ROCKFALL HAZARD RATING SYSTEM

Many miles of highway pass through terrain with adjacent rock slopes that are subject to rockfall, which is due in part to construction practices in the past that relied on overly aggressive excavation techniques. Although these techniques facilitated removal of broken material, they commonly resulted in slopes more prone to rockfall. The Rockfall Hazard Rating System (RHRS) is intended to be a proactive tool that allows transportation agencies to rationally address their rockfall hazards instead of simply reacting to rockfall accidents. The RHRS provides a defensible, standardized way to spend the limited construction funds available by numerically differentiating the apparent risk at rockfall sites. The Oregon Department of Transportation (ODOT) began developing the RHRS in 1984. Funding from an FHWA-sponsored Highway Planning and Research (HPR) grant allowed ODOT to complete development of the system and test it at over 3,000 sites. Much of the RHRS's rating is subjective. Proper training in RHRS application is necessary to ensure the consistency of ratings between different raters. The responsibility for slope evaluations and design concepts should rest with experienced individuals. ODOT's staff of engineering geologists have demonstrated that reasonable and repeatable slope ratings can be achieved.