In response to flood damage along Tacoma Rail’s Mountain Division Line near Elbe, Washington, our team conducted a comprehensive field assessment, structural inspection, and conceptual engineering analysis. This included a Type, Size, and Location (TS&L) study that outlined three potential alternatives for replacing the storm-damaged Nisqually River Trestle.
- Assessment Findings: The TS&L study confirmed the need to replace both end abutments, regardless of the selected bridge design. We explored both single-span and multi-span configurations, considering materials such as steel and concrete, along with open-deck and ballasted-deck options.
- Conceptual Engineering and Analysis: Using in-house railroad bridge design tools and AREMA design standards, our team developed conceptual designs for the three most viable bridge alternatives. These designs accommodated a Cooper E 80 live load suitable for diesel locomotives, with cost estimates derived from WSDOT’s Bridge Design Manual and data from the National Railroad Construction and Maintenance Association.
- Preferred Alternative Selection: After careful analysis using a decision matrix, we selected a two-span steel plate girder bridge as the optimal solution. This choice balanced cost-efficiency, hydraulic performance, and minimized environmental permitting challenges.
Final Design and Construction Planning:
Our team finalized the design, preparing construction plans, specifications, and detailed cost estimates. The project involved constructing two new spans with abutments and required over 1,500 cubic yards of riprap fill along the Nisqually River.
Environmental Compliance and Permitting:
Leading the environmental compliance process, our team facilitated coordination with regulatory agencies to ensure streamlined permitting. The project qualified for the Nationwide Permit Program, thanks to early engagement with the US Army Corps of Engineers, expediting the project timeline.
Through strategic design and environmental planning, this project restored a vital rail connection with a cost-effective, environmentally sound solution tailored to the unique challenges of the site.
