A resilient coastal connection that puts people first

Delivering a continuous Class I multi‑use trail between Eureka and Arcata presented a combination of physical, environmental and operational constraints. The alignment is tightly bound by US Highway 101 on one side and active railroad infrastructure and coastal wetlands on the other, leaving little room for error. Large sections of shoreline had a history of flooding, erosion and structural degradation, placing both existing infrastructure and future trail users at risk. 

A critical obstacle was maintaining uninterrupted trail continuity across Eureka Slough without forcing users into high‑risk highway crossings. Replacing the existing railroad bridge was not viable due to cost, environmental impact and the need to preserve rail operations. 

Subsurface conditions added further complexity. Soft bay margin soils required careful geotechnical solutions to manage settlement and long‑term performance, particularly for new bridge structures and raised corridor sections. All works had to meet modern safety and ADA accessibility standards along the full 4.25‑mile corridor, while navigating complex permitting and construction sequencing within environmentally sensitive areas.  

We treated the trail as a regional transportation facility rather than a recreational add‑on. Our team combined transportation design, structural and geotechnical engineering, coastal and shoreline protection, drainage and hydraulics and environmental coordination into a single, cohesive delivery strategy. 

To maintain continuity across Eureka Slough, we converted an existing 725‑foot active railroad bridge to cooperative rail‑with‑trail use. This avoided full bridge replacement, preserved rail operations and delivered a safe, uninterrupted crossing for trail users.

We addressed flood risk and long‑term resilience by repairing approximately 6,600 feet of shoreline revetment and raising roughly one mile of railroad prism in the most vulnerable reach. Working within historical footprints, these interventions restore protective function while limiting environmental impacts.

Throughout the corridor, we applied context‑sensitive geometry, carefully managed grades and cross slopes and designed typical sections with sufficient width and shoulders to support mixed speeds and high user volumes. The result is a fully separated, ADA‑accessible facility engineered for durability, safety and long‑term performance in a demanding coastal environment.

Safely connecting Eureka and Arcata for the first time, this continuous 4.25‑mile Class I multi‑use trail transforms a previously unsafe route that relied on highway shoulders into a predictable, low‑conflict corridor for people walking, cycling and travelling with mobility aids.

Beyond mobility, the project strengthens coastal resilience by stabilizing vulnerable shoreline segments and improving flood resistance along a critical transportation corridor, supporting both trail users and adjacent infrastructure as sea levels rise and extreme weather events increase. 

The project opened to the community in June 2025 and has been recognized as the ASCE 2026 Outstanding Bikeways and Trails Project of the Year.

As a completed link in regional and statewide trail networks, the corridor expands access to the Humboldt Bay shoreline for more connected communities. It demonstrates how thoughtfully engineered active transport infrastructure can function as essential public infrastructure, delivering safety, accessibility and long‑term resilience in even the most constrained environments.

As cities rethink how people move, we’re working with teams facing similar challenges. Learn more about our work in transportation infrastructure.