A $91 million dredging effort has begun on Lake Decatur.

City officials said Thursday that it's the biggest public works project the area has seen since the lake was created in the 1920s. Four basins will be dredged throughout the next six years to increase the lake's capacity by about 30 percent. The lake supplies water to large industrial customers and residents in Decatur and Mount Zion.

In April 2013, the Decatur City Council decided to more than double water rates over a three-year period to help fund the costs of the dredging project.

According to reports, sediment that has accumulated and reduced the lake's capacity over time will be removed. The lake is expected to gain 3.5 to 6 feet of depth in the dredged areas.