Spiro Tunnel at Park City, Utah

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This page was last updated on July 14, 2025.

Overview

The Spiro Tunnel was a transportation and drainage tunnel in Park City, Utah. It was started in 1916 and completed to its final length of 15,000 feet in 1922.

There were additional minor extensions along portions of its length, known as drifts, that allowed access into different parts of the various ore bodies. Additional access was provided by numerous upward extensions, known as raises, from these drifts. These extensions continued to provide ore for shipment either direct to the smelters, if the ore was high grade, from the tunnel portal near the mouth of Thayne's canyon. Ore with lower grade content was taken up by hoist to the Silver King Coalition company's reduction mill near the top of Woodside Gulch, and from there the concentrate was sent by that company's aerial tramway down to Park City.

The main objective of the new tunnel was to open the western part of the Park City mining district for mining and to provide drainage for the tremendous amount of water that plagued all the mines in the district. At the time the tunnel was started, there was a western part of the district, controlled by Silver King Consolidated company, a central part, controlled by the Silver King Coalition Mines company, and an eastern part, controlled by the Ontario and Daly-Judge companies.

In later years the water flowing from the tunnel, at about 3,000 gallons per minute, became the major source of municipal water for the town of Park City.

Timeline

February 15, 1916
"The unusually heavy snow and bad weather have upset all plans for the commencement of work on the new tunnel and aerial tram at the Silver King Consolidated at Park City. Manager Solon Spiro states that the work will be undertaken as soon as possible, and that the tramway will be in operation before the end of summer." (Salt Lake Mining Review, February 15, 1916)

(All during 1914 and 1915 there were comments about the production of the Silver King Consolidated mine being limited by bad roads, especially in the spring season. Production was being limited with the purpose of delivering only enough revenue to cover expenses and dividends for the Silver King Consolidated company. Because of the size of the ore body, and its uniformity throughout the property, additional tonnage could easily be obtained, if desired, but would be limited by the bad roads and the availability of teams and wagons. The road most often being used was the abandoned former Crescent Tramway narrow gauge railroad, which had been abandoned in 1896.)

February 29, 1916
"The Silver King Consolidated Mining Company of Park City, Utah, will construct a mill of from 150 to 200 tons capacity at the mouth of the new tunnel to be run this summer. Solon Spiro of Salt Lake is president and general manager of the company. An aerial tramway from the mine to the mill is to be built also." (Salt Lake Mining Review, February 29, 1916)

March 15, 1916
"The aerial tramway from the mine to the mill is to he nearly three miles in length. Mining machinery will also be installed at the mouth of the proposed deep tunnel." (Salt Lake Mining Review, March 15, 1916)

April 15, 1916
"Work on the new drain tunnel will start as soon as the snow goes off." (Salt Lake Mining Review, April 15, 1916)

September 15, 1916
"The deep drainage and transportation tunnel is now in a distance of more than 300 feet. Owing to the loose nature of the ground it has been necessary to do the work to date by hand, but one side of the face is now in the solid formation and it is expected to put the power drills to work by the middle of the present month." (Salt Lake Mining Review, September 15, 1916)

October 21, 1916
Silver King Consolidated Mining Company completed their aerial tramway between the mine and their mill, as distance of 10,200 feet, 52 buckets, five cubic feet each, traveling at 400 feet per minute. The new aerial tramway "went into commission" on October 21st, and will save about 75 percent of transportation costs. (Salt Lake Mining Review, October 30, 1916)

October 30, 1916
The new Spiro tunnel had progressed about 700 feet, with progress being about 8 feet per day. Total planned length is 14,000 feet. (Salt Lake Mining Review, October 30, 1916)

November 1916
The mill of the Silver King Consolidated went into operation. The mill was connected to the mine by an aerial tram. The Spiro tunnel was making progress. (Goodwin's Weekly, July 14, 1917)

January 15, 1917
"The tram carries fifty-two buckets, each of five cubic feet capacity, and moves at the rate of 400 feet per minute, giving it a carrying total of twenty tons an hour or 480 tons a day. The company saves 75 per cent of the original cost of shipping by wagon, and more than 85 per cent on the cost of up-freight, besides the inestimable value of being able to keep its transportation system open both winter and summer." (Salt Lake Mining Review, January 15, 1917)

(No reference in available online newspapers to the Silver King Consolidated aerial tramway after late February 1917. This aerial tramway should not be confused with the aerial tramway of the Silver King Coalition Mines company, which remained in use until 1952.)

