CHAPTER 1303 Stormwater Management Standards

[Ord. No. 12-2019, art. III, § 13301, eff. 3-20-2019; Ord. No. 34-2021, § 1, eff. 10-11-2021]

For all regulated activities that result in cumulative earth disturbances equal to or greater than ten thousand (10,000) square feet, or the addition of five thousand (5,000) square feet of impervious area, or lower thresholds as defined in the Zoning Ordinance, unless preparation of an SWM Site Plan is specifically exempted in Section 1303.02:

Preparation and implementation of an approved SWM Site Plan is required.

No regulated activities shall commence until the City issues written approval of an SWM Site Plan, which demonstrates compliance with the requirements of this Title.

SWM Site Plans approved by the City, in accordance with Section 1304.06, shall be on site throughout the duration of the regulated activity.

These standards apply to the landowner and any person engaged in regulated activities.

Riparian buffer requirements per Section 1303.05 are applicable regardless of whether or not the disturbance thresholds triggering SWM Site Plan review are met.

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 Title and to meet all requirements under PA Code Title 25 and the Clean Streams Law. Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Program Manual (E&S Manual4), No. 363-2134-008, as amended and updated.

Impervious areas from a project site:

The measurement of impervious areas shall include all of the impervious areas in the project site even if development is to take place in stages.

For development taking place in stages, the entire development plan must be used in determining conformance with this Title.

For projects that add impervious areas to a site, the total impervious areas is subject to the requirements of this Title and of Title 9, the Zoning Code. The total impervious areas calculation shall include the sum of the remaining pre-development impervious areas plus any newly created post-development impervious areas, if applicable.

Stormwater flows onto adjacent or downstream property shall not be created, increased, decreased, relocated, impeded, or otherwise altered without written permission of the affected property owner(s). Notification shall include a description of the proposed development and the stormwater flows that are being created, increased, decreased, relocated, impeded, or otherwise altered. Adjacent property shall at a minimum include any property having a shared boundary with the subject property of the SWM Site Plan, however, if in the judgement of the Designated Plan Reviewer additional properties are being affected, additional notifications may be required. Proof of notification (signed postal receipt for example) shall be included as part of the SWM plan submission to the City. Such stormwater flows shall be subject to the requirements of this Title.

All regulated activities shall include such measures as necessary to:

Protect health, safety, and property.

Meet the water quality goals of this Title by implementing measures to:

Minimize disturbance to floodplains, wetlands, natural slopes over twenty-five (25) percent, existing native vegetation, trees and wooded areas.

Maintain or extend riparian buffers.

Minimize soil disturbance and soil compaction.

Avoid erosive flow conditions in natural flow pathways.

Minimize thermal impacts to waters of this Commonwealth.

Disconnect impervious surfaces by directing runoff to pervious areas, wherever possible.

Incorporate green infrastructure methods described in the City of Pittsburgh Stormwater Design Manual. In cases where green infrastructure is infeasible, as determined within the City of Pittsburgh Stormwater Design Manual, the SWM Site Plan shall meet the requirements in Section 1303.033.

Infiltration BMPs should be dispersed throughout the project site at strategic locations, made as shallow as practicable, and located to maximize use of natural on-site infiltration features provided that the geological and soil conditions are conducive to infiltration. Locations where infiltration is prohibited within the City are defined within the City of Pittsburgh Stormwater Design Manual.

All BMPs should completely drain both the volume control and rate control capacities over a period of time not less than twenty-four (24) and not more than seventy-two (72) hours from the end of the design storm.

The design storm precipitation depths to be used in the analysis of volume control and peak rates of discharge shall be as obtained in the City of Pittsburgh Stormwater Design Manual.

For all regulated activities, SWM BMPs shall be designed, implemented, operated, and maintained to meet the purposes and requirements of this Title and to meet all requirements under PA Code Title 25, the Clean Streams Law, and the Storm Water Management Act.

Regulated activities shall incorporate BMPs and their design standards as listed in the City of Pittsburgh Stormwater Design Manual.

The City may, after consultation with DEP, approve measures for meeting the State Water Quality Requirements other than those in this Title, provided that they meet the minimum requirements of, and do not conflict with, state law including, but not limited to, the Clean Streams Law.

