Cal Engineering & Geology was retained by San Mateo County Department of Public Works as part of our on-call contract to investigate an emergency landslide, with a 50-foot portion of Old La Honda Road slipping down the hillside.  When called to the site, CE&G prepared a topographic survey utilizing an Unmanned Aerial Systems (UAS) drone program for the acquisition and analysis of high-resolution orthoimagery and high density, photogrammetrically derived point clouds.  Utilizing this data, a geotechnical and geologic investigation was performed for the hillside failure.  Geotechnical design recommendations were developed for a soldier beam and lagging wall to restore cross-sectional roadway width and locally stabilize the hillside slope.  CE&G then prepared a plan set with specifications for construction of the retaining wall.  Since access to the site was difficult with narrow roads and tight turns, the foundation for the soldier pile wall consisted of drilled pier anchored into the existing bedrock utilizing both a rebar cage and soldier beam as pier reinforcement.  CE&G also provided submittal reviews, responded to contractor requests for information, and provided construction observation and testing services.