Borough of West View, PA Article IV Stormwater Management for Water Quality

§ 240-13 General requirements for stormwater management.

All regulated earth disturbance activities within the municipality shall be designed, implemented, operated and maintained to meet the purposes of this chapter, through these two elements: 1) erosion and sediment control during the disturbance activities (e.g., during construction); and 2) water quality protection measures after completion of earth disturbance activities (e.g., after construction), including operations and maintenance.

A. No earth disturbance activities within the municipality shall commence until the requirements of this chapter are met.

B. Impervious areas:

(1) The measurement of impervious areas shall include all of the impervious areas in the total proposed development even if development is to take place in stages.

(2) For development taking place in stages, the entire development plan must be used in determining conformance with this chapter.

(3) For projects that add impervious area to a parcel, the total impervious area on the parcel is subject to the requirements of this chapter.

C. Stormwater flows onto adjacent property shall not be created, increased, decreased, relocated, or otherwise altered without written notification of the adjacent property owner(s). Such stormwater flows shall be subject to the requirements of this chapter.

D. SWM site plans approved by the municipality, in accordance with § 240-11, shall be on site throughout the duration of the regulated activity.

E. Erosion and sediment control during regulated earth disturbance activities shall be addressed as required by § 240-17.

F. Postconstruction water quality protection shall be addressed as required by § 240-18. Operations and maintenance of permanent stormwater BMPs shall be addressed as required by Article IV.

G. All best management practices (BMPs) used to meet the requirements of this chapter shall conform to the state water quality requirements and more stringent requirements as determined by the municipality.

H. Infiltration BMPs should be spread out, made as shallow as practicable and located to maximize use of natural on-site infiltration features while still meeting the other requirements of this chapter.

I. Storage facilities should completely drain both the volume control and rate control capacities over a period of time not less than 24 hours nor more than 72 hours from the end of the design storm.

J. The design storm volumes to be used in the analysis of peak rates of discharge should be obtained from the Precipitation-Frequency Atlas of the United States, Atlas 14, Volume 2, Version 3.0, U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Hydrometeorological Design Studies, Silver Spring, Maryland. NOAA's Atlas 145 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.

K. Techniques described in Appendix 2 (Low-Impact Development)[1] 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 2 is included as an attachment to this chapter.

L. Additional requirements.

(1) In conjunction with meeting the requirements of this chapter, the applicant shall refer to and meet all conditions and requirements set forth in the Borough of West View's Municipal Separate Storm Sewer System (MS4) Prohibited Discharge Ordinance.

(2) In conjunction with meeting the requirements of the chapter, the applicant shall refer to and meet all conditions and requirements set forth in the Borough of West View's total maximum daily load (TMDL) plan as adopted and revised.

M. Exemptions.

(1) Regulated activities that disturb areas less than 2,500 square feet are exempt from the peak rate control and the SWM site plan preparation requirement of this chapter.

(2) 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.

(3) 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.

(4) All Borough development activities, Borough road work, Borough utility activities, and Public Works activities are exempt from this chapter in its entirety.

(5) For a parcel or tract of land held under single ownership, only one application for a small development, as defined above, shall be permitted before requiring a stormwater management plan for the entire parcel. A project cannot be phased to circumvent the stormwater requirements by using the exemption for small developments.

N. Small developments.

(1) At the time of application, the Borough Zoning Officer shall determine if the development qualifies as a "small development" and, therefore, is eligible for a simplified stormwater plan submission. For the purposes of this chapter, a small development is:

(a) Any development which results (or will result when fully constructed) in the creation of 5,000 or less square feet of impervious surface area, including roofs, patios, driveways, and sidewalks.

(b) The Borough Engineer shall review the proposed provisions for stormwater management for small developments. The Borough shall determine if the proposed development site is part of a larger parcel or tract for which a stormwater management plan was approved previously and, therefore, subject to any specific stormwater management controls contained in the prior plan.

(c) For a parcel or tract of land held under single ownership, only one application for a small development, as defined above, shall be permitted before requiring a stormwater management plan for the entire parcel. A project cannot be phased to circumvent the stormwater requirements by using the exemption for small developments. When calculating new impervious area for determining whether a development qualifies as a "small development," the cumulative total of all impervious areas constructed within five years of the application date shall be considered.

(2) The Small Project Stormwater Management Plan Application included in Appendix 5[2] may be used for projects under 5,000 square feet of proposed impervious surface. The Small Project Stormwater Management Plan Application allows documentation of new impervious surface, credits through disconnection of impervious surfaces and tree planting, and sizing of volume control BMPs and rate control facilities that may be required.

[2] Editor's Note: Appendix 5 is included as an attachment to this chapter.

(3) Should the applicant choose not to use the Small Project Stormwater Management Plan Application (Appendix 5),[3] a plan addressing peak rate and volume controls must be submitted and shall include a plan which describes narratively and graphically the type and location of proposed on-site stormwater management techniques or the proposed connection to an existing storm sewer system. The plan should show accurately site boundaries, five-foot interval contours, location of watershed and/or subarea boundaries on the site (if applicable), and any watercourses, floodplains or existing drainage facilities or structures located on the site. Where the applicant is proposing to connect to an existing storm sewer, the applicant shall submit documentation showing that sufficient capacity exists in the storm sewer from the point of connection to the point of outlet in the natural drainage system. The plan and supporting documentation must be prepared by a registered professional engineer.

[3] Editor's Note: Appendix 5 is included as an attachment to this chapter.

O. Volume controls.

(1) The low-impact development practices provided in the BMP Manual shall be utilized for all earth disturbance activities to the maximum extent practicable. Water volume controls shall be implemented using the Design Storm Method in Subsection O(1)(a) or the Simplified Method in Subsection O(1)(b) below. For regulated activity areas equal or less than one acre that do not require hydrologic routing to design the stormwater facilities, this chapter establishes no preference for either methodology; the applicant may select either methodology on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology, and other factors.

(a) The Design Storm Method (CG-1 in the BMP Manual[4]) is applicable to any size of regulated activity. This method requires detailed modeling based on site conditions.

[1] Do not increase the postdevelopment total runoff volume for all storms equal to or less than the two-year, twenty-four-hour duration precipitation.

[2] For modeling purposes:

[a] Existing (predevelopment) nonforested pervious areas must be considered meadow or its equivalent.

[b] Twenty percent of existing impervious area, when present, shall be considered meadow in the model for existing conditions.

[4] Editor's Note: See § 240-37A.

(b) The Simplified Method (CG-2 in the BMP Manual[5]) provided below is independent of site conditions and should be used if the Design Storm Method is not followed. This method is not applicable to regulated activities greater than one acre or for projects that require design of stormwater storage facilities. For new impervious surfaces:

[1] Stormwater facilities shall capture at least the first two inches of runoff from all new impervious surfaces.

[2] At least the first one inch of runoff from new impervious surfaces shall be permanently removed from the runoff flow — i.e., it shall not be released into the surface waters of this commonwealth. Removal options include reuse, evaporation, transpiration, and infiltration.

[3] Wherever possible, infiltration facilities should be designed to accommodate infiltration of the entire permanently removed runoff; however, in all cases at least the first 0.5 inch of the permanently removed runoff should be infiltrated.

[5] Editor's Note: See § 240-37A.

P. Rate controls.

(1) Postdevelopment discharge rates shall not exceed the predevelopment discharge rates for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year storms. If it is shown that the peak rates of discharge indicated by the postdevelopment analysis are less than or equal to the peak rates of discharge indicated by the predevelopment analysis for one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year, twenty-four-hour storms, then the requirements of this section have been met. Otherwise, the applicant shall provide additional controls as necessary to satisfy the peak rate of discharge requirement.

Q. Design storms.

(1) The SCS Type II Rainfall Distribution shall be used for all analyses. The rainfall depth to be utilized for design storm frequencies shall be as follows:

Design Storm (year)	Rainfall Depth, 24 Hours (inches)
1	1.97
2	2.35
5	2.88
10	3.30
25	3.90
50	4.40
100	4.92

(2) Individual site standalone detention facilities shall be constructed for all single-family lot developments or single-family lots located in land developments which for terrain reasons cannot utilize the development's detention systems. Individual site standalone detention facilities shall consist of gravel filled sumps, ponds, tanks or other approved facilities, sized in accordance with standard details in the Borough Construction Standards.

(3) Storage volumes for total impervious areas greater than 5,000 square feet shall be calculated using the methods outlined in this section.

