Laura Jo Welter, The Triplicate

As a geologist, I have worked in mineral exploration for 34 years in the North Fork, Middle Fork and South Fork canyons of the Smith River and along most of the ridges bordering Highway 199 from the Collier tunnel northeast to Cave Junction.

The Middle Fork Canyon of the Smith River along Highway 199 sits on top of an active crustal zone. It lies over an ocean plate, which is being pulled under the continent by the forces of continental drift beneath our coastal region.

The undercut slopes along Highway 199 that were necessitated by the construction of the current road have left the inner canyon walls of the Middle Fork of the Smith River in extremely precarious condition.

We can count on the geologic forces beneath the canyon walls to stay

predictable and stable for Highway 199 to remain open as our major

connection to the interior and Interstate 5 to the east. But what could

happen if the area beneath Highway 199 were subjected to forces

unprecedented since its completion, a mere second ago in geologic time?

Let us take a look at an article from the Crescent City Courier

newspaper dated Nov. 29, 1873 (long before the completion of modern

Highway 199):

Great earthquake

A few minutes before 9 p.m. on the 22nd. Fire bell and City Hotel

bell rang on their own bewildering everyone. Everyone rushed to the

streets (in) a bewildering state. Nearly all chimneys in Smith River

Valley shaken down. Shock most violent in the sand hills, cracks 6 to 8

inches wide appeared. The ground cracked at Low Divide and on the

Gasquet Trail. Several brick buildings in Crescent City were damaged.

Half of the chimneys in Crescent City were damaged or shaken down. The

shock at Happy Camp lasted 25 seconds. Hanging pails swung at a 45

degree angle.

In addition, a 1993 summary from the U.S. Geological Survey website reported the following:

All chimneys were knocked down in the Smith River valley. Chimneys

also fell at Crescent City and hardly a brick building in town escaped

damage. Chimneys were damaged in many places as far north as Port

Orford, Oregon and east to Jacksonville, Oregon. Cracks in the ground

were observed on the trail from Crescent City to Gasquet in Del Norte

County. Felt south to San Francisco and north to Portland, Oregon.

This region has not experienced a seismic event of this magnitude

since 1873 and notably not since the completion of modern Highway 199. A

recurrence of such an earthquake in the region is inevitable - it is

only a matter of time.

A recurrence today would likely result in massive slope failures

along the undercut slopes bordering Highway 199. More undercutting and

back cutting as proposed in the current Highway 199 STAA proposal would

further destabilize the canyon walls and increase the probability and

severity of landslide occurrences.

The South Fork Smith River canyon is still recovering from landslides

which blocked the entire flow of the upper South Fork of the Smith

River on two occasions: the first filling the river bed below

Rattlesnake Lake on Dec. 28, 1965 and the second repeating the same

damage on Jan. 24, 1970.

Both slides created temporary lakes behind enormous debris dams that

filled the bed of the upper South Fork with approximately 4 million

cubic yards of landslide debris, wiping out the road and burying acres

of critical anadromous fish habitat. For these obvious and consequential

reasons, it is imperative that the proposed Highway 199 STAA project be

not approved.

David Rhodes is a geologist living in Crescent City.