The Ossining Weir



The weirs along the Old Croton Aqueduct were small structures that were built right over or next to the aqueduct, allowing the weir tender to have direct access to the aqueduct tunnel. The weirs had secondary tunnels that could direct water from the main aqueduct channel into nearby streams if the water flow was too high. The weir tenders could control the aqueduct’s water in three ways: 1. Altering the heights of boards to control the aqueduct’s water depth; 2. Dropping stop planks in the aqueduct to completely block its flow; and 3. Opening screw gates to get rid of water in one section of the aqueduct.

Like several other structures that are part of the Old Croton Aqueduct, the weirs are built in an Egyptian Revival style, chosen for its associations with permanence and because its forms could be easily created by stonemasons. All of the weirs have pilasters along their corners, belt coursing, and a projecting cornice. The weir has a single metal-door entrance, no windows, and a ventilating hole in its brick-arched roof. The New Ossining Weir is twenty feet long, ten feet wide, and thirty feet high, including the portion of the weir that is built underground for the waste-water conduit.

The aqueduct’s weirs serve as some of the larger visible elements of the system along its path. While six weirs had been built along the Old Croton Aqueduct when it was first constructed in the late 1830s and early 1840s, it was decided to increase the functionality of four of these weirs in the 1880s, making it possible not only to divert water and control its depth, but to stop it completely at the site of the weirs. This would allow the aqueduct to be shut off in sections, making its maintenance much easier and faster. It seems that the Ossining New Weir was the only one of these later weirs that was an entirely new construction, rather than being a mere alteration to a preexisting weir, as happened in Tarrytown, Yonkers, and Kingsbridge. A new building was required in Ossining because a waste-weir pipe nearly two thousand feet long would have needed to be built if they altered the already-existing weir in Ossining.


The interior is opened only for guided tours. Please see below for upcoming walks and tours of the weir.

Park at the Parks & Rec Center.

Current or upcoming events at this location

Photo Christopher Payne
Saturday, June 1, 2024 - 10:00am
Walk Leader: 
Pete Dispensa
Friends of the Old Croton Aqueduct

Free, easy, 2-hour tour. Meet at the front (upper level/south side) of the Joseph Caputo Center, which is located at 95 Broadway, Ossining, NY, 10562, just west of Rte. 9/Highland Ave. at the junction of Croton Ave., Rte. 133 (from Metro-North Ossining Train Station by taxi or 15-minute uphill walk - parking lots nearby). After a brief walk, descend into the Weir in Ossining and explore the original 1842 brick water tunnel and learn its history.

Required: pre-registration. Walk may be rescheduled if weather does not cooperate.

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I am always elated when I see something I have never seen before and today was such a day. Today, along with a group of about 10 participants, I was given the opportunity to tour one of the OCA weirs at Ossining, NY. The tour was given by the very knowledgeable and pleasant tour leader, Aram. Kudos to him for giving up his Saturday mornings to do these Friends of the Croton Aqueduct sponsored tours.