For regulated activities discharging stormwater to surface Waters of the Commonwealth via privately and/or publicly owned separate storm sewers, BMPs shall meet or exceed pollutant filtration requirements within the City of Pittsburgh Stormwater Design Manual.

For regulated activities within high pollutant loading hotspot areas, all BMPs used to meet the volume and/or rate control requirements shall incorporate pretreatment to prevent BMP performance decline due to pollutants. Guidelines for pollutant loading hotpot areas and pretreatment design methods shall meet requirements within the City of Pittsburgh Stormwater Design Manual.

The order of preference for all stormwater discharge connections, regardless if subject to stormwater regulations, shall be 1.) the surface waters of the Commonwealth, 2.) a public separate storm sewer, and 3.) a public combined sewer. All stormwater connections and the minimum distance threshold for mandatory connection shall meet requirements within Title Four: Public Spaces Chapter 433: Illegal Surface Stormwater Connections, the PWSA Developers Manual, and the City of Pittsburgh Stormwater Design Manual.

Surface stormwater discharges from a project site to the public right-of-way are prohibited and all stormwater discharges must connect as per the connection requirements in Section 1303.01.q. In the event that surface discharges to the right-of-way are unavoidable per an alternatives analysis submitted to the City demonstrating that the connection options in Section 1303.01.q are not feasible, a "no-harm" downstream hydraulic analysis is required at the discretion of the City to ensure that sufficient conveyance capacity exists to convey the discharge without risk to public safety. "No-harm" downstream hydraulic analysis shall meet the requirements within the City of Pittsburgh Stormwater Design Manual.

All stormwater runoff and groundwater originating from a project site are the sole responsibility of the property owner to provide for, and maintain, private stormwater management infrastructure that safely conveys all discharge flows. No discharges shall result in a public safety and/or nuisance risk to adjacent public and private property. In the event of insufficient capacity to meet this requirement, the developer must construct new or existing infrastructure upgrades, either on adjacent private property or to the public right-of-way infrastructure. Cost for upgrades shall be provided at developer's expense. Depending on the type of the upgrade, the City at its discretion may require regular maintenance, at the developer's expense, to ensure long-term functionality.

§ 1303.02 Exemptions.

[Ord. No. 12-2019, art. III, § 13302, eff. 3-20-2019; Ord. No. 34-2021, § 1, eff. 10-11-2021]

Agricultural activity is exempt from the SWM Site Plan preparation requirements of this Title provided the activities are performed according to the requirements of PA Code Title 25, Chapter 102.

Roadway resurfacing and maintenance projects, which do not increase impervious area, and underground infrastructure projects are exempt from the provisions of this Title, provided the activities meet the requirements of all other municipal, state and federal requirements.

Demolition of a residential structure by the City or other governmental body.

Exemptions from any provisions of this Title shall not relieve the applicant from the requirements in Section 1303.01.e through k, which require all disturbance and development activities, regardless of SWM Site Plan review requirements, to comply with other relevant state and local codes.

The City may deny or revoke any exemption pursuant to this Section at any time for any project that the City believes may pose a threat to public health and safety or the environment.

If conditions exist that prevent the reasonable implementation of water quality and/or quantity control practices on site, upon written request by the applicant, the City may at its sole discretion accept off-site stormwater management practices, retrofitting, stream restorations, or other practices that provide water quality and/or quantity control equal or greater than onsite practices for the volume which the applicant has demonstrated to be infeasible to manage and treat on site.

§ 1303.03 Volume Controls.

[Ord. No. 12-2019, art. III, § 13303, eff. 3-20-2019; Ord. No. 34-2021, § 1, eff. 10-11-2021]

Preferred and approved stormwater BMPs, as identified in the City of Pittsburgh Stormwater Design Manual, shall be used for meeting the regulatory requirements for all regulated activities. Water volume controls shall be implemented using the Design Storm Method in subsection A or the Simplified Method in subsection B below.

The Design Storm Method (CG-1 in the PA BMP Manual) is applicable as a method to any size of regulated activity. This method requires detailed modeling based on site conditions. The following shall be incorporated into the Design Storm Method:

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

Runoff from at least the annual 95th Percentile Rainfall Event using future climate change rainfall projections within the City of Pittsburgh Stormwater Design Manual shall be permanently removed from the runoff flow, i.e., it shall not be released into the sewer system or surface waters of this Commonwealth.

