Visitors can get an inside look at the gatehouse that controls the dam at Hopkinton Lake this Saturday.

Rangers with the U.S. Army Corps of Engineers will give three 40-minute tours of the Hopkinton Dam gatehouse at noon, 12:40 and 1:20 p.m. on Saturday, July 20. Parking is available at the Hopkinton Lake Project Office, 2097 Maple St.

The tour will include a discussion about the history of the dam, part of the Hopkinton-Everett Lakes Flood Risk Management Project, opened in 1962 as part of an extensive series of flood-control projects in New Hampshire.

Hopkinton Dam is 790 feet long and 76 feet high and can create a 3,700-acre lake, while nearby Everett can create a 2,900-acre lake. The lakes have a combined storage capacity of 51 billion gallons and are linked by a canal, which lets water be diverted between them as flood conditions require.