You may have noticed some big grooves out on the East Wall. These were formed during a major debris flow and flood event July 28, 1999. That year, April through July precipitation was 49% above normal. Particularly heavy rainfall in late July had completely saturated the soils. A powerful thunderstorm July 28 overwhelmed many areas creating significant debris flows and flooding at A-Basin, the Loveland Pass area, and along I-70. Debris flows closed the interstate. The ski area suffered extensive damage to its parking lots and base area facilities. It was a notable event and deeply impressed those who experienced it.