94-636: The Yerba Buena Tunnel , also known as the Yerba Buena Island Tunnel , is a highway tunnel in San Francisco, California . It is the part of San Francisco–Oakland Bay Bridge complex that crosses Yerba Buena Island . The Yerba Buena Tunnel carries ten lanes of Interstate 80 (I-80) on two decks, connecting the two component spans of the Bay Bridge, the western suspension span and the eastern self-anchored suspension span . At
188-434: A central truck deck on the lower level. After Key System trains stopped running over the bridge in 1958, bids were opened on October 11, 1960, to rebuild the tunnel. The rebuild consisted of multiple stages of work: After the reconstruction, the tunnel would handle only road traffic. The upper deck was lowered to accommodate heavy truck traffic, as each deck would now carry five lanes of unidirectional traffic. The upper deck
282-652: A company called the "Realty Syndicate" which acquired large tracts of undeveloped land throughout the East Bay. The Realty Syndicate also built two large hotels, each served by a San Francisco-bound train, the Claremont and the Key Route Inn , and a popular amusement park in Oakland called Idora Park . Streetcar lines were also routed to serve all these properties, thereby enhancing their value. In its early years,
376-521: A ferry terminal near Yerba Buena Island . Filling for the causeway had been started by a short-lived narrow-gauge railroad company in the late 19th century, the California and Nevada Railroad . "Borax" Smith acquired the causeway from the California and Nevada upon its bankruptcy. On December 4, 1924, six people were killed in a train collision on the mole. On May 6, 1933, a major fire erupted on
470-449: 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
564-498: A pair of pantographs , invented and manufactured by the Key System's own shops, were installed to collect current from overhead wires to power a pair of electric motors on each car, one on each truck (bogie). The design of rolling stock changed over the years. Wood gave way to steel, and, instead of doors at each end, center doors were adopted. The later rolling stock consisted of specially designed "bridge units" for use on
658-625: A petition with the PUC "against the Key System, seeking restoration of the bus service on the #70 Chabot Bus line". The city councils of Oakland, Berkeley and San Leandro opposed the removal of street cars. The traffic planners supported removal of the streetcar lines to facilitate movement of automobiles. Local governments in the East Bay attempted to purchase the Key System, but were unsuccessful. Streetcars were converted to buses during November/December 1948. In 1949 National City Lines, General Motors and others were convicted of conspiring to monopolize
752-467: 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,
846-424: A single arch-shaped bore (in cross-section), and the tunnel roof was constructed using 16-inch (410 mm) steel I-beam ribs spaced 3 feet (0.91 m) apart to support the rock, which were then embedded in concrete up to 3 feet (0.91 m) thick at the crown. No cave-ins occurred during the excavation of the tunnel. After the roof was completed, the remaining core of rock between the tunnel roof and lower deck
940-421: 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
1034-410: A temporary falsework erected in the middle of the lower deck, and the other side rested on the shoulder of the tunnel wall previously used to support the old upper deck. After the two halves were fastened together, a steel form was used to close the 1-foot-6-inch-wide (0.46 m) gap between halves, and concrete was poured in the gap. The upper deck rests on 12-inch-wide (30 cm) shoulders built into
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#17327660689071128-434: 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
1222-747: 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,
1316-917: 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 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
1410-432: 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
1504-409: Is 76 feet (23 m) wide and 58 feet (18 m) high overall, and the dimensions of the tunnel interior are 66 feet (20 m) wide and 53 feet (16 m) high. In 1936, it was hailed as the world's largest-bore tunnel. The cross-sectional area of the upper half is 1,500 square feet (140 m), and the lower half is 1,000 square feet (93 m). The tunnel has two decks. As originally completed,
1598-529: 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. Key System The Key System (or Key Route ) was a privately owned company that provided mass transit in the cities of Oakland , Berkeley , Alameda , Emeryville , Piedmont , San Leandro , Richmond , Albany , and El Cerrito in
1692-472: Is an urgent warning to each and every one of you that there is a careful, deliberately planned campaign to swindle you out of your most important and valuable public utilities–your Electric Railway System". The new owners made a number of rapid changes. In 1946 they cut back the A-1 train route and then the express trains in 1947. The company increased fares in 1946 and then in both January and November 1947. During
1786-505: 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
1880-494: 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
1974-449: Is restricted by the tunnel portal, and lower deck clearance is restricted by the upper deck. Tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and 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
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#17327660689072068-401: 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
2162-515: 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
2256-698: 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
2350-569: 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
2444-471: 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
2538-848: 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
2632-472: 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
2726-636: The San Francisco–Oakland Bay Bridge , bringing Key System trains to the then-new Transbay Terminal in San Francisco's downtown. The bridge railway and Transbay Terminal were shared with the Southern Pacific 's Interurban Electric and the Western Pacific 's Sacramento Northern railroads. The Key System's first trains were composed of standard wooden railroad passenger cars , complete with clerestory roofs. Atop each of these,
2820-533: The Temescal District of Oakland. The Elmhurst Carhouse was in the east Oakland district of Elmhurst , on East 14th (International Blvd.) between 94th and 96th Avenues. The Northern Carhouse was in Richmond where today's AC Transit has a bus yard. In the early years of operation, these were supplemented by a number of smaller carbarns scattered throughout the East Bay area, many of them inherited from
2914-679: 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
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3008-610: 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
3102-562: The eastern San Francisco Bay Area from 1903 until 1960, when it was sold to a newly formed public agency, AC Transit . The Key System consisted of local streetcar and bus lines in the East Bay, and commuter rail and bus lines connecting the East Bay to San Francisco by a ferry pier on San Francisco Bay , later via the lower deck of the Bay Bridge . At its height during the 1940s, the Key System had over 66 miles (106 km) of track. The local streetcars were discontinued in 1948 and
3196-489: 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
3290-449: The 1200 volts used by the SP commuter trains. The cars had an enclosed operator's cab in the right front, with passenger seats extending to the very front of the vehicle, a favorite seat for many children, with dramatic views of the tracks ahead. The exterior color of the cars was orange and silver. Interior upholstery was woven reed seat covers in one of the articulated sections, and leather in
3384-689: 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
3478-638: 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
3572-716: 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 ;
3666-400: The Bay Bridge was part of the upper deck lining in late summer 1936. This included the emplacement of regularly spaced refuge bays ("deadman holes") along the south wall of the lower deck tunnel, escape alcoves common in all railway tunnels into which track maintenance workers could duck if a train came along. These remain and are visible to eastbound motorists today. The completed tunnel bore
3760-493: The Bay Bridge, including the construction of the Yerba Buena Tunnel. Before starting excavation, the ground through which the western half of the tunnel would be bored was stabilized by injecting cement grout under pressure through 25 1.5-inch (38 mm) holes bored into the loose rock over the crown of the tunnel. After excavating the western and eastern open portals, three drifts were bored from west to east along
3854-848: The Great Crash of 1929 , a holding company called the Railway Equipment & Realty Co. was created, with the subsidiary Key System Ltd running the commuter trains. In 1938, the name became the Key System . During World War II , the Key System built and operated the Shipyard Railway between a transfer station in Emeryville and the Kaiser Shipyards in Richmond. National City Lines acquired 64% of
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3948-645: The Masonite pads had swelled due to rainwater infiltration, cracking the tunnel walls and allowing moisture in to the reinforcing steel. Repairs to the degraded concrete started in February 2017. Drains and catch basins were replaced to reduce the likelihood of clogging, and fiberglass-reinforced mortar was used to patch removed concrete. The repairs, which required some daytime lane closures, were expected to last until June 2017. California Department of Transportation engineer C.H. Purcell served as chief engineer for
