Investigation of the December 12, 2013, fatal rock fall at 368 West Main Street, Rockville, Utah

Book excerpt: On the afternoon of December 12, 2013, a large, joint-controlled block of the Shinarump Conglomerate Member of the Chinle Formation, with an estimated volume of almost 1400 cubic yards and weighing about 2700 tons, detached from the cliff face at the top of the Rockville Bench in Rockville, Utah. The block fell on to the steep Moenkopi Formation slope below the cliff, and shattered into numerous cobble- to very large boulder-sized fragments. The fragments moved rapidly downslope before striking and destroying a house, detached garage, and car at 368 West Main Street in Rockville. The two occupants in the house were killed. The purpose of this 20-page investigation wast to document the characteristics of the fatal rock fall; evaluate future rock-fall hazard at and near the site; and provide recommendations for homeowners, the Town of Rockville, and other officials to consider in managing rock-fall risk. Although the first fatal event, this rock fall is the sixth large rock fall within the Town of Rockville in the 35 years prior to December 12, 2013. Five of those events occurred within the past nine years, and at least three of those struck and damaged structures at the base of the Rockville Bench.