U.S. Highway 16A - From two miles east of Custer to Jct. S.D. Highway 36
Project Summary:
The project consists of the replacement of various pipe culverts on U.S. Highway 16A that have exceeded their useful life. Additional work on the project includes removing and replacing existing asphalt surfacing, repairing in-slope erosion adjacent to the highway, and improving the intersection of U.S. Highway 16A and Wildlife Loop Road.
The project also consists of the replacement of a concrete arch culvert that has exceeded its useful life.
Project Updates:
April 17, 2026 - Completed Work: On Thursday, April 2, 2026, the two-mile closure on U.S. Highway 16A was reopened to traffic from the intersection of Highway 16A and Iron Mountain Road to Custer State Park’s Wildlife Loop Road.
Within the previously closed segment, crews placed gravel on the new box culvert roadway, installed temporary guardrail, and completed permanent seeding.
Work also continued on the construction of two twin box culverts utilizing temporary traffic signals.
The contractor continued realignment work on Custer State Park’s Wildlife Loop Road, which includes approximately 600 feet of roadway.
Anticipated Work April 15, 2026 – May 15, 2026:
The contractor will continue realignment work on approximately 600 feet of Custer State Park’s Wildlife Loop Road, construct two twin box culverts, and complete roadway dig-out repairs. Additional culverts will also be installed throughout the project.
Loose gravel will be present throughout the project area until asphalt paving is completed.
Beginning Tuesday, April 20, asphalt paving operations will start at pipe and dig-out locations.
Beginning Wednesday, May 4, asphalt milling operations will begin along the 13-mile segment between Custer State Park’s east and west entrances.
Asphalt paving is tentatively scheduled for completion by July 4.
Motorists should expect flaggers, a pilot car, and temporary traffic signals in active work zones.
April 2, 2026:
REOPENED: As of 3 p.m. MT on Thursday, April 2, 2026, the two-mile closure on U.S. Highway 16A in Custer State Park has reopened. The six mile gravel detour will no longer be in use.
Additional work on the project includes replacement of multiple pipe culverts, guardrail installation, and a 600-foot realignment of Wildlife Loop Road within Custer State Park. An asphalt mill and overlay will also take place along 13 miles of U.S. Highway 16A between the east and west entrances of Custer State Park. View the full press release at https://shorturl.at/J64Fu.
Access is available to all Custer State Park amenities.