Ohio has lowered Guilford Lake by 20 feet as part of a $14 million dam rehabilitation project to address structural deficiencies and meet modern safety requirements. According to the Ohio Department of Natural Resources (ODNR), the reservoir reached full drawdown during preparations for construction, which includes replacing the existing spillway and improving the dam’s drainage system and embankment stability. The work is intended to help the dam safely manage major flood events and protect downstream communities. Construction was reported to be on schedule in June 2026, with the lake expected to begin refilling in winter 2026–27 and reach normal levels by spring 2027, weather permitting.
Why did Ohio lower Guilford Lake for dam rehabilitation
The rehabilitation follows engineering evaluations that identified deterioration in the dam’s concrete spillway, including separation at its joints. The existing spillway also lacked sufficient capacity to safely pass the Probable Maximum Flood (PMF), the largest flood considered in the project’s design requirements. ODNR said the dam’s embankment had insufficient safety factors for seepage and stability, while its internal drainage system had reached the end of its design life.The department stated that addressing these deficiencies was necessary to protect downstream communities and preserve Guilford Lake as a recreational resource. The dam has undergone several major interventions since its original construction, including a full reconstruction in 1933 and modifications in 1957, 1968 and 1983. The current rehabilitation is designed to bring the structure into compliance with modern dam safety regulations and prepare it for continued service in the coming decades.
How will Ohio’s new spillway improve Guilford Lake Dam safety
The rehabilitation includes a new labyrinth spillway designed to pass the Probable Maximum Flood without overtopping the dam’s embankment. According to ODNR, the design is intended to maintain the lake’s normal pool elevation once the reservoir returns to its usual operating level. It is also intended to keep downstream discharges during significant storm events consistent with pre-rehabilitation conditions.Work on the embankment involves excavating the existing structure to install a modern drainage and filter system with monitoring capabilities. The embankment will then be rebuilt and reinforced with additional material at its downstream toe. In its June 2026 update, ODNR reported that the existing spillway demolition had been completed and concrete had been poured for both the upper and lower cutoff walls of the new spillway. Installation of a new toe drain had also begun on the eastern side of the spillway, while the stilling basin at the base of the structure was the next component scheduled for concrete work.
What is the timeline for Guilford Lake’s $14 million project
The Ruhlin Company was approved as the contractor after bids for the project were opened on 23 October 2025. ODNR reported that the project would cost approximately $14 million and that the state’s Controlling Board had approved the contractor and released the funding. Construction preparations included establishing a field office, installing perimeter fencing and signage, and putting erosion controls in place. A cofferdam made from sheet piling and water-control measures were also installed to allow the existing spillway to be demolished.Public access to the construction site remains prohibited, although the state park campground remains open. ODNR has stated that fishing is permitted outside the construction area, but swimming is prohibited throughout the lake. Vehicles are not allowed on the exposed lakebed, and the department has warned visitors to avoid ice because it may be unsafe as water levels change. The construction site is being monitored remotely, and periodic photographs of progress are available through the Guilford Lake State Park Facebook page.According to the project schedule published by ODNR, substantial completion of construction is anticipated in winter 2026–27, when the lake is expected to begin refilling. The department has identified spring 2027 as the target for completing the refill, subject to weather conditions. Although the lake will remain closed to the public during construction, ODNR does not anticipate long-term road closures, with most of the work expected to be accessed through the southeastern entrance. The rehabilitation is intended to address the dam’s identified safety deficiencies while restoring the reservoir to its normal operating level.