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Three oxides of xenon are known : xenon trioxide ( XeO |
3 ) and xenon tetroxide ( XeO |
4 ) , both of which are dangerously explosive and powerful oxidizing agents , and xenon dioxide ( XeO2 ) , which was reported in 2011 with a coordination number of four . XeO2 forms when xenon tetrafluoride is poured over ice . Its crystal structure may allow it to replace silicon in silicate minerals . The XeOO + cation has been identified by infrared spectroscopy in solid argon . |
Xenon does not react with oxygen directly ; the trioxide is formed by the hydrolysis of XeF |
6 : |
XeF |
6 + 3 H |
2O → XeO |
3 + 6 HF |
XeO |
3 is weakly acidic , dissolving in alkali to form unstable xenate salts containing the HXeO − |
4 anion . These unstable salts easily disproportionate into xenon gas and perxenate salts , containing the XeO4 − |
6 anion . |
Barium perxenate , when treated with concentrated sulfuric acid , yields gaseous xenon tetroxide : |
Ba |
2XeO |
6 + 2 H |
2SO |
4 → 2 BaSO |
4 + 2 H |
2O + XeO |
4 |
To prevent decomposition , the xenon tetroxide thus formed is quickly cooled to form a pale @-@ yellow solid . It explodes above − 35 @.@ 9 ° C into xenon and oxygen gas . |
A number of xenon oxyfluorides are known , including XeOF |
= = Iconography = = |
= = = Textual descriptions = = = |
The Agamic texts like the Amsumadbhedagama , the Uttara @-@ kamaikagama and the Purva @-@ Karanagama prescribe the iconography of the Kalyanasunadara icon . |
A young four @-@ armed Shiva and a beautiful two @-@ armed Parvati should be the central figures , performing the panigrahana ( " accepting the hand " ) ritual of a Hindu wedding , where the groom accepts the bride by taking her right hand in his . Shiva stands in tribhanga posture , with one of his legs straight and firmly on the ground and the other one slightly bent . Shiva wears a jata @-@ mukuta ( a headdress formed of piled , matted hair ) on his head , adorned with a crescent moon . He wears serpents as earrings , as a waist band and as a necklace . Various gold ornaments adorn his body . His back hands carry a parashu ( axe ) and a mriga ( deer ) . His front left hand makes the varada mudra ( " blessing @-@ giving gesture " ) and his front right hand is stretched ahead to receive the hand of the bride . A dark @-@ complexioned Parvati , adorned in silk and gold finery , stands to the left of Shiva , blushing with her head bent slightly as she extends her right arm to hold Shiva 's right hand . She holds a nilotpala ( blue lotus ) in her left arm . |
The god Vishnu and his consorts Lakshmi and Bhudevi should be represented as taking the place of Parvati 's parents in the ceremony . The four @-@ armed Vishnu should be shown in the background in between Shiva and Parvati ; in one of his front hands is a golden pot from which he pours water over the hands of the couple , symbolizing giving away the bride to the groom . He holds his usual attributes , the sudarshana chakra ( discus ) and a shankha ( conch ) , in his back arms . Vishnu 's wives , dressed in royal finery , stand behind Parvati and hold her waist , symbolizing the handing over . |
The four @-@ headed god Brahma should be shown seated on the ground in the foreground officiating as the wedding priest and making offerings to the homa ( sacred fire ) in the kunda ( fire @-@ altar ) . The four @-@ armed god holds a sruka and sruva ( sacrificial ladle and spoon ) in his front arms and a kamandalu ( water @-@ pot ) and akshamala ( rosary ) in his back arms . The presence of the fire also indicates another important ritual of the Hindu wedding , saptapadi ( " seven steps " ) where the bride and groom go around the fire seven times . |
The figure of Shiva should be tallest , followed by that of Vishnu , Parvati and Vishnu 's wives . Various deities like the eight guardians of the directions , the eight Vasus , the seven Matrika goddesses , celestial beings such as Yakshas and Gandharvas , sages and siddhas may be depicted standing with folded arms in the background . |
= = = Depictions = = = |
The complete scene of the wedding is not always depicted . Sometimes , only the principal participants are shown . Chola bronzes featuring only Shiva and Parvati as described in the wedding scene are found . South Indian sculptures , like those from Madurai , feature only the couple and Vishnu . In this configuration , Parvati is depicted in the centre with Vishnu on the left giving away her hand to Shiva on the right . Sometimes as in the Elephanta Caves , Parvati 's biological father Himavan , instead of Vishnu , is depicted giving away his daughter to Shiva . |
Other deviations from the texts may appear in the attributes held by the divine couple . Parvati may hold a mirror , instead of the lotus . Shiva may be shown holding the trishula ( trident ) and damaru ( drum ) in his back hands . Regional variations in iconography may also occur . In Bengal , Shiva holds a karttari ( knife ) , the ceremonial weapon that a Hindu groom from Bengal is expected to carry in a wedding . |
