirements.

K. Implement an illegal discharge detection and elimination program to address nonstormwater discharges into the Township's separate storm sewer system.

L. Permit the unimpeded flow of natural watercourses.

M. Ensure the drainage of all low points along the streets and other applicable areas.

N. Intercept, retain, or detain surface water runoff in a manner reasonably related to the extent and grade of the area drained.

O. Provide positive drainage away from buildings.

§ 22-603 Statutory Authority.

1. The Township is empowered to regulate land use activities that affect runoff by the authority of the Act of October 4, 1978, 32 P.S., P.L. 864 (Act 167), Section 680.1 et seq., as amended, the "Storm Water Management Act."

2. The Township also is empowered to regulate land use activities that affect runoff by the authority of the Act of July 31, 1968, P.L. 805, No. 247, The Pennsylvania Municipalities Planning Code, as amended by Act 170 of December 21, 1988, and Act 131 of December 14, 1992.

3. Chapter 102 of the Rules and Regulations of the Department of Environmental Protection, Subpart C, Protection of Natural Resources, Article II, Water Resources, imposes requirements on earthmoving activities which create accelerated erosion or a danger of accelerated erosion and which require planning and implementation of effective soil conservation measures.

§ 22-604 Applicability.

1. This Chapter shall apply to any regulated activity within the Township, and all stormwater runoff entering into the Township's separate storm sewer system from lands within the boundaries of the Township.

2. Earth disturbance activities and associated stormwater management controls are also regulated under existing state law and implementing regulations. This Chapter shall operate in coordination with those parallel requirements; the requirements of this Chapter shall be no less restrictive in meeting the purposes of this Chapter than state law.

3. The following activities are defined as regulated activities and shall be regulated by this Chapter:

A. Land development.

B. Subdivision.

C. Land/earth disturbance activities.

D. Construction of new or additional impervious or semi-pervious surfaces (driveways, parking lots, etc.).

E. Construction of new buildings or additions to existing buildings.

F. Diversion or piping of any natural or man-made stream channel.

G. Installation of stormwater management facilities or appurtenances thereto.

H. Mining operations.

I. Nursery, forest or agriculture operations.

J. Other activities, which would cause an increase in stormwater runoff.

§ 22-605 Repealer.

Any ordinance or ordinance provision(s) of the Township inconsistent with any of the provision(s) of this Chapter is hereby repealed to the extent of the inconsistency only.

§ 22-606 Severability.

Should a court of competent jurisdiction declare any section(s) or provision(s) of this Section invalid, such decision shall not affect the validity of any of the remaining section(s) or provision(s) of this Chapter.

§ 22-607 Compatibility with Other Ordinance Requirements.

1. Approvals issued pursuant to this Chapter do not relieve the applicant of the responsibility to comply with or to secure required permits or approvals for activities regulated by any other applicable codes, rules, statutes, or ordinances. To the extent that this Chapter imposes more rigorous or stringent requirements for stormwater management, the specific requirements contained in this Chapter shall be followed.

2. Nothing in this Chapter shall be construed to affect any of the Township's requirements regarding stormwater matters which do not conflict with the provisions of this Chapter, such as local stormwater management design criteria (e.g., inlet spacing, inlet type, collection system design and details, outlet structure design, etc.). Conflicting provisions in other Township ordinances or regulations shall be construed to retain the requirements of this Chapter addressing State water quality requirements.

§ 22-608 Township Liability.

The degree of stormwater management sought by the provisions of this Chapter is considered reasonable for regulatory purposes. This Chapter shall not create liability on the part of the Township, any appointed or elected official of the Township, the Dauphin County Conservation District or any officer, engineer or employee thereof for any erosion, sedimentation or flood damages or flood damages that result from reliance on this Chapter or any administrative decision lawfully made there under.

§ 22-609 Duty of Persons.

Notwithstanding any provision(s) of this Chapter, including exemptions, any landowner or any person engaged in the alteration or development of land which may affect stormwater runoff characteristics shall implement such measures as are reasonably necessary to prevent injury to health, safety, or other property. Such measures also shall include actions as are required to manage the rate, volume, direction, and quality of resulting stormwater runoff in a manner which otherwise adequately protects health, property, and water quality.

§ 22-610 General Requirements.

1. All regulated activities in the Township, which are not granted an exemption under § 22-611, shall submit a drainage plan consistent with this Chapter to the Township for review. These criteria shall apply to the total proposed development even if development is to take place in stages. Impervious cover shall include, but not be limited to: additional indoor living space, decks, patios, garages, storage sheds and similar structures, roofs, parking or driveway areas, and any new streets and sidewalks. Any areas designed to initially be gravel or crushed stone shall be assumed to be impervious. The Drainage Plan shall be approved prior to the final approval of the regulated activity.

2. All regulated activities within the Township shall be designed, implemented, operated, and maintained to meet the purposes of this Chapter, through these three elements:

A. Erosion and sediment control during the earth disturbance activities (e.g., during construction),

B. Water quality protection measures after completion of earth disturbance activities (e.g., post construction), including operations and maintenance.

C. Drainage and stormwater management

3. No earth disturbance activities within the Township associated with any regulated activities shall commence until the requirements of this Chapter are met.

4. All BMPs used to meet the requirements of this Chapter shall be designed, installed, operated, and maintained to conform to the State water quality requirements, the requirements of the Clean Streams Law and implementing regulations, and any more stringent requirements as determined by the Township.

5. Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this Chapter.

6. The existing points of concentrated drainage that discharge onto adjacent property shall not be altered without permission of the altered property owner(s) and shall be subject to any applicable discharge criteria specified in this Chapter.

7. Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this Chapter. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the developer 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.

8. Where watercourses traverse a development site, drainage easements shall be provided conforming to the line of such watercourses. The terms of the easement shall prohibit excavation, the placing of fill or structures, and any alterations that may adversely affect the flow of stormwater within any portion of the easement. Also, maintenance, including mowing of vegetation within the easement may be required, except as approved by the appropriate governing authority.

9. All natural streams, channels, swales, drainage systems and surface water concentrations shall be maintained in their existing condition unless an alteration is approved by the Township and all encroachment activity shall comply with the requirements of Chapter 105 (Dam Safety and Waterway Management) of Pa. Title 25, Environmental Protection. Any stormwater management facility intended to meet the requirements of this Chapter that constitutes an encroachment or enclosure, as described in Chapter 105, will require a DEP permit.

