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74-765: The MacArthur Tunnel , formally known as the General Douglas MacArthur Tunnel , is a highway tunnel in San Francisco, California . It is located within the Presidio of San Francisco , now part of the Golden Gate National Recreation Area . The tunnel carries California State Route 1 under a large hill and under the Presidio Golf Course. It connects Park Presidio Boulevard (Hwy 1) in

148-695: A canal . The central portions of a rapid transit network are usually in the tunnel. Some tunnels are used as sewers or aqueducts to supply water for consumption or for hydroelectric stations. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment. Secret tunnels are built for military purposes, or by civilians for smuggling of weapons , contraband , or people . Special tunnels, such as wildlife crossings , are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks . A tunnel

222-577: A Task Force Committee on Transportation to study the state transportation system and recommend major reforms. One of the proposals of the task force was the creation of a State Transportation Board as a permanent advisory board on state transportation policy; the board would later merge into the California Transportation Commission in 1978. In September 1971, the State Transportation Board proposed

296-487: A concrete tunnel 1,300 feet (400 m) long. The 1,300-foot (400 m) long tunnel accommodates a four-lane roadway. A tunnel was required because the land above the tunnel was being used by the Army for a parade ground and golf course, so leaving an open cut for the highway was impossible. It was constructed by a cut-and-cover sequence: excavating along the tunnel route, fitting steel arch forms, pouring concrete on top of

370-449: A large factor in the decision making process. Civil engineers usually use project management techniques for developing a major structure. Understanding the amount of time the project requires, and the amount of labor and materials needed is a crucial part of project planning. The project duration must be identified using a work breakdown structure and critical path method . Also, the land needed for excavation and construction staging, and

444-467: A pipe jack, with the span of some box jacks in excess of 20 metres (66 ft). A cutting head is normally used at the front of the box being jacked, and spoil removal is normally by excavator from within the box. Recent developments of the Jacked Arch and Jacked deck have enabled longer and larger structures to be installed to close accuracy. There are also several approaches to underwater tunnels,

518-421: A specialized method called clay-kicking for digging tunnels in clay-based soils. The clay-kicker lies on a plank at a 45-degree angle away from the working face and rather than a mattock with his hands, inserts with his feet a tool with a cup-like rounded end, then turns the tool with his hands to extract a section of soil, which is then placed on the waste extract. Clay-kicking is a specialized method developed in

592-434: A tube can be sunk into a body of water, which is called an immersed tunnel. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support system strong enough to carry the load of what is to be built above the tunnel. There are two basic forms of cut-and-cover tunnelling: Shallow tunnels are often of the cut-and-cover type (if under water, of

666-752: A tunnel for the Funston approach in July 1936, but formal approval of the plans and a permit to begin construction were not signed until August 1938 as the plans that had been reviewed – and the accompanying permission to construct on the Presidio – were conceptual up to that point. The Redwood Empire Association called upon city and Golden Gate Bridge District directors to rename the Funston approach just before it opened in 1940, suggesting possibilities such as "Golden Gate Bridge Parkway," "Golden Gate Bridge-Way," and "Golden Gate Bridge–Redwood Empire-way." The completion of

740-747: A tunnel than a sufficiently strong bridge). Some water crossings are a mixture of bridges and tunnels, such as the Denmark to Sweden link and the Chesapeake Bay Bridge-Tunnel in Virginia . There are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001. One of the worst railway disasters ever,

814-432: A tunnel. Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong , this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront. The 1934 Queensway Tunnel under

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888-560: Is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel. California Department of Transportation Caltrans manages the state's highway system , which includes the California Freeway and Expressway System , supports public transportation systems throughout

962-505: Is intended to carry both the Istanbul metro and a two-level highway, over a length of 6.5 km (4.0 miles). The French A86 Duplex Tunnel  [ fr ] in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of 10 km (6.2 miles). Although each level offers a physical height of 2.54 m (8.3 ft), only traffic up to 2 m (6.6 ft) tall

1036-494: Is relatively long and narrow; the length is often much greater than twice the diameter , although similar shorter excavations can be constructed, such as cross passages between tunnels. The definition of what constitutes a tunnel can vary widely from source to source. For example, in the United Kingdom, a road tunnel is defined as "a subsurface highway structure enclosed for a length of 150 metres (490 ft) or more." In

