Thunder Creek Bridge Replacement (2005)

North Cascades National Park Service Complex » Thunder Creek Bridge Replacement (2005) » Document List

The former Thunder Creek suspension bridge was destroyed by flooding in October 2003. In 2004, the NPS removed the remains of the bridge (except for the concrete abutment on the east bank) and began a planning process (Environmental Assessment) to evaluate bridge replacement options with the goal of providing visitors in Ross Lake National Recreation Area with a safe, sustainable means of access to the popular Thunder Creek Trail.

The Plan / Environmental Assessment that was completed for this proposal considered three alternatives: (A) No Action- -Do not rebuild the bridge; (B) Preferred Alternative- -Rebuild the bridge approximately 0.5 mile upstream from the former bridge site at a location more secure from flooding; and (C) Retrofit the the North Cascades highway bridge over Thunder Arm (Diablo Lake Reservoir) with an all-purpose walkway as a means of getting visitors to the eastern side of the Thunder Creek valley, which would include construction of a 1.5 mile new trail up the eastern side of Thunder Arm. Under all alternatives, the remains of the former bridge, including the concrete bridge abutment on the east bank, would be completely removed and the bridge site would be rehabilitated.

On April 25, 2005, the Superintendent of North Cascades National Park Complex and the Regional Director of the Pacific West Region, National Park Service signed the Finding of No Significant Impact (FONSI)/decision document for this EA, identifying alternative B as the selected alternative for implementation.

This alternative, implemented in Spring 2005, reconstructed a new, single span steel bridge with wooden decking approximately one-half mile upstream from the former bridge. This location minimizes the risk of future flood damage by securing the bridge on upland bedrock and riverine terrace landforms that are less susceptible to flooding. A 0.5 mile extension trail was also built from the former bridge site to the new bridge site.

Enclosed within the documents section of this webpage is the full environmental assessment and the Finding of No Significant Impact.

Contact Information

Elly Boerke, Environmental Protection Specialist