Furnace Bridge, also known as Lower Mayville, is a gravity-type dam located in Mayville, Wisconsin, along the East Branch Rock River. Built in 1848, this dam serves primarily for recreational purposes, with a height of 14 feet and a length of 180 feet. The dam has a significant hazard potential, with a fair condition assessment as of May 2020.

Managed by the Wisconsin Department of Natural Resources, Furnace Bridge is state-regulated, permitted, inspected, and enforced to ensure safety and compliance. With a maximum storage capacity of 140 acre-feet and a normal storage of 68 acre-feet, the dam plays a crucial role in water resource management for the surrounding area. The dam's spillway is controlled, with a width of 93 feet, and it has a very high risk classification according to the data provided.

Overall, Furnace Bridge is a historic structure that not only provides recreational opportunities but also plays a vital role in water storage and management in Dodge County, Wisconsin. With its significant hazard potential and very high risk classification, it is essential for authorities to continue monitoring and maintaining this dam to ensure the safety of the surrounding community and the sustainability of the water resources it impacts.