Various wedding guests are depicted in the scene . Shiva 's attendant ganas enjoy the festivities ; playing drums or dancing . The vahanas ( vehicles ) of the couple , Shiva 's bull Nandi and Parvati 's lion , are sometimes pictured in the scene . In vertical panel depictions , the celestial guests are often shown flying over Shiva and Parvati . While the gods are pictured flying on their respective vahanas ( e.g. Indra on his elephant , Agni on a ram ) and with their consorts ; semi @-@ divine beings like Vidyadharas fly without vehicles . An anachronism found in a few Kalyanasundara scenes is the presence of the yet @-@ unborn children of Shiva and Parvati , Ganesha and Kartikkeya . Examples of this anachronism are found at the Rameshvara Cave of Ellora , and in a 9th @-@ century sculpture from Uttar Pradesh now housed in Los Angeles County Museum of Art . |
= = Worship = = |
Though Kalyanasundara icons are found across India in caves , sculptures and temple walls , no sect is centred on their worship . The icon is a popular feature on temple gopurams ( temple towers ) . |
In South Indian Shiva temples like those in Tiruvenkadu and Chidambaram , the bronze Kalyanasundara images of Shiva and Parvati are used in annual temple festivals to commemorate the divine union . Special halls are reserved for the annual ceremonial wedding of the deities . The Kalyanasundara bronzes are used only in this festival and kept unused the rest of the year . |
At the Meenakshi Amman Temple , women worship the Kalyanasundara sculpture to find husbands . |
Kalyanasundara is worshipped in Thirumanancheri as god of Marriages . The idols of Lord shiva in the form of Kalyanasundara and Parvathi is worshipped by the unmarried men and women for early marriage . There are also people who have completed the marriages come here to complete rituals . |
= SS El Sol = |
SS El Sol was a cargo ship built in 1910 for the Morgan Line , a subsidiary of the Southern Pacific Company . During World War I , she was known as USAT El Sol in service with the United States Army and as USS El Sol ( ID @-@ 4505 ) in service with the United States Navy . At the end of war , she reverted to her original name of SS El Sol . |
SS El Sol was one of four sister ships that carried cargo and a limited number of passengers for the Morgan Line . She was acquired by the U.S. Army after the United States entered World War I in April 1917 , and converted to carry horses and mules to France . In August 1918 , the ship was transferred to the U.S. Navy and continued transporting animals through the end of the war . |
El Sol returned to the Morgan Line in 1919 and sailed with them until March 1927 , when she sank in New York Harbor after colliding with Sac City of the American Diamond Line . A portion of the ship 's cargo was salvaged but the ship was scrapped later in the year . |
= = Early career = = |
SS El Sol was a cargo and passenger steamship launched on 11 May 1910 by the Newport News Shipbuilding and Dry Dock Co. of Newport News , Virginia ( yard no . 130 ) , and delivered to the Atlantic division of the Morgan Line on 20 August 1910 . She was the first of four sister ships ; the other three being El Mundo , El Oriente , and El Occidente . El Sol was 6 @,@ 008 gross register tons ( GRT ) , was 430 feet 1 inch ( 131 @.@ 09 m ) long by 53 feet 1 inch ( 16 @.@ 18 m ) abeam , and made 16 knots ( 30 km / h ) . The vessel sailed for the Morgan Line , the brand name of the Southern Pacific Steamship Company ( a subsidiary of the Southern Pacific Railroad ) , which employed her to carry cargo and a limited number of passengers between New York ; New Orleans , the eastern terminus of the Southern Pacific line ; and Galveston , Texas . |
= = World War I = = |
After the United States declared war on Germany in April 1917 , El Sol was requisitioned by the United States Shipping Board ( USSB ) on behalf of the United States Army , who designated her as an animal transport ship . Although there is no information about the specific conversion of El Sol , for other ships this typically meant that any second- or third @-@ class passenger accommodations had to be ripped out and replaced with ramps and stalls for the horses and mules carried . |
Sources do not reveal all of El Sol 's movements , but it is known that she departed on her second trip to France from Newport News on 10 February 1918 . Carrying 650 animals , El Sol headed to New York to join in a convoy with fellow Army transport Pastores , and U.S. Navy troop transports Covington , DeKalb , Manchuria , George Washington , President Grant , and Susquehanna . The convoy was escorted by Huntington when it departed from New York on 18 February , and arrived at Saint @-@ Nazaire on 4 March . Ten animals on board El Sol died or were destroyed during the crossing . |
The next recorded activity of El Sol was on 3 August , when she was transferred from the Army to the U.S. Navy and commissioned the same day with Lieutenant Commander G. Anderson , USNRF , in command . El Sol was assigned to the Naval Overseas Transportation Service ( NOTS ) and continued to carry animals and supplies for the U.S. Army . |
By August , each animal transport ship had a transport veterinarian and a permanent veterinary detachment to care for the animals while on board the ship . El Sol had also been joined by two of her sister ships , El Oriente and El Occidente in animal transport duty . She next departed Newport News on 23 August 1918 with 520 horses and mules on board . Upon arrival at Saint @-@ Nazaire on 19 September , El Sol delivered her complete load of animals ; none had died during the passage . After returning to the U.S. , El Sol departed again on 30 October with another 620 animals on board . Docking in Bordeaux on 13 November — two days after the Armistice — she again delivered her full load of animals . |
El Sol made two more roundtrips for the NOTS over the next five months . While returning to the United States from her last NOTS sailing in late March 1919 , El Sol responded to distress calls from Scranton , a Navy troop transport which had a damaged rudder and was disabled . El Sol came to the aid of the stricken ship , which was 900 nautical miles ( 1 @,@ 700 km ) east of New York , to attempt to take her under tow . During the day on 28 March , Scranton attempted to run a towline to El Sol by sending a launch in the rolling seas , but it capsized , killing three men . Ultimately , El Sol stood by Scranton for over 40 hours until minesweeper Penguin arrived and took Scranton under tow . |
At the conclusion of her last NOTS voyage on 3 April , El Sol was converted to a troop transport and assigned to the Navy 's Cruiser and Transport Force on 15 April . El Sol returned 2 @,@ 714 healthy and wounded American servicemen from France in two voyages . Decommissioned on 18 September , El Sol was returned to the Morgan Line soon after . |
= = Postwar civilian service = = |
El Sol resumed cargo service with the Morgan Line , where she had 8 years of uneventful operation . On 11 March 1927 , however , El Sol was inbound to New York with a $ 1 @,@ 000 @,@ 000 cargo of pig iron , copper , and bales of cotton . When a heavy fog settled over New York Harbor , Captain Charles H. Knowles ordered his ship to anchor until the fog cleared . As El Sol was being maneuvered into position at about 07 : 45 , the American Diamond Line ship Sac City hit a glancing blow to El Sol , bounced off and then struck El Sol a second time , ripping through El Sol 's plating . Sac City 's bow had some slight damage , but El Sol sank quickly in about 60 feet ( 18 m ) of water about a half @-@ mile ( 800 m ) south of the Statue of Liberty . Out of El Sol 's crew of 45 men , 44 were rescued ; the ship 's carpenter , who could not swim , was last seen clutching the ship 's rail as it went below the surface . |
El Sol settled on the bottom at a 45 ° angle with only the tops of her masts protruding above the surface ; the Morgan Line house flag — a blue house flag with a red M inside a white star — still fluttered in the breeze . Even though the sunken vessel was not considered a hazard to navigation , in another fog two days later a Staten Island Ferryboat nearly hit El Sol 's wreck . |
In a hearings before the United States Steamboat Inspection Service , Captain Knowles of El Sol and the captain of Sac City were both cleared of wrongdoing in the collision , and the blame was laid on the heavy fog . On 31 July , The New York Times reported on the cargo salvage operations still underway on the wreck of El Sol . In three months of continuous operations , the salvage company reported that about 35 % of the sunken ship 's cargo had been recovered . The hulk of El Sol was scrapped later in 1927 . |
= Hoover Dam = |
Hoover Dam , once known as Boulder Dam , is a concrete arch @-@ gravity dam in the Black Canyon of the Colorado River , on the border between the U.S. states of Nevada and Arizona . It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30 , 1935 , by President Franklin D. Roosevelt . Its construction was the result of a massive effort involving thousands of workers , and cost over one hundred lives . The dam was controversially named after President Herbert Hoover . |
Since about 1900 , the Black Canyon and nearby Boulder Canyon had been investigated for their potential to support a dam that would control floods , provide irrigation water and produce hydroelectric power . In 1928 , Congress authorized the project . The winning bid to build the dam was submitted by a consortium called Six Companies , Inc . , which began construction on the dam in early 1931 . Such a large concrete structure had never been built before , and some of the techniques were unproven . The torrid summer weather and lack of facilities near the site also presented difficulties . Nevertheless , Six Companies turned over the dam to the federal government on March 1 , 1936 , more than two years ahead of schedule . |
