The Michigan Clean Marina Program designated four additional clean marinas in the state.

They are Duncan L. Clinch Marina in Traverse City; Seng’s Marina in Manistee; Grosse Pointe Yacht Club in Grosse Pointe Shores; and River Bend Marina in Harrison Township.

All have been certified for a three-year term through 2018.

Two other marinas were recertified as clean marinas — Harbor Springs Municipal in Harbor Springs and Yacht Basin Marina in Holland. Those marinas were recertified for a five-year term through 2020.

To date, 49 Michigan marinas have obtained and are maintaining the certification.

“More boaters are becoming aware of the program and are searching out these facilities as places they want to patronize,” Michigan Boating Industries Association president Nicki Polan said in a statement. “It is not difficult, and there are both financial and environmental gains that come with this effort.”