View towards the Potomac River of the missing section of Seneca Creek Aqueduct on the Chesapeake and Ohio Canal

The Seneca Creek Aqueduct is located at Mile 22.7 on the Chesapeake and Ohio Canal towpath. A large parking lot is at the site. See the Locks and Lockhouses web page for an interactive location map.

The Seneca Creek Aqueduct and Lock 24 were constructed as one unit, the only instance of this on the entire Chesapeake and Ohio Canal. This was required because the canal on one side of Seneca Creek is at a higher elevation than the canal on the other side. Boats heading downstream would cross the creek via the aqueduct and immediately enter the lock to be lowered down to the level of the east bank section of the canal. Those heading upstream would enter the lock to be raised to the height of the aqueduct, then proceed across the creek.

A canal aqueduct is a nifty little feat of engineering that solves the problem of what to do when a canal crosses paths with a creek or river. Both are waterways, but the canal is a self-contained channel and cannot temporarily merge with the river because all of its water will spill out uncontrollably. The solution is to elevate the canal over the waterway via a bridge. In essence, a large, elevated bathtub must be built—water cannot be leaking out of the bottom and sides. This is done with a thick layer of clay and stone on the bottom and solid stone walls for sides.