Overview
- The formation was first filmed by a local boater in mid‑summer and appeared in a Sentinel‑2 satellite image taken July 21, then vanished from some image passes on August 5 before being re‑located near the Ospika inlet on Aug. 31.
- BC Hydro estimates the tree‑covered mat measures about 9,800 square metres and confirmed it remains intact but beached roughly 30 kilometres from its earlier detected position.
- The agency’s leading explanation is that years of stacked logs, roots and vegetation became buoyant when Williston Reservoir reached its highest level since 2012 and spillway releases in June–July mobilized the material.
- Experts point to known precedents for floating vegetative mats that can persist and drift for years, and officials say detection gaps can reflect changes in position or being sheltered against a shoreline.
- BC Hydro is tracking the mass by satellite and overflights, has advised people not to approach because it could break up, and said it is watching for movement that could threaten boaters or reservoir infrastructure.