Xaltozan Bridge

Xaltozan Bridge
View of the bridge from the Xaltozan Epitaph monument
Carries	12 lanes of motor vehicle traffic Rail traffic
Crosses	Xaltozan narrows
Locale	Angatahuaca bay Aztaco Republic
Other name(s)	Xaltozan Bridge Narrows Bridge
Maintained by	Cenyacanaliztli Zazaca Angatahuaca Angatahuaca Transportation Authority
Characteristics
Total length	13,700 ft (4,176 m)
Width	103 ft (31 m)
Height	693 ft (211 m)
Longest span	4,260 ft (1,298 m)
Clearance above	15 ft (4.57 m) (upper level) 14.4 ft (4.39 m) (lower level)
Clearance below	228 ft (69.5 m) at mean high water
History
Designer	Soona Kamilli and Tangaxuan Shanarani
Construction start	August 14, 1949 (1949-08-14)
Opened	December 22, 1954 (1954-12-22)

The Xaltozan Bridge is a suspension bridge spanning the mouth of Angatahuaca bay in the Aztaco Republic, Zacapican. It links the eastern and western banks of the Xaltozan narrows, the only means of maritime access to the economically vital port of Angatahuaca-Amegatlan from the Gulf of Matlayahualoyan and the Amictlan ocean. The design of the bridge creates an impressive 1,300 meter main span, the longest spans of any bridge in Zacapican and one of the longest in the world, with a clearance of some 70 meters below it to allow for the relatively unencumbered transit of vessels including some of the largest modern container ships through the waterway below. The crossing creates an important bypass route for rail and vehicle traffic seeking to avoid the busy Angatahuaca metropolitan zone in their travel along the southern Aztaco coastline, and would significantly shorten travel from one side of the bay to the other during local and regional trips. Because of the advