ASI Group

Narrows Dam: A Comprehensive Plan for Data Collection

3D image of dam and surrounding area

ASI Marine (ASI) was contracted by Cube Yadkin Generation, LLC (an affiliate of Eagle Creek Renewable Energy) to provide underwater inspection services at the Narrows Dam complex located in Troy, North Carolina. ASI utilized remote inspection technologies to assist the Dam Safety Team in gathering data to satisfy regulatory requirements. To meet the client’s needs, ASI responded to the inquiry by developing a comprehensive plan to collect all pertinent data points in a format that would allow for accurate future comparisons. The scope included collecting information relative to the general condition of the Tailwater, Tailrace, and the Bypass Spillway Plunge Pool as well as performing an internal inspection of four penstocks.

The data ASI provided improved our understanding and interpretation over historic collection methods.

Chief Dam Safety Engineer, Eagle Creek Renewable Energy

Each area to be inspected required its own methodology for collecting data. Using a custom sensor suite at the Tailwater and Tailrace, ASI was able to deliver clear elevation along the river bottom and show the irregular shape on the east end. Cross-sectional profiles were collected to confirm that no undermining was present. Despite the challenges in accessing the Bypass Spillway Plunge Pool, ASI was able to collect geo-referenced point cloud data to record erosion and undermining. Within the penstocks, ASI measured the thickness of the steel at specific locations and recorded any anomalies, debris, or sediment accumulation.  

two technicians setting up surveying equipment along dam
ASI technicians quickly mobilize to the site and set up their equipment

The final written report and processed inspection data, in combination with future inspection deliverables, provides stake holders with a clear picture of the rate at which erosion is occurring and assists in the development of maintenance and repair methodologies. The high accuracy of this data provides the client with geo-referenced point cloud data of the erosion and undermining which can be monitored into the future. Previous technology applications were limited in repeatability and accuracy.

3D point cloud data bathymetric image side view of plunge pool
Bathymetric image showing a side view of the plunge pool

Deliverables to the client included edited inspection video, processed 3D point cloud data, bathymetric color contour maps, 2D mosaic imagery, inspection images and cross-sectional profiles. ASI was thrilled to hear from the client that, “The data ASI provided improved our understanding and interpretation over historic collection methods.”

A case study of the Narrows Dam investigation will be presented in greater detail in September at ASDSO’s 2022 Dam Safety Conference at Baltimore Convention Center in Maryland. To join our live presentation, register for the event here.

If you want to learn more about our data collection methods, contact us today.