10. Any stormwater management facilities regulated by this Chapter that will be located in or adjacent to waters of the Commonwealth (including wetlands) shall be subject to approval by DEP under regulations at 25 Pennsylvania Code Chapter 105 through the joint permit application process, or, where deemed appropriate by DEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the developer or his agent to show that the land in question cannot be classified as wetlands; otherwise, approval to work in the area must be obtained from DEP.

A. Where no wetlands will be impacted by the proposed subdivision or land development the applicant shall provide the certification on the plan:

"I, (signature of consultant and date), hereby certify that there are no wetlands on the subject property, the proposed project will not impact off-site wetlands, and wetland permits are not required from the state or federal government."

11. Culverts, bridges, storm sewers, or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam are subject to permit by DEP under regulations at 25 Pennsylvania Code Chapter 105.

12. All earth disturbance activities are subject to permit requirements by DEP under regulations at 25 Pennsylvania Code Chapter 102.

13. Any stormwater management facilities regulated by this Chapter that will be located on State highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).

14. Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., are encouraged, where soil conditions permit, to reduce the size or eliminate the need for detention facilities.

15. Developers are encouraged to incorporate designs to take advantage of the stormwater credits presented in the Spring or Paxton Creek Act 167 Stormwater Management Plans.

16. Special Conditions for Areas Falling within Defined Exceptional Value and High Quality Sub-Watersheds. The temperature and quality of water and streams that have been declared as exceptional value and high quality is to be maintained as defined in Chapter 93, Water Quality Standards, Title 25, of Pennsylvania Department of Environmental Protection Rules and Regulations. Temperature sensitive BMPs and stormwater conveyance systems are to be used and designed with storage pool areas and supply outflow channels and should be shaded with trees. This will require modification of berms for permanent ponds and relaxation of restrictions on planting vegetation within the facilities, provided that the capacity for volumes and rate controls is maintained. At a minimum, the southern half on pond shorelines will be planted with shade or canopy trees within 10 feet of the pond shoreline. In conjunction with this requirement, the maximum slope allowed on the berm area to be planted is 10 to one. This will lessen the destabilization of berm soils due to root growth. A long-term maintenance schedule and management plan for the thermal control BMPs is to be established and recorded for all development sites.

17. Techniques described in Appendix D[1] (Low Impact Development) of this Chapter are encouraged because they reduce the costs of complying with the requirements of this Chapter and the State water quality requirements.

[1] Editor's Note: Appendix D is included as an attachment to this Chapter.

18. Infiltration for stormwater management is encouraged where soils and geology permit, consistent with the provisions of this Chapter and, where appropriate, infiltration is encouraged for capturing and treating any part of the water quality volume or for otherwise meeting the purposes of this Chapter.

19. The Township may, after consultation with DEP, approve alternative methods for meeting the State water quality requirements other than those in this Section, provided that they meet the minimum requirements of, and do not conflict with, State law, including, but not limited to, the Clean Streams Law.

20. All developments that create impervious surface or change the existing topography, except for exemptions provided in § 22-611, shall demonstrate that adequate capacity will be provided to contain the ground water recharge and to treat the water quality requirements, as described under §§ 22-617 and 22-618 of this Chapter.

21. If a regulated activity by this Chapter is to be performed by any individual, firm, contractor or other entity other than that which submitted the Drainage Plan, such entity shall, by signature, acknowledge awareness of the plan requirements before the start of the regulated activity.

22. Although there are no stormwater control methods restricted from or required for use, the following considerations apply to the selection and use of any method:

A. The Township may approve or disapprove those methods based on geologic, topographic, hydrologic, soil, aesthetic, safety, health or other considerations.

B. The following is a list of methods which may be used for stormwater control. The choice of control method is not limited to these methods and any method selected should be carefully suited to the requirements of the project and the characteristics of the site:

(1) Detention basins.

(2) Roof-top storage.

(3) Parking lot storage.

(4) Infiltration structures.

(5) Porous pavement.

(6) Grassed channels.

(7) Underground storage.

(8) Cisterns.

NOTE: For further description of those and other methods, see the Pennsylvania Stormwater Best Management Practices Manual.

§ 22-611 Exemptions.

1. Two exemptions (Exemption 1, Release Rates, Water Quality Volume, Channel Protection Volume, and Drainage Plan Submission; and Exemption 2, Ground Water Recharge) from this Chapter may be granted at the discretion of the Township. The applicant must demonstrate that the following BMPs are being utilized to the maximum extent practicable to receive consideration for either of the two exemptions:

A. Design around and limit disturbance of floodplains, wetlands, natural slopes over 15%, existing native vegetation, and other sensitive and special value features;

B. Clearly show limits of disturbance on construction plans;

C. Maintain riparian and forested buffers;

D. Limit grading and maintain non-erosive flow conditions in natural flow paths;

E. Maintain existing tree canopies near impervious areas;

F. Minimize soil disturbance and reclaim disturbed areas with topsoil and vegetation;

G. Direct runoff to pervious areas;

H. Utilize stormwater credits presented in the Spring or Paxton Creek Act 167 Stormwater Management Plans; and

I. Utilize guidance listed in the Pennsylvania Stormwater Best Management Practices Manual.

2. Exemption 1: Release Rates, Water Quality Volume, Channel Protection Volume, and Drainage Plan Submission. An exemption of these requirements contained within this Chapter for all regulated activities within the Township may be granted at the discretion of the Township in accordance with the following:

A. An exemption of Release Rates, Water Quality Volume, Channel Protection Volume, and Drainage Plan Submission may be granted in accordance with Table 611.1 to determine the maximum additional impervious area (and associated minimum separation distance) that can be placed on a development site. This exemption shall be granted only if the Township determines that proposed development/additional impervious area will not adversely impact the following:

(1) Capacities of existing drainageways and storm sewer systems;

(2) Velocities and erosion;

(3) Quality of runoff, if direct discharge is proposed;

(4) Existing known problem areas;

(5) Safe conveyance of the additional runoff; and

(6) Downstream property owners.

B. Development that is planned to occur in stages or phases will be considered in its entirety for the purposes of determining the exemption.

	Table 611.1 Exemption Criteria
	Parcel Size* (acres)	Minimum Separation Distance (feet)	Maximum Additional Impervious Area — Since The Date of Adoption of This Chapter (square feet)
	0.5	10	2,700
	1.0	50	4,600
	1.5	100	6,200
	2.0	125	7,600
	2.5	150	9,000
	3.0	175	10,300
	3.5	200	11,500
	4.0	225	12,700
	4.5	250	13,800
	5.0	275	15,000
	>5.0	300	15,000

*

NOTE: Parcel size to be rounded to the nearest half-acre for the purpose of utilizing Table 611.1.