Removal options include reuse, evaporation, transpiration, and infiltration. Demonstration of technical infeasibility for the removal of runoff shall meet infeasibility criteria thresholds established within the City of Pittsburgh Stormwater Design Manual. If removal of the runoff is deemed infeasible, and the Designated Plan Reviewer agrees, runoff shall be detained and meet water quality release rate requirements as stipulated within the City of Pittsburgh Stormwater Design Manual. Fee-in lieu payments for not meeting the volume requirement within this Chapter are provided in Section 1303.03.F.

For modeling purposes:

Existing (pre-development) non-forested pervious areas shall be calculated using permeability coefficients for meadow in good condition, in efforts to be as conservative as possible in existing conditions modeling.

Twenty (20) percent of existing impervious area, when present, shall be calculated using permeability coefficients for meadow in good condition in the model for existing conditions. The intent of this is to start calculations from a baseline that is closer to naturally-occurring, pre-urbanization conditions, realizing that impervious cover has detrimental hydrologic impacts.

The Simplified Method (CG-2 in the PA BMP Manual) 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 (1) acre or for projects that require design of stormwater storage facilities. For impervious surfaces:

Stormwater facilities shall capture at least the first two (2) inches of runoff from impervious surface.

Runoff from at least the 95th Percentile Rainfall Event using future climate change rainfall projections within the City of Pittsburgh Stormwater Design Manual shall be permanently removed from the runoff flow, i.e., it shall not be released into the sewer system or surface waters of this Commonwealth.

Removal options include reuse, evaporation, transpiration, and infiltration. Demonstration of technical infeasibility for the removal of runoff shall meet infeasibility criteria established within the City of Pittsburgh Stormwater Design Manual. If removal of runoff is deemed infeasible, and the Designated Plan Reviewer agrees, runoff shall be detained and meet design requirement for non-infiltrating BMPs as stipulated within the City of Pittsburgh Stormwater Design Manual.

Volume control incentives and offsets.

Applicants that manage additional volume in excess of the requirements of this Title may be eligible for a volume control incentive grant payment per additional cubic foot of storage volume provided up to two and one-half (2.5) inches of precipitation over impervious surfaces either within the proposed development or within lands outside of the proposed development but owned by the applicant. Volume control incentive grant payment rates shall be as stipulated in the City of Pittsburgh Stormwater Design Manual and are subject to the availability of funds.

Applicants meeting the volume control requirement using a combination of preferred BMPs, water reuse, and active controls as defined in the City of Pittsburgh Stormwater Design Manual, will be eligible for a five-business day SWM Site Plan review.

Subject to requirements outlined in the City of Pittsburgh Stormwater Design Manual, applicants may offset the volume control requirement by managing an equivalent area of impervious surface outside of the project site but within lands owned by the applicant.

Subject to requirements outlined in the City of Pittsburgh Stormwater Design Manual, applicants may implement volume control projects on lands owned by the applicant to offset volume requirements for future development projects. Should volume control requirements change between the time when the offsetting project is implemented and when the future development project occurs, the volume control offset will be prorated accordingly. Volume offsets shall be transferable in the event that the property is sold or otherwise transferred to a different owner than the applicant.

Volume control offset projects must fully meet the requirements of this Title.

Approval of volume control offsets under this Title does not necessarily authorize this approach for meeting NPDES permit requirements.

In cases where the applicant believes that meeting the volume control requirement is technically infeasible using preferred or approved BMPs, the applicant must either submit an innovation approval request per Section 1303.03(e) and/or submit a technical infeasibility determination as part of the SWM Site Plan to determine if volume control requirements can be met in whole or in part using an in-lieu fee payment as described in Section 1303.03(f). The technical infeasibility determination report shall at least include, but is not limited to, engineering calculations, geologic reports, results of geotechnical investigations and infiltration testing, hydrologic analyses, and site maps, as defined in the City of Pittsburgh Stormwater Design Manual. Within the technical infeasibility determination report, applicants must demonstrate the technical infeasibility of each approved BMP for each drainage area within the proposed project site according to BMP-specific technical infeasibility criteria defined in the City of Pittsburgh Stormwater Design Manual.

