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

Project Detour Map: 

Project Updates:

Nov. 19, 2025: 

Oct. 15, 2025 – Nov. 15, 2025, Completed Work:
Within the two-mile segment of U.S. Highway 16A, demolition of the existing box culvert is complete, and excavation for the new box culvert is ongoing. New pipe culverts and gabion baskets are being installed. Tree removal at the four new gabion wall locations has been completed. The project will continue through the winter, and the two-mile closure will remain in place until early April 2026. Final project completion is October 30, 2026.

The U.S. Highway 16A closure remains in place from the intersection of Highway 16A/Iron Mountain Road to Custer State Park’s Wildlife Loop Road and will remain in effect until April 2026. Custer State Park and Iron Mountain Road are OPEN. Detour route traffic control signing is installed. Within the closure, guardrail has been removed to allow for box and pipe culvert replacement. Some existing pipe culverts have received joint repairs and new lining.

A detour is in place using S.D. Highway 36 to Custer County’s Ritterberger Road, then south two miles to the Cobb Road intersection, west one mile on Cobb Road, south 1.5 miles on Cobb Road to LH Road, west approximately two miles on LH Road to Custer State Park’s Wildlife Loop Road, then north two miles back to Highway 16A. Motorists should note that Ritterberger Road, Cobb Road, and LH Road include six miles of gravel. The Wildlife Loop section is paved and posted at 25 mph.

Anticipated Work Nov. 15, 2025 – Dec. 15, 2025:
Within the two-mile closure, the contractor will continue excavation and undercut for the new box culvert and then begin backfilling operations. Replacement of aging pipe culverts with new pipe and gabion baskets will also continue.

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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.

Project Photos:

Project Contract Amount: