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Guernsey Dam, Wyoming

REASON FOR PHOTOGRAMMETRY: To determine the extent of concrete deterioration at Guernsey Dam’s south spillway y tunnel. Defining the damaged area and depth saved several million dollars.

PEOPLE INVOLVED: Joe Kottenstette, 303-445-2966

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 how we evaluate issues that are affected by these measurements. These methods have
improved both the quality and quantity of data that we obtain, enhancing the ability to visualize complex geometry and evaluate related issues.

We have applied photogrammetric measurement projects to geologic and topographic mapping of exposed abutments, excavated foundation surfaces, monitoring of rock erosion, concrete spalls, changes to sediment beds of scale models as they are exposed to various stream flow conditions, and joint surface roughness measurements.

This paper presents an example of concrete spall measurements at the Guernsey Dam’s south spillway. The spillway tunnel was being evaluated for possible use after being abandoned 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 several million dollar price tag forced Reclamation to quantify the extent of the damage and evaluate the need for repairs. We used photogrammetric methods 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.

Accurate 3d model cansometimes be developed without survey control. The known orientation and length of the 6 foot ruler in this image was used to orient the photogrammetry model in 3d space.


Guernesy intake\

Photos of the Guernsey intake shaft.

Model of the Guernsey intake

Model of the Guernsey intake shaft.


Camera positions at Guernsey tunnel

Schematic for overlaying photos for the Guernsey tunnel.

showing damage


Photo showing damage at the Guernsey intake.  Photos in the tunnels used a boat with two flash points.


model shot

Analysis of photos showing the tunnel walls.


Contact Bryan Simpson, 303-445-3094, for more information on photogrammetry at Reclamation.