Demand was strong for municipal bonds from the District of Columbia Water and Sewer Authority that mature in 100 years, the first public utility to sell so-called Century Bonds, according to Bloomberg News.

The Water and Sewer Authority sold $350 million in taxable bonds that mature in October 2144, to fund tunnel building as part of a $2.6 billion project to update the city’s sewer system, Bloomberg reports.

Because of strong demand, the authority increased the offering by $50 million from an originally planned $300 million offering.

The tunnels are associated with the D.C. Clean Rivers Project and the District dubbed the bonds “Green Bonds.”

Read more at Bloomberg here.