(4) All stormwater detention facilities shall be located at least 10 feet from foundation walls in a location approved by the Borough. All pipe from roof drains to a point 10 feet from the structure shall be a minimum Schedule 40 PVC pipe or approved equal.

(5) Predevelopment conditions. The cover type for all sites will be considered to be the hydrologic conditions at the time of the development application. Twenty percent of all existing impervious surface shall be considered meadow in good condition. All hydrologic parameters used to calculate peak flow rates shall use the appropriate specifications pertaining to these conditions.

R. Method of computation.

(1) All computations used in conjunction with the analysis and design of stormwater management facilities shall be based on one or more of the following methods:

(a) TR-55-Soil Conservation Service Technical Release No. 55.

(b) TR-20-Soil Conservation Service Technical Release No. 20.

(c) Modified Rational Method.

(d) Penn State Runoff Model.

(e) Virginia Tech/Penn State Runoff Model.

(f) These methods for determining peak discharge shall be used to:

[1] Determine predevelopment runoff conditions;

[2] Analyze the impact of development; and

[3] Perform calculations in the design of any detention/retention facilities used in controlling runoff.

(2) These methods of runoff computation developed and used by the Soil Conservation Service and other authorities are hereby adopted by the Borough.

(3) The use of the Basic Rational Method in estimating runoff may be employed in the design of the storm sewer system within the development. The storm sewer system shall be interpreted as the conduits, culverts, inlets and appurtenant features for the conveying of stormwater to, through or from a development site to the point of final discharge or control facility. The Rational Method shall not be used in the analysis of stormwater runoff from the development in its entirety or in conjunction with the design of any retention/detention facilities or other runoff control measures.

S. Stormwater detention facilities.

(1) All detention facilities shall be equipped with multistage outlet structures to provide discharge control for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year storm frequencies. Provisions shall also be made for safely passing the postdevelopment one-hundred-year storm runoff flows without damaging (i.e., impairing the continued function of) the facilities.

(2) Shared-storage facilities, which provide detention of runoff for more than one development site, may be considered within a single subarea. Such facilities shall meet the design criteria contained in this section. In addition, runoff from the development sites involved shall be conveyed to the facility in a manner so as to avoid adverse impacts, such as flooding or erosion, to channels and properties located between the development site and the shared-storage facility.

(3) Other considerations which should be incorporated into the design of the detention facilities include:

(a) Inflow and outflow structures shall be designed and constructed to prevent erosion. Bottoms of impoundment-type structures shall be protected from soil erosion.

(b) Control and removal of debris, both in the storage structure and in all inlet or outlet devices, shall be a design consideration.

(c) Inflow and outflow structures, pumping stations and other structures shall be protected and designed to minimize safety hazards.

(d) Provide fencing at least six feet in height around the entire perimeter of all ponds/basins.

(e) Side slopes of storage ponds shall not exceed a ratio of three to one (3:1) horizontal to vertical dimension.

(f) Landscaping shall be provided for the facility which harmonizes with the surrounding area.

(g) All stormwater detention facilities shall be screened from view of existing roads or streets located within the Borough, which is a minimum of six feet in height with sufficient access for maintenance vehicles. The screening material must be approved by the Borough. Landscaping of the pond embankment shall not be permitted at any time.

(h) The facility shall be located to facilitate maintenance, considering the frequency and type of equipment that will be required. The facility shall be equipped with an access road at least 10 feet wide and with a maximum of grade of 15%.

(i) All pond outlet structures shall have suitable antiseep collars, gaskets, barriers and/or seals to prevent leakage and piping of water through the pond embankment. All storm pipe installed through a pond embankment shall be constructed of reinforced concrete pipe.

(j) Provide a minimum of one foot of freeboard above the one-hundred-year design storm event as it passes through the emergency spillway.

(k) A geotechnical investigation report for the construction of the stormwater detention/retention and infiltration facilities must be provided including design recommendations for embankment construction, interior and exterior slopes, drainage swales and infiltration areas.

T. Single-family lots.

(1) Retention/detention facilities shall be constructed for all existing single-family lot developments or single-family lots located in land developments which for terrain reasons cannot utilize the development's retention/detention systems. Retention facilities shall consist of gravel filled sumps, ponds, tanks or other approved facilities, sized in accordance with standards of this chapter.

