Tofty Road MP 15.4 Sullivan Creek Drainage Improvements Project No. NSHHWY00574

The Alaska Department of Transportation & Public Facilities (DOT&PF), is upgrading a low-water creek ford crossing at Sullivan Creek by raising the grade of the road and installing new culverts.

Photo: Mining truck crosses the low-ford crossing at Sullivan Creek.

Project Purpose & Need

The purpose of this project is to provide a reliable crossing and improve drainage across Sullivan Creek on Tofty Road. The current low-ford crossing presents a significant problem with ice building within the roadway (known as aufeis), making traffic passage difficult in the winter and spring.

The creek bed where it crosses Tofty Road has been flattened out by equipment and vehicles driving over it, and the flow of water in Sullivan Creek has decreased from its historic levels due to decades-old mining operations. In the summer and fall, the 16-ft wide creek widens out and slows down across the roadway, which creates a pool of standing water approximately 25-40 feet wide. In the winter and spring, this slow-moving ponded area ices up, causing overflow or aufeis to form and creating problems for travelers.

Installing new drainage features and adding several feet of gravel to the roadway will maintain the flow of the creek across the road and substantially reduce seasonal icing near the creek crossing. These enhancements will allow for improved route reliability for travelers moving between the Elliott Highway and the Road to Tanana.

Project Scope

We are working to install new culverts and rock drainage structures, and to build up a section of road with gravel material. Work on this project includes:

• Installing a large culvert or bank of culverts to ensure flow across Tofty Road from north to south
• Installing a rock structure at the inlet and outlet slopes to armor culverts from being damaged or being plugged by seasonal aufeis
• Widening a section of roadway in the vicinity of crossing from 20 to 28 feet
• Raising road profile approximately 750 feet and reducing the sharp horizontal curve
• Addressing erosion by installing riprap rock basins at culvert ends
• Finishing roadway surface with new gravel wearing course

Conventional construction methods will be used to construct this project. Traffic disruptions are expected to be minimal.

Project Development & Timeline

Our project staff is currently working on finalizing design. Construction on this project is expected to begin in the summer or fall of 2021.