1110-401: Is sometimes necessary during the excavation of a tunnel. They are usually circular and go straight down until they reach the level at which the tunnel is going to be built. A shaft normally has concrete walls and is usually built to be permanent. Once the access shafts are complete, TBMs are lowered to the bottom and excavation can start. Shafts are the main entrance in and out of the tunnel until

1184-515: Is that the open building pit is muted after tunnel construction; no roof is placed. Some tunnels are double-deck, for example, the two major segments of the San Francisco–Oakland Bay Bridge (completed in 1936) are linked by a 160-metre (540 ft) double-deck tunnel section through Yerba Buena Island , the largest-diameter bored tunnel in the world. At construction this was a combination bidirectional rail and truck pathway on

1258-698: Is the Siloam Tunnel , built in Jerusalem by the kings of Judah around the 8th century BC. Another tunnel excavated from both ends, maybe the second known, is the Tunnel of Eupalinos , which is a tunnel aqueduct 1,036 m (3,400 ft) long running through Mount Kastro in Samos , Greece. It was built in the 6th century BC to serve as an aqueduct . In Ethiopia , the Siqurto foot tunnel , hand-hewn in

1332-429: Is usually completely enclosed except for the two portals common at each end, though there may be access and ventilation openings at various points along the length. A pipeline differs significantly from a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for foot or vehicular road traffic , for rail traffic, or for

1406-569: The Balvano train disaster , was caused by a train stalling in the Armi tunnel in Italy in 1944, killing 426 passengers. Designers try to reduce these risks by installing emergency ventilation systems or isolated emergency escape tunnels parallel to the main passage. Government funds are often required for the creation of tunnels. When a tunnel is being planned or constructed, economics and politics play

1480-673: The Federal-Aid Highway Act of 1956 for the construction of its portion of the Interstate Highway System . Over the next two decades after Collier-Burns, the state "embarked on a massive highway construction program" in which nearly all of the now-extant state highway system was either constructed or upgraded. In hindsight, the period from 1940 to 1969 can be characterized as the "Golden Age" of California's state highway construction program. The history of Caltrans and its predecessor agencies during

1554-785: The Funston Avenue tunnel , taking its name from the approach. Other residents would call it the Park Presidio approach. Caltrans currently has two official names for the tunnel, which is designated 34-0016 under the National Bridge Inventory . The tunnel is known as both the Presidio Tunnel and the General Douglas MacArthur Tunnel , having added the MacArthur tunnel designation by Senate Concurrent Resolution 86, introduced by Milton Marks during

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1628-772: The National Environmental Policy Act and the California Environmental Quality Act forced Caltrans to devote significant time, money, people, and other resources to confronting issues such as "air and water quality, hazardous waste, archaeology, historic preservation, and noise abatement." The devastating 1971 San Fernando earthquake compelled the agency to recognize that its existing design standards had not adequately accounted for earthquake stress and that numerous existing structures needed expensive seismic retrofitting . Maintenance and construction costs grew at twice

1702-471: The Port Authority of New York and New Jersey was not aware of this bill and had not asked for a grant for such a project. Increased taxes to finance a large project may cause opposition. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the groundwater conditions, the length and diameter of

1776-848: The Queens-Midtown Tunnel between Manhattan and the borough of Queens on Long Island ; the Detroit-Windsor Tunnel between Michigan and Ontario ; and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia ; the 1934 River Mersey road Queensway Tunnel ; the Western Scheldt Tunnel , Zeeland, Netherlands; and the North Shore Connector tunnel in Pittsburgh, Pennsylvania . The Sydney Harbour Tunnel

1850-722: The Richmond District to US 101 on the Doyle Drive viaduct, and the Golden Gate Bridge . When the Golden Gate Bridge opened in 1937, the approach for northbound traffic to Marin County was carried solely by Doyle Drive, from the east. Although a second approach from the south, known as the Funston Avenue approach , was included in the initial plans for the bridge, it was not ready in time for

1924-472: The River Mersey at Liverpool was chosen over a massively high bridge partly for defense reasons; it was feared that aircraft could destroy a bridge in times of war, not merely impairing road traffic but blocking the river to navigation. Maintenance costs of a massive bridge to allow the world's largest ships to navigate under were considered higher than for a tunnel. Similar conclusions were reached for