(2) Storage volumes for roof areas greater than 5,000 square feet shall be calculated using the methods outlined in.

U. Easements. Easements for stormwater management facilities shall be required to have a minimum width of 20 feet. Where a subdivision or land development is, or will be, traversed by a watercourse, there shall be provided a stormwater or drainage easement of a width sufficient for the purpose, but not less than 20 feet. The stormwater detention facilities must be provided within a drainage easement. An access easement must be provided from the public right-of-way to the stormwater detention facility with a minimum width of 20 feet.

(1) Stormwater management easements are required for all areas used for off-site stormwater control, unless a waiver is granted by the Borough.

(2) Stormwater management easements shall be provided by the property owner if necessary for: 1) access for inspections and maintenance; or 2) preservation of stormwater runoff conveyance, infiltration, and detention areas and other BMPs, by persons other than the property owner. The purpose of the easement shall be specified in any agreement under § 240-24.

(3) Facilities, areas, or structures used as stormwater management BMPs shall be enumerated as permanent real estate appurtenances and recorded as deed restrictions or conservation easements that run with the land.

(4) Operation and management plans for stormwater management approved pursuant to 25 Pa. Code § 102 after the date of this chapter shall be recorded as a restrictive deed covenant that runs with the land.

(5) If a conservation easement is provided, the long-term ownership, access, maintenance, and use restrictions must be identified on the recording plan.

V. Flood-prone areas.

(1) Land identified as flood-prone on maps issued by the Federal Insurance Administration shall be subject to the regulations of the National Flood Insurance Program and shall comply with the provisions of the Borough Floodplain Ordinance.[6]

[6] Editor's Note: See Ch. 116, Part 1, Building Permits; Floodplain Management.

(2) The one-hundred-year floodplain shall be delineated by one of the following methods:

(a) The Flood Insurance Study (FIS) by the Federal Emergency Management Agency (FEMA).

(b) A hydrologic report prepared by an individual registered in the Commonwealth of Pennsylvania to perform such duties. Calculations and channel hydraulic characteristics used to determine floodplain limits shall be provided.

(3) Municipal liability disclaimer. Approval of a stormwater management plan by the Borough shall not be construed as an indication that said plan complies with the requirements, laws, or standards of any agency of the commonwealth, which may or may not govern said activity.

§ 240-14 Permit requirements by other government entities.

The following permit requirements may apply to certain regulated earth disturbance activities, and must be met prior to commencement of regulated earth disturbance activities, as applicable:

A. All regulated earth disturbance activities DEP subject to permit requirements by regulations under 25 Pa. Code Chapter 102;

B. Work within natural drainageways subject to permit by DEP under 25 Pa. Code Chapter 105;

C. Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by DEP under 25 Pa. Code Chapter 105.

D. Any stormwater management facility that would be located on a state highway right-of-way, or require access from a state highway, shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT); and

E. 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 subject to permit by DEP under 25 Pa. Code Chapter 105.

§ 240-15 Construction criteria for stormwater control facilities.

Stormwater management facilities shall be constructed in accordance with the following minimum specifications:

A. All workmanship and materials shall conform to the Borough Construction Standards as provided in the Borough of West View Code, Chapter 240. In addition, all workmanship and materials shall conform to the latest edition of PennDOT Form 408.

B. All connections to existing storm sewer pipes shall be made by construction of a suitable junction box (inlet or manhole) to provide access for clean-out. No blind connections shall be permitted.

C. All pond outlet structure pipes shall have suitable gaskets to prevent leakage and piping of water through the pond embankment.

D. All pipe outlets shall discharge onto a stone rip-rap blanket to prevent erosion of soil. Rip-rap will be sized considering pipe exit velocities.

E. Controls shall be installed at initial stages of earthmoving and otherwise as outlined in the staging of earthmoving activities section of the erosion and sedimentation control plan.

F. The discharge of stormwater runoff shall be to a well-defined drainagecourse which has a defined bed and bank. If stormwater runoff cannot be discharged to a defined drainagecourse, documentation of written permission from each downstream property owner shall be provided for all properties between the source of discharge and the defined drainagecourse.

§ 240-16 Maintenance criteria for stormwater control facilities.

Maintenance is an essential part of the successful functioning of a stormwater management system and the following shall be required:

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

(1) Removal of silt from all debris basins, traps or other structures or measures when 40% of capacity is filled with silt.

(2) Disposal of collected silt in a manner which will not adversely affect the environment.

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

(4) Establishment or re-establishment of vegetation by seeding and mulching or sodding of scoured areas where vegetation has not been successfully established. A developer or landowner retains this obligation as to property he or she has developed or improved even if the proper season for "seeding" occurs initially sometime after the project is otherwise completed in whole or as to a particular phase.

(5) Installation of necessary controls sufficient to protect against problems caused by storm events within design frequencies.

(6) Removal of all temporary measures upon completion of the project.

B. After acceptance of the plan by the Borough. In the event that the Borough accepts public improvements in the plan, except in cases where an agreement between the developer and the Borough has been executed to the contrary, the maintenance shall be the responsibility of the Borough and shall include, where necessary:

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

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

(3) Removal of trees and shrubs from pond embankments.

(4) Repair of animal burrows and removal of animals causing same.

C. If the Borough does not accept the facilities, it shall be the responsibility of the developer to inspect all permanent facilities to see that corrective action is taken where necessary.

(1) Stormwater facilities located on private property shall be maintained by the owner or his agent; however, this does not relieve the owner or his agent of the obligation to inspect his own facilities. The Borough reserves the right to enter upon private property to make periodic reasonable inspections and to require the owner to take necessary corrective actions. An easement shall be recorded granting access over private property to the stormwater facilities.

(2) The owner shall convey to the Borough easements and/or rights-of-way to assure access for periodic inspections by the Borough and maintenance if required.

(3) The owner shall keep on file with the Borough the name, address and telephone number of the person or company responsible for maintenance activities; in the event of a change, new information will be submitted to the Borough within 10 days of the change.

(4) The owner shall establish any special maintenance funds or other financing sources, in accordance with the approved maintenance plan.

D. The owner shall pay the amount due to the Special Stormwater Facility Maintenance Fund.

(1) Persons installing stormwater storage facilities will be required to pay a specified amount to the West View Borough Stormwater Facility Maintenance Fund to help defray the costs of periodic inspections and annual maintenance expenses. The amount of the deposit shall be determined as follows:

(a) If the storage facility is to be privately owned and maintained, the deposit shall cover the cost of periodic inspections performed by the Borough for a period of 10 years, as estimated by the Borough. After that period of time, inspections will be performed by the Borough and billed directly to the owner.

(b) If the storage facility is to be owned and maintained by the Borough, the deposit shall cover the estimated annual costs for maintenance and inspections for 10 years, as estimated by the Borough.

(c) The amount of the deposit to the maintenance fund covering annual inspection and maintenance costs shall be converted to present worth of the annual series values. The Borough Manager shall determine the present-worth equivalents, which shall be subject to the final approval of the Borough Supervisors.

(2) If the storage facility is proposed, which also serves as a recreation facility, such as a lake or ball field, the Borough may reduce or waive the amount of the maintenance fund based on the value of the land for public recreation purposes.

(3) If at some future time any storage facility (whether publicly or privately owned) is eliminated due to the installation of storm sewers or another storage facility (i.e., a distributed storage facility), the unused portion of the maintenance fund will be applied to the cost of abandoning the facility and connecting to the storm sewer system or other facility. Any amount of the deposit remaining after the costs of abandonment are paid will be returned to the owner.

E. If the owner fails to maintain the stormwater control facilities, following due notice by the Borough to correct the problems, the Borough shall perform the necessary maintenance or corrective work. The owner shall reimburse the Borough for all costs.

F. Additional items may be included in the maintenance agreement where determined necessary to guarantee the satisfactory maintenance of all facilities. The maintenance agreement shall be subject to the review and approval of the Borough's Solicitor.

§ 240-17 Erosion and sediment control during regulated earth disturbance activities.

A. No regulated earth disturbance activities within the municipality shall commence until approval by the municipality of an erosion and sediment control plan for construction activities.

B. DEP has regulations that require an erosion and sediment control plan for any earth disturbance activity of 5,000 square feet or more, under 25 Pa. Code § 102.4(b).

C. In addition, under 25 Pa. Code Chapter 92,[1] a DEP "NPDES Construction Activities" permit is required for any earth disturbance one acre or more. This includes earth disturbance on any portion of, part of or during any stage of a larger common plan of development.

