A. 
For all regulated activities, unless specifically exempted in § 324-302:
(1) 
Preparation and implementation of an approved SWM site plan is required.
(2) 
No regulated activities shall commence until the municipality issues written approval of an SWM site plan, which demonstrates compliance with the requirements of this chapter.
(3) 
The SWM site plan shall demonstrate that adequate capacity will be provided to meet the volume and rate control requirements, as described under §§ 324-304 and 324-305 of this chapter.
(4) 
The SWM site plan approved by the municipality shall be on site throughout the duration of the regulated activities.
B. 
For all regulated earth disturbance activities, erosion and sediment control BMPs shall be designed, implemented, operated, and maintained during the regulated earth disturbance activities (e.g., during construction) to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code (including, but not limited to Chapter 102, Erosion and Sediment Control) and the Clean Streams Law.[1] Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Program Manual (E&S Manual), No. 363-2134-008 (April 15, 2000), as amended and updated.
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
C. 
For all regulated activities, stormwater BMPs shall be designed, installed, implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code and the Clean Streams Law, conform to the state water quality requirements, meet all requirements under the Storm Water Management Act[2] and any more stringent requirements as determined by the municipality.
[2]
Editor's Note: See 32 P.S. § 680.1 et seq.
D. 
The municipality may, after consultation with PADEP, approve measures for meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with state law, including, but not limited to, the Clean Streams Law.
E. 
All regulated activities shall include, to the maximum extent practicable, measures to:
(1) 
Protect health, safety, and property.
(2) 
Meet the water quality goals of this chapter by implementing measures to:
(a) 
Minimize disturbance to floodplains, wetlands, natural slopes, existing native vegetation and woodlands.
(b) 
Create, maintain, or extend riparian buffers and protect existing forested buffers.
(c) 
Provide trees and woodlands adjacent to impervious areas whenever feasible.
(d) 
Minimize the creation of impervious surfaces and the degradation of waters of the Commonwealth and promote groundwater recharge.
(e) 
Protect natural systems and processes (drainageways, vegetation, soils, and sensitive areas) and maintain, as much as possible, the natural hydrologic regime.
(f) 
Incorporate natural site elements (wetlands, stream corridors, mature forests) as design elements.
(g) 
Avoid erosive flow conditions in natural flow pathways.
(h) 
Minimize soil disturbance and soil compaction.
(i) 
Minimize thermal impacts to waters of the Commonwealth.
(j) 
Disconnect impervious surfaces by directing runoff to pervious areas wherever possible and decentralize and manage stormwater at its source.
F. 
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 developments 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 developed parcel, to the maximum extent practicable and at the discretion of the Municipal Engineer, the total impervious area on the parcel may be subject to the requirements of this chapter.
G. 
If diffused flow is proposed to be concentrated and discharged onto adjacent property, the applicant must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge, or otherwise prove that no erosion, sedimentation, flooding, or other harm will result from the concentrated discharge.
(1) 
Applicant must provide written permission for proposed concentrated flow across adjacent properties if no existing drainage channel or watercourse exists.
(2) 
Such stormwater flows shall be subject to the requirements of this chapter.
H. 
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.
I. 
Where watercourses traverse a development site, drainage easements (encompassing the one-hundred-year elevation with a minimum width of 20 feet) 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.
J. 
When it can be shown that, due to topographic conditions, natural drainageways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainageways. Work within natural drainageways shall be subject to approval by PADEP under regulations at 25 Pa. Code Chapter 105 through the joint permit application process or, where deemed appropriate by PADEP, through the general permit process.
K. 
Any stormwater management facilities or any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures, etc.) that are regulated by this chapter, that will be located in or adjacent to waters of the Commonwealth (including wetlands), shall be subject to approval by PADEP under regulations at 25 Pa. Code Chapter 105 through the joint permit application process or, where deemed appropriate by PADEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the applicant 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 PADEP.
L. 
Should any stormwater management facility require a dam safety permit under PADEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety.
M. 
Any stormwater management facilities regulated by this chapter that will be located on or discharged onto state highway rights-of-ways shall be subject to approval by the Pennsylvania Department of Transportation (PENNDOT).
N. 
