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 Timeline:
Early Sept. 2025 - Fall of 2026
- The overall completion date is Oct. 30, 2026.
- No construction from Sept. 23, 2025, to Sept. 28, 2025, during Custer State Park’s Buffalo Roundup.
- Closure with detour will be in affect from Monday, Oct. 6, 2025, through Friday, April 3, 2026.
- No work:
- Sturgis Rally
- July 26, 2025 to Aug. 10, 2025
- Aug. 1, 2025 to Aug. 17, 2026
- Buffalo Roundup
- Sept. 23 to Sept. 28, 2025
- Sept. 22 to Sept. 27, 2026
- Sturgis Rally
Project Detour Map:
Project Updates:
Oct. 27, 2025:
Sept. 15, 2025 – Oct. 15, 2025, Completed Work:
On Monday, Oct. 6, 2025, a two-mile road closure was implemented on U.S. Highway 16A from the intersection of Highway 16A/Iron Mountain Road to Custer State Park’s Wildlife Loop. Custer State Park and Iron Mountain Road remain open. Detour route signs have been installed. Within the closure, guardrail has been removed to allow replacement of pipe culverts and the box culvert. Some existing pipe culverts have had joints repaired and new linings installed.
The detour route runs from the intersection of S.D. Highway 36 and Custer County’s Ritterberger Road, south two miles to Cobb Road, west one mile on Cobb Road, south 1.5 miles on Cobb Road to LH Road, west approximately two miles on LH Road to the Wildlife Loop Road, then north two miles on the Wildlife Loop Road back to Highway 16A. Motorists should note that Ritterberger Road, Cobb Road, and LH Road include six miles of gravel. The Wildlife Loop Road is asphalt with a 25 mph speed limit.
Anticipated Work Oct. 15, 2025 – Nov. 15, 2025:
Within the two-mile closure, the contractor will continue removing the existing box culvert and begin constructing the new one. Existing pipe culverts will also be removed and replaced with new culverts set in gabion baskets.
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Sept. 12, 2025:
Beginning at 11 a.m. MT on Monday, Oct. 6, 2025, a road construction project is scheduled to begin on U.S. Highway 16A near Custer. The reconstruction project to replace a box culvert structure and multiple pipe culverts is located 14 miles east of Custer or nine miles west of the S.D. Highway 79 intersection.
Highway 16A will be closed from the intersections of Highway 16A/Iron Mountain Road to Custer State Park’s Wildlife Loop. This closure will be in place until April 2026. Additional work will include replacing multiple pipe culverts, building gabion walls, and mill and overlay asphalt from Custer State Park’s east entrance to the west entrance for 13 miles. Custer State Park’s Wildlife Loop and Iron Mountain Road will remain open throughout the project.
During the Highway 16A closure, there will be a detour in place. The detour route is from the intersection of S.D. Highway 36 and Custer County’s Ritterberger Road, south two miles to Cobb Road intersection, west one mile on Cobb Road, south one and one-half miles on Cobb Road to the intersection of LH Road, west approximately two miles on LH Road to Custer State Park’s Wildlife Loop Road, and then north two miles on the Wildlife Loop Road back to Highway 16A. Motorists should be aware that the detour on Ritterberger Road, Cobb Road, and LH Road includes six miles of gravel. The Wildlife Loop Road is two miles of asphalt with a reduced speed limit of 25 mph.
S.D. Highway 40 between Hermosa and Keystone also provides a detour option for area motorists.
Additional Project Information:
There will not be any active road construction work happening during the timeframe of Sept. 22 - 28, 2025, for the Custer State Park’s Buffalo Roundup event.
The prime contractor of this $15.6 million project is Paul Reed Construction & Supply, Inc. of Gering, NE. The overall project completion date is October 2026.
