Mosier Twin Tunnels

Mosier Twin Tunnels

Mosier Twin Tunnels West Portal, ca 1930

Mosier Twin Tunnels West Portal, ca 1930

Mosier Twin Tunnels Walkway, ca. 1930

Mosier Twin Tunnels Walkway, ca. 1930

Mosier Twin Tunnels West Portal, August 1994

Mosier Twin Tunnels West Portal, August 1994


Carrying the Historic Columbia River Highway through headlands between Hood River and Hosier, Wasco County, Oregon; beginning at milepost 72.

Date of Construction

1920, 1921, and 1938


Unknown, maybe John Arthur Elliott, locating engineer, or Conde B. McCullough, Oregon State Bridge Engineer


A. D. Kern, contractor


Oregon Department of Transportation

Present Use

Closed since 1953; reopened to non-motorized traffic in 1995


The only set of highway tunnels with adits or windows in Oregon. One of the few examples of this type of tunnel in the United States.

Mosier Twin Tunnels

In 1914 and 1915, the Hood River and Wasco County courts contracted with John Arthur Elliott, a locating engineer, and his crews to prepare a plan and profile of the proposed Historic Columbia River Highway through their counties. Many voters in both counties were reluctant to spend money on constructing the HCRH, including employing a locating engineer to survey a route. Hood River County only approved their bond issue to cover construction on the condition that local businessman Simon Benson would guarantee to make up the difference it costs overran the bond. Indeed, Benson paid at least $13,000 for costs in Hood River County. Many citizens of Wasco County were equally reluctant to spend their own funds on a new highway. They were satisfied with the present county road system which included grades of up to 18 percent on routes between Hood River and The Dalles.

By late March 1914, John Arthur Elliott reported to Henry L. Bowlby, state highway commissioner, his recommendations for possible road alignments for the HCRH between Hood River and The Dalles. The connection between Hood River and Mosier presented particularly difficult problems. The two alternatives that Elliott put forward included a river route, which followed the general course of the OWRN main line with some variation in elevation to meet certain passes. It was only 5.8 miles long and rose only to an elevation of 160′, and used portions of an abandoned railroad grade. He estimated the construction as quite expensive because of the heavy grading necessary to carry the road around many basalt cliffs.

The second alternative was a route that left Hood River and went over the Mosier Hills separating the two towns. Elliott’s estimation for constructing a hill route noted equally expensive problems. The existing county road east of Hood River ran on grades of up to 12 percent out of the city to an elevation of nearly 1,600′ at the summit, before dropping down into Mosier at grades nearing 18 percent. While he could “develop” road to maintain a grade not to exceed 5 percent out of Hood River by creating a series of loops, he found it difficult to bring the road back down to Mosier because the hillsides sloped toward the river and ended in a high bluff.

Each route had its advantages. The distance between Hood River and Mosier by rail was just over six miles and the proposed river routes for the Historic Columbia River Highway were only slightly longer. The proposed summit route, even at 13 miles, had its advantages also. Elliott believed that in keeping with the practice of advertising the HCRH as a “scenic highway through the Columbia River gorge,” its design should partially to the wishes of tourists. “The aim of a scenic highway . . . is to show the country,” wrote Elliott. He added, “Not a traveler goes through Hood River without wondering where Mount Hood is and the famous Hood River orchards are. To put a scenic highway down in the river where none of this can be seen would be passing a section made up of views which would leave a lasting impression on the traveler.

The route that Elliott proposed as the best alternative for the HCRH from Hood River to Mosier was a compromise. It rose out of Hood River on a 5 percent grade, up into the Hood River Valley as far as the “Gravel Pit,” and above the majority of cliffs along the river to a summit of 1,107′ before descending on a grade not over 5 percent to Mosier, Nevertheless, Elliott’s route was, for the most part, never constructed because it was still too long at 10.7 miles. By late 1916, Elliott left his position with the Oregon State Highway Commission to work as highway engineer for Wasco County. Meanwhile, there was continued skepticism among Wasco County voters about the necessity of any realignment, other than a river route. Some recommended merely adding “heavy” fences to the existing steep county road to “assist poor drivers in negotiating the hill.” Others saw the best and most economical route as the one following the river. By October 1917, the Oregon State Highway Commission prepared yet another route plan, this time under the direction of Roy A. Klein, the new locating engineer for the HCRH.