Hoover Dam impounds Lake Mead , the largest reservoir in the United States by volume . The dam is located near Boulder City , Nevada , a municipality originally constructed for workers on the construction project , about 30 mi ( 48 km ) southeast of Las Vegas , Nevada . The dam 's generators provide power for public and private utilities in Nevada , Arizona , and California . Hoover Dam is a major tourist attraction ; nearly a million people tour the dam each year . The heavily travelled U.S. 93 ran along the dam 's crest until October 2010 , when the Hoover Dam Bypass opened . |
= = Background = = |
= = = Search for resources = = = |
As the United States developed the Southwest , the Colorado River was seen as a potential source of irrigation water . An initial attempt at diverting the river for irrigation purposes occurred in the late 1890s , when land speculator William Beatty built the Alamo Canal just north of the Mexican border ; the canal dipped into Mexico before running to a desolate area Beatty named the Imperial Valley . Though water from the Imperial Canal allowed for the widespread settlement of the valley , the canal proved expensive to maintain . After a catastrophic breach that caused the Colorado River to fill the Salton Sea , the Southern Pacific Railroad spent $ 3 million in 1906 – 07 to stabilize the waterway , an amount it hoped vainly would be reimbursed by the Federal Government . Even after the waterway was stabilized , it proved unsatisfactory because of constant disputes with landowners on the Mexican side of the border . |
As the technology of electric power transmission improved , the Lower Colorado was considered for its hydroelectric @-@ power potential . In 1902 , the Edison Electric Company of Los Angeles surveyed the river in the hope of building a 40 @-@ foot ( 12 m ) rock dam which could generate 10 @,@ 000 horsepower ( 7 @,@ 500 kW ) . However , at the time , the limit of transmission of electric power was 80 miles ( 130 km ) , and there were few customers ( mostly mines ) within that limit . Edison allowed land options it held on the river to lapse — including an option for what became the site of Hoover Dam . |
In the following years , the Bureau of Reclamation ( BOR ) , known as the Reclamation Service at the time , also considered the Lower Colorado as the site for a dam . Service chief Arthur Powell Davis proposed using dynamite to collapse the walls of Boulder Canyon , 20 miles ( 32 km ) north of the eventual dam site , into the river . The river would carry off the smaller pieces of debris , and a dam would be built incorporating the remaining rubble . In 1922 , after considering it for several years , the Reclamation Service finally rejected the proposal , citing doubts about the unproven technique and questions as to whether it would in fact save money . |
= = = Planning and agreements = = = |
In 1922 , the Reclamation Service presented a report calling for the development of a dam on the Colorado River for flood control and electric power generation . The report was principally authored by Davis , and was called the Fall @-@ Davis report after Interior Secretary Albert Fall . The Fall @-@ Davis report cited use of the Colorado River as a federal concern , because the river 's basin covered several states , and the river eventually entered Mexico . Though the Fall @-@ Davis report called for a dam " at or near Boulder Canyon " , the Reclamation Service ( which was renamed the Bureau of Reclamation the following year ) found that canyon unsuitable . One potential site at Boulder Canyon was bisected by a geologic fault ; two others were so narrow there was no space for a construction camp at the bottom of the canyon or for a spillway . The Service investigated Black Canyon and found it ideal ; a railway could be laid from the railhead in Las Vegas to the top of the dam site . Despite the site change , the dam project was referred to as the " Boulder Canyon Project " . |
With little guidance on water allocation from the Supreme Court , proponents of the dam feared endless litigation . A Colorado attorney proposed that the seven states which fell within the river 's basin ( California , Nevada , Arizona , Utah , New Mexico , Colorado and Wyoming ) form an interstate compact , with the approval of Congress . Such compacts were authorized by Article I of the United States Constitution but had never been concluded among more than two states . In 1922 , representatives of seven states met with then @-@ Secretary of Commerce Herbert Hoover . Initial talks produced no result , but when the Supreme Court handed down the Wyoming v. Colorado decision undermining the claims of the upstream states , they became anxious to reach an agreement . The resulting Colorado River Compact was signed on November 24 , 1922 . |
