An end to overflows at Edgewater?
Innovative tunnel solution could eliminate a legacy environmental challenge at Cleveland beach
The combined sewer outfall at Edgewater, the giant waffle-shaped flap-gate at the west edge of the beach, has a long history. Now, the possibility of eliminating overflows there once and for all may finally have a future.
New analysis of our Westerly treatment plant service area and its interceptor sewer network indicate an innovative tunnel solution has potential to mitigate the surge forces that have led to past overflows.
And if pre-design efforts confirm the solution can weather a full variety of storm conditions, the complete elimination of overflows at Edgewater could be in the making.
Update October 8, 2025: Our CEO Kyle Dreyfuss-Wells appeared on today’s episode of Sound of Ideas to talk about this project opportunity in the context of our combined sewer history (and our future).
Reducing combined sewer overflows
Since 1972, the Sewer District has been reducing combined sewer overflows (CSOs) across the region. From 9 billion gallons a year in the 1970s to 4.5 billion in 2010, that reduction was due to system expansion and treatment plant improvements, enabling the capture of stormwater runoff volumes that had formerly overwhelmed sewers for decades.
Our Project Clean Lake CSO-control program has reduced that annual volume by another 2 billion gallons since 2011, with more than 2 billion addition gallons of capture yet to be realized by 2036. The improvements are making a difference, but the Edgewater outfall, known on our permits as CSO-069, has long remained an essential relief point at a very busy sewer junction. How did an unconventional relief alternative take shape in 2025?
Where the Edgewater outfall factors in
The combined sewer where the outfall meets the beach dates back to the 1890s. In the 1970s, CSO-069 overflowed a mixture of sewage and stormwater up to 50 times a year to prevent back-ups in homes, businesses, streets, and the wastewater treatment plant. Today, thanks to system improvements, that number is now less than twice on average and limited to heavy sudden storms — a vastly better total, but not zero.
Despite extensive facility studies before and during Project Clean Lake, ending overflows altogether at Edgewater had not been possible due to the function of the sewers in the area and the necessity for pressure relief along the last stretch of interceptor before reaching the CSO facilities at our Westerly plant.
The proposed solution on the table today? Not a larger or deeper tunnel for storage, but instead, a higher-elevated “surge” tunnel to mitigate the forces (water volume and air pressure) that trigger Edgewater overflows.
A surge solution
Planning and Design Program Manager Doug Lopata presented the Edgewater Beach Surge Tunnel concept to Trustees August 21, an effort more than a year in the making.
Complete with animations and flow data, the report explained the current improvements underway in the Westerly service area, circumstances under which overflows occur, and how a new stretch of tunnel constructed at a slightly higher elevation could serve a function similar to a stream’s floodplain during heavy storms, allowing space for the flow and its forces to dissipate without filling as storage and escalating to an overflow event at the Edgewater outfall.
“We have gone from 126 permitted CSO locations across the Sewer District down to 112 currently on the permit,” Lopata explained, indicating we have eliminated CSO locations in the past where it makes sense. “We also have more [opportunities] in the hopper to get us under 100 in the next 10 years, hopefully.”
More work to do
The pre-design phase of the Edgewater Beach Surge Tunnel is still underway, with further storm data testing this year, followed by Westerly equipment adjustments still to come when its CSO facilities (partially shown here) go online in 2026.
At the same time, we are reviewing project budget (now estimated to be $20 million), and discussions with stakeholders are underway to understand how we may approach the project’s design and construction, bids for which may come as early as 2027.