Minimization of impervious surfaces and infiltration of runoff through seepage beds, infiltration trenches, etc., are encouraged, where soil conditions and geology permit, to reduce the size or eliminate the need for detention facilities.
O. 
Infiltration BMPs should be dispersed throughout the site, 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.
P. 
Roof drains shall not be connected to streets, sanitary or storm sewers, or roadside ditches in order to promote overland flow and infiltration/percolation of stormwater where it is advantageous to do so. When it is more advantageous to connect directly to streets or storm sewers, then the Municipality shall permit it on a case-by-case basis.
Q. 
Applicants are encouraged to use low-impact development practices to comply with the requirements of this chapter and the state water quality requirements.
R. 
When stormwater management facilities are proposed within 1,000 feet of a downstream municipality, the developer shall notify the downstream municipality and supply a copy of the SWM Plan, if requested, for review and comment.
A. 
Under no circumstance shall the applicant be exempt from implementing such measures as necessary to:
(1) 
Meet State water quality standards and requirements under Title 25 of that Pennsylvania Code and the Clean Streams Law.[1]
[1]
Editor's Note: See 32 P.S. § 680.1 et seq.
(2) 
Protect health, safety, and property.
(3) 
Meet special requirements for high quality (HQ) and exceptional value (EV) watersheds.
B. 
The applicant must utilize the following BMPs to the maximum extent practicable to receive consideration for the exemptions:
(1) 
Design around and limit disturbance of floodplains, wetlands, natural slopes over 15%, existing native vegetation, and other sensitive and special value features.
(2) 
Maintain riparian and forested buffers.
(3) 
Limit grading and maintain nonerosive flow conditions in natural flow paths.
(4) 
Maintain existing tree canopies near impervious areas.
(5) 
Minimize soil disturbance and reclaim disturbed areas with topsoil and vegetation.
(6) 
Direct runoff to pervious areas.
C. 
The applicant's proposed development/additional impervious area may 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.
(6) 
Downstream property owners.
D. 
Single-family residential activities are exempt from these requirements, provided the construction:
(1) 
Complies with §§ 324-301G and 324-302A, B and C; and
(2) 
Has a building setback 75 feet from downstream property lines; and
(3) 
Driveways:
(a) 
Runoff must discharge onto pervious surface with a gravel strip or other spreading device.
(b) 
No more than 1,000 square feet of paved surface may discharge to any one point.
(c) 
The length of flow on the pervious surface must exceed the length of the paved surface flow.
(4) 
The municipality can require more information or require mitigation of certain impacts through installation of stormwater management BMPs if there is a threat to property, health, or safety.
E. 
An applicant proposing regulated activities, after demonstrating compliance with § 324-302A, B, and C, may be exempted from various requirements of this chapter according to the following table:
New Impervious Area1, 2
(square footage)
Applicant Must Provide
0 to 2,500
No submission
2,500 to 5,000
Documentation of impervious surfaces (Small Projects SWM Application)3
> 5,000
Rate controls, volume controls and SWM site plan
NOTES:
1
New impervious area since the date of adoption of this chapter.
2
Gravel in existing condition shall be considered pervious and gravel in proposed condition shall be considered impervious.
3
The first page of the Small Projects SWM Application included in Appendix E[2] may be used to document new impervious surfaces.
[2]
Editor's Note: Appendix E is included as an attachment to this chapter.
F. 
An applicant proposing regulated activities, after demonstrating compliance with § 324-302A, B, and C, may be exempted from various requirements of this chapter if documentation can be provided that a downstream man-made water body (i.e., reservoir, lake, or man-made wetlands) has been designed or modified to address the potential stormwater flooding impacts of the proposed development.
(1) 
Volume control requirements specified in § 324-304 may be exempted for a regulated activity if facilities were already planned, approved and permitted as part of another project, such as a subdivision.
(2) 
Rate control requirements specified in § 324-305 may be exempted for a regulated activity if facilities were already planned, approved and permitted as part of another project, such as a subdivision.
G. 
The purpose of this section is to ensure consistency of stormwater management planning between local ordinances and NPDES permitting (when required) and to ensure that the applicant has a single and clear set of stormwater management standards to which the applicant is subject. The Municipality may accept alternative stormwater management controls under this section, provided that:
(1) 
The Municipality, in consultation with the PADEP, determines that meeting the volume control requirements (see § 324-304) is not possible or places an undue hardship on the applicant.