[1] Editor's Note: Chapter 92 of Title 25 of the Pennsylvania Code was reserved 10-8-2010, effective 10-9-2010. It was replaced by Chapter 92a, National Pollutant Discharge Elimination System (NPDES) Permitting, Monitoring and Compliance.

D. Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or County Conservation District must be provided to the municipality. The issuance of an NPDES Construction Permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements of Subsection A.

E. A copy of the erosion and sediment control plan and any required permit, as required by DEP regulations, shall be available at the project site at all times.

F. A copy of the erosion and sediment control plan and any required permit, as required by PADEP regulations, shall be available at the project site at all times.

G. Measures shall be designed and used during construction as per approved plans from the ACCD and in accordance with the details presented in the PADEP Chapter 102 Revised Erosion and Sedimentation Control Program Manual. The following DEP Construction Details shall be included and made a part of the construction plans:

(1) Silt barrier fence.

(2) Rock construction entrance.

(3) Diversion swale.

(4) Sediment trap outlet.

(5) Rock filter.

(6) Sediment basin.

(7) Soil erosion matting.

H. Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office of Allegheny County Conservation District must be provided to the Borough. The issuance of an NPDES Construction Permit [or permit coverage under the statewide General Permit (PAG-2)] satisfies the requirements of Subsection A.

I. A copy of the erosion and sediment control plan and any required permit, as required by DEP regulations, shall be available at the project site at all times.

§ 240-18 Water quality requirements after regulated earth disturbance activities are complete.

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

B. The BMPs must be designed, implemented and maintained to meet state water quality requirements, and any other more stringent requirements as determined by the municipality.

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

(1) Infiltration: replication of preconstruction stormwater infiltration conditions;

(2) Treatment: use of water quality treatment BMPs to ensure filtering out of the chemical and physical pollutants from the stormwater runoff; and

(3) 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).

D. DEP has regulations that require municipalities to ensure design, implementation and maintenance of best management practices ("BMPs") that control runoff from new development and redevelopment after regulated earth disturbance activities are complete. These requirements include the need to implement postconstruction stormwater BMPs with assurance of long-term operations and maintenance of those BMPs.

§ 240-19 Stormwater performance standards.

A. Applicants are encouraged to design conveyance systems that encourage infiltration and improve water quality wherever practicable.

B. Wherever conveyance channels are necessary, drainage shall be maintained by an open channel with landscape banks designed to carry the one-hundred-year, twenty-four-hour stormwater runoff from upstream contributory areas. If the runoff from stormwater collection and conveyance facilities would drain over land to a stormwater detention facility, the twenty-five-year frequency storm event may be used. All open channels shall be designed with one foot of freeboard above the design energy gradeline of the design runoff condition.

C. Flood relief channels shall be provided and designed to convey the runoff from the one-hundred-year, twenty-four-hour storm, such that this flow is conveyed to a natural drainagecourse with a defined bed and bank.

D. The distance between manholes shall not exceed 300 feet apart for pipe sizes up to 24 inches in diameter and not more than 450 feet apart for larger pipe sizes. Inlet spacing shall not exceed 300 feet.

E. Where drainage swales are used in lieu of, or in addition to, storm sewers, they shall be designed to carry the required runoff without erosion and in a manner not detrimental to the properties they cross. Drainage swales shall provide a minimum grade of 1% but shall not exceed a grade of 9%. Drainage swales used strictly for conveyance are not the same as open vegetated channels.

F. Use of grassed swales or open vegetated swales in lieu of curbing to convey, infiltrate and/or treat stormwater runoff from roadways is encouraged. Inlets shall be placed at the shoulder swale draining the street and shall be located no closer than four feet from the edge of the cartway.

G. Water quality inlets. Storm drainage systems that collect runoff from parking areas and/or loading areas exceeding 5,000 square feet of impervious coverage and discharge to stormwater management systems, including surface or subsurface infiltration systems, shall have a minimum of one water quality inlet per each acre of drainage area. The purpose of water quality inlets is to remove oil, grease, and heavy particulates or total suspended solids, hydrocarbons and other floating substances from stormwater runoff. Methods other than water quality inlets may be permitted if the applicant demonstrates to the Borough's satisfaction that any such alternative will be as effective and as easily maintained. Periodic cleaning of these systems shall be addressed in the operation and maintenance plan submitted to the Borough.