1998-679: The United Kingdom of digging tunnels in strong clay-based soil structures. This method of cut and cover construction required relatively little disturbance of property during the renewal of the United Kingdom's then ancient sewerage systems. It was also used during the First World War by Royal Engineer tunnelling companies placing mines beneath German lines, because it was almost silent and so not susceptible to listening methods of detection. Tunnel boring machines (TBMs) and associated back-up systems are used to highly automate

2072-610: The canton of Glarus . The borehole has a diameter of 8.03 metres (26.3 ft). The four TBMs used for excavating the 57-kilometre (35 mi) Gotthard Base Tunnel , in Switzerland , had a diameter of about 9 metres (30 ft). A larger TBM was built to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands, with a diameter of 14.87 metres (48.8 ft). This in turn

2146-489: The water table . This pressurizes the ground ahead of the TBM cutter head to balance the water pressure. The operators work in normal air pressure behind the pressurized compartment, but may occasionally have to enter that compartment to renew or repair the cutters. This requires special precautions, such as local ground treatment or halting the TBM at a position free from water. Despite these difficulties, TBMs are now preferred over

2220-689: The 16th century as a metaphor for a narrow, confined space like the inside of a cask. Some of the earliest tunnels used by humans were paleoburrows excavated by prehistoric mammals. Much of the early technology of tunneling evolved from mining and military engineering . The etymology of the terms "mining" (for mineral extraction or for siege attacks ), " military engineering ", and " civil engineering " reveals these deep historic connections. Predecessors of modern tunnels were adits that transported water for irrigation , drinking, or sewerage . The first qanats are known from before 2000 BC. The earliest tunnel known to have been excavated from both ends

2294-638: The 1960s. The main idea of this method is to use the geological stress of the surrounding rock mass to stabilize the tunnel, by allowing a measured relaxation and stress reassignment into the surrounding rock to prevent full loads becoming imposed on the supports. Based on geotechnical measurements, an optimal cross section is computed. The excavation is protected by a layer of sprayed concrete, commonly referred to as shotcrete . Other support measures can include steel arches, rock bolts, and mesh. Technological developments in sprayed concrete technology have resulted in steel and polypropylene fibers being added to

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2368-403: The 1970s, as its institutional focus shifted from highway construction to highway maintenance. The agency was forced to contend with declining revenues, increasing construction and maintenance costs (especially the skyrocketing cost of maintaining the vast highway system built over the past three prior decades), widespread freeway revolts , and new environmental laws . In 1970, the enactment of

2442-716: The 1971 Kingsway Tunnel under the Mersey. In Hampton Roads, Virginia , tunnels were chosen over bridges for strategic considerations; in the event of damage, bridges might prevent US Navy vessels from leaving Naval Station Norfolk . Water-crossing tunnels built instead of bridges include the Seikan Tunnel in Japan; the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City ;

2516-470: The 1985–86 Legislative Session. The top face of the south entrance to the tunnel is a popular target for graffiti vandals due to broken barbed-wire fences. During the 2016 United States presidential campaign, taggers sprayed the words "SF VS TRUMP," only to have the tag changed to "SF [hearts] TRUMP" a few days later. Tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and

2590-650: The 20th century was marked by many firsts. It was one of the first agencies in the United States to paint centerlines on highways statewide; the first to build a freeway west of the Mississippi River ; the first to build a four-level stack interchange ; the first to develop and deploy non-reflective raised pavement markers, better known as Botts' dots ; and one of the first to implement dedicated freeway-to-freeway connector ramps for high-occupancy vehicle lanes . In 1967, Governor Ronald Reagan formed

2664-500: The Department of Transportation, of which the most important was the Department of Public Works and its Division of Highways. The California Department of Transportation began official operations on July 1, 1973. The new agency was organized into six divisions: Highways, Mass Transportation, Aeronautics, Transportation Planning, Legal, and Administrative Services. Caltrans went through a difficult period of transformation during

2738-631: The Funston Avenue approach was celebrated with a two-day gala in April 1940. The construction contract for the Funston Avenue approach was awarded in September 1938 to Macco Construction company, who had built the approach for southbound traffic over the Waldo Grade . The Macco contract was awarded at their bid of US$ 593,042 (equivalent to $ 12,836,600 in 2023) and included the laying of

