Ko Road Preliminary Rockfall Hazard Assessment and Mitigation Design

Hawaii Department of Land and Natural Resources (DLNR)

Hanapepe, Kauai, Hawaii

Ko Road

Hart Crowser completed a preliminary rockfall hazard assessment of an approximately half mile long cliff-adjacent section of Ko Road that traverses DLNR lands and are now nearing completion of final rockfall mitigation design for the project. After at least two rockfall events affected the roadway, DLNR contracted with Hart Crowser to conduct a preliminary evaluation of rockfall hazard through this road segment. We found a significant public safety risk and recommended mitigation measures be designed to reduce the risk to acceptable levels. Using state of the art photogrammetric methods, we completed 3-dimensional analyses of rockfall risk and design mitigation measures to address the risk. The measures are not yet finalized, but will include netting for the most hazardous portion of the project, and may include future fencing for areas of lesser risk. In addition to our remote modeling, we completed rappelling traverses down the cliff face to confirm the remote sensing data. Our work necessitated coordinatinof several non-technical, but critical tasks, including traffic control, coordinating access through private lands to the cliff top, and communicating with local public school personnel to ensure our work did not adversely affect operations of the adjacent school. Our design work currently includes civil support from Lyon Associates and survey assistance from Esaki Survey. We are developing a full set of plans and specifications for construction in 2015/2016.