RPA collaborated with a number of state and federal entities to create a feasibility assessment for a challenging stretch of US Highway 93 between RP 40.0 and 44.5. The study assessed geotechnical limitations, hydraulic considerations, wetland impacts, cultural influences, and right-of-way requirements to assess improvement possibilities in terms of impacts, construction costs, and feasibility. The study’s findings will be utilized to inform project development decisions and future environmental re-evaluations.

Key Project Elements

Project Description

US Highway 93 (US 93) is an important highway corridor and supports local, regional, and nationwide transportation. The Ninepipe segment extends from Reference Post (RP) 40.0 to 44.5 south of Ronan, MT in Mission Valley. The corridor is situated in a highly sensitive ecological and cultural environment through federal and tribal lands designated for wildlife management, environmental protection, and cultural preservation. Improvements to the corridor are needed to address poor existing traffic operations, projected increases in traffic volumes, multiple safety concerns, and a lack of dedicated pedestrian and bicycle facilities.

Building from an alternative identified in previous environmental documentation, RPA worked collaboratively with the Montana Department of Transportation (MDT), the Confederated Salish and Kootenai Tribes (CSKT), and multiple environmental resource agencies to identify a feasible reconstruction concept that would optimize benefits and reduce impacts. The study evaluated geotechnical constraints, hydraulic considerations, wetland impacts, cultural influences, and right-of-way needs to evaluate improvement options in terms of impacts, construction costs, and feasibility considerations. Findings from this study will be used to assist MDT in project development decisions and will support a future environmental re-evaluation.

Project Details​


Montana Department of Transportation