4042-709: 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
4136-599: 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
4230-673: The United States. Of the large bridge units, three are at the Western Railway Museum near Rio Vista, California while another is at the Orange Empire Railway Museum in southern California. The initial connection across the Bay to San Francisco was by ferryboat via a causeway and pier (" mole "), extending from the end of Yerba Buena Avenue in Oakland, California , westward 16,000 feet (4,900 m) to
4324-496: The Yerba Buena Cable Anchorage, Tunnel & Viaduct segment was opened for bids on March 28, 1933, and awarded to the low bidder, Clinton Construction Company of California, for $ 1,821,129.50 (equivalent to $ 34 million in 2023). Yerba Buena Island was the main site of the official groundbreaking for the Bay Bridge on July 9, 1933, when President Franklin D. Roosevelt remotely set off a dynamite blast on
4418-400: 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
4512-532: The commuter trains to San Francisco were discontinued in 1958. The Key System's territory is today served by BART and AC Transit bus service. The system began as a consolidation of several streetcar lines assembled in the late 1890s and early 1900s by Francis Marion "Borax" Smith and his business interests. After having made a fortune in Borax and gained his nickname, "Borax", the entrepreneur turned to real estate and electric traction for streetcars. The Key System
4606-502: 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
4700-450: The concrete wall had caused the reinforcing steel to corrode and expand, forcing a chunk of the tunnel wall out. A subsequent California Department of Transportation (Caltrans) investigation identified 12 spots on both sides of the tunnel wall in the lower deck space showed signs of corrosion-induced damage, but no immediate risk of further spalling. The apparent cause was rainwater leaking from upper deck drains. Caltrans engineers speculated
4794-421: The eastern side of the island at 12:58 p.m. local time. Former President Herbert Hoover and Governor James Rolph were onsite; the two men were the first to turn over the earth with ceremonial golden spades. Other ceremonies took place simultaneously in San Francisco (on Rincon Hill ) and Oakland Harbor. The Yerba Buena Tunnel opened, along with the rest of the Bay Bridge, on November 12, 1936. As of 2019,
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#17327660689074888-409: 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
4982-441: 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
5076-405: 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
5170-507: The idea of using a stylized map on which the system's routes resembled an old-fashioned key, with three "handle loops" that covered the cities of Berkeley, Piedmont (initially, "Claremont" shared the Piedmont loop) and Oakland, and a "shaft" in the form of the Key pier, the "teeth" representing the ferry berths at the end of the pier. The company touted its 'key route', which led to the adoption of
5264-640: 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
5358-399: The increasing use of buses. Initially a separate company, it was formed by the merger of six local street railroads. The numbering of the streetcar lines changed several times over the years. The Key System's streetcars operated out of several carbarns. The Central Carhouse was on the east side of Lake Merritt on Third Avenue. The Western Carhouse was located at 51st and Telegraph Avenue in
5452-435: 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
5546-468: 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
5640-629: 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
5734-682: The name "Key System". In 1908, the SFOSJR changed its name to the San Francisco, Oakland & San Jose Consolidated Railway ; it changed to the San Francisco-Oakland Terminal Railway in 1912. Smith was ousted from the company in 1913. After it went bankrupt in December 1923, it was re-organized as the Key System Transit Co. , adopting a marketing concept as the name of the company. Following
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#17327660689075828-424: The new bridge, articulated cars sharing a common central truck and including central passenger entries in each car, a forerunner of the design of most light rail vehicles today. Several of these pairs were connected to make up a train. Power pickup was via pantograph from overhead catenary wires, except on the Bay Bridge where a third rail pickup was used. The Key's trains ran on 600 volt direct current , compared to
5922-551: The new upper deck and old upper deck, and the overall elevation change of 26 inches (660 mm) caused drivers to slow to 15 miles per hour (24 km/h), resulting in traffic jams. The first accident caused by "The Hump", the nickname the bridge acquired after prominent warning signs advertising its presence, occurred just twelve minutes after it was first deployed on November 25, 1961. The new precast upper deck units were each 7 feet 8 inches (2.34 m) long, and were installed in two halves. One side of each half rested on
