Incorporating Green Infrastructure into Stormwater Management Ordinances


The purpose of this report is to provide municipalities in Allegheny County, PA with guidance for incorporating additional green stormwater infrastructure measures in their Act 167 Stormwater Management plans and stormwater ordinances. In addition, this content offers guidance on options for municipalities to defray the costs of stormwater management, as well as provides resources for MS4/CSO communities.

How to Use This Information

Under the Ordinance Text tab, you will find hyperlinks that take you to sections of existing Act 167 ordinances in Pennsylvania. This guidance is organized according to where such language would be placed in the Allegheny County Model Act 167 Ordinance. All of the sections highlighted provide novel methods for incorporating green infrastructure into the model ordinance. Hyperlinks to the full ordinances, as well as an explanation of why a section might be useful to a municipality, can be found alongside the text.

Under the Other Municipal Tools tab, there are resources detailing other important tools for municipalities updating their stormwater ordinances. These include how green stormwater infrastructure can help MS4 and CSO Communities, and Additional Examples of land use ordinances where green stormwater management strategies, such as low-impact development and non-structural BMPs, can be advanced.

The Municipal Stormwater Fee section highlights several examples of municipal stormwater fee programs implemented in other areas of Pennsylvania, as well as resources that accompany them, such as reports and studies.

Why Green Infrastructure?

Using green infrastructure to manage stormwater improves water quality, conserves water resources, reduces flooding, and protects public health. The Allegheny County Model Act 167 Ordinance finds that:

"The use of green infrastructure (GI) and low impact development (LID) are intended to address the root cause of water quality impairment by using systems and practices which use or mimic natural processes...Green infrastructure practices and LID contribute to the restoration or maintenance of pre-development hydrology."

Allegheny County's Act 167 Phase 2 Stormwater Management Plan provides the following guidance:

"Reducing the total volume of runoff is key in minimizing the impacts of development. Volume reduction can be achieved through reuse, infiltration, transpiration, and evaporation [...] The proposed volume controls for this plan include two pieces:

1. Reduction of runoff generated through utilization of Green Infrastructure (GI) and Low Impact Development (LID) practices to the maximum extent practicable.

2. Permanent removal of a portion of the runoff volume generated from the total runoff flow to the maximum extent practicable."

For water quality, the plan relies on "A combination of source reduction measures through non-structural BMPs and water quality treatment through use of structural BMPs [...]. Reducing the amount of runoff to be treated is the preferred strategy to meet this goal:

      • Minimize disturbance to floodplains, wetlands, natural slopes over 8%, and existing native vegetation.
      • Preserve and maintain trees and woodlands. Maintain or extend riparian buffers and protect existing forested buffer. Provide trees and woodlands adjacent to impervious areas whenever feasible.
      • Establish and maintain non-erosive flow conditions in natural flow pathways.
      • Minimize soil disturbance and soil compaction. [...]
      • Disconnect impervious surfaces by directing runoff to pervious areas, wherever possible.
      • Establish riparian buffers along streams to slow overland flow to the stream through the presence of a band 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."

For more information on how green infrastructure can help your municipality with stormwater management, check out these resources:

Allegheny County Act 167 Phase 2 Stormwater Management Plan

Resources from 3 Rivers Wet Weather

PA DEP Stormwater BMP Manual

EPA Green Infrastructure Site

Community Coordination

Implementing green stormwater infrastructure can be improved by working with neighboring communities. Everything that happens upstream affects neighbors downstream, and taking action now in conjunction with other municipalities in your watershed can reduce flooding. Communities using a collaborative approach to planning and ordinance development have included the Girty's Run, Pine Creek, Squaw Run and Deer Creek watershed. Ordinances in the watershed, as well as municipal investments in green stormwater infrastructure, benefited from this coordination.

3 Rivers Wet Weather (3RWW) will be updating this site to reflect additional examples of green stormwater infrastructure provisions in Act 167 ordinances. To propose a provision to be included, please contact