3. Exemption 2: Ground Water Recharge. An exemption of this requirement for all regulated activities within the Township may be granted at the discretion of the Township in accordance with the following:

A. An exemption of Ground Water Recharge may be granted if the maximum additional impervious coverage is 2,000 square feet or less. Development sites that generate greater than 2,000 square feet of new impervious cover are not eligible for this exemption based on additional impervious coverage. The 2,000 square foot maximum additional impervious cover applies to the total amount of additional impervious cover to be placed on a development site whether the project is a single phase or will occur in multiple phases. It does not include existing impervious cover placed on a development site prior to the adoption of this Chapter.

B. An exemption of Ground Water Recharge may be granted if the Township, based upon data provided by the applicant, determines that the Ground Water Recharge requirements are not suitable in the following areas:

(1) High groundwater table (need minimum of three feet from bed of infiltration facility to seasonal high groundwater elevation).

(2) Shallow depth to bedrock (need minimum of two feet from bed of infiltration facility to top of bedrock).

(3) High risk of sinkhole development, to be determined on a case-by-case basis.

4. At the discretion of the Township, the applicant may be required to provide a detailed geotechnical evaluation.

5. Under no circumstance shall the applicant be exempt from implementing such measures as necessary to:

A. Meet State water quality standards/requirements.

B. Protect health, safety, and property.

C. Meet special requirements for high quality (HQ) and exceptional value (EV) watersheds.

§ 22-612 Stormwater Management Districts.

1. The Township is hereby divided into stormwater management districts in accordance with the Paxton Creek Stormwater Management Plan, the Paxton Creek Release Rate Map, the Spring Creek Stormwater Management Plan and the Spring Creek Release Rate Map. The official release rate district maps are available for inspection at the Township office. All areas within the districts are subject to the specified release rates. The two-, ten-, and twenty-five-year design storms are all subject to the specified release rates.

2. If the developer can show that the post-development hydrograph matches the predevelopment hydrograph for peak flows and volume, for all design storms, then meeting the requirements of the release rates are not required.

3. Specific Watershed Requirements:

A. Paxton Creek Watershed: Specified Release Rate Districts. For all districts in this category, the future runoff must be controlled to the specified release rate. That is, the post-development runoff rate must be less than or equal to the predevelopment rate multiplied by the specified release rate for that district.

B. Paxton Creek Watershed: Provisional No Detention Districts. These watershed areas may discharge post-development peak runoff without detention facilities. However, the developer must prove that the "local" runoff conveyance facilities which transport runoff from the site to the main channel have adequate capacity to safely transport unattenuated increased peak flows for a twenty-five-year storm in accordance with § 22-613(3). If there is inadequate capacity, the developer shall either use 100% release rate control or provide increased capacity of downstream drainage facilities to convey increase peak flows consistent with § 22-613(3). When determining if adequate capacity exists in the local watershed drainage network, the developer must assume that the entire local watershed is developed per current zoning and that all new development will use the least restrictive runoff controls specified by this Section.

C. Spring Creek Watershed: Specified Release Rate Districts. For all districts in this category, the future runoff must be controlled to the specified release rate. That is, the post-development runoff rate must be less than or equal to the predevelopment rate multiplied by the specified release rate for that district.

D. Areas Not Within the Paxton Creek or Spring Creek Watershed. For all areas within the Township but outside the Paxton Creek or Spring Creek Watersheds, the future peak rate of runoff for the two-, ten- and twenty-five-year design storms must be controlled to the existing rate.

E. The exact location of any given development site, or activity regulated by this Chapter relative to the release rate district boundaries shall be determined by mapping the release rate district boundaries using two foot topographic contour mapping provided as part of the Drainage Plan.

F. For the proposed development site located entirely within one release rate district, the total runoff from the site shall meet the required release rate criteria. For sites with multiple discharge points, any individual point may be designed to a 100% release rate, provided that the total runoff from the site is controlled to the applicable release rate for that district.

G. For a proposed development site which is located within two or more release rate districts, the maximum runoff discharged at any point shall be equal to the release rate for the district in which the discharge point is located. In the event that a portion of the site is located in a provisional no detention area, no runoff from portions of the site located in areas subject to release rate controls may be drained to or through the provisional no detention area.

H. Each development site shall be considered separately and shall conform to the criteria of the district in which it is located. In no case may the release rate for an area be exceeded as credit for a reduction below the criteria or any other restrictions on a separate site.

I. Regional detention facilities will be permitted, provided that adequate conveyance is available or provided from the site to the facility. The acceptability and discharge characteristics of the facility will be determined on a case by case basis, by the Township Engineer, using the calibrated model developed for the Paxton Creek Act 167 Plan or Spring Creek Act 167 Plan, as applicable.

§ 22-613 Stormwater Management District Implementation Provisions.

1. Off-Site Areas. Off-site areas that drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site.

2. No-Harm Option. For any proposed development site, the developer has the option of using a less restrictive runoff control (including no detention) if the developer can prove that no harm would be caused by discharging at a higher runoff rate than existing conditions. The no-harm option is used when a developer can prove that the post-development hydrographs can match pre-development hydrographs, or if it can be proven that the post-development conditions will not cause increases in peak flows at all points downstream. Proof of no harm would have to be shown based upon a downstream impact evaluation which shall include a downstream hydraulic capacity analysis consistent with § 22-613(3) to determine if adequate hydraulic capacity exists. The developer shall submit this evaluation of the impacts due to increased downstream stormwater flows in the watershed to the Township.

A. The downstream impact evaluation shall include hydrologic and hydraulic calculations necessary to determine the impact of hydrograph timing modifications due to the proposed development upon a dam, highway, structure, natural point of restricted stream flow, or any stream channel section, established with the concurrence of the Township.

B. Proof of no harm must be shown from the point of discharge through entire downstream network to the mouth of Paxton Creek or Spring Creek, as applicable, at the Susquehanna River. For those areas outside of the Paxton Creek and Spring Creek Watersheds, proof of no harm must be shown through the entire downstream network to the ultimate discharge point at the Susquehanna River.

C. The peak flow values to be used for downstream areas for the design return period storms (two-, ten-, and twenty-five-year) shall be the values from the calibrated model for the Paxton Creek or Spring Creek Watershed Act 167 Plans. These flow values can be obtained from the watershed plan.