Legislation to authorize the dam was introduced repeatedly by Representative Phil Swing ( R @-@ Calif . ) and Senator Hiram Johnson ( R @-@ Calif . ) , but representatives from other parts of the country considered the project as hugely expensive and one that would mostly benefit California . The 1927 Mississippi flood made Midwestern and Southern congressmen and senators more sympathetic toward the dam project . On March 12 , 1928 , the failure of the St. Francis Dam , constructed by the city of Los Angeles , caused a disastrous flood that killed up to 600 people . As that dam was a curved @-@ gravity type , similar in design to the arch @-@ gravity as was proposed for the Black Canyon dam , opponents claimed that the Black Canyon dam 's safety could not be guaranteed . Congress authorized a board of engineers to review plans for the proposed dam . The Colorado River Board found the project feasible , but warned that should the dam fail , every downstream Colorado River community would be destroyed , and that the river might change course and empty into the Salton Sea . The Board cautioned : " To avoid such possibilities , the proposed dam should be constructed on conservative if not ultra @-@ conservative lines . " |
On December 21 , 1928 President Coolidge signed the bill authorizing the dam . The Boulder Canyon Project Act appropriated $ 165 million for the Hoover Dam along with the downstream Imperial Dam and All @-@ American Canal , a replacement for Beatty 's canal entirely on the U.S. side of the border . It also permitted the compact to go into effect when at least six of the seven states approved it . This occurred on March 6 , 1929 with Utah 's ratification ; Arizona did not approve it until 1944 . |
= = = Design , preparation and contracting = = = |
Even before Congress approved the Boulder Canyon Project , the Bureau of Reclamation was considering what kind of dam should be used . Officials eventually decided on a massive concrete arch @-@ gravity dam , the design of which was overseen by the Bureau 's chief design engineer John L. Savage . The monolithic dam would be thick at the bottom and thin near the top , and would present a convex face towards the water above the dam . The curving arch of the dam would transmit the water 's force into the abutments , in this case the rock walls of the canyon . The wedge @-@ shaped dam would be 660 ft ( 200 m ) thick at the bottom , narrowing to 45 ft ( 14 m ) at the top , leaving room for a highway connecting Nevada and Arizona . |
On January 10 , 1931 , the Bureau made the bid documents available to interested parties , at five dollars a copy . The government was to provide the materials ; but the contractor was to prepare the site and build the dam . The dam was described in minute detail , covering 100 pages of text and 76 drawings . A $ 2 million bid bond was to accompany each bid ; the winner would have to post a $ 5 million performance bond . The contractor had seven years to build the dam , or penalties would ensue . |
The Wattis Brothers , heads of the Utah Construction Company , were interested in bidding on the project , but lacked the money for the performance bond . They lacked sufficient resources even in combination with their longtime partners , Morrison @-@ Knudsen , which employed the nation 's leading dam builder , Frank Crowe . They formed a joint venture to bid for the project with Pacific Bridge Company of Portland , Oregon ; Henry J. Kaiser & W. A. Bechtel Company of San Francisco ; MacDonald & Kahn Ltd. of Los Angeles ; and the J.F. Shea Company of Portland , Oregon . The joint venture was called Six Companies , Inc. as Bechtel and Kaiser were considered one company for purposes of 6 in the name . The name was descriptive and was an inside joke among the San Franciscans in the bid , where " Six Companies " was also a Chinese benevolent association in the city . There were three valid bids , and Six Companies ' bid of $ 48 @,@ 890 @,@ 955 was the lowest , within $ 24 @,@ 000 of the confidential government estimate of what the dam would cost to build , and five million dollars less than the next @-@ lowest bid . |
The city of Las Vegas had lobbied hard to be the headquarters for the dam construction , closing its many speakeasies when the decision maker , Secretary of the Interior Ray Wilbur came to town . Instead , Wilbur announced in early 1930 that a model city was to be built in the desert near the dam site . This town became known as Boulder City , Nevada . Construction of a rail line joining Las Vegas and the dam site began in September 1930 . |
= = Construction = = |
= = = Labor force = = = |
