SEAS was contracted by the USACE Nashville District through the Huntington District to provide topographic and hydrographic mapping and horizontal and vertical control surveys at Dale Hollow Lake Dam and Powerhouse in north central Tennessee. The survey included:

• Inland Hydrographic utilizing Multibeam (MB) and high-resolution side scan sonar surveys above and below the dam, power plant headrace, and tailrace
• Topographic Surveys utilizing Terrestrial LiDAR scanning of downstream side of dam, stilling basin, 1000’ of river shoreline and tailrace
• Control recovery of existing control marks and set one (1) new mark. Performed GNSS static observations and second order leveling to update / establish horizontal and vertical control around the dam site.

CONTROL SURVEY: SEAS personnel observed primary control marks for 5+ hours on two different days in different quadrants of the day. Secondary control marks were located via RTK observations, multiple times. Elevations were established on all control marks via second order leveling with a digital level. Primary control marks were published using NGS OPUS share. USMARTS and control cards were created for all marks.

TOPOGRAPHIC SURVEY: A FARO Focus 3D X330 Terrestrial Laser scanner was used for topographic data collection below the dam. Scans were performed on the shoreline, stilling basin, downstream side of dam, and all structures associated with the dam. SEAS used GPS and a Robotic Total Station to survey in sufficient control to register the scan point clouds. Scan target spheres on bipods were setup on control points during the scans.

INLAND HYDROGRAPHIC SURVEYS: MB and side scan data was collected in an area 700’ x 3,000’ above the dam and from the dam to 1,000-feet downstream. SEAS coordinated with the dam personnel to raise the lower pool during the hydrographic data collection and lower the pool during the topographic LiDAR data collection, which provided maximum coverage between the hydrographic and topographic data sets. All positioning data was Post Processed Kinematic (PPK).

DATA PROCESSING & DELIVERABLES: Scans were processed with FARO’s SCENE software. Certainty 3D TopoDOT in MicroStation was used to extract 3D point and vector information from the LiDAR point cloud. A 3D model file was created which contains the dam, powerhouse, survey control marks, survey data, etc… The edited, thinned multibeam data and the key 3D terrain points extracted from the LIDAR were imported into MicroStation. The multibeam data below the dam was combined with the 3D terrain points from the point cloud to create a surface of the Obey River and tailrace area (1’ Contours). Another surface was generated with the multibeam data above the dam and a model of the upstream face (although not required, an extra model was provided, adding value provided by SEAS).