Crooks' Hollow Dam (alternatively, Dundas Town Dam) is a buttressed gravity dam, built of concrete in 1916 on Spencer Creek in Greensville, Ontario, Canada. About 100 yards upstream from the ruins of the much earlier Cockburn sawmill and dam, it replaced that dam in supplying water by pipe to Dundas for all uses. It also provided much greater flood control, and, more than the Cockburn dam, supplied a managed flow for water power users in the industries downstream. The Dundas Star commented on its completion: "... an excellent piece of work. It is now hoped there will be no further difficulty about securing an adequate water supply for many years to come."
The dam was built in such a way that pure, cool water was drawn from the bottom of the reservoir for the existing pipe to Dundas; and for impure, warmed water to be sent over the spillways for industrial use downstream. The dam was created with reservoir expansion in mind, from 10,000,000 to 15,000,000 gallons, by the simple addition of another 3 feet of stoplogs.