January 31, 1918
Silver King Consolidated Mining Company took over the California-Comstock group of claims. (Salt Lake Mining Review, January 30, 1918)

November 30, 1918
The Spiro tunnel had reached a distance of 8,700 feet. (Salt Lake Mining Review, November 30, 1918, "Dips, Spurs, and Angles")

July 30, 1920
The Spiro tunnel had reached "better than 13,000 feet". (Salt Lake Mining Review, July 30, 1920, "Around The State")

April 20, 1921
From the April 2, 1921 issue of Engineering & Mining Journal magazine.

Work was started during the summer of 1916, and has been continuously prosecuted since that time. The breast is now 14,400 ft. from the portal. The period of time comprised in this review is four years, extending from July 1, 1916, to July 1, 1920, and the length of bore considered is 12,944 ft.

Location -- Park City, Utah.
Purpose -- Development, drainage, transportation.
Character of rock penetrated -- Limestone, shale, quartzite.
Size broken -- 8x9 ft.; ditch on side, 3x4 ft.
Cross section -- 84 sq. ft.
Grade -- 3 ft. rise in 1,000 ft.
Power -- Purchased electric current.
Air pressure -- 100 lb., generated by electrically driven compressor.
Air line -- 4-in. O. D. casing.
Ventilator pipe -- 18-in. steel, dipped.
Water line to drills -- 1-1/2-in. black pipe.
Drills -- Pneumatic hammer.
Drill mounting -- Horizontal bar.
Explosives -- 50 per cent gelatine dynamite in cuts; 35 per cent in sides.
Number of holes per round -- 16 to 24.
Average depth drilled -- 5 to 8 ft.
Cars -- 20 cu. ft., roller bearing.
Type of haulage -- Horse.
Track of switches -- 30-lb. rail, 18-in. gage.

Each machine man has his own drill, and following each shift the drill was trucked out, cleaned, oiled, tested, and, if necessary, repaired. This method insured a machine that worked perfectly when placed on the bar and obviated the claim so commonly made that the man on the previous shift had left a "bum" drill. It also proved a big saving in drill repairs.

The average sizes of timber used were: Sills, 6x10; legs, 8x8; caps, 8x10; and lagging, 2-in. rough. These sizes were varied somewhat to suit heavy or swelling ground. The sets were placed 5 ft. from center to center on the average, and where timber sets were not required the sills were placed on grade at 5 ft. centers and hitched into the walls for the entire distance.

The surface plant is modern, with a well-equipped blacksmith shop, a machine shop, a carpenter shop, a change room, magazines, and adequate storage rooms.

July 30, 1921
The Spiro tunnel had reached 14,400 feet. (Salt Lake Mining Review, July 30, 1921, "Around The State")

May 13, 1922
"The Spiro tunnel was driven 904 feet during the year, making its total length 15,014 feet on January 1, 1922." (Engineering and Mining Journal, Volume 113, Number 19, May 13, 1922, page 843)

(No references after this 1922 report show any additional length for the Spiro Tunnel.)

November 15, 1922
The first objective of the Spiro tunnel of a length of 15,000 feet had been attained. Numerous additional shafts and drifts in other directions were being driven to access known ore reserves. An assessment of 10 percent of stock value had been issued to cover additional costs. (Salt Lake Mining Review, November 15, 1922)

(When finished, the Spiro Tunnel was directly under the California-Comstock group of mining claims at the far southwestern end of the larger company's properties. The Silver King Consolidated company had purchased the California-Comstock group in 1918.)

July 7, 1923
"The Silver King Consolidated Mining Co. has driven the Spiro tunnel about 15,000 ft. along the northwestern edge of the productive area. The tunnel has entered ground in which orebodies of considerable size were mined from the Thaynes formation in the 1880’s and 1890’s. The more favorable Park City and Weber formations are deeply buried here, and these are now being prospected from the Spiro tunnel." (Engineering and Mining Journal, Volume 116, Number 1, July 7, 1923, page 13)

(Some sources in later histories show a final length of 17,000 feet, but this distance has not yet been documented in contemporary sources. The additional 2,000 feet may have been the result of including the numerous horizontal tunnels, known as "drifts," in various directions from the underground "station" where the main tunnel met the hoist to the surface.)

(The gauge of the railroad track for the Spiro tunnel is not yet known, but photos suggest it to be 24 inches, in a reflection of the narrowness of the tunnel itself.)

