Route of the Olympian Culvert Evaluation

AESI conducted a comprehensive infrastructure risk assessment for 17 large culverts and tunnels beneath earthen railroad embankments along the Route of the Olympian in Mineral County, Montana. These culverts, originally constructed over 100 years ago by the now-defunct Milwaukee Road Railroad, had not been maintained for more than 50 years, presenting significant structural and hydraulic risks. The purpose of the study was to evaluate geotechnical and hydrologic failure risks and prioritize necessary repairs.

The project involved advanced geotechnical explorations, drone aerial surveys, hydrologic and hydraulic modeling, and slope stability design. AESI utilized Monte-Carlo simulations and numerical modeling to develop a “reliability index” ranking from 0 to 1 for each culvert, providing a data-driven approach to risk assessment. A UAV drone was used to gather 3D topographic survey data in remote areas, while software tools such as Slope/W and HY-8 helped assess the geotechnical and hydraulic reliability of each structure. The final Geotechnical Investigation Report outlined repair prioritization strategies and detailed various rehabilitation options, ranging from cleaning and lining to full replacement using micro-tunneling techniques.

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The project presented unique challenges due to the age and deteriorated condition of the culverts, the lack of prior maintenance records, and the complexity of assessing massive earthen embankments. Additionally, the remote location and varying terrain required innovative survey and modeling approaches to accurately evaluate structural integrity and failure risks.

AESI’s analysis provided a clear and systematic approach to culvert remediation planning. The final report delivered prioritized repair recommendations based on geotechnical, hydraulic, and structural risks, giving USFS Region 1 a valuable tool for phased infrastructure improvements. By integrating advanced modeling techniques and risk-based evaluations, AESI ensured that repair efforts would be strategically targeted to maximize safety and cost-effectiveness.

“[AESI] professionally provided insightful, effective, and efficient engineering innovations that achieved or exceeded all needs and expectations. The product of this effort is a report with clear narrative, colored tables, and graphic displays that is immediately a very constructive tool for managers to being remediation planning.” – Traci Sylte, USFS