(2) 
The alternative controls are documented to be acceptable to PADEP for NPDES requirements pertaining to post-construction stormwater management requirements.
(3) 
The alternative controls are in compliance with all other sections of this chapter, including, but not limited to, §§ 324-301D and 324-302A through C.
H. 
Agricultural activities are exempt from requirements of this chapter, provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
I. 
Forest management and timber operations are exempt from the rate and volume control requirement and SWM site plan preparation requirement of this chapter, provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102. It should be noted that temporary roadways are not exempt.
(1) 
All temporary and permanent haul roads that are not to receive an asphalt wearing course shall be designed and constructed consistent with recommendations of the Center for Dirt and Gravel Road Studies and the Pennsylvania State Conservation Commission's Dirt and Gravel Road Maintenance Program.
A. 
The provisions of this chapter are the minimum standards for the protection of the public welfare.
B. 
All waiver requests must meet the provisions of § 324-303G and H.
(1) 
Waivers shall not be issued from implementing such measures as necessary to:
(a) 
Meet state water quality standards and requirements.
(b) 
Protect health, safety, and property.
(c) 
Meet special requirements for high quality (HQ) and exceptional value (EV) watersheds as defined by Pa. Code Title 25, Chapter 93, Water Quality Standards.
(2) 
Municipalities will then consider waivers in accordance with § 324-301D, which states that the municipality may, after consultation with PADEP, approve measures for meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with, state law, including, but not limited to, the Clean Streams Law.[1]
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
C. 
If an applicant demonstrates to the satisfaction of the governing body of the Municipality that any mandatory provision of this chapter is unreasonable or causes unique or undue unreasonableness or hardship as it applies to the proposed project, or that an alternate design may result in a superior result within the context of §§ 324-102 and 324-103 of this chapter, the governing body of the Municipality, upon obtaining the comments and recommendations of the Municipal Engineer, may grant a waiver or relief so that substantial justice may be done and the public interest is secured, provided that such waiver will not have the effect of nullifying the intent and purpose of this chapter.
D. 
The applicant shall submit all requests for waivers in writing and shall include such requests as a part of the plan review and approval process. The applicant shall state in full the facts of unreasonableness or hardship on which the request is based, the provision or provisions of the ordinances that are involved, and the minimum waiver or relief that is necessary. The applicant shall state how the requested waiver and how the applicant's proposal shall result in an equal or better means of complying with the intent or purpose and general principles of this chapter.
E. 
The Municipality shall keep a written record of all actions on waiver requests.
F. 
The Municipality may charge a fee for each waiver request, which shall be used to offset the administrative costs of reviewing the waiver request. The applicant shall also agree to reimburse the Municipality for reasonable and necessary fees that may be incurred by the Municipal Engineer in any review of a waiver request.
G. 
In granting waivers, the Municipality may impose reasonable conditions that will, in its judgment, secure substantially the objectives of the standards or requirements that are to be modified.
H. 
The Municipality may grant applications for waivers when the following findings are made, as relevant:
(1) 
That the waiver shall result in an equal or better means of complying with the intent of this chapter.
(a) 
The waiver is the minimum necessary to provide relief.
(b) 
The applicant is not requesting a waiver based on cost considerations.
(c) 
Existing down-gradient stormwater problems will not be exacerbated.
(d) 
Runoff is not being diverted to a different drainage area.
(e) 
Increased flooding or ponding on off-site properties or roadways will not occur.
(f) 
Potential icing conditions will not occur.
(g) 
Increase of peak flow or volume from the site will not occur.
(h) 
Erosive conditions due to increased peak flows or volume will not occur.
(i) 
Adverse impact to water quality will not result.
(j) 
Increased one-hundred-year floodplain levels will not result.
(k) 
Infiltration of runoff throughout the proposed site has been provided where practicable and pre-development groundwater recharge protected.
(l) 
Peak flow attenuation of runoff has been provided.
(m) 
Long-term operation and maintenance activities are established.
