The lower section of William O'Brien State Park in Marine on St. Croix has closed until next year to allow for a $4.1 million remake of the trails and buildings, including a new picnic shelter, accessibility upgrades to the two existing shelters, two new bathroom buildings, improvements to the Riverway campground shower building, a larger swim beach at Lake Alice and more green space.

The closures include everything east of Hwy. 95. Many of the changes will improve accessibility to the trails and river, including a new accessible canoe and kayak launch that uses a floating dock and roller bar ramps to help paddlers of all abilities launch a canoe or kayak.

The changes were recommended in a 2008 state park management plan for O'Brien. The Riverside Trail will also be resurfaced to make it better for wheelchairs or strollers. The DNR also plans to make accessibility improvements to the park office building.

The park area to the west of Hwy. 95 remains open, including the park office and interpretive center, the Savanna campground, Wedge Hill group camp, and camper cabins; and most of the park's 17 miles of hiking trails.