Between October 1 and December 31, 2012, the Historic Columbia River Highway will be closed to all traffic between Larch Mountain Road and Latourell Road during restoration of portions of the highway and viaduct at Crown Point. The popular Vista House at Crown Point will also be closed during this time. The almost 100-year-old viaduct and its 29 support columns and related retaining walls are in need of significant repairs and strengthening. In addition to restoring the viaduct, the work will include rehabilitation of the curb and gutter, repair of several areas of slope instability, and removal of old pavement overlays and installation of new pavement between East Larch Mountain Road and Latourell Falls Bridge. The historic highway is one of only two roads in the United States designated as a National Historic Landmark, National Scenic Byway, and National Historic District.
As a subcontractor to David Evans and Associates, Inc., GRI provided geotechnical services to develop design alternatives for restoring the viaduct, which will include new foundations; repair, replacement, or improvement of retaining walls; and new roadway pavement. Our work included review of available information for the structure, a site reconnaissance, preparation of an exploration work plan, and subsurface explorations in a sensitive environmental and scenic area. The challenging site conditions and project requirements have given rise to innovative and cost-effective solutions that will extend the life of this remarkable facility for at least another 50 years.