Klein and his associates eventually founded an alignment that followed the river most of the distance. It was farther away from the OWRN main line than the previous river route to avoid closing the tracks because of rock blasting operations. It reached a summit of 522′ and the distance between Hood River and Hosier was reduced to 6.3 miles, all the while maintaining a grade of 5 percent or less. The most difficult part of this route, riding high above the water-level OWRN main line on cuts and fills as it hugged the curves of the basalt slopes, was to traverse the leading edge of a basalt bench (a portion of the Bingen Anticline) and run east to a gravel mantle. Evidently, Oregon State Highway Department engineers considered a tunnel the most efficient means to accomplish this difficult task. The firm of A. D. Kern, of Portland, received contracts in 1919 to grade and macadamize the Hood River to Hosier section of the Historic Columbia River Highway and to excavate the Hosier Twin Tunnels.

Design and Description

The Portland firm of A. D. Kern was awarded a contract on January 7, 1919 to excavate 2.3 miles of the Historic Columbia River Highway and cut the Hosier Twin Tunnels. It brought in men, horses, and wagons, along with a Bucyrus 18B steam shovel, a Marion Standard-Gauge 6 0 shovel, 3 0 four-yard ore cars and several Ingersoll-Rand air drills. With thirty men, A. D. Kern could move an average of 1,600 cubic yards of material a day.

The Mosier Twin Tunnels (from west to east) consisted of one 81′ bore, 24′ of open space, and one 288′ bore. Total length was 493′, with 369′ of that in bores. The ideal finished dimensions were a vertical clearance of 16′-0″ with an 8′-8″ radius measured from a springline of 7′-4″ from the roadbed. Roadway width was 17′-4″ Two windows measuring 8′ to 10′ were bored in the longer, or eastern tunnel to admit light to the shaft and for travelers to glimpse beautiful vistas of the Columbia River Gorge.

No records exist concerning the actual boring operations on the Hosier Twin Tunnels. Nevertheless, documentation on boring the Mitchell Point Tunnel, some 10 miles west of the Hosier Twin Tunnels illustrates the obstacles encountered by excavators. The tunnels were cut through Columbia River Basalt. The formations encountered at the site between Hood River and Hosier included unstable columnar basalt which had the tendency to cause overbreak when excavators cut the tunnel heading. What John Arthur Elliott, locating and designing engineer, observed when cutting Mitchell Point Tunnel gives insight into the problems A, D. Kern probably encountered cutting the Mosier Twin Tunnels.

The usual process for boring a tunnel was to excavate as far as possible with men and equipment, then cut and remove the heading, and then cut and remove the bench, all the while hoping not to create overbreak, or cutting out more than the dimensions prescribed by the contractor. With bores like the Hosier Twin Tunnels and the Mitchell Point Tunnel, care was taken to prevent a weakening of the outer wall and of taking too much basalt from window openings, or adits. John Arthur Elliott, locating and designing engineer for the Mitchell Point Tunnel observed that the proper combination of firing order, lengths of fuses, and number of sticks of 4 0 percent DuPont dynamite had much influence on how the heading broke. The wrong combination caused much overbreak and could weaken the outer wall.

Immediately after each shot in the heading, which began about 7′ above the roadbed, crews loaded the material into ore cars that were carted off for disposal. Then the roof was trimmed down with hammers and picks to remove all loose material. After this, the bench was removed, and the process started over again until the tunnel was completely bored. Once past the points where adits were intended, crews cut these windows by drilling a hole half way through the wall at the floor of the heading, and then loaded it with just enough explosives to break the hole. Next, workers broke away the loosened rock with picks hammers and small plugs, enlarging the ring until they achieved the desired diameter. This process continued until both tunnel bores were completed.

Care was taken to prevent any debris from rolling onto the OWRN mainline several hundred feet below the tunnel site and throughout the section of alignment extending east and west from the bores. Before blasting, crews constructed rubble walls and timber barricades along the railroad company tracks, at a cost of nearly $3,800, to prevent chunks of basalt from landing on the right-of-way and delaying trains. Even so they probably only made heavy excavations or blasted with dynamite between train schedules. The contractor also had telegraph company and railroad company communication wires removed from poles and buried along side the tracks, at a cost of over $8,200, to prevent damage to them from falling rock. A dispatcher’s box was probably kept near the site to make note of all unscheduled and delayed trains.

As the final phase of construction, a cliff walk was constructed from the area between the two tunnels to the west adit of the east tunnel. It consisted of a walkway with a masonry guardrail, and provided motorists a chance to walk out to the cliff’s edge to glimpse spectacular views of the Columbia River Gorge.

By July 12, 1920, A. D. Kern had completed its contract at a cost of $219,339.57. This included $19,938.60 for the actual tunnel construction; $3,395.05 for rubble wall and rail the observation gallery, and a penalty of $790.50 for overbreak (263.5 cubic yards at $3.00). The rest of the contract covered clearing, grubbing and excavation, and supplies and labor for masonry walls and concrete. All costs for constructing this unit of the HCRH, which included the tunnel and 2.3 miles of grading were paid through state funds.

