Construction of a new 6.65-mile long mountain biking and walking trail at Fellows Lake will start Monday, the first phase in an eventual 33-mile, $1.8 million trail expansion north of Springfield.

It will be the newest major recreation improvement at Fellows Lake, which this winter will also see its aging boat marina replaced by City Utilities and a new playground constructed nearby in a separate project.

The “Dirt 66” mountain bike/walking trail project is being funded by Springfield-based TrailSpring, Inc., a nonprofit that has been working to expand biking opportunities in the Springfield area.

“The Dirt 66 Trail System is designed to accommodate entry-level beginners, primarily moderate, and a few advanced trails,” said Jessica Pearson, executive director of TrailSpring. “The Dirt 66 Trails are going to change the dynamic for the region by improving quality of life and creating new economic activity.”