Applicants wishing to meet volume control requirements using innovative BMPs not listed as preferred or approved BMPs may submit an innovation approval request to the City authorizing the use of innovative technologies on a case-by-case basis. The innovation approval request must include 1) evidence that the BMP is approved by a recognized third party certification program listed in the City of Pittsburgh Stormwater Design Manual, or 2) performance data collected in accordance with data collection protocols listed in the City of Pittsburgh Stormwater Design Manual, or 3) a study plan for a pilot project in accordance with pilot project study plan requirements provided in the City of Pittsburgh Stormwater Design Manual and for which the pilot project proposes to provide management for no more than ten (10) percent of the total regulated drainage area of the project site.

Applicants must pay, as a pre-requisite of City issuance of SWM Site Plan approval, a one time fee in-lieu payment for each drainage area for which the volume control requirement cannot be met using preferred or approved BMPs, and for which the City has determined that the technical infeasibility determination is justified, less any areas for which the volume control requirement is being met using offsets or via an innovation approval request. The one time fee in-lieu payment shall be six hundred thousand dollars ($600,000.00) per acre-inch of the required volume for each drainage area to meet the volume control requirement per Section 1303.03. The fee in-lieu payment amount may be adjusted annually after January 1, 2022 based on the percentage change in the United States Bureau of Labor Statistics Consumer Price Index for All Urban Consumers for all items for the Pittsburgh area. Fee in-lieu payments are not available as a compliance alternative to meet rate control requirements.

Determination of technical infeasibility by the City for purposes of issuing SWM Site Plan approval shall not imply that technical infeasibility has been established for purposes relating to obtaining NPDES permit authorization.

§ 1303.04 Rate Controls.

[Ord. No. 12-2019, art. III, § 13305, eff. 3-20-2019; Ord. No. 34-2021, § 1, eff. 10-11-2021]

Rate control requirements are regulated based on the project site location and its respective watershed. Special rate control watersheds include: Allegheny County Act 167 watersheds (Section 1303.04.a) and Public Health and Safety watersheds (Section 1303.04.b). For project sites that overlap both Allegheny County Act 167 watersheds and Public Health and Safety watersheds, rate control calculations for both provisions shall be performed and the more stringent release rate shall govern. For areas not covered by either Allegheny County Act 167 watersheds or the Public Health and Safety watersheds, rate control requirements are regulated to the requirements in Section 1303.04.c.

For areas covered by the maximum-allowable release rate map from the approved Allegheny County Act 167 Stormwater Management Plan:

For the 1-, 2-, 5-, 10-, 25-, 50-, and 100-year, twenty-four-hour rainfall events, the post-development peak discharge rates will follow the applicable approved release rate maps and procedures incorporating the use of future climate rainfall projections provided in the City of Pittsburgh Stormwater Design Manual.

For areas covered by the City public health and safety release rate map:

The City has identified watersheds with infrastructure that are subject to capacity restrictions and therefore pose a risk to public health and safety associated with basement sewage backups and surface flooding. The public health and safety release rate requirement minimizes the impact of runoff from development within the identified watersheds. For watersheds identified on the public health and safety release rate maps, post-development discharge rates shall not exceed the pre-development discharge rates for the 1-, 2-, 5-, 10-, 25-, 50-, and 100-year, 24-hour rainfall events using the rainfall estimates and procedures incorporating the use of future climate change rainfall projections provided within the City of Pittsburgh Stormwater Design Manual. Post-development discharge rates also shall meet the public health and safety release rate requirements using future climate change rainfall projections within the City of Pittsburgh Stormwater Design Manual.

For areas not covered by the maximum-allowable release rate map from the approved Allegheny County Act 167 Stormwater Management Plan (Refer to Section 1303.04.a), or by the City public health and safety release rate map (refer to Section 1303.04.b):

Post-development discharge rates shall not exceed the pre-development discharge rates for the 1-, 2-, 5-, 10-, 25-, 50-, and 100-year, 24-hour rainfall events using the rainfall estimates and procedures incorporating the use of future climate change rainfall projections provided within the City of Pittsburgh Stormwater Design Manual.

For modeling purposes, whether or not the area is covered by a City public health and safety and/or an Allegheny County Act 167 maximum-allowable release rate map:

Existing (pre-development) non-forested pervious areas shall be calculated using permeability coefficients for meadow in good condition.