Soon after the dam was authorized , increasing numbers of unemployed people converged on southern Nevada . Las Vegas , then a small city of some 5 @,@ 000 , saw between 10 @,@ 000 and 20 @,@ 000 unemployed descend on it . A government camp was established for surveyors and other personnel near the dam site ; this soon became surrounded by a squatters ' camp . Known as McKeeversville , the camp was home to men hoping for work on the project , together with their families . Another camp , on the flats along the Colorado River , was officially called Williamsville , but was known to its inhabitants as " Ragtown " . When construction began , Six Companies hired large numbers of workers , with more than 3 @,@ 000 on the payroll by 1932 and with employment peaking at 5 @,@ 251 in July 1934 . " Mongolian " ( Chinese ) labor was prevented by the construction contract , while the number of blacks employed by Six Companies never exceeded thirty , mostly lowest @-@ pay @-@ scale laborers in a segregated crew , who were issued separate water buckets . |
As part of the contract , Six Companies , Inc. was to build Boulder City to house the workers . The original timetable called for Boulder City to be built before the dam project began , but President Hoover ordered work on the dam to begin in March 1931 rather than in October . The company built bunkhouses , attached to the canyon wall , to house 480 single men at what became known as River Camp . Workers with families were left to provide their own accommodations until Boulder City could be completed , and many lived in Ragtown . The site of Hoover Dam endures extremely hot weather , and the summer of 1931 was especially torrid , with the daytime high averaging 119 @.@ 9 ° F ( 48 @.@ 8 ° C ) . Sixteen workers and other riverbank residents died of heat prostration between June 25 and July 26 , 1931 . |
The Industrial Workers of the World ( IWW or " Wobblies " ) , though much @-@ reduced from their heyday as militant labor organizers in the early years of the century , hoped to unionize the Six Companies workers by capitalizing on their discontent . They sent eleven organizers , several of whom were arrested by Las Vegas police . On August 7 , 1931 , the company cut wages for all tunnel workers . Although the workers sent away the organizers , not wanting to be associated with the " Wobblies " , they formed a committee to represent them with the company . The committee drew up a list of demands that evening and presented them to Crowe the following morning . He was noncommittal . The workers hoped that Crowe , the general superintendent of the job , would be sympathetic ; instead he gave a scathing interview to a newspaper , describing the workers as " malcontents " . |
On the morning of the 9th , Crowe met with the committee and told them that management refused their demands , was stopping all work , and was laying off the entire work force , except for a few office workers and carpenters . The workers were given until 5 p.m. to vacate the premises . Concerned that a violent confrontation was imminent , most workers took their paychecks and left for Las Vegas to await developments . Two days later , the remainder were talked into leaving by law enforcement . On August 13 , the company began hiring workers again , and two days later , the strike was called off . While the workers received none of their demands , the company guaranteed there would be no further reductions in wages . Living conditions began to improve as the first residents moved into Boulder City in late 1931 . |
A second labor action took place in July 1935 , as construction on the dam wound down . When a Six Companies manager altered working times to force workers to take lunch on their own time , workers responded with a strike . Emboldened by Crowe 's reversal of the lunch decree , workers raised their demands to include a $ 1 @-@ per @-@ day raise . The company agreed to ask the Federal government to supplement the pay , but no money was forthcoming from Washington . The strike ended . |
= = = River diversion = = = |
Before the dam could be built , the Colorado River needed to be diverted away from the construction site . To accomplish this , four diversion tunnels were driven through the canyon walls , two on the Nevada side and two on the Arizona side . These tunnels were 56 ft ( 17 m ) in diameter . Their combined length was nearly 16 @,@ 000 ft , or more than 3 miles ( 5 km ) . The contract required these tunnels to be completed by October 1 , 1933 , with a $ 3 @,@ 000 @-@ per @-@ day fine to be assessed for any delay . To meet the deadline , Six Companies had to complete work by early 1933 , since only in late fall and winter was the water level in the river low enough to safely divert . |
Tunneling began at the lower portals of the Nevada tunnels in May 1931 . Shortly afterward , work began on two similar tunnels in the Arizona canyon wall . In March 1932 , work began on lining the tunnels with concrete . First the base , or invert , was poured . Gantry cranes , running on rails through the entire length of each tunnel were used to place the concrete . The sidewalls were poured next . Movable sections of steel forms were used for the sidewalls . Finally , using pneumatic guns , the overheads were filled in . The concrete lining is 3 feet ( 1 m ) thick , reducing the finished tunnel diameter to 50 ft ( 15 m ) . The river was diverted into the two Arizona tunnels on November 13 , 1932 ; the Nevada tunnels were kept in reserve for high water . This was done by exploding a temporary cofferdam protecting the Arizona tunnels while at the same time dumping rubble into the river until its natural course was blocked . |