2812-709: The Middle Ages, crosses a mountain ridge. In the Gaza Strip , the network of tunnels was used by Jewish strategists as rock-cut shelters, in first links to Judean resistance against Roman rule in the Bar Kokhba revolt during the 2nd century AD. A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which will reduce

2886-517: The Pacific coast states and provinces of Canada, Mexico and the United States. Citizens from the North Bay and other northern counties were encouraged to participate in the opening ceremonies. Delegates from British Columbia; the states of California, Oregon, and Washington; and the consul general of Mexico all attended and spoke at the dedication ceremonies. In 1949, the tunnel was known locally as

2960-512: The State of California into 12 districts, supervised by district offices. Most districts cover multiple counties ; District 12 ( Orange County ) is the only district with one county. The largest districts by population are District 4 ( San Francisco Bay Area ) and District 7 ( Los Angeles and Ventura counties). Like many state agencies, Caltrans maintains its headquarters in Sacramento , which

3034-536: The United States, the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m (75 ft) and a diameter greater than 1,800 millimetres (5.9 ft)." The word "tunnel" comes from the Middle English tonnelle , meaning "a net", derived from Old French tonnel , a diminutive of tonne ("cask"). The modern meaning, referring to an underground passageway, evolved in

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3108-400: The blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground. This may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel (or "drift tunnel") may be driven ahead of the main excavation. This smaller tunnel is less likely to collapse catastrophically should unexpected conditions be met, and it can be incorporated into

3182-502: The concrete mix to improve lining strength. This creates a natural load-bearing ring, which minimizes the rock's deformation . By special monitoring the NATM method is flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel strengthening . In pipe jacking , hydraulic jacks are used to push specially made pipes through

3256-642: The construction of the Bartlett Dam in Arizona. Construction of the tunnel began in October 1938 and was complete by January 1940; the Funston Avenue approach was dedicated for service on April 21, 1940. The Funston Avenue approach and the Nineteenth Avenue approach were both dedicated and opened for traffic on April 21, 1940, in themed ceremonies designed to promulgate friendly relations between

3330-464: The creation of a state department of transportation charged with responsibility "for performing and integrating transportation planning for all modes ." Governor Reagan mentioned this proposal in his 1972 State of the State address , and Assemblyman Wadie P. Deddeh introduced Assembly Bill 69 to that effect, which was duly passed by the state legislature and signed into law by Reagan later that same year. AB 69 merged three existing departments to create

3404-409: The entire tunnelling process, reducing tunnelling costs. In certain predominantly urban applications, tunnel boring is viewed as a quick and cost-effective alternative to laying surface rails and roads. Expensive compulsory purchase of buildings and land, with potentially lengthy planning inquiries, is eliminated. Disadvantages of TBMs arise from their usually large size – the difficulty of transporting

3478-441: The final tunnel or used as a backup or emergency escape passage. Alternatively, horizontal boreholes may sometimes be drilled ahead of the advancing tunnel face. Other key geotechnical factors: For water crossings, a tunnel is generally more costly to construct than a bridge. However, both navigational and traffic considerations may limit the use of high bridges or drawbridges intersecting with shipping channels, necessitating

3552-454: The forms, and returning the fill to the top of the cured concrete. Fill removed from the initial excavation was stockpiled near Mountain Lake , which would serve as the southern drainage point for the Funston approach upon its completion, since the Army also required no drainage onto Presidio property. Tunnel sections were built in 28-foot (8.5 m) lengths, and work was started from each end of

3626-561: The founding of the Transportation Laboratory and the creation of seven administrative divisions, which are the predecessors of the 12 district offices in use as of 2018 . The original seven division headquarters were located in: In 1913, the California State Legislature began requiring vehicle registration and allocated the resulting funds to support regular highway maintenance, which began

3700-405: The ground behind a TBM or shield. This method is commonly used to create tunnels under existing structures, such as roads or railways. Tunnels constructed by pipe jacking are normally small diameter bores with a maximum size of around 3.2 metres (10 ft). Box jacking is similar to pipe jacking, but instead of jacking tubes, a box-shaped tunnel is used. Jacked boxes can be a much larger span than