Sale To Silver King Coalition Mines

On May 19, 1924, Silver King Coalition Mines Company announced that it had purchased control of the adjacent Silver King Consolidated Mining Company. The Silver King Consolidated was the owner of a 15,000-foot tunnel (later known as the Spiro Tunnel) started in 1916 and meant to drain the company's workings. The surface acreage of the combined companies totaled 3,800 acres, with 2,400 coming from Coalition, and 1,400 acres coming from Consolidated, which also operated a flotation mill at the mouth of its tunnel. The purchase option expired on June 16, 1924. The sale was finalized on June 6, 1924 when the last stock of Consolidated was purchased. A connection between the Spiro Tunnel and the 1300 level of the Silver King Coalition mine was to be completed within a month, and would greatly improve the combined mines ventilation, transportation and safety. (Salt Lake Mining Review, May 15, 1924, "tomorrow"; May 30, 1924; Park Record, May 23, 1924, "Monday"; June 6, 1924)

(Also mentioned in the Park Record June 6th article was that the portal of the Spiro Tunnel was situated directly on the Denver & Rio Grande branch to Park City. This was not actually the case. The portal of the Spiro Tunnel, located along today's Three Kings Drive at the Park City municipal water plant, immediately west of the golf course, was in fact over 2,000 feet from the rail line. There is no record or document showing a railroad spur to the Spiro Tunnel, so transportation of ore and concentrates from the Spiro Tunnel would have required the use of wagons, which would then dump into rail cars by using a raised platform.)

(No reference has been found that ore was shipped from the Spiro Tunnel after its purchase by Silver King Coalition in 1924. This indicates that the 15,000-foot Spiro Tunnel was used almost solely for ventilation, and for transportation of miners and materials. The Silver King Coalition company already had its newly rebuilt concentrator mill at the top of Thayne's Canyon, and its aerial tramway connecting the mine and mill with the ore loading station in downtown Park City.)

(Solon Spiro passed away on July 31, 1929, at age 65. He was living with his brother-in-law in Cincinnati at the time, on an extended vacation from his home in New York City.)

(Solon Spiro came from Germany to Park City in 1881 to help his uncle in the mercantile business. He later managed a store in Park City, and began investing in mining claims in the area. In 1900, he sold out his mercantile interests to concentrate on mining.)

"In the spring of 1936, the Silver King Coalition announced plans to sink a new shaft east of the old California-Comstock shaft in Thaynes Canyon. At the 1,800- foot level, it would connect with the western end of the Spiro Tunnel. The shaft reached the Spiro Tunnel in May 1939, helping ventilate some of the old workings and providing access to new ore bodies." (From The Ground Up, Park City, pages 329-332)

In 1937, the Silver King Coalition Mines company began sinking a new vertical shaft from near the top of Thaynes Canyon at the far western end of the company's holdings. When it was completed in 1940, the new shaft had reached its final depth of 1700 feet downward and connected with the Spiro Tunnel. The new tunnel was a triple compartment shaft and was equipped with an electric hoist. The actual final depth was 1800 feet, to provide for a sump for the pumping of water out of the working areas of the mine, with the flow exiting by way of the Spiro drain tunnel. The new shaft would provide better access to the western parts of the company's holdings. Ore from the new areas would not transported through what was called the "Silver King Con. Tunnel" (the existing Spiro tunnel), only waste rock. Because the transportation costs were lower, ore from the new workings would be hoisted to the surface and sent to the Silver King Coalition Mines company's reduction mill in Thaynes Canyon. (Salt Lake Tribune, January 31, 1937; Park Record, September 22, 1938; Davis County Reflex-Journal, December 26, 1940)

(The new vertical shaft and its connection to the Spiro tunnel would provide access to the northwestern parts of the company property, as well as provide transportation of waste rock from the areas being mined. It would also provide ventilation of the new areas. Aerial photos of the portal area taken in 1953 show large waste dumps at the tunnel portal. During the mid and late 1940s, rock from the waste dump, being high quality hard limestone, was sold to the state highway department, which crushed it and used the material to improve local roads.)

(The September 22, 1938 issue of the Park Record newspaper included a graphic illustration showing the new shaft in relation to the present Silver King Coalition shaft, and the portal of the Spiro tunnel. Part of the planning for the new "Thaynes Canyon Shaft" included a connection with the Alliance Tunnel, which in-turn provided access to the eastern parts of the Silver King Coalition workings, along with better ventilation. The connection with the Alliance tunnel was at its 900 Level, and the 1250 Level of the new Thaynes Canyon shaft.)