Repair and Maintenance

Boring the Mosier Twin Tunnels was a monumental task for the Oregon State Highway Department and A. D. Kern. In June 1920, even before the contract was completed, a consulting engineer, Lyman Griswold feared that the shorter, or west tunnel was “a serious menace to travel in its present condition.” He believed that the state needed to enlarge the bore to permit installation of a wooden lining. Soon, the OSHD’s Bridge Department, under the direction of Conde B. McCullough, was preparing plans for lining the west tunnel with concrete and constructing a “monumental” west portal. Meanwhile, by September, Division Engineer H. C. Ingle reported that there was a “big fall of rock” which came out of the west portal of the west tunnel.

At the same time, the Bridge Department was designing a rock catch roof structure for the cliff walk. It was a masonry structure consisting of a windowed wall resting upon the masonry guard rail already in place and a reinforced-concrete roof extending over all of the cliff walk except for the portion laying between the tunnels. The obvious purpose of the rock catchment was to protect pedestrians from showers of rock from the unstable formations on the hill above. There was no provision in September 192 0 plans for a similar structure covering the open roadbed between the tunnels nor the adjacent portion of the cliff walk. Finally, the cliff walk rock catch was never built. Available literature gives no clues concerning discussions among highway department officials regarding this structure. One plan suggests that subsequently the Bridge Department erected barriers and warning signs, along with vertical steel pipes in the adits, in hopes of deterring pedestrians from accessing the cliff walk. However, as late as 1932, after a boy was killed by falling rocks as he stood on the cliffwalk, highway department personnel corresponded about possibly erecting safety barricades.

By late fall of 192 0, the Bridge Department abandoned plans for a concrete lining in the west tunnel when continual rock movement “made a rigid lining inadvisable,” and focused instead on lining the bore with 12″ x 12″ timber sets on 4′-0″ centers, with 4″ X 6″ cedar lagging, and 6″ x 6′ felloe guards. In addition, cord wood was used to backfill the hollow left by overbreak. The lining created a width curb-to-curb of 17′-6″ and a vertical clearance of 16′-0″ at the center of the roadway. By April 1921, the department also had completed a project to line about 60′ of each end of the east tunnel, with a vertical clearance of only 15′-6″.

The Oregon State Highway Department also built masonry portals for both tunnels to stabilize the ends of each bore and create pleasing entrances for motorists. It hired a Mr. C. Camillo of Portland to oversee their construction, with a crew of four stonecutters, three masons, six laborers, and one carpenter. Camillo had previously worked on the Shepperd’s Dell portion of the HCRH, completing masonry retaining walls there during the road’s original construction. Beginning in the week of December 18, 1920, Camillo’s crew commenced quarrying stone and shortly started laying stone for the four portals. They finished during the first week of April 1921, after placing keystone at the top of the east tunnel’s east portal and the west tunnel’s west portal reading “A. D. 1921.” Total cost for lining the tunnels and erecting portal masonry was $20,371.87.

With the advent of larger and more powerful automobiles and freight trucks by the early 1930s, accidents in and around the tunnels increased. Most involved sideswipes with other vehicles or the tunnel portals. The posted speed through near the tunnels was 15 miles per hour. Even as early as 1920, highway department officials expressed concern over speeding motorists and hoped to curtail the problem by placing stop signs at the east portal of the east tunnel and the west portal of the west tunnel. In 1938, the department considered placing traffic lights at the outside end of the tunnels as a deterrent to speeders. Yet they believed that this posed too great a risk to those who were forced to stop at the west portal of the west tunnel because of repeated raveling of rock. As an alternative, the tunnel portals were widened and the tunnels relined to achieve a width of 20′-0″.

In 1938, the highway department dismantled or cut back the portal rings for each of the four portal walls on the Hosier Twin Tunnels and replaced them with cast reinforced-concrete with imitation voissoirs. It also relined both tunnels, removing the often decaying 1921 lining and replacing it with 8″ x 12″ timber sets spaced solid, or side-by-side, with 2″ lagging, and backfilled with cedar cordwood. The department achieved a vertical clearance at the center of the roadway of 17′-2″, compared with 16′-0″ with the original lining. A realistic vertical clearance for vehicles using two 9′-0″ traffic lanes and I’-O” shoulders, was 11′-6″, compared to the unrealistic 7′-0″ traffic lanes to achieve a 11′-6″ vertical clearance.

