Toutle River View from Old Pacific Highway 99 Bridge

The Washington State Highway 99 (Old Pacific Highway) Bridge survived the May 18, 1980 lahar. Here, the front of the mudflow from the South Fork Toutle River passed by at about 1:00 p.m. P.D.T. on May 18; the mudflow from the North Fork of the Toutle River arrived at about 8:30 p.m. High-mudflow marks may still be visible on nearby trees. Houses rafted on the lahar surface crashed into the bridge superstructure. Water temperature here was 91 degrees F (33 degrees C) at 9:45 a.m. May 19. Peak floods probably arrived here around 10:00 p.m. May 18, fourteen hours after the 9:32 a.m. eruption.

-- Excerpt from: Doukas, 1990, Road Guide to Volcanic Deposits of Mount St. Helens and Vicinity, Washington: USGS Bulletin 1859, 53p.