Combined Sewer Overflow Abatement Program (CSOAP)

The Rochester Pure Waters District (RPWD) of Monroe County constructed the Combined Sewer Overflow Abatement Program (CSOAP) tunnel system in the 1980s and 1990s  to  mitigate  the  occurrence  of  combined  sewer  overflows (CSOs)  from  the  existing  City of Rochester sewer collection system into the Genesee River and Irondequoit Bay. 

As part of the comprehensive system of large-diameter, lined and unlined deep-rock tunnels, the district also constructed a pedestrian arch bridge and access pathways across the river between Maplewood and Seneca parks in 1985. The bridge carries two, 6-foot-diameter sewer pipes underneath its deck that convey CSOAP flow from the west side of the City east to the St. Paul Boulevard Tunnel and on to the Frank E. Van Lare Wastewater Treatment Plant. Crossing the gorge above rather  than below  the river  surface eliminated  the need for  downstream pumping to the POTW and also allowed construction of the pedestrian walkway along the suspended conduit, providing access to the parks on either side of the gorge. 

Erdman Anthony was Engineer of Record for the original design of the St. Paul Boulevard Tunnel System, a subset of the Rochester Pure Water’s Combined Sewer Overflow Abatement Program. We also provided construction support and observation for the project. As noted, the bridge supports two 6 foot diameter pipes that connect the western segment of the city’s combined sewage and storm collecting system to a new tunnel on the east side of the river. Erdman Anthony designed the new 3 mile tunnel, bridge, and two junction and control structures. 

The form of the bridge was dictated in part by the high, steeply sloping banks of the gorge. Since each bank is in densely wooded parkland, the designers had to develop a bridge that harmonized with its surroundings and carried the pipes at the required elevation or gravity flow. As a bonus, the bridge carries a pedestrian path on top of the pipes that links the parkland on the two banks and allows access to a stretch of formerly inaccessible woodland. The bridge’s twin arch ribs span 475 feet and rise 80 feet from their spring line. Steel bents, spaced 25 feet apart along the ribs, carry the pipes. The pipes not only carry waste water but also serve a structural function as well, acting as continuous beams with 25-foot spans that carry a precast concrete deck.

In the EPA’s Guidance for Long-Term Control Plan advocates the use of creative thinking in the development of CSO reduction alternatives. It notes that the initial identification of alternatives should involve some degree of brainstorming and free thinking. In addition, the CSO Control Policy encourages permitting authorities to consider innovative and alternative approaches and technologies that achieve the objectives of this policy and the Clean Water Act. The document specifically calls out this project as an example of creative thinking in the resolution of CSO issues.

Project Details


Rochester, NY


Monroe County Department of Environmental Services

Project Contact

Daniel Ziemianski, PE
  • Daniel Ziemianski, PE
  • 716-631-1241 x 1103
Bookmark and Share