Green Infrastructure Feasibility Study for Bridgeport and New Haven, CT

Authors:

  • Brittany Chamberlin-Martin
  • Sandeep Mehrotra and Matthew Jones - Hazen and Sawyer

Before surrounding wastewater treatment plants upgraded to Biological Nutrient Removal, nitrogen discharges dangerously lowered dissolved oxygen levels and threatened the health of Long Island Sound.

Save the Sound, a program of Connecticut Fund for the Environment, has undertaken a study into the feasibility of utilizing green infrastructure for combined sewer overflow (CSO) abatement in Bridgeport and New Haven, Connecticut. These cities border the Long Island Sound, one of the most densely populated regions in the United States, and combined contain more than 80 CSO outfalls.

Innovative solutions were needed to address issues related to CSOs, sewer backups, and street flooding within both of these cities. Green infrastructure, the use of natural processes and stormwater reuse to manage runoff in combined sewer areas, presented an inventive approach to tackle these issues; however, a thorough understanding of the issues affecting implementation and an estimation of potential benefits was necessary to optimize the effectiveness of this wet weather management strategy.

The study addressed the feasibility of green infrastructure implementation throughout Bridgeport and New Haven, development of a framework for implementation, cost-benefit analyses, and consideration of the effect green infrastructure implementation could have on job creation. A variety of green infrastructure source controls were evaluated during the course of the feasibility study, including various bioretention configurations, subsurface infiltration, blue roofs, green roofs, permeable pavement, rainwater harvesting, infiltration basins, and pocket wetlands. Factors affecting source control feasibility and performance included climate, open space requirements, soil properties, topography, drainage infrastructure, maintenance requirements, and public acceptance and involvement. Special emphasis was placed on identifying and evaluating opportunities where green infrastructure could be utilized synergistically with other efforts within these cities, such as incorporating permeable pavement into repaving operations or utilizing enhanced tree pits and other vegetated practices for beautification efforts.

Analyses associated with the feasibility study relied extensively upon the long term control plans developed by the water pollution control authority (WPCA) for each city, as well as a range of GIS data. GIS data were not only utilized to evaluate general feasibility, but also identify regions where stormwater source controls were most needed, would face the fewest implementation challenges, and provide the greatest benefits. Site specific retrofit opportunities were also identified for conceptual plan development. Cost-benefit analyses considered not only direct stormwater control improvements, but also ancillary benefits such as improved aesthetics and better public understanding of water quality issues. Results of this feasibility study are expected to provide valuable information to the cities of Bridgeport and New Haven, as well as similar areas throughout the Northeast, supporting the effective use of this innovative wet weather management strategy to reduce the negative impacts of CSOs.

To request a copy of the full paper, please contact the author at mjones@hazenandsawyer.com.

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