Environmental Assessment: Thunder Creek Bridge Replacement

The former Thunder Creek suspension bridge was destroyed by flooding in October 2003. The remains of the bridge were removed in summer 2004, except for the concrete abutment on the east bank. An EA is currently being prepared to evaluate bridge replacement options. The purpose of the EA is "to provide visitors in Ross Lake NRA with a safe, sustainable means of access to the popular Thunder Creek Trail."

The preferred alternative is to reconstruct a new, single span steel bridge with wooden decking approximately one-half mile upstream from the former bridge. This location would minimize the risk of future flood damage by securing the bridge on upland bedrock and riverine terrace landforms less susceptible to flooding. A 0.5 mile extension trail would also be built from the former bridge site to the new bridge site. Other alternatives under consideration include: (A) No Action--Do not rebuild the bridge, 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. Alternative C would also include construction of a 1.5 mile new trail up the eastern side of Thunder Arm. The trail would reconnect with the existing Thunder Creek trail in the vicinity of the Thunder backcountry camp.

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.

Document Content:

Thunder Creek Bridge Replacement   (2.9 MB, PDF file) Disclaimer: Links within the above document(s) were valid as of the date published. Note: Some of the files may be in PDF format and can be viewed using the Adobe Acrobat Reader software. You may download a free copy of from Adobe Systems.