D. Developer-proposed runoff controls which would generate increased peak flow rates at storm drainage problem areas would, by definition, be precluded from successful attempts to prove no harm, except in conjunction with proposed capacity improvements for the problem areas.

E. A financial distress shall not constitute grounds for granting a no-harm exemption.

F. Capacity improvements may be provided as necessary to implement the no-harm option, which proposes specific capacity improvements to demonstrate that a less stringent discharge control would not create any harm downstream.

G. Any available capacity in the downstream conveyance system as documented by a developer may be used by the developer only in proportion to his development site acreage relative to the total upstream undeveloped acreage from the identified capacity (i.e., if his site is 10% of the upstream undeveloped acreage, he may use up to 10% of the documented downstream available capacity).

H. Any municipality approving a no-harm option shall notify all downstream municipalities of such approval. The approving municipality shall make all relevant information used to prove a no-harm option available upon request to any municipality with the Paxton Creek Watershed and the Spring Creek Watershed.

I. Any no-harm justifications shall be submitted by the developer as part of the Drainage Plan submission. The burden of proof shall rest on the developer.

3. Downstream Hydraulic Capacity Analysis. Any downstream capacity hydraulic analysis conducted in accordance with this Chapter shall use the following criteria for determining adequacy for accepting increased peak flow rates:

A. Natural or man-made channels or swales must be able to convey the increased runoff associated with a twenty-five-year return period event within their banks at velocities consistent with protection of the channels from erosion. Acceptable velocities shall be based upon criteria included in the DEP Erosion and Sediment Pollution Control Program Manual.

B. Natural or man-made channels or swales must be able to convey the increased twenty-five-year return period runoff without creating any hazard to persons or property.

C. Culverts, bridges, storm sewers, or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with DEP, Chapter 105 regulations (if applicable), and, at a minimum, pass the increased twenty-five-year return period runoff, except for facilities located within a designated floodplain area which must, at a minimum, conform to FEMA and local floodplain ordinance requirements.

4. Regional Detention Alternatives. For certain areas within the watershed, it may be more cost-effective to provide one control facility for more than one development site than to provide an individual control facility for each development site. The initiative and funding for any regional runoff control alternatives is the responsibility of prospective developer(s). The design of any regional control basins must incorporate reasonable development of the entire upstream watershed. The peak outflow of a regional basin would be determined on a case-by-case basis using the hydrologic model of the watershed consistent with protection of the downstream watershed areas. "Hydrologic model" refers to the calibrated model as developed for the Paxton Creek Stormwater Management Plan.

5. Capacity improvements may be provided as necessary to permit direct discharge in a provisional no detention district, to implement any regional or subregional detention alternatives, or to implement a no-harm option which proposes specific capacity improvements to document the validity of less stringent discharge control which would not create any harm downstream.

§ 22-614 Calculation Methodology.

1. Stormwater runoff from all development sites shall be calculated using either the Rational Method or a Soil-Cover-Complex methodology.

A. Any stormwater runoff calculations involving drainage areas greater than 20 acres, including on- and off-site areas, shall use a generally accepted calculation technique that is based on the NRCS Soil Cover Complex Method. Table 614.1 summarizes acceptable computation methods. It is assumed that all methods will be selected by the design professional based on the individual limitations and suitability of each method for a particular site.

B. The Township may approve the use of the Modified Rational Method to estimate peak discharges from drainage areas that contain less than 20 acres. However, the Modified Rational Method may not be used to compute the volume of stormwater runoff.

C. The Township may approve the use of any generally accepted full hydrograph approximation technique that shall use a total runoff volume that is consistent with the volume from a method that produces a full hydrograph.

D. All calculations consistent with this Chapter using the Soil Cover Complex Method shall use the appropriate design rainfall depths for the various return period storms presented in Table A-1 in Appendix A[1] of this Chapter. If a hydrologic computer model is used for stormwater runoff calculations, then the duration of rainfall shall be 24 hours along with a Soil Conservation Service Type II rainfall distribution.

[1] Editor's Note: Appendix A is included as an attachment to this Chapter.

E. For the purpose of predevelopment flow rate determination, undeveloped land shall be considered as "meadow" good condition, or "range" unless the natural ground cover generates a lower Rational "C" value or curve number (i.e. forest).

F. For the purpose of post-development flow rate determination, the proposed ground cover shall be used to determine the Rational "C" value or curve number.

G. All calculations using the Rational Method shall use rainfall intensities consistent with appropriate times of concentration for overland flow and return periods from the Intensity Duration Frequency (IDF) Curves from the Pennsylvania Department of Transportation, latest version.

H. Times of concentration for overland flow may be calculated using the methodology presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS), for developed sites. Times of concentration for channel and pipe flow shall be computed using the Manning equation.

(1) The length of the flow path for sheet flow shall not exceed 150 feet and the length of the flow path for shallow concentrated flow shall not exceed 1,000 feet.

I. Times of concentration for undeveloped sites may also be computed using the SCS equation for lag time:

Time of Concentration = Tc = [(Tlag/.6) * 60] (minutes)

	Where:
		Tlag	=	Lag time (hours)
		L	=	Hydraulic length of watershed (feet)
		Y	=	Average overland slope of watershed (percent)
		S	=	Maximum retention in watershed as defined by:
		S	=	[(1,000/CN) - 10]
		CN	=	SCS curve number for watershed as defined by the SCS Loss Method

J. Runoff coefficients (C) for both existing and proposed conditions for use in the Rational Method shall be obtained from Table A-3 in Appendix A of this Chapter.

K. Runoff curve numbers (CN) for both existing and proposed conditions to be used in the Soil Cover Complex Method shall be obtained from Table A-2 in Appendix A of this Chapter.

L. Where uniform flow is anticipated, the Manning equation shall be used for hydraulic computations and to determine the capacity of open channels, pipes, and storm sewers. Values for Manning roughness coefficient "n" shall be consistent with Table A-4 in Appendix A of this Chapter. Manning equation should not be used for analysis of pipes under pressure flow or for analysis of culverts.

M. The design of any stormwater detention facilities intended to meet the performance standards of this Chapter shall be verified by routing the future two-, ten-, twenty-five- and one-hundred-year hydrographs through these facilities using the Storage-Indication Method or Modified Puls Method. For drainage areas greater than 20 acres in size, the design storm hydrograph shall be computed using a calculation method that produces a full hydrograph.

