The parents of Peter Terbush who died after a rock fall at Yosemite's Glacier Point are suing the National Park Service in a $10-million wrongful death lawsuit. Jim Terbush, Peter's father, a climber himself, contends that the rock slide was the fault of the National Park Service who allowed bathroom water to overflow from old bathrooms and sewage pipes at the top of the cliff. Geologist Skip Watts theorises that water from a 300,000-gallon storage tank pooled in fractures and put pressure on the rock, acting like a lever to start a slide. Gerry Wieczorek of the U.S. Geological Survey contends that the theory cannot be proved or disproved and that most of the 500 slides in Yosemite since 1850 have been caused by the effect of the freeze-thaw cycle, heavy rainfall and earthquakes. Jim Terbush started his lawsuit after Yosemite National Park redacted a dozen key documents he hoped would answer questions about what happened.