Rate control incentives and points of interest.

Applicants that provide rate control in excess of the requirements of this Chapter may be eligible for a rate control incentive grant payment per additional acre-inch of storage volume provided. Rate control incentive payment rates shall be as stipulated in the City of Pittsburgh Stormwater Design Manual and are subject to the availability of funds.

Rate control and volume control incentive grant payments are not additive.

Subject to requirements outlined in the City of Pittsburgh Stormwater Design Manual, applicants may meet rate control requirements at a downstream point of interest that includes lands owned by the applicant but outside of the project site, so long as the point of interest is located upslope of the discharge to the public sewer system.

§ 1303.05 Riparian Buffers.

[Ord. No. 12-2019, art. III, § 13305, eff. 3-20-2019; Ord. No. 34-2021, § 1, eff. 10-11-2021]

In order to protect and improve water quality, a riparian buffer easement shall be created and recorded as part of any subdivision or land development that encompasses a riparian buffer, regardless of whether other requirements from this Title apply. The intent of this Title in establishing a riparian buffer is to protect and improve stream water quality. The riparian buffer is intended to slow overland flow to the stream through the presence of native grasses, trees and shrubs, allowing infiltration/groundwater recharge; causing deposition of sediment, nutrients, pesticides, and other pollutants in the buffer rather than in the stream; and reducing erosion by providing stream bank stabilization. The trees provide shade for streams; keeping waters cooler and reducing evaporation.

Except as required by PA Code Title 25 Chapter 102, the riparian buffer easement shall be required for all streams with a contributing watershed area of greater than ten (10) acres. The riparian buffer easement shall be measured to be a minimum of thirty-five (35) feet from the top of the streambank (on each side).

Minimum management requirements for riparian buffers:

No use or construction within the riparian buffer shall be permitted that is inconsistent with the intent of the riparian buffer as described in Section 1303.05.A.

Existing native vegetation shall be protected and maintained within the riparian buffer easement.

Whenever practicable, invasive vegetation shall be actively removed and the riparian buffer easement shall be planted with native trees, shrubs and other vegetation to create a diverse native plant community appropriate to the intended ecological context of the site.

The riparian buffer easement shall be enforceable by the City and shall be recorded in the appropriate County Recorder of Deeds Office, so that it shall run with the land and shall limit the use of the property located therein. The easement shall allow for the continued private ownership and shall count toward the minimum lot area required by zoning, unless otherwise specified in the Zoning Ordinance.

Any permitted use within the riparian buffer easement shall be conducted in a manner that will maintain the extent of the existing 100-year floodplain, improve or maintain the stream stability, and preserve and protect the ecological function of the floodplain.

Stormwater drainage pipes shall be permitted within the riparian buffer easement, but they shall cross the easement in the shortest practical distance. Other structural stormwater management facilities are not permitted within the riparian buffer easement.

The following conditions shall apply when public and/or private recreation trails are permitted by the City within riparian buffers:

It is preferred that trails be designed to be permeable and for non-motorized use only; however, impermeable trails are permitted provided they have adequate drainage.

Trails shall be designed to have the least impact on native plant species and other sensitive environmental features.

Septic drainfields and sewage disposal systems shall not be permitted within the riparian buffer easement and shall comply with setback requirements established under PA Code Title 25, Chapter 73.

Underground utilities shall be permitted within the riparian buffer easement; however, work shall be performed to minimize disturbance area and removal of trees. Restoration within the riparian buffer easement shall be with native species of trees, grasses, and other plantings.

Where tree removal is necessary, an existing tree survey, tree replacements, and landscape restoration plan shall be designed by a registered professional with the requisite experience. Tree replacements shall follow the tree replacement requirements of the Zoning Ordinance for trees greater than twelve (12) inches DBH (diameter at breast height), or a one-to-one replacement rate for trees lesser than twelve (12) inches DBH.

Aboveground utilities shall only be permitted to cross the easement perpendicular to the easement or in the shortest practical distance. Existing utilities may remain and be maintained as required.

§ 1303.06 (Reserved) [1]

[1]

Editor's Note: Former § 1303.06, which pertained to standards for green infrastructure and low-impact development and derived from Ord. 12-2019, eff. 3-20-2019, was repealed by Ord. 34-2021, eff. 10-11-2021.