6016-483: 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
6110-464: The opening of the Bay Bridge in 1936, it was the world's largest-bore tunnel. Preliminary surveys to lay out the route of the planned Bay Bridge were held in April 1931. Dedication ceremonies were held on February 24, 1932, and by April 1932, the final design for the Bay Bridge, including the single-bore tunnel through Yerba Buena Island, had been completed and submitted for approval. The contract to build
6204-540: 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
6298-405: The order (some units of which had already been painted for the Key and delivered to Oakland) to its own Los Angeles Transit Lines , where they ran until 1963. The last Key streetcars ran on November 28, 1948, replaced by buses. From the beginning, the Key System had been conceived as a dual real estate and transportation system. "Borax" Smith and his partner Frank C. Havens first established
6392-411: The other, the smoking section. The flooring was linoleum . During WWII, the roofs were painted gray for aerial camouflage. After acquisition by National City Lines, all Key vehicles including the bridge units were re-painted in that company's standard colors, yellow and green. Until the Bay Bridge railway began operation, Key commuter trains had no letter designation. They were generally referred to by
6486-414: The ownership of these companies. In 1948 National City Lines proposed a plan to convert all the streetcars to buses. They placed an advertisement in the local papers explaining their plan to 'modernize' and 'motorize' Line 14. The Oakland City Council opposed the plan by 5–3. The Public Utilities Commission (PUC) supported the plan which included large fare increases. In October 1948, 700 people signed
6580-479: The path of the tunnel: one at the crown and the other two at the lower corners. The first drift broke through in July 1934, approximately one year after the start of construction. A ceremonial party led by Governor Merriam celebrated the completion of the first 12-foot-square (3.7 m) drift on July 24 by walking through it, followed by a short speech. The space between the three drifts was then excavated, resulting in
6674-693: The period there were many complaints of overcrowding. On April 9, 1947, nine corporations and seven individuals (constituting officers and directors of certain of the corporate defendants) were indicted in the Federal District Court of Southern California on two counts: ' conspiring to acquire control of a number of transit companies, forming a transportation monopoly ' and 'Conspiring to monopolize sales of buses and supplies to companies owned by National City Lines'. They were convicted of conspiring to monopolize sales of buses and supplies. They were acquitted of conspiring to monopolize
6768-551: The pier end of the mole, consuming the ferry terminal building as well as gutting the ferryboat Peralta . The pier was subsequently reconstructed further south and a new terminal building erected. The Key System operated a fleet of ferries between the Key Route Pier and the San Francisco Ferry Building until January 15, 1939, when a new dual track opened on the south side of the lower deck of
6862-469: The pre-Key companies acquired by "Borax" Smith. The Key streetcars were originally painted dark green and cream white, then orange. They were re-painted in the green and yellow scheme of National City Lines after NCL acquired the Key System. The Key System had ordered 40 trolley coaches from ACF-Brill in 1945 to convert the East Bay trolley lines. The new NCL management canceled the Key's trackless program in 1946 before wire changes were made, and diverted
6956-559: The principal street or district they served, though the Key System did not have any formal naming scheme outside of letter designations. D was reserved for a proposed line into Montclair alongside the Sacramento Northern interurban railway. Shortly after opening of the Bay Bridge to train traffic, the Key System continued to use its pier for special service trains for ferry service to the 1939 Golden Gate International Exposition on Treasure Island — these were given
7050-522: 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
7144-490: 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,
7238-413: The railroad in order to gain access to its right of way and waterfront operations, as well as use the abandoned pier as a starting point for his own passenger mole . Transbay service began on October 26, 1903, with a four-car train carrying 250 passengers, departing downtown Berkeley for the ferry to San Francisco . Before the end of 1903, Frank C. Havens , the general manager of the SFOSJR, devised
7332-482: 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
