Historic Dam Restoration, Windsor, Vermont

Built in 1834, the Upper Windsor Dam in Windsor, Vermont, is one of the oldest masonry storage dams in the U.S. It appears on the American Society of Civil Engineers list of historic engineering landmarks and on the National Register of Historic Places.

The dam originally functioned as a source of hydropower and hydroelectric power. In 2013, the Town of Windsor took steps to rehabilitate the dam’s lower level outlet (LLO), which had not been operated in years. Rehabilitation would require dredging sediment and debris from the area of the LLO; placing, sealing, and draining a cofferdam for access to the LLO; completing repairs; and re-establishing full operation of the gate.

e4sciences performed three bathymetric surveys: one before dredging, one during dredging, and one after dredging was complete. Comparison of these surveys validated the volume of material removed by dredging. e4sciences also acquired side-scan sonar, sub-bottom reflection seismology, and sonar sector scanning. With these measurements, e4sciences imaged the debris on the reservoir floor, the dam face on the waterside, the top of rock, the thickness of reservoir silt, and the lower level outlet. Underwater sonar sector scanning revealed horizontal cracking in the dam face that was later exposed when the reservoir level was lowered.