Following the completion of the dam , the entrances to the two outer diversion tunnels were sealed at the opening and halfway through the tunnels with large concrete plugs . The downstream halves of the tunnels following the inner plugs are now the main bodies of the spillway tunnels . The inner diversion tunnels were plugged at approximately one @-@ third of their length , beyond which they now carry steel pipes connecting the intake towers to the power plant and outlet works . The inner tunnels ' outlets are equipped with gates that can be closed to drain the tunnels for maintenance . |
= = = Groundworks , rock clearance and grout curtain = = = |
To protect the construction site from the Colorado River and to facilitate the river 's diversion , two cofferdams were constructed . Work on the upper cofferdam began in September 1932 , even though the river had not yet been diverted . The cofferdams were designed to protect against the possibility of the river flooding a site at which two thousand men might be at work , and their specifications were covered in the bid documents in nearly as much detail as the dam itself . The upper cofferdam was 96 ft ( 29 m ) high , and 750 feet ( 230 m ) thick at its base , as thicker than the dam itself . It contained 650 @,@ 000 cubic yards ( 500 @,@ 000 m3 ) of material . |
When the cofferdams were in place and the construction site was drained of water , excavation for the dam foundation began . For the dam to rest on solid rock , it was necessary to remove accumulated erosion soils and other loose materials in the riverbed until sound bedrock was reached . Work on the foundation excavations was completed in June 1933 . During this excavation , approximately 1 @,@ 500 @,@ 000 cu yd ( 1 @,@ 100 @,@ 000 m3 ) of material was removed . Since the dam was an arch @-@ gravity type , the side @-@ walls of the canyon would bear the force of the impounded lake . Therefore , the side @-@ walls were excavated too , to reach virgin rock as weathered rock might provide pathways for water seepage . |
The men who removed this rock were called " high scalers " . While suspended from the top of the canyon with ropes , the high @-@ scalers climbed down the canyon walls and removed the loose rock with jackhammers and dynamite . Falling objects were the most common cause of death on the dam site ; the high scalers ' work thus helped ensure worker safety . One high scaler was able to save life in a more direct manner : when a government inspector lost his grip on a safety line and began tumbling down a slope towards almost certain death , a high scaler was able to intercept him and pull him into the air . The construction site had , even then , become a magnet for tourists ; the high scalers were prime attractions and showed off for the watchers . The high scalers received considerable media attention , with one worker dubbed the " Human Pendulum " for swinging co @-@ workers ( and , at other times , cases of dynamite ) across the canyon . To protect themselves against falling objects , some high scalers took cloth hats and dipped them in tar , allowing them to harden . When workers wearing such headgear were struck hard enough to inflict broken jaws , they sustained no skull damage , Six Companies ordered thousands of what initially were called " hard boiled hats " ( later " hard hats " ) and strongly encouraged their use . |
The cleared , underlying rock foundation of the dam site was reinforced with grout , called a grout curtain . Holes were driven into the walls and base of the canyon , as deep as 150 feet ( 46 m ) into the rock , and any cavities encountered were to be filled with grout . This was done to stabilize the rock , to prevent water from seeping past the dam through the canyon rock , and to limit " uplift " — upward pressure from water seeping under the dam . The workers were under severe time constraints due to the beginning of the concrete pour , and when they encountered hot springs or cavities too large to readily fill , they moved on without resolving the problem . A total of 58 of the 393 holes were incompletely filled . After the dam was completed and the lake began to fill , large numbers of significant leaks into the dam caused the Bureau of Reclamation to look into the situation . It found that the work had been incompletely done , and was based on less than a full understanding of the canyon 's geology . New holes were drilled from inspection galleries inside the dam into the surrounding bedrock . It took nine years ( 1938 – 47 ) under relative secrecy to complete the supplemental grout curtain . |