7426-522: The sale of buses and related products to their subsidiary transit companies throughout the U.S. Between 1946 and 1954 transbay fares increased from 20¢ to 50¢ ($ 3 to $ 6 adjusted for inflation). Fares in this period were used to operate and for 'motorisation' which included streetcar track removal, repaving, purchase of new buses and the construction of bus maintenance facilities. Transbay ridership fell from 22.2 million in 1946 to 9.8 million in 1952. The Key System's famed commuter train system
7520-458: The same letter designations. AC Transit preserved the letter-designated routes when it took over the Key System two years later, and are still in use; AC Transit's B, C, E, F, G and H lines follow roughly the corresponding Key routes and neighborhoods. The Key System's streetcars operated as a separate division under the name "Oakland Traction Company", later changed to "East Bay Street Railways. Ltd", and finally to "East Bay Transit Co.", reflecting
7614-542: 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
7708-537: The special designation "X". The service was discontinued at the end of the first year of the Exposition and not revived for the 1940 season. On September 13, 1942, a stop was opened at Yerba Buena Island to serve expanded wartime needs on adjacent Treasure Island. It remained after the war until the end of all rail service on the Key System. The A, B, C, E and F lines were the last Key System rail lines. Train service ended on April 20, 1958, replaced by buses using
7802-425: The stock in the system in 1946. The same year E. Jay Quinby hand published a document exposing the ownership of National City Lines ( General Motors , Firestone Tire , and Phillips Petroleum ). He addressed the publication to The Mayors; The City Manager; The City Transit Engineer; The members of The Committee on Mass-Transportation and The Tax-Payers and The Riding Citizens of Your Community . In it he wrote "This
7896-400: 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,
7990-432: The tunnel lacks an official name. On January 30, 2016, a chunk of concrete the size of an automobile tire fell from the tunnel wall into the slow lane of eastbound traffic on the lower deck of the Yerba Buena Tunnel, causing a minor accident. The concrete fell from where the upper deck is connected to the tunnel wall. Based on an examination of photographs, a professor from Georgia Tech postulated that water infiltration into
8084-451: The tunnel wall, padded by 1 ⁄ 2 -inch-thick (1.3 cm) Masonite. The planned completion date for tunnel reconstruction was July 1962, but "The Hump" was not dismantled until October 27, 1962. The San Francisco Chronicle marked the occasion by quipping "[The Hump] produced more jams than Grandma ever made." After reconstruction, both the upper and lower decks featured 16 feet (4.9 m) of vertical clearance. Upper deck clearance
8178-428: 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
8272-413: The upper deck was reserved for automobile traffic, and carried six lanes, each 9 feet 8 inches (2.95 m) wide. The lower deck was further divided into three lanes of traffic for heavy trucks (each 10 feet 4 inches [3.15 m] wide), and two railroad tracks on the south side (27 feet [8.2 m] wide for both tracks). The initial design in 1932 called for the two rail tracks to flank
8366-575: 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
8460-411: Was dedicated to westbound traffic, and the lower deck was dedicated to eastbound traffic. The impact to traffic during reconstruction of the tunnel was minimized mainly by working outside normal commuting hours and through the use of a portable steel bridge 26 feet (7.9 m) long and 58 feet (18 m) wide, designed to fit between the curbs of the existing upper deck. The bridge spanned the gap between
8554-434: Was dismantled in 1958 after many years of declining ridership as well by the corrupt monopolistic efforts of National City Lines. The last run was on April 20, 1958. In 1960, the newly formed publicly owned AC Transit took over the Key System's facilities. Most of the rolling stock was scrapped, with some sold to Buenos Aires, Argentina. Several streetcars, interurbans and bridge units were salvaged for collections in
8648-399: Was excavated using a power shovel. By May 1935, work on removing the core was progressing and 40 steel ribs had been placed; concrete embedment was just starting. Removal of the core was completed on November 18, 1935. Once the excavation was complete, the upper deck was placed and the interior ceiling above the upper deck was lined with tiles. The last concrete poured during the construction of
8742-489: Was founded as the San Francisco, Oakland, and San Jose Railway (SFOSJR) , incorporated in 1902. After consolidating local lines under one company, Smith sought to compete with the Southern Pacific commuter ferry market as well as develop new streetcar suburbs in the East Bay . The troubled California & Nevada Railroad had begun construction of a ferry pier in Oakland, but its plans were never realized. Smith purchased
8836-732: 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
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