4.3.2.2 2 Risk-Based Rock-Fall Management Program

Risk-Based Rock-Fall Management Program / Colorado DOT

Colorado DOT responds to between 50 and 70 geotechnical emergencies a year. The traditional approach to managing rockfalls was based on the size and frequency of rockfalls. This approach did not consider the criticality of the facilities that could be impacted by a geohazard event. Since 2013, the Colorado DOT has used a risk-based approach to evaluate and prioritize geohazard mitigation activities based on the size of the geohazard areas and the frequency of falls. Colorado DOT’s approach includes a measure of Risk Exposure (RE), which is based on three components:

• Average Annual Daily Traffic (AADT).
• Likelihood of a Vehicle Being Affected by a Geohazard Event. This metric considers site-distance, the number of previous rock-fall accidents, and a measure of how frequently a vehicle is below the hazard on a daily basis.
• Reduction Factor. This considers the effectiveness of prior mitigation actions, to reduce the RE score.

Colorado DOT’s geohazards program uses the RE to allocate an annual budget of about $10 million to manage geohazards. Due to the inherent uncertainty of geohazard management, in addition to the geohazard management program, maintenance staff regularly patrol highways known to have geohazards. If a hazard requiring immediate action is identified, maintenance crews respond promptly. Using the RE for prioritization allows Colorado DOT to focus its efforts on reducing the impact of geohazards on users of the highway system.