3774-640: The immersed-tube type), while deep tunnels are excavated, often using a tunnelling shield . For intermediate levels, both methods are possible. Large cut-and-cover boxes are often used for underground metro stations, such as Canary Wharf tube station in London. This construction form generally has two levels, which allows economical arrangements for ticket hall, station platforms, passenger access and emergency egress, ventilation and smoke control, staff rooms, and equipment rooms. The interior of Canary Wharf station has been likened to an underground cathedral, owing to

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3848-435: The inevitable smoke and steam. A major disadvantage of cut-and-cover is the widespread disruption generated at the surface level during construction. This, and the availability of electric traction, brought about London Underground's switch to bored tunnels at a deeper level towards the end of the 19th century. Prior to the replacement of manual excavation by the use of boring machines, Victorian tunnel excavators developed

3922-481: The inflation rate in this era of high inflation; the reluctance of one governor after another to raise fuel taxes in accordance with inflation meant that California ranked dead last in the United States in per capita transportation spending by 1983. During the 1980s and 1990s, Caltrans concentrated on "the upgrading, rehabilitation, and maintenance of the existing system," plus occasional gap closure and realignment projects. For administrative purposes, Caltrans divides

3996-468: The large TBM to the site of tunnel construction, or (alternatively) the high cost of assembling the TBM on-site, often within the confines of the tunnel being constructed. There are a variety of TBM designs that can operate in a variety of conditions, from hard rock to soft water-bearing ground. Some TBMs, the bentonite slurry and earth-pressure balance types, have pressurized compartments at the front end, allowing them to be used in difficult conditions below

4070-629: The lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck. In Turkey, the Eurasia Tunnel under the Bosphorus , opened in 2016, has at its core a 5.4 km (3.4 miles) two-deck road tunnel with two lanes on each deck. Additionally, in 2015 the Turkish government announced that it will build three -level tunnel, also under the Bosporus. The tunnel

4144-582: The next year. In 1921, the state legislature turned the Department of Engineering into the Department of Public Works, which continued to have a Division of Highways. That same year, three additional divisions (now districts) were created, in Stockton, Bishop, and San Bernardino. In 1933, the state legislature enacted an amendment to the State Highway Classification Act of 1927, which added over 6,700 miles of county roads to

4218-483: The older method of tunnelling in compressed air, with an airlock/decompression chamber some way back from the TBM, which required operators to work in high pressure and go through decompression procedures at the end of their shifts, much like deep-sea divers . In February 2010, Aker Wirth delivered a TBM to Switzerland, for the expansion of the Linth–Limmern Power Stations located south of Linthal in

4292-402: The open cut. The tunnel was made as long as possible without having to add forced ventilation to dilute carbon monoxide from automobile exhaust, and a 24-by-24-foot (7.3 by 7.3 m) shaft was built mid-way along the tunnel to provide passive ventilation, with the capacity to add a fan later for forced exhaust through the shaft, if necessary. The steel arch forms had previously been used during

4366-520: The opening; just a year after opening, traffic over the bridge had doubled by 1938, adding urgency to completing the Funston approach. In March 1936, General Paul Malone made clear the Army's position: that the Funston approach would include a tunnel or else the Army would not approve the planned route through the San Francisco Presidio. General George S. Simonds , the successor to Gen. Malone, indicated tentative approval of plans for

4440-540: The operation of empty and loaded trains at the same time. The temporary way is replaced by the permanent way at completion, thus explaining the term " Perway ". The vehicles or traffic using a tunnel can outgrow it, requiring replacement or enlargement: An open building pit consists of a horizontal and a vertical boundary that keeps groundwater and soil out of the pit. There are several potential alternatives and combinations for (horizontal and vertical) building pit boundaries. The most important difference with cut-and-cover

4514-522: The project is completed. If a tunnel is going to be long, multiple shafts at various locations may be bored so that entrance to the tunnel is closer to the unexcavated area. Once construction is complete, construction access shafts are often used as ventilation shafts , and may also be used as emergency exits. The New Austrian Tunnelling method (NATM)—also referred to as the Sequential Excavation Method (SEM) —was developed in

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4588-490: The proper machinery must be selected. Large infrastructure projects require millions or even billions of dollars, involving long-term financing, usually through issuance of bonds . The costs and benefits for an infrastructure such as a tunnel must be identified. Political disputes can occur, as in 2005 when the US House of Representatives approved a $ 100 million federal grant to build a tunnel under New York Harbor. However,