N. The Township has the authority to require that computed existing runoff rates be reconciled with field observations and conditions and site history. If the designer can substantiate, through actual physical calibration, that more appropriate runoff and time of concentration values should be utilized at a particular site, then appropriate variations may be made upon review and recommendation of the Township.

O. Principal outlet structures for stormwater management facilities shall be designed to meet the performance standards of this Chapter using any generally accepted hydraulic analysis technique or method.

	Table 614.1 — Acceptable Computation Methodologies for Stormwater Management Plans
	Method*	Method Developed By	Applicability
	TR-20 or Commercial Package Based on TR-20	USDA — NRCS	When use of full model is desirable or necessary
	TR-55 Or Commercial Package Based on TR-55	USDA — NRCS	Applicable for plans within the models limitations
	HEC — HMS	U.S. Army Corps of Engineers	When full model is desirable or necessary
	PSRM	Penn State University	When full model is desirable or necessary
	Rational Method or Commercial Package based on Rational Method	Emil Kuiching (1889)	For sites less than 20 acres
	Other Methods	Various	As approved by the Municipal Engineer

*

NOTE: Successors to the above methods are also acceptable. These successors include Win TR55 for TR-55 and Win TR20 for TR-20.

§ 22-615 Erosion and Sedimentation Requirements During Earth Disturbance.

1. No earth disturbance activities within the Township shall commence until approval by the Dauphin County Conservation District of an Erosion and Sediment Control Plan for construction activities.

2. When 5,000 square feet or more of earth disturbance activities are proposed, an Erosion and Sedimentation Control Plan must be submitted to the Dauphin County Conservation District and the Township in accordance with 25 Pennsylvania Code § 102.4(b). In addition, a letter from the Dauphin County Conservation District approving the Erosion and Sedimentation Control Plan must be obtained.

3. DEP has regulations, under 25 Pa. Code Chapter 92, that a DEP NPDES Construction activities permit is required and must be obtained from the Dauphin County Conservation District and or DEP for earth disturbance activities.

4. Evidence of any necessary permit(s) for earth disturbance activities from the Southcentral Regional DEP office or Dauphin County Conservation District must be provided to the Township.

5. A copy for 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.

6. Design Criteria for Erosion Control Facilities. All erosion control facilities shall be designed at a minimum to meet the design standards and specifications of the latest revision of the Erosion and Sediment Pollution Control Program Manual, published by DEP. Grassed waterways allow recharge of groundwater. The usage of grassed waterways is not recommended in areas of year-round or seasonally high groundwater tables unless provision is made to handle long duration flows, for example by means of subsurface drainage or stone centered waterways.

7. Construction Standards for Erosion Control Facilities. Construction standards for erosion control facilities shall be in accordance with the approved plans and accompanying specifications. The construction standards for erosion control facilities outlined in the latest revision of the Erosion and Sediment Pollution Control Program Manual published by DEP shall be considered the minimal acceptable standard. Controls shall be installed at initial stages of earthmoving and otherwise as outlined in the staging of earthmoving activities section of the soil erosion and sediment control plan.

8. Maintenance Criteria for Erosion Control Practices. Maintenance is an essential part of the successful functioning of an erosion control system.

A. Maintenance during development of a project shall be the responsibility of the developer and/or landowner and shall usually include, but not be limited to:

(1) Removal of silt from all debris basins, traps or other structures or measures when capacity of those structures is reached. (See DEP's Erosion and Sediment Pollution Control Program Manual, current edition.).

(2) Periodic maintenance of temporary control facilities such as replacement of straw bale dikes, straw filters or similar measures.

(3) Establishment or reestablishment of vegetation by seeding and mulching or sodding of scoured areas or areas where vegetation has not successfully been established.

(4) Installation of necessary controls to correct unforeseen problems caused by storm events within design frequencies.

(5) The contractor or developer shall be responsible for removal of all temporary measures and installation of permanent measures upon completion of the project.

B. After dedication of facilities to the Township, except in cases where agreements to the contrary have been previously executed, maintenance shall be the responsibility of the Township and shall include:

(1) Mowing to maintain adequate stands of grass and to control weeds. Chemical weed control may be used if State and local regulations are met. Selection of seed mixtures should reflect the type of maintenance desired by the Township.

(2) Removal of silt from all permanent structures which trap silt or sediment is essential to keep this material from building up in grassed waterways and reducing their capacity.

(3) It shall be the responsibility of the Township to inspect all permanent facilities and to see that corrective action is taken where necessary.

§ 22-616 Water Quality Requirements after Regulated Earth Disturbance.

1. No regulated earth disturbance activities within the Township shall commence until approval by the Township of a plan which demonstrates compliance with State water quality requirements after construction is complete.

2. The BMPs must be designed, implemented, and maintained to meet State water quality requirements, and any other more stringent requirements as determined by the Township.

3. To control post-construction stormwater impacts from earth disturbance activities, State water quality requirements can be met by a variety of BMPs, including site design, which provide for replication of pre-construction stormwater infiltration and runoff conditions, so that post-construction stormwater discharges do not degrade the physical, chemical or biological characteristics of the receiving waters. As described in the DEP Comprehensive Stormwater Management Policy (#392-0300-002, September 28, 2002), this may be achieved by the following:

A. Groundwater Recharge/Infiltration: replication of pre-construction stormwater infiltration conditions;

B. Water Quality Treatment: use of water quality treatment BMPs to ensure filtering out of the chemical and physical pollutants from the stormwater runoff; and

C. Stream Bank and Streambed Protection: management of volume and rate of postconstruction stormwater discharges to prevent physical degradation of receiving waters (e.g., from scouring).

4. DEP has regulations that require the Township to ensure design, implementation, and maintenance of BMPs that control runoff from new development and redevelopment after 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.

§ 22-617 Groundwater Recharge Volume (Infiltration/Recharge/Retention).

1. The ability to retain and maximize the ground water recharge capacity of the area being developed or redeveloped is encouraged. Design of the infiltration/recharge stormwater management facilities shall give consideration to providing ground water recharge to compensate for the reduction in the percolation that occurs when the ground surface is paved and roofed over. These measures are encouraged, particularly in hydrologic soil groups A and B and shall be utilized wherever feasible.

2. The annual recharge volume requirement shall be specified for a site as follows:

A. Percent Volume Method

	Rev = [(S)(Rv)(A)] / 12
	Where:
		Rev	=	Groundwater Recharge Volume (ac-ft)
		S	=	Soil Specific Recharge Factor
		Rv	=	0.05 + 0.009(I)
		I	=	Percent Impervious Cover (i.e., use I = 20 when there is 20% impervious cover)
		A	=	Site area (acres)

B. Percent Area Method

	Rev=(S)(Ai)
	Where:
		Rev	=	Groundwater Recharge Volume (ac-ft)
		S	=	Soil Specific Recharge Factor
		Ai	=	Measured impervious cover (acres)

	Hydrologic Soil Group	Soil Specific Recharge Factor (S)
	A	0.39
	B	0.26
	C	0.14
	D	0.07

C. The recharge volume is considered part of the total water quality volume WQ_v that must be provided at a site and can be achieved either by a structural practice (e.g., infiltration, bioretention), a nonstructural practice (e.g., buffers, disconnection of rooftops), or a combination of both.

D. Drainage areas having no impervious cover and no proposed disturbance during development may be excluded from the Re_v calculations. Designers are encouraged to use these areas as nonstructural practices for Re_v treatment.

E. Note: Re_v and WQ_v are inclusive. When treated separately, the Re_v may be subtracted from the WQ_v when sizing the water quality BMP.

3. Basis for Determining Recharge Volume.

A. Developers are encouraged to incorporate designs to take advantage of the stormwater credits presented in the Spring or Paxton Creek Act 167 Stormwater Management Plans.

B. If more than one HSG is present at a site, a composite soil-specific recharge factor shall be computed based on the proportion of total site area within each HSG. The recharge volume provided at the site shall be directed to the most permeable HSG available.

C. The "Percent Volume" method is used to determine the Re_v treatment requirement when structural practices are used to provide recharge. These practices must provide seepage into the ground and may include infiltration and exfiltration structures (e.g., infiltration, bioretention, dry swales or sand filters with storage below the under drain). Structures that require impermeable liners, intercept groundwater, or are designed for trapping sediment (e.g., forbays) may not be used. In this method, the volume of runoff treated by structural practices shall meet or exceed the computed recharge volume.

D. The "Percent Area" method is used to determine the Re_v treatment requirements when nonstructural practices are used. Under this method, the recharge requirements are evaluated by mapping the percent of impervious area that is effectively treated by an acceptable nonstructural practice and comparing it to the minimum recharge requirements.

E. Acceptable nonstructural practices include filter strips that treat rooftop or parking lot runoff, sheet flow discharge to stream buffers, and grass channels that treat roadway runoff.

F. The recharge volume criterion does not apply to any portion of a site designated as a stormwater hotspot or any project considered as redevelopment. In addition, the Township Board of Commissioners may alter or eliminate the recharge volume requirement if the site is situated on unsuitable soils (e.g., marine clays, karst, or in an urban redevelopment area). In this situation, nonstructural practices (Percent Area Method) shall be implemented to the maximum extent practicable and the remaining or untreated Re_v included in the WQ_v treatment.

G. Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase, as to maintain their maximum infiltration capacity.

H. If Re_v is treated by structural or non-structural practices separate and upstream of the WQ_v treatment, the WQ_v is adjusted accordingly.

4. Soils Evaluation.

A. A detailed soils evaluation of the project site shall be performed to determine the suitability of recharge facilities. The evaluation shall be performed by a qualified professional, and at a minimum, address soil permeability, depth of bedrock, susceptibility to sinkhole formation, and subgrade stability, hydrologic soil groups and natural and man-made features.

(1) Soil percolation or infiltration rates must be based on actual field tests and may not be assumed from data contained within the Dauphin County Soils Survey.

B. Extreme caution shall be exercised where infiltration is proposed in geologically susceptible areas such as strip mine or limestone areas. Extreme caution shall also be exercised where salt or chloride would be pollutant since soils do little to filter this pollutant and it may contaminate the groundwater. It is also extremely important that the design professional evaluate the possibility of groundwater contamination from the proposed infiltration/recharge facility and recommend a hydrogeologic justification study be performed if necessary. Whenever a basin will be located in an area underlain by limestone, a geological evaluation of the proposed location shall be conducted to determine susceptibility to sinkhole formations. The design of all facilities over limestone formations shall include measures to prevent groundwater contamination and, where necessary, sinkhole formation.

C. The Township may require the installation of an impermeable liner in detention basins. A detailed hydrogeologic investigation may be required by the Township. The Township may require the developer to provide safeguards against groundwater contamination for uses which may cause groundwater contamination, should there be a mishap or spill.

D. It shall be the developer's responsibility to verify if the site is underlain by limestone. The following note shall be attached to all Drainage Plans and signed and sealed by the developer's engineer/surveyor/landscape architect/geologist: "I, ____________________, certify that the proposed detention basin (circle one) is/is not underlain by limestone."

E. Where pervious pavement is permitted for parking lots, recreational facilities, non-dedicated streets, or other areas, pavement construction specifications shall be noted on the plan.

F. Recharge/infiltration facilities may be used in conjunction with other innovative or traditional BMPs, stormwater control facilities, and nonstructural stormwater management alternatives.

G. All recharge/infiltration facilities shall be designed to completely drain within 72 hours from the end of the storm.

H. Infiltration structures shall be designed for required storm volume based on field-determined capacity at the elevation of the proposed infiltration surface.

§ 22-618 Water Quality Volume Requirements.

1. In addition to the general standards and design criteria requirements of this Chapter, the land developer shall comply with the following water quality requirements unless otherwise exempted by provisions of this Chapter.

A. The size of the water quality facility shall be based upon the following equation:

	WQv = [(P)(Rv)(A)] / 12
	Where:
		WQv	=	Water Quality Volume (ac-ft)
		P	=	1.1 inches of rainfall
		Rv	=	0.05 + 0.009(I)
		I	=	Percent Impervious Cover (i.e., use I = 20 when there is 20% impervious cover)
		A	=	Site Area (acres)

B. Treatment of the WQ_v shall be provided at all developments where stormwater management is required. A minimum WQ_v of 0.2 acre-inches shall be met at sites or in drainage areas that have less than 15% imperious cover.

C. Drainage areas having no impervious cover and no proposed disturbance during development may be excluded from the WQ_v calculations. Designers are encouraged to maximize the use of these areas as nonstructural practices for WQ_v treatment.

D. The design of the facility shall consider and minimize the chances of clogging and sedimentation potential. Orifices smaller than three inches diameter are not recommended. However, if the design engineer can provide proof that the smaller orifices are protected from clogging by use of trash racks, etc., smaller orifices may be permitted.

E. Developers are encouraged to incorporate designs to take advantage of the stormwater credits presented in the Spring or Paxton Creek Act 167 Stormwater Management Plans.

F. To comply with the requirements of § 22-618, the developer may submit original and innovative designs to the Township for review and approval. Such designs may achieve the water quality objectives through a combination of BMPs.

G. In selecting the appropriate BMPs or combinations thereof, the developer shall consider the following:

(1) Total contributing area;

(2) Permeability and infiltration rate of the site soils;

(3) Slope and depth to bedrock;

(4) Seasonal high water table;

(5) Proximity to building foundations and wellheads;

(6) Erodibility of soils; and

(7) Land availability and configuration of the topography.

H. The following additional factors should be considered when evaluating the suitability of BMPs used in control water quality at a given development site:

(1) Peak discharge and required volume control;

(2) Stream bank erosion;

(3) Efficiency of the BMPs to mitigate potential water quality problems;

(4) The volume of runoff that will be effectively treated;

(5) The nature of the pollutant being removed; and

(6) Maintenance requirements.

§ 22-619 Stream Bank Protection Requirements.

1. Stream bank protection, including riparian buffer, shall be considered in implementing performance standards. If a stormwater storage facility needs to be constructed then, to protect channels from erosion, the outflow structure shall be designed to provide the twenty-four-hour extended detention of the one-year twenty-four-hour storm event. The method for determining the Channel Protection Storage Volume (Cp_v) requirement is detailed in Appendix C[1] of this Chapter.

[1] Editor's Note: Appendix C is included as an attachment to this Chapter.

2. Basis for Determining Channel Protection Storage Volume, Cp_v:

A. The models HEC-HMS, TR-55 and TR-20 (or an equivalent approved by the Township) shall be used for determining peak discharge rates.

B. Rainfall depth for the one-year, twenty-four-hour storm event in Dauphin County is 2.5 inches.

C. Off-site areas shall be modeled as present land use in good condition for the one-year storm event.

D. The Cp_v is not required at sites where the one-year post-development peak discharge (qi) is less than or equal to 2.0 cfs. A Cp_v office diameter (d_o) of less than three inches is subject to approval by the Township and is not recommended unless an internal control for orifice protection is used.

E. Cp_v shall be addressed for the entire site. If a site consists of multiple drainage areas, Cp_v may be distributed proportionately to each drainage area.

F. Extended detention storage provided for the Cp_v does not meet the WQ_v requirement (i.e., Cp_v and WQ_v shall be treated separately).

G. The stormwater storage needed for the Cp_v may be provided above the WQ_v storage in stormwater ponds and wetlands thereby meeting all storage criteria except Re_v in a single facility with appropriate hydraulic control structures for each storage requirement.

H. Infiltration is not recommended for Cp_v control because of large storage requirements.

§ 22-620 Design Standards for Stormwater Management and Conveyance Facilities.

1. The existing points of natural drainage discharge onto adjacent property shall not be altered without the written approval of the affected landowners.

2. Stormwater runoff or natural drainage water shall not be diverted so as to overload existing drainage systems, or create flooding or the need for additional drainage structures on other private properties or public lands, without approved provisions being made by the applicant for properly handling such conditions.

3. Where a watercourse runs across or through a subdivision, a drainage easement, which conforms with the line of such watercourse shall be provided.

4. Storm drainage facilities, as required, shall be placed in front of the curb line when located in a street right-of-way. When located in undedicated land, they shall be placed within an easement, as approved by the Township, who may require additional width of easement as circumstances warrant.

5. Retention/Detention Basin Criteria:

A. Where a stormwater detention basin is proposed, the plan shall include a proposal to prevent such basin from becoming a safety hazard or public nuisance and for regular perpetual maintenance of the basin to insure its continuous effectiveness.

B. All controls designed to meet the requirements of this Chapter shall meet the applicable release rate criteria for the two-, ten- and twenty-five-year return period storms.

C. Any stormwater management facility (i.e., detention basin) designed to store runoff and requiring a berm or earthen embankment, required or regulated by this Chapter, shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year post-development conditions. The height of embankment must be set as to provide a minimum one-foot of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year post-development inflow. Soils used for the construction of basins shall have low-erodibility factors ("K" factors). Any facility that constitutes a dam, as defined in DEP Chapter 105 regulations, may require a permit under dam safety regulations.

D. Any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures) and any work involving wetlands as directed in DEP Chapter 105 regulations (as amended or replaced from time to time by DEP) shall be designed in accordance with Chapter 105 and will require a permit from DEP. Any water obstruction that does not fall under Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the twenty-five-year design storm with a minimum one-foot of freeboard measured below the lowest point along the top of the roadway.

E. The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The Township shall reserve the right to disapprove any design that would result in the occupancy or continuation of an adverse hydrologic or hydraulic condition within the watershed.

F. Basins which are not designed to release all stormwater shall be specifically identified as retention basins or permanent pond basins. All other basins shall have provisions for dewatering, particularly the bottom, and shall not create swampy and/or unmaintainable conditions. Sod-lined or stone lowflow channels may be used to dewater the bottom of a basin. The minimum slope of any surface on the bottom of the pond shall be 1.5%.

G. Retention basins and/or detention basins which are designed with earth fill embankments shall incorporate the following standards:

(1) The minimum top width of embankments up to eight feet in height shall be equal to 2/3 of the embankment height, but in no case shall the top width be less than five feet.

(2) The side slopes of the earth fill shall not be less than three horizontal to one vertical.

(3) A cut off trench and key trench of impervious material shall be provided under all embankments exceeding four feet in height.

(4) All pipes and culverts through embankments shall be fitted with properly spaced and sized cut off collars.

(5) No outlet structure from a detention basin or swale shall discharge directly onto a Township or State road, but may discharge into a culvert under a Township or State road.

(6) Any basin may be required to be fenced with a minimum of four-foot-high fence of a material acceptable to the Township. Gates shall be provided where required. The Board of Commissions shall make the decision to require fencing based on potential hazards at the site such as detention versus retention capability, slope, depth of water and length of detention time.

(7) All facilities shall have access roads and easements where necessary.

