SSI was brought in to provide a condition assessment of the pipe. After the initial cleaning, the sonar inspection showed the flows were still restricted to 45%. A second cleaning was undertaken after which SSI found flow obstruction was less than 7%. SSI’s inspection documented little structural damage. With the siphon condition documented, a spot repair to the northern elbow was preformed, avoiding a 30 million dollar six month replacement cost in one of Seattle’s busiest most congested traffic areas.

Sonar Profile Calculations

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Sonar profile calculations of obstruction before and after cleanup of Montlake siphon - a sediment peak was found at chainage 258 ft.

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SSI can create "As Built" drawings to give precise calculations of erosion and damage to pipelines.

3D Images

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The right photo above was taken of the Montlake siphon opening. The sonar 3D visualization is a digital image of the same siphon below waterline looking down to the siphon elbow. Note: the ragging on the ladder rungs in the 3D image.