(When first completed in 1940, the new Thaynes Canyon shaft included a pump with the capacity of 4000 gallons per minute, which pumped water from the sump at the 1800 level, up to the Spiro tunnel level. In June 1945, a second pump of the same capacity was added to dewater new parts of the "west end" of the mine which was adding a flow that the single pump was unable to handle. By July 1948, the flow from the Spiro tunnel was reported as being 4600 gallons per minute. -- Park Record, June 14, 1945; Uintah Basin Standard, July 23, 1948)

(In June 1950 the Silver King Coalition Mines company removed the electrical lines and transformers from the portal area of the Spiro tunnel. This indicates that the tunnel was out of service, especially the electric mine trains that used trolley wire, powered by these transformers. In addition to powering the locomotives in the Spiro tunnel, the electrical service was used to power the air compressors that furnished air to operate the drills in some parts of the mine. The electrical service was also used by Park City to pump water up to its reservoir for municipal use, and the city was forced to make other arrangements. -- Park Record, June 29, 1950)

(In June 1954, three persons were arrested after being caught stealing copper trolley wire from the out-of-service Spiro tunnel. -- Park Record, June 3, 1954)

(Sources during the 1960s continued to show that the tunnel was closed in 1937 when the area of the mine that it served was closed. Later research has found this to be in error.)

By the early 1960s the United Park City Mines company, successor to Silver King Coalition Mines company and owner of the rights to over 10,000 acres in the Park City district, together with Park City, held a ground breaking ceremony for the construction of an aerial enclosed-gondola 2-1/2 mile tramway, as the first step of a new multi-million dollar, major year-round playground resort to be called "The Treasure Mountains." Within a year the gondola was completed, along with a chair lift and two J-bar tows. By February 1964, the United Park City Mines company had 100 employees working on the resort side of the company, which they called their recreation division. In May 1970, United Park City Mines sold 4,200 acres to Treasure Mountain Resort Company for the purposes of resort and recreational development, and leased to the resort company another 6,100 acres for the development of ski lifts and ski runs.

Starting Saturday January 10, 1965, the Spiro Tunnel was used as what the media called a "tunnel ski lift." With a 15,000 feet trip horizontally, and another 1700 feet vertically, it was likely one of the most unique ski lifts in the history of the sport. Planning had started in May 1964, to get the safety and environmental clearances needed to operate the tunnel train and mine hoisting system as a public utility where only a mining activity was before.

Skiers would enter into the mine in specially modified train cars that would take them three miles into the tunnel where a mine hoist transported them upward to the surface and they would ski down. When the decision was made to reopen the tunnel to provide an all-weather ski lift and tourist attraction, more than $250,000 was poured back into the tunnel for renovation and repairs. "Many timbers had to be replaced, and the water had covered a great deal of the track, making in unserviceable. In addition, the walls of the tunnel had sloughed off in several places." (Park Record, January 14, 1965)

The use of the Spiro tunnel as a "ski lift" for the public only lasted five seasons, through Spring 1969, at the end of the 1968-1969 ski season. The tunnel train was used in January 1969 for the Fifth Annual Lowell Thomas Classic when the contestants used the tunnel and hoist system due to high winds that kept the gondola tram from operating safely. That was apparently the last use of the unique tunnel train and hoist as a "ski lift."

The tunnel train was used as part of the mining museum during the summer season starting in summer 1965. As each season came and went there were more and more complaints about summer season visitors being uncomfortable with the constant overhead dripping in the underground tunnel. The train ride and museum lasted until the end of the 1976 summer tourist season, after having an abbreviated 1975 season due to high insurance costs. The cost of insurance for that final season in 1976 was found to be too expensive. No insurance company would provide the coverage, so the mining company at the time, Park City Ventures company, paid the premiums, but only for that one year.

After that, the operation ended and the tunnel entrance sat abandoned. But not really. As residential and commercial development began to surround the tunnel entrance, Park City was active in protecting the tunnel because it furnished 30 percent of the city's water supply. There seemed to be too many occasional attempts by some adventurer to break the locks and take a private unguided tour of the 15,000 feet of tunnel. In 2020, the city and nearby developers pooled their resources and in May 2021 finished a proper restoration of the tunnel entrance, with proper security and historical markers.

More Information

Spiro Tunnel at Silver Star -- at Park City History, with a photo gallery

Driving The Spiro Tunnel -- at Park City History

Spiro Tunnel- A Restoration and Dedication -- at Visit Park City, restoration completed in 2022

Public gets rare look inside the Spiro Tunnel -- at KPCW; a rare open house in 2021

Way We Were: Driving the Spiro Tunnel -- at The Park Record newspaper in 2021

Park City celebrates rehabilitation of mining-era tunnel, a crucial water supply -- at The Park Record newspaper in 2021

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