A long-proposed extension of SR 504 to the eastern side of the Mount St. Helens area gained traction in the early 2000s, sparking outcry from scientists and environmentalists. The route, connecting Coldwater Lake to the existing Forest Highway 99 near Windy Ridge and beyond to Forest Highway 25, was supported by officials from Cowlitz and Lewis counties as a tourist draw and a potential evacuation route. WSDOT studied several options for the proposed highway, which enjoyed mixed public support, and estimated a cost of $18.5 million to construct one option and $44 million for another (equivalent to $ and $, respectively, in 2019 dollars). The proposed highway was rejected by state legislators due to its cost, despite attempts at salvaging the cheaper proposal by converting it into a toll road.