6. General Requirements for Stormwater Collection.

A. The design criteria for storm sewers and man-made channels (i.e., swales) shall be the ten-year frequency storm, unless more restrictive frequencies are required by Chapter 105 of the Department of Environmental Protection regulations, with intensities based on the times of concentration for PennDOT Intensity Duration Frequency (IDF) curves, and runoff coefficients based on land use for each drainage area. A minimum time of concentration of five minutes shall be used. Computation methods shall be based on the Rational Method or Soil Cover Complex Method. The Township, pursuant of recommendations of the Township Engineer, may require a design storm of higher intensity be used when on site or surrounding conditions, such as history of flooding downstream or the capacity of the receiving stream or stormwater system indicate such a variation to be necessary.

B. Storm drainage systems shall be provided to allow unimpeded flow of natural watercourses except as modified by stormwater detention facilities or open channels consistent with this Section.

C. Storm drainage facilities and appurtenances shall be so designed and constructed as to minimize erosion at discharge points and in watercourse channels. Adequate erosion protection shall be provided along all open channels and at all points of discharge.

D. When connecting to an existing storm sewer system, the applicant must demonstrate that the proposed system will not exacerbate any existing stormwater problems.

E. Pipe Design.

(1) Pipes shall be designed so as to provide a minimum velocity of 2 1/2 feet per second when flowing full.

(2) At a minimum, pipe capacities shall be computed using both the Manning Equation for full flow capacity and the Inlet Control Nomographs in Hydraulic Design Series 5 by the Federal Highway Administration, dated September 1985. For inlets, the maximum headwater elevation must be less than the top of grate. Outlet control calculations shall be required for special circumstances such as high tailwater conditions, long runs of pipe, excessive bends and other losses, etc. Alternate methods of headwater computation may be accepted at the discretion of the Municipal Engineer.

(3) All pipe shall conform to and be constructed in conformance with the specifications set forth in the Pennsylvania Department of Transportation, Publication 408, as amended and as shown on approved drawings.

(4) Pipe sizes, lengths and slopes shall be shown on the approved drawings.

F. Inlets.

(1) Storm drainage inlets shall be provided at all low points and hydraulically intermediate points on a system. Location and spacing of inlets shall be based on the hydraulic capacity of each inlet related to the flow received and amount of flow bypassed from upstream inlets, but shall not be greater than 600 feet. Inlets shall be placed so street drainage shall not cross intersections or street crowns.

(2) The maximum allowable spread of water on streets is 1/2 of a travel lane. Computations should be provided which demonstrate compliance with this spread requirement.

(3) All street inlet tops shall be the combination curb and gutter inlet referred to as PennDOT Type "C," with a ten-inch curb reveal to allow an automatic two-inch depressed condition to existing when used on an eight-inch curb. All inlet tops shall be precast concrete with heavy-duty bicycle-safe steel grating. Weep holes shall be provided on all inlet tops at the appropriate elevations to completely drain the sub grade prior to placing the base course and surface course. In private parking areas, streets and yard areas with no curbing, Type M inlet tops shall be used.

(4) Inlets shall be constructed in accordance with the specifications as set forth in the Pennsylvania Department of Transportation, Publication 408, as amended, and as detailed on the Roadway Construction Standard drawing (RC-34).

(5) Inlet foundations shall be a minimum of eight inches of plain concrete. Inlet walls shall be precast concrete. All pipes entering or existing inlets shall be cut flush with the inlet wall.

(6) Inlets must be sized to accept the specified pipe sizes without knocking out of any inlet corners.

(7) Any inlets or junction boxes over five feet in depth shall be equipped with ladder rings.

(8) Inlets shall not have a sump condition in the bottom. Pipes shall be flush with the bottom of the box or concrete channels shall be poured. Sumped inlets may be permitted where specifically utilized for water quality purposes.

G. Manholes.

(1) Manholes shall be constructed in accordance with the specifications as set forth in the Pennsylvania Department of Transportation, Publication 408, as amended, and as detailed on the Roadway Construction Standard drawings (RC-39).

(2) Manholes shall be pre-cast concrete units.

H. Roof Leaders, Foundation Drains, Springs and Sump Pumps.

(1) In order to promote overland flow and infiltration/percolation of stormwater where it is advantageous to do so, roof drains, foundation drains, sump pumps, etc., shall not be connected to streets, sanitary sewers, or storm sewers. When it is more advantageous to connect directly to streets or storm sewers, the Township shall permit it on a case-by-case basis.

(2) Roof drains and sump pumps shall discharge to infiltration areas or vegetative BMPs to the maximum extent practicable.

(3) Stormwater roof drains shall not discharge water directly over a sidewalk.

(4) Stabilized outlets shall be provided for footer drains, flood drains, and downspouts.

(5) All underground or surface springs encountered during or after construction of roadways or buildings shall be adequately piped or drained to the nearest storm drainage system. The Township Roadway Inspector or Township Engineer shall be contacted when a spring is encountered. The Inspector or Engineer may make a site investigation and make written recommendations to the developer for correcting the problem. Such recommendations shall be binding on the developer unless the Board of Commissioners, upon the request of the developer, agree to permit an alternative solution.

(6) Subbase drains shall be provided at all low points in cut areas, toe of slope areas and other areas as dictated by proven engineering principles and design judgment. Subbase drains shall be designed and constructed in accordance with the Pennsylvania Department of Transportation Design Criteria and Publication 408 Specifications. All drains shall be connected to a storm drainage system.

(7) All land development projects shall be designed and constructed in order to provide proper drainage of stormwater runoff with minimal impact on adjoining properties, unless an area specifically designed for stormwater detention is provided.

7. Compliance with Department of Environmental Protection (DEP) Chapter 105 Regulations.

A. The design criteria in this Chapter are intended for usage in conjunction with the Chapter 105 Regulations of DEP, entitled "Dam Safety and Waterway Management." All information and regulations contained in Chapter 105 shall be considered to be incorporated into this Chapter as if reproduced in full.

B. DEP permit in accordance with Chapter 105 shall be required for any obstruction or encroachment in the regulated waters of the Commonwealth prior to the approval of the final plan. In the event any question or conflict arises between this Section and the DEP Chapter 105 Regulations, the design criteria contained in the DEP regulations shall govern.

8. Compliance with Pennsylvania Department of Transportation Publication 408 Specifications.

A. All materials, workmanship and methods of work shall comply with the Pennsylvania Department of Transportation Publication 408 Specifications, as accepted and commonly used by the Township, and such specifications shall be considered to be incorporated into this Section as if copied in full. In the event a conflict arises between the requirements and specifications of this Section and the Publication 408 Specifications, the Township Engineer shall resolve the difference, and his opinion shall be binding.