U.S. Highway 93 – MDT Improvements

AESI provided comprehensive design services for the reconstruction of a 6-mile segment of US-93 for MDT.  This project was part of the large-scale design effort, under the Design Management team of Skillings-Connolly, to reconstruct 56 miles of US-93 from Evaro to Polson.  The project was a unique partnership between MDT, FHWA, and the Confederated Salish and Kootenai Tribes and was considered a “landmark” project for this area of the country.

This project included: rural and urban roadway reconstruction, a new couplet around Arlee, reconstruction of twelve county roads, and accommodating extensive irrigation systems that cross or parallel the project.  Extensive analysis and design for storm drainage and irrigation conveyance was required throughout the 6-mile project corridor.  A new storm drain system for Arlee was designed, including several retention and detention ponds and a 2,300 foot open channel/piped outfall.  The design successfully addressed constraints posed by existing conditions such as limited right-of-way, irrigation facilities, existing city streets and infrastructure, and limited discharge points.

The Agency Creek wildlife crossing was a particularly challenging problem.  Prior to the project, the creek crossed the highway and terminated in a gravel pit with no downstream connection to Finley Creek.  As part of the highway design, AESI designed over 2,800 feet of open channel to convey Agency Creek to Finley Creek bypassing the gravel pit.  This new channel connection posed many design challenges including: a channel in the railroad right-of-way, a railroad crossing (double 10-ft x 3-ft box culverts), irrigation ditch crossings via culvert bridges, a county road crossing, and a tie-in to Finley Creek Flats open channel on CSKT tribal land.

There were many unique and challenging design issues throughout this complex corridor.  These included sensitive environmental and tribal cultural issues, architectural designs, and wildlife considerations.  AESI welcomed the extensive design coordination and detailed effort a project of this magnitude requires.  This project gave AESI solid experience with coordination efforts between MDT, the design management team, project architects, tribal representatives, Flathead Agency Irrigation District, MRL, Arlee Sewer District, utility companies, and the residents of Arlee.