Spirt Lake Tunnel Repair Survey at Mt. St. Helens

January 22, 2016

Our Professional Land Surveyors are establishing survey control in the Spirit Lake Tunnel and marking the locations for the work to take place using robotic total station survey equipment. The Tunnel Alignment will then be reproduced to include a control map listing the record, as-measured control points, and the alignment of the tunnel stationing. This project is 6,000 feet into the tunnel, and will result in finalized as-built drawings for the 60' repair area. The unique nature of the work is based around its location and the schedule; work in a tunnel that is always wet, with running water from 2” to 40” deep, dark, and strongly ventilated is difficult. The crew spent their days a mile and a quarter inside the 11’ diameter tunnel. The remote location is a 2 ½ hour commute from the nearest town. The crew worked Friday-Tuesday, 14 hours each day and our office technical staff worked each evening starting around 8pm when data could be sent in from the remote location. Data was processed each night so new information could be used the next day.  After construction is complete, our consultant (i-Ten Associates) will create a Terrestrial Lidar Scan using a FARO 3d Lidar Scanner of the repair portion of the tunnel. Construction is scheduled to be complete by May 2016. 

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