Toutle River "Coal Banks" Bridge

Looking upstream at the new Coal Banks Bridge, after previous bridge was destroyed on May 18, 1980.
USGS Photo by Lyn Topinka, April 4, 1983

"Coal Banks" bridge is the local name for the bridge that crosses the Toutle River about a mile (1.6 kilometers) northeast of the town of Toutle (about 31 miles or 50 kilometers downstream from the volcano). It was probably named for the lenses of soft coal that crop out slightly downstream in landslide blocks derived from the Toutle Formation (upper Eocene to Oligocene). The bridge is a short distance downstream of the confluence of the North Fork and South Fork Toutle Rivers. An earlier bridge here was destroyed by the 1980 North Fork Toutle lahar when logs jammed beneath it and it floated off its foundation. The bridge was rebuilt so that the roadway is higher than the previous bridge. This was accomplished by extending the original bridge piers, which survived passage of the lahar.

-- Excerpts from: Pringle, 1993, Roadside Geology of Mount St. Helens National Volcanic Monument and Vicinity: Washington Department of Natural Resources, Division of Geology and Earth Resources Information Circular 88

"Coal Banks Bridge" on May 18, 1980

Downstream (at 10 o'clock) is the location of the gaging station where mudflow marks were as high as 53 feet (16 meters) above the gage datum, about 39 feet (12 meters) higher than the South Fork Toutle River lahar. About 0.8 miles (1.3 kilometers) downstream is a constriction in the Toutle River valley, probably the cause of blockage and subsequent ponding of the North Fork Toutle River. Peak flow probably occurred at 7:00 p.m. P.D.T. May 18. Just downstream of Washington Highway 504 is Outlet Creek, which drains Silver Lake. Upstream (1:00 o'clock), to the left, is the North Fork Toutle River, and to the right (2:30 o'clock) is Mount St. Helens, and in the middle ground is Harry Gardner Park (2:30 o'clock). Upstream in the high west bank are lahars and fluvial deposits of the Pine Creek eruptive period overlying deposits of the Smith Creek, Swift Creek, and Ape Canyon eruptive periods. Both bridges, here and about one mile (1.6 kilometers) SE, over the South Fork Toutle River, survived the South Fork Toutle River lahar. Later, at 6:10 p.m., the North Fork Toutle River lahar destroyed the Washington Highway 504 bridge.

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