Envision rating system applied to vehicle access restoration on a low-volume road in USA

Abstract

An unpaved, 4·2 km, single-lane road provides access to fire department facilities in mountains adjacent to urban Los Angeles, California, USA. Severe storms in 2005 blocked the road in many places, with widespread shallow slides and a few major slope movements up to 90 m wide and 120 m high. Repair measures considered for restoring vehicle access were expensive and likely to be damaged by future slope movements. About two-thirds of the road is located on an ancient 280 ha landslide. Safety factors required for typical public works projects were unattainable, so the selected restoration objective was repairable deformation passable by field vehicles. The two worst locations were repaired in 2009 with gabion baskets and welded-wire walls. Material quantities from preliminary designs were used with field engineering during construction. Vehicle access to the remainder of the road was restored as routine maintenance by fire department personnel and equipment. Sustainability elements in all five categories of the 2011 Envision rating system were applied retrospectively to the restoration project, including preserving historic and cultural resources, addressing conflicting regulations, reducing excavated materials taken off-site, avoiding unsuitable development on steep slopes and preparing for long-term adaptability.