Date: Thursday, October 20, 2016
Location: CCBI Room 115, 626 High Street NE, Salem, OR 97301
Time: 12:00 pm to 1:30 pm
Cost: $15 Professionals, $5 Students
Topic: Spirit Lake Tunnel Repair
RSVP: Please RSVP by 12:00 pm Monday, September 12th. To RSVP, CLICK HERE. The new window that opens up will allow you to register and indicate your preference for paying for the event. You can choose to either pay with a credit card at the time you register or indicate that you will pay at the door (cash only). Please note that all payments are non-refundable after the RSVP cut-off time. While the preferred registration method is clicking the link, we can also accept your RSVP via email at email@example.com or by calling Erik McCarthy at (503) 485-5490.
Background: On May 18, 1980, the Mount St. Helens eruption resulted in one of the largest debris avalanches in recorded history. The debris avalanche blocked the natural outlet of Spirit Lake. To prevent an uncontrolled and catastrophic lake break-out, the U.S. Army Corps of Engineers constructed the Spirit Lake Outlet Tunnel from 1984 to 1985. During original tunnel construction, the greatest difficulty occurred within the 300-foot wide "Julie" and "Kathy L" shear zone complex. During inspections in 2014 and 2015, a 32-foot segment at the upstream end of the complex - which had experienced slow heave in the past - showed an increase in heave of approximately 2 feet, which decreased the hydraulic capacity of the tunnel below acceptable limits.
Working with the U.S. Forest Service (who owns the project and provided funding), the Corps designed a repair using a rib-set shotcrete support system. In addition to removing and arresting the heave, the 2015/2016 repair was sized to be compatible with any future rehabilitation involving stabilizing and re-grading the invert profile of the "Julie" and "Kathy L" shear zone complex. The contract was awarded in September 2015 for $3 million and the repair was completed in March 2016.
Guest Speaker Biography –
Jeremy Britton is the Chief of the Geotechnical, Civil, and Environmental Design Section for the U.S. Army Corps of Engineers, Portland District. He has been with Portland District for 13 ½ years. Britton has a Ph.D. from Virginia Tech in geotechnical engineering and is a registered Professional Engineer in the state of Oregon.