H. Suitable drainage structures, culverts, storm sewers, swales and related installations shall be provided along roads to insure removal of stormwater from all gutters, at all low points and at intervals elsewhere not exceeding 600 feet, such that the width of stormwater flow in any gutter does not exceed 1/4 of the total cartway width.

I. No stormwater pipe (public or private) shall be less than 15 inches in diameter. All stormwater pipes shall be concrete unless otherwise approved by the Borough. The minimum pipe slope shall be such that a minimum of two feet per second velocity is maintained. Where a culvert or pipe is used to replace a stream, the cross-sectional area shall be at least as large as the original stream channel. All stormwater BMPs shall be constructed in accordance with the Borough's "Standard Details." Minimum pipe cover shall conform to the manufacturer's recommendations. Stormwater conveyance pipes utilized in BMPs shall have a pipe size of four-inch diameter or larger.

J. When requested by the Borough the developers shall obtain or grant a minimum twenty-foot-wide drainage easement over all storm sewers, drainage swales, channels, etc., that are a component of the stormwater management system when located within undedicated land. All permanent detention basins and/or other stormwater management facilities providing stormwater control for other than a single residential lot shall be located within a defined drainage easement that allows proper legal access and maintenance vehicle access.

K. All stormwater collection and conveyance facilities (pipes, swales, and structures) shall be designed for a one-hundred-year design storm event, unless the runoff would naturally drain overland to a stormwater detention facility, in which case a twenty-five-year design storm event may be used. All drainage facilities shall be designed to contain the energy gradeline for the peak flow rate for the design storm within the structures a minimum of two feet below surface elevation. The hydraulic grade line must be within the pipe. Swales and channels shall provide at least one foot of freeboard above the energy gradeline. Backwater effects of pipes discharging under surcharge conditions shall be included in the calculations.

L. Where open watercourses for stormwater drainage are used the following standards shall apply:

(1) Artificial channels shall be of trapezoidal cross section, with the channel width at the bottom at least 10 times the maximum water depth which would be produced by the one-hundred-year design storm and with rough, permeable and flexible sides and bottom. No artificial channel shall be used to replace a natural stream.

(2) At all points in the drainage system the velocity shall be less than the erosion threshold of the conveyance material, including at the outlet from the construction area or subdivision site.

(3) Provide a minimum of one foot of freeboard above the twenty-five-year design storm event for drainage swales.

M. All workmanship and materials shall conform to the latest edition of PennDOT Form 408 and be supplied by manufacturers or suppliers listed in PennDOT's Bulletin 15.

N. All connections to existing storm sewer pipes shall be made by construction of a suitable junction box (inlet or manhole) to provide access for cleanout. No blind connections shall be permitted.

O. Manhole and inlet castings shall conform to the Pennsylvania Department of Transportation Form 408 and PennDOT Standards for Roadway Construction. Inlet grates shall be bicycle safe. Frames and grates shall be cast iron. Concrete frames shall not be permitted.

P. All roof drains shall discharge to an on-lot sump, or to a storm sewer system which is controlled by a detention pond. Outlets from roof drain sumps shall not discharge directly to fill slopes. Outlets shall not discharge directly to the gutter line of any street. All pipes from roof drains shall be a minimum four-inch PVC or SDR 26 pipe. Four-inch Schedule 40 PVC is required for a distance of 10 feet from the foundation of the dwelling. No stormwater drainage system shall be permitted to be constructed through any curbing on any public street. Minimum pipe size for sump stormwater piping is four inches.

Q. All bridges and culverts shall be designed to support expected loads and to carry expected flows and shall be designed to meet current standards of the Pennsylvania Department of Transportation. All bridges and culverts shall be subject to all permits required by the Pennsylvania Department of Environmental Protection, Bureau of Dams and Waterways.

R. Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP.

S. Disposal of stormwater from roof and driveway drains:

(1) Unless otherwise approved by the Borough, no stormwater from roofs or driveway drains shall be discharged to the street surface or curb underdrain.

(2) Acceptable methods of disposal include properly designed dry sumps, grassed or other round surfaces with adequate consideration being given to erosion protection, storm sewers, or any other method approved by the Borough.

T. BMP operations and maintenance requirements are described in Article V of this chapter.