(n) 
The receiving streams and/or water bodies will not be adversely impacted in flood-carrying capacity, aquatic habitat, channel stability and erosion and sedimentation.
A. 
The low-impact development practices provided in the BMP Manual and in Appendix B[1] of this chapter shall be utilized for all regulated activities to the maximum extent practicable.
[1]
Editor's Note: Appendix B is included as an attachment to this chapter.
B. 
The Small Projects SWM Application included in Appendix E[2] may be used for projects under 5,000 square feet of new impervious surface and single-family home construction. The Small Projects SWM Application allows documentation of new impervious surface, credits through disconnection of impervious surfaces and tree planting, and sizing of volume control BMPs that may be required.
[2]
Editor's Note: Appendix E is included as an attachment to this chapter.
C. 
Stormwater runoff volume controls shall be implemented using the Design Storm Method or the Simplified Method as defined 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 method; therefore, the applicant may select either method on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology, and other factors.
(1) 
The Design Storm Method (CG-1 in the BMP Manual) is applicable to any sized regulated activity. This method requires detailed modeling based on site conditions.
(a) 
Do not increase the post-development total runoff volume when compared to the pre-development total runoff volume for the two-year/twenty-four-hour storm event.
(b) 
For hydrologic modeling purposes:
[1] 
Existing nonforested pervious areas must be considered meadow (good condition) for pre-development hydrologic calculations.
[2] 
Twenty percent of existing impervious area, when present within the proposed project site, shall be considered meadow (good condition) for pre-development hydrologic calculations for redevelopment.
(2) 
The Simplified Method (CG-2 in the BMP Manual) 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 detailed design of stormwater storage facilities. For new impervious surfaces:
(a) 
Stormwater facilities shall capture at least the first two inches of runoff from all new impervious surfaces.
(b) 
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 surface waters of the Commonwealth. Removal options include reuse, evaporation, transpiration, and infiltration.
(c) 
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.
(d) 
Actual field infiltration tests at the location of the proposed elevation of the stormwater BMPs are required. Infiltration test shall be conducted in accordance with the BMP Manual. Notification of the Municipality shall be provided to allow witnessing of the testing.
(3) 
In cases where it is not possible or desirable to use infiltration-based best management practices to partially fulfill the requirements in either § 324-304C(1) or (2), the following procedure shall be used:
(a) 
At a minimum, the following documentation shall be provided to justify the decision to not use infiltration BMPs:
[1] 
Description of and justification for field infiltration/permeability testing with respect to the type of test and test locations.
[2] 
An interpretive narrative describing existing site soils and their structure as these relate to the interaction between soils and water occurring on the site. In addition to providing soil and soil profile descriptions, this narrative shall identify depth to seasonal high-water tables and depth to bedrock, and provide a description of all subsurface elements (fragipans and other restrictive layers, geology, etc.) that influence the direction and rate of subsurface water movement.
[3] 
A qualitative assessment of the site's contribution to annual aquifer recharge shall be made, along with identification of any restrictions or limitations associated with the use of engineered infiltration facilities.
[4] 
The provided documentation must be signed and sealed by a professional engineer or geologist.
(b) 
The following water quality pollutant load reductions will be required for all disturbed areas within the proposed development:
Pollutant Load
Units
Required Reduction
Total suspended solids (TSS)
Pounds
85%
Total phosphorous (TP)
Pounds
85%
Total nitrate (NO3)
Pounds
50%
(c) 
The performance criteria for water quality best management practices shall be determined from the Pennsylvania Stormwater Best Management Practices Manual, most current version.
D. 
The applicable worksheets from the BMP Manual must be used in calculations to establish volume control.
A. 
Lands contained within Washington County that have not had release rates established under an approved Act 167 Stormwater Management Plan:
(1) 
Post-development discharge rates shall not exceed the pre-development discharge rates for the one-, two-, ten-, twenty-five-, fifty-, and one-hundred-year storms.
B. 
Lands contained within Washington County that have had release rates established under an approved Act 167 Stormwater Management Plan:
(1) 
Chartiers creek watershed. The post-development peak discharge rates shall be in accordance with the approved release rate map for the individual watershed. Release rates include 50%, 70% and 100% for the ten-, twenty-five-, fifty- and one-hundred-year storms.