The Use of Lidar in Mapping and Assessing Bedrock Foundations-Paper

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USACE geologists used a Trimble SX-10 scanning total station to document bedrock foundations during Phase 5 construction of Bluestone Dam’s modified stilling basin in Hinton, West Virginia. The work addressed the need for accurate geological records while minimizing the time vulnerable bedrock remained exposed to weathering, seepage, and potential scour.<br /><br />The team collected high-density LiDAR point clouds, imagery, and survey data from foundation floors and sidewalls. After removing non-geological objects from the scans, they produced orthophotos, topographic maps, excavation reports, and 3D models. Geologists mapped geological features and contacts in the field using printed orthophotos as a guide, improving spatial accuracy and eliminating the painted or stringed grids used in previous projects. Senior geologists reviewed maps before foundations were approved for concrete placement.<br /><br />From 2022 to 2023, the method was applied to 19 apron monoliths, three divider-wall monoliths, and eight key sections. It documented more than 73,000 square feet of foundation and over 7,000 square feet of sidewalls. The resulting digital products provide a detailed record for construction reporting and future dam-safety evaluations.<br /><br />The approach was implemented at relatively low cost using equipment and survey expertise already available to the district. Experience showed that scans were clearer when taken from elevated viewpoints and when each monolith was fully closed to construction activity during scanning. Standing water and limited survey-control visibility sometimes required additional drainage, prisms, or rescanning.<br /><br />LiDAR improved the speed and precision of documentation, but it does not replace a geologist’s field inspection and interpretation. Future work may add tablet-based mapping, automated measurements of geological orientations, and virtual or augmented reality tools for reviewing foundation conditions.
Keywords
USACE
Trimble SX-10
LiDAR
bedrock foundations
Bluestone Dam
stilling basin
geological mapping
point clouds
dam safety
orthophotos