Bringing a historic waterway into the future
As part of the Manayunk Schuylkill Canal Diversion Facility & Canal Intake Project, the Philadelphia Water Department (PWD) engaged Ramboll to deliver a full suite of engineering services for major upgrades to Flat Rock Dam. The scope included a new intake structure, a waste weir – a structure used to provide controlled release of water from the dam – and a sluiceway, along with associated site improvements.
The project was completed and officially opened in June 2025, successfully meeting all design requirements and restoring flow to the Manayunk Canal – a historic, two-mile stretch that was originally built in the 1820s to support coal transport. In addition, the dam was brought into compliance with dam safety regulations, with early water quality results indicating significant improvements.
“The Flat Rock Dam project was not just another water infrastructure project, as we were working to rehabilitate and protect 200 years of history,” says James Quinn, Project Officer in Ramboll’s Dams & Water Resources team in the US.
“The overall goal was to bring the dam into compliance with dam safety regulations and to reintroduce flow and improve water quality in the canal, which had remained stagnant for many years.”
Resilient design ensuring damage control and community safety
Located within the Schuylkill River floodplain, Flat Rock Dam experiences frequent flooding, making a resilient design essential. The project therefore focused on future-proofing the dam to ensure both damage control and enhanced water quality for the downstream community.
“Portions of the dam have been in place since the early 1800s, so they did not meet modern engineering standards during large flood events,” explains James Quinn.
“With the new design, the dam will safely weather major storms, preserving the water control functionality that is critical to maintaining operational continuity to deliver long-term environmental benefits.”
A unique approach to complex engineering challenges
During the early stages of the project, the team applied a range of contemporary technologies to support geotechnical investigations and analysis.
“We used drones during the construction process, along with hydraulic models including 1D, 2D, and 3D CFD, to inform the final layout of the project elements. This ensured the project could provide adequate flow to the Manayunk Canal while safely passing flows from large storm events,” says James.
CFD – Computational Fluid Dynamics – is a numerical modeling approach used to simulate fluid flow in one or more dimensions. In addition, mandatory project sequencing was incorporated into the design to support prudent risk management during reconstruction, while also facilitating the preservation of the historic intake and lock structure.
The project was successfully completed in September 2025.
About Flat Rock Dam
Flat Rock Dam is in the Manayunk neighborhood of Philadelphia, Pennsylvania, on the Schuylkill River. It was originally constructed around 1818 as part of the Schuylkill Canal, a 112-mile system that was a major engineering accomplishment for its time and used to transport coal from the mines in central Pennsylvania to the markets in Philadelphia.