Use of Photogrammetric Measurements in a Concrete Damage Survey: Guernsey Dam South Spillway: Fid-Bau Portal

Use of Photogrammetric Measurements in a Concrete Damage Survey: Guernsey Dam South Spillway

Kottenstette, Joseph

The Bureau of Reclamation (Reclamation) uses close-range digital photogrammetry to obtain three-dimensional (3D) digital measurements. The rapid acquisition of photographs and the effectiveness of the photogrammetry software has revolutionized the evaluation of issues that are affected by these measurements. These methods have improved both the quality and quantity of data obtained and enhanced the ability to visualize complex geometry and evaluate related issues. Reclamation has applied photogrammetric measurement technology to obtain geologic and topographic mapping of exposed abutments and excavated foundation surfaces, to measure joint surface roughness, and to monitor rock erosion, concrete spalls, and changes to sediment beds of scale hydraulic models as they are exposed to various stream flow conditions. This paper presents an example of concrete spall measurements at Guernsey Dam's south spillway. The spillway tunnel was being evaluated for possible use after being unused for many years. Initial judgments indicated a need to replace a significant portion of the tunnel lining after years of freeze thaw damage. The damaged area and depth were not well-defined, and the high cost associated with replacing a significant portion of the tunnel lining justified additional study to quantify the extent of the damage and evaluate the need for repairs. Photogrammetric methods were used to develop an accurate, scaled 3D model of the tunnel lining. This resulted in a better evaluation and, more specifically, quantified the areas needing repair, leading to a much less expensive solution.