The department again considered installing traffic signals in 1942 after reports of vehicles scraping portal rings due to excessive speed or wide loads. It looked at the issue for several years before deciding on how to improve traffic safety at the tunnels. One department maintenance engineer wrote in 1947 that he thought that one-way traffic signals were appropriate but worried about liability if a vehicle were in the path of the almost routine rock falls at the west tunnel’s west portal. The motor transport industry actually was a firm promoter of using traffic signals at the tunnels, but the engineer observed that even though the tunnels were signed for 15 miles per hour west bound, which was downhill, “the trucks roar through frequently at 30 to 40 miles an hour.” “Trucks have been involved in most of our serious accidents in these tunnels,” he added, “and speed has been the contributing factor.” Another incident, such as one in 1941, involved a truck and trailer colliding with a tractor trailer combination, with the second vehicle colliding with the west portal of the east tunnel and losing its load of 30′ steel pipe.

After much discussion about the best method for regulating traffic speed and improving safety in the Hosier Twin Tunnels, the highway department decided to install speed control signals and floodlighting instead of one-way signals. This solution was implemented at the request of local residents who regularly traveled this section of the HCRH and worried about becoming victims of rock falls while waiting to enter the west tunnel’s west portal.

In May 1949, this safety system included signs stating “Traffic Signals Ahead,” and “Tunnel Speed 20 Miles,” along with a third sign, “Proceed on flashing Amber – Two Way Traffic,” which was connected to an actuator and a red-amber light. Vehicles passing over a trip pad at 20 miles per hour or less caused the signal light to turn from red to a flashing amber, while for those traveling at speeds exceeding 20 miles per hour the lights remained red, requiring drivers to stop. In addition, the department installed 300-watt floodlights at the east and west ends of the tunnel area to give better nighttime illumination. Nevertheless, representatives of the trucking industry continued to protest the highway department’s decision to maintain two-way traffic in the tunnels.

By November, the department acquiesced to the trucking industry’s demands. After monitoring vehicle volume and speed, it decided to re-signal the tunnels for one-way traffic. Because of concerns about grade and the time it took for trucks to pass through the rock fall area, east bound vehicles received a continuous green light unless a vehicle approached the tunnels from the east. In addition, the point where eastbound traffic was stopped if the signals were actuated was moved to a point 125′ west of the west tunnel. Finally, the department installed a wire fence 100′ above the west tunnel’s west portal to prevent all rocks except large boulders from cascading on to the roadway.

Even with the new signal installation, the highway department continued to investigate the possibilities for enlarging the tunnels to create a 24′-0″ roadway and 14’-0″ vertical clearances. The estimated cost for doing this in 1950 was nearly $100,000. But before the department could move ahead with these plans, almost continuous raveling of rocks above the west tunnel’s west portal caused department engineers to reassess their views about the tunnels’ continued use. A talus bank under the cliff high above the west tunnel had started to slide. In March 1953, the local maintenance engineer reported that a sizable section of the rock face had fallen and littered the pavement near the west tunnel’s west portal with debris measuring from 6″ to 3′, with some pieces weighing over one ton. Several automobiles were damaged, and one man was hospitalized. Shortly, the highway department closed the Hosier Twin Tunnels section of the HCRH and diverted traffic on to a nearby section of the nearly completed water-level route, the new alignment for U.S. 30.

The highway department abandoned the Historic Columbia River Highway between Hood River and Mosier, with the end portions going to Hood River and Wasco counties, and the middle section, including the tunnels, reverting to adjacent landowners. The unused tunnels became a liability for the department. It feared that in their present state they might completely collapse, strewing rubble along the Union Pacific Railroad’s mainline (the old OWRN mainline). They also posed a liability for the department concerning trespassers injured by falling rock. So, in 1954, they were backfilled with rubble in an attempt to stabilize them and deter trespassers.

Over the next thirty years the Gorge gradually reclaimed the Hosier Twin Tunnels. Continual rock slides both near the west tunnel’s west portal and between the tunnels gradually made them barely distinguishable from the surrounding landscape. Most modern motorists passing along U.S. 30 (later Interstate SON and then Interstate 84) had no idea that once the main east-west trunk route from Portland passed along this portion of the Columbia River high above on the cliff’s edge.

Within the last decade, the Oregon Department of Transportation and private citizens have worked to reclaim abandoned sections of the HCRH for public use. The state plans to reopen Hosier Twin Tunnels and much of the Mosier-to-Hood River portion of the HCRH to pedestrians, bicyclists, and disabled persons.

Excerpted from Historic American Engineering Record, Mosier Twin Tunnels, HAER OR-36-T.
Historian: Robert W. Hadlow, Phd., September 1995.
Transmitted by: Lisa M. Pfueller, September, 1996.