Dec 11, 2019

Reducing CSOs & Saving Millions

This case study originally appeared in Water & Wastes Digest December 2019 issue as "City Reduces Combined Sewer Overflows & Saves $145 Million"

xylem, inc.,

More than a century ago, the city of Buffalo, N.Y., pioneered a state-of-the-art combined sewer system that collected and transmitted sanitary and storm water flows within a single pipe system to the Buffalo River, Scajaquada Creek and the Niagara River. As its population grew, Buffalo added a major wastewater treatment facility and upgraded its sewer system, but the vast majority of wet weather flows continued to be sent to the city’s receiving waters. In recent years, this accounted for nearly 2 billion gal of combined sewer overflow (CSO) annually.

In 2006, federal and state regulators pursued a consent decree requiring enhancements to Buffalo’s collection system. The Buffalo Sewer Authority (BSA) developed a comprehensive watershed improvement strategy, and in 2014 BSA received approval of its long-term control plan, with an estimated budget of $525 million. Given the city’s reduced taxpayer base, BSA needed to find a solution that was effective but more cost-efficient, so the city once again embraced pioneering technology.

With costly investments in new gray infrastructure deemed infeasible, BSA worked with Xylem to create a real-time decision support system (RT-DSS) across the city. The strategy leveraged new technology to optimize existing infrastructure, building and controlling in-line storage vaults that transformed Buffalo’s massive gravity sewer system into a managed conveyance and storage system. 

The first three sites have cut Buffalo’s CSO volume by 450 million gal, and the program could end up reducing CSOs by three to four times as much as initially projected. In addition to driving critical environmental progress, BSA was able to present a revised LTCP expected to save the city at least $145 million. 

About the author

Xylem Inc.,, 443.766.7873