Together is Better – Complimenting Assessments Utilizing Rope Access and Unmanned Aerial Vehicles

Inspecting and documenting dams, spillways and appurtenant structures has various challenges including access to the dam, obtaining accurate measurements of observed deficiencies, and documenting findings accurately so the information can be used and repeated during future assessments. The purpose of this presentation is to provide benefits and drawbacks of two specific inspection techniques including rope access and unmanned aerial vehicles. The goal is to conclude that utilizing the two techniques together produces the best of both worlds and eliminates the drawbacks for the two. Utilizing the two methods in conjunction will reduce overall costs to dam owners and also provide high level data that can be repeated in order to inform owners of potential risks and deficiencies which may become a dam safety concern. The presentation will include several case studies including the following:
The City of San Diego Murray Dam: The team mobilized the UAS team to gather imagery and LiDAR of the multi-arch dam data in order to aide in the creation of a Bentley model of the exposed upstream and entire downstream portion of the dam. The data from these flights was run through HDR’s artificial intelligence crack detection software to aid the engineers with identifying and cataloging possible defects in the structure. These results from the UAS developed model assisted the rope access team by allowing them to focus their follow-up inspection efforts on features determined to be high priority. Many of the interior components of the dam structure were very restrictive from a rope access standpoint and the high resolution imagery was crucial for cataloging areas of interest.
City of San Diego Morena Dam: The rope access and UAS team deployed at the same time to inspect the upstream concrete face of Morena Dam. The UAS team collected images that were used to create a 3D model as well as a 2D orthomosaic. The orthomosaic was used to digitally catalogue and accurately show the locations of the defects the rope access team observed and noted with their inspections. The main challenge with the assessment was due to the 8-inch upstream concrete facing being constructed via two separate 4-inch pours. The rope access team sounded the entire upstream face and although the face appeared to be in good condition, the face was evaluated to have significant amounts of concrete delamination due to the inadequate bonding between the two separate pours. The UAS and rope access team was able to perform a far superior assessment of the upstream face in comparison to only one method being used.