How another main road to island communities is closed (again) even after wildfire risk has faded

The road to Bamfield, and the Huu-ay-aht and Ditidaht First Nations, is closed for the foreseeable future due to damage by the Mount Underwood fire. A similar thing happened to highway 4 east of Port Alberni in the summer of 2023. The issue is slope instability - but what exactly is that? And how do you repair it?