= = = Concrete = = = |
The first concrete was poured into the dam on June 6 , 1933 , 18 months ahead of schedule . Since concrete heats and contracts as it cures , the potential for uneven cooling and contraction of the concrete posed a serious problem . Bureau of Reclamation engineers calculated that if the dam was built in a single continuous pour , the concrete would take 125 years to cool and the resulting stresses would cause the dam to crack and crumble . Instead , the ground where the dam was to rise was marked with rectangles , and concrete blocks in columns were poured , some as large as 50 ft square ( 15 m ) and 5 feet ( 1 @.@ 5 m ) high . Each five @-@ foot form contained a series of 1 @-@ inch ( 25 mm ) steel pipes through which first cool river water , then later ice @-@ cold water from a refrigeration plant was run . When an individual block had cured and had stopped contracting , the pipes were filled with grout . Grout was also used to fill the hairline spaces between columns , which were grooved to increase the strength of the joins . |
The concrete was delivered in huge steel buckets 7 feet high ( 2 @.@ 1 m ) and almost 7 feet in diameter ; Crowe was awarded two patents for their design . These buckets , which weighed 20 short tons ( 18 t ) when full , were filled at two massive concrete plants on the Nevada side , and were delivered to the site in special railcars . The buckets were then suspended from aerial cableways , which were used to deliver the bucket to a specific column . As the required grade of aggregate in the concrete differed depending on placement in the dam ( from pea @-@ sized gravel to 9 @-@ inch or 23 cm stones ) , it was vital that the bucket be maneuvered to the proper column . When the bottom of the bucket opened up , disgorging 8 cu yd ( 6 @.@ 1 m3 ) of concrete , a team of men worked it throughout the form . Although there are myths that men were caught in the pour and are entombed in the dam to this day , each bucket only deepened the concrete in a form by an inch , and Six Companies engineers would not have permitted a flaw caused by the presence of a human body . |
A total of 3 @,@ 250 @,@ 000 cubic yards ( 2 @,@ 480 @,@ 000 m3 ) of concrete was used in the dam before concrete pouring ceased on May 29 , 1935 . In addition , 1 @,@ 110 @,@ 000 cu yd ( 850 @,@ 000 m3 ) were used in the power plant and other works . More than 582 miles ( 937 km ) of cooling pipes were placed within the concrete . Overall , there is enough concrete in the dam to pave a two @-@ lane highway from San Francisco to New York . Concrete cores were removed from the dam for testing in 1995 ; they showed that " Hoover Dam 's concrete has continued to slowly gain strength " and the dam is composed of a " durable concrete having a compressive strength exceeding the range typically found in normal mass concrete " . Hoover Dam concrete is not subject to alkali – silica reaction ( ASR ) as the Hoover Dam builders happened to use nonreactive aggregate , unlike that at downstream Parker Dam , where ASR has caused measurable deterioration . |
= = = Dedication and completion = = = |
With most work finished on the dam itself ( the powerhouse remained uncompleted ) , a formal dedication ceremony was arranged for September 30 , 1935 , to coincide with a western tour being made by President Franklin D. Roosevelt . The morning of the dedication , it was moved forward three hours from 2 p.m. Pacific time to 11 a.m. ; this was done because Secretary of the Interior Harold L. Ickes had reserved a radio slot for the President for 2 p.m. but officials did not realize until the day of the ceremony that the slot was for 2 p.m. Eastern Time . Despite the change in the ceremony time , and temperatures of 102 ° F ( 39 ° C ) , 10 @,@ 000 people were present for the President 's speech in which he avoided mentioning the name of former President Hoover , who was not invited to the ceremony . To mark the occasion , a three @-@ cent stamp was issued by the United States Post Office Department — bearing the name " Boulder Dam " , the official name of the dam between 1933 and 1947 . After the ceremony , Roosevelt made the first visit by any American president to Las Vegas . |
Most work had been completed by the dedication , and Six Companies negotiated with the government through late 1935 and early 1936 to settle all claims and arrange for the formal transfer of the dam to the Federal Government . The parties came to an agreement and on March 1 , 1936 , Secretary Ickes formally accepted the dam on behalf of the government . Six Companies was not required to complete work on one item , a concrete plug for one of the bypass tunnels , as the tunnel had to be used to take in irrigation water until the powerhouse went into operation . |
= = = Construction deaths = = = |
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