4662-482: The risk of encountering unforeseen ground conditions. In planning the route, the horizontal and vertical alignments can be selected to make use of the best ground and water conditions. It is common practice to locate a tunnel deeper than otherwise would be required, in order to excavate through solid rock or other material that is easier to support during construction. Conventional desk and preliminary site studies may yield insufficient information to assess such factors as

4736-542: The sheer size of the excavation. This contrasts with many traditional stations on London Underground , where bored tunnels were used for stations and passenger access. Nevertheless, the original parts of the London Underground network, the Metropolitan and District Railways, were constructed using cut-and-cover. These lines pre-dated electric traction and the proximity to the surface was useful to ventilate

4810-445: The state and provides funding and oversight for three state-supported Amtrak intercity rail routes ( Capitol Corridor , Pacific Surfliner and San Joaquins ) which are collectively branded as Amtrak California . In 2015, Caltrans released a new mission statement: "Provide a safe, sustainable, integrated and efficient transportation system to enhance California's economy and livability." The earliest predecessor of Caltrans

4884-811: The state highway system. To help manage all the additional work created by this massive expansion, an eleventh district office was founded that year in San Diego. The enactment of the Collier–Burns Highway Act of 1947 after "a lengthy and bitter legislative battle" was a watershed moment in Caltrans history. The act "placed California highway's program on a sound financial basis" by doubling vehicle registration fees and raising gasoline and diesel fuel taxes from 3 cents to 4.5 cents per gallon. All these taxes were again raised further in 1953 and 1963. The state also obtained extensive federal funding from

4958-400: The tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and the shape of the tunnel and appropriate risk management. There are three basic types of tunnel construction in common use. Cut-and-cover tunnels are constructed in a shallow trench and then covered over. Bored tunnels are constructed in situ, without removing the ground above. Finally,

5032-411: The tunnel, working towards the center, allowing two to three sections of tunnel to be completed per week. The open cut-and-cover method was deemed economical because of the relatively small amount of material that would need to be removed. During the construction of the tunnel, two tees and one green for the golf course were temporarily relocated, and a footbridge was constructed to allow golfers to cross

5106-428: The two most common being bored tunnels or immersed tubes , examples are Bjørvika Tunnel and Marmaray . Submerged floating tunnels are a novel approach under consideration; however, no such tunnels have been constructed to date. During construction of a tunnel it is often convenient to install a temporary railway, particularly to remove excavated spoil , often narrow gauge so that it can be double track to allow

5180-449: Was a Division of Highways. California voters approved an $ 18 million bond issue for the construction of a state highway system in 1910, and the first California Highway Commission was convened in 1911. On August 7, 1912, the department broke ground on its first construction project, the section of El Camino Real between South San Francisco and Burlingame , which later became part of California State Route 82 . The year 1912 also saw

5254-503: Was constructed to provide a second harbour crossing and to alleviate traffic congestion on the Sydney Harbour Bridge , without spoiling the iconic view. Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather, and shipping during construction (as in the 51.5-kilometre or 32.0-mile Channel Tunnel ), aesthetic reasons (preserving the above-ground view, landscape, and scenery), and also for weight capacity reasons (it may be more feasible to build

5328-501: Was no longer adequate for the needs of the state's rapidly growing population. After the commissioners submitted their report to the governor on November 25, 1896, the legislature replaced the Bureau with the Department of Highways. Due to the state's weak fiscal condition and corrupt politics, little progress was made until 1907, when the legislature replaced the Department of Highways with the Department of Engineering, within which there

5402-732: Was superseded by the Madrid M30 ringroad , Spain, and the Chong Ming tunnels in Shanghai , China. All of these machines were built at least partly by Herrenknecht . As of August 2013 , the world's largest TBM was " Big Bertha ", a 17.5-metre (57.5 ft) diameter machine built by Hitachi Zosen Corporation , which dug the Alaskan Way Viaduct replacement tunnel in Seattle, Washington (US). A temporary access shaft

5476-609: Was the Bureau of Highways, which was created by the California Legislature and signed into law by Governor James Budd in 1895. This agency consisted of three commissioners who were charged with analyzing the roads of the state and making recommendations for their improvement. At the time, there was no state highway system, since roads were purely a local responsibility. California's roads consisted of crude dirt roads maintained by county governments, as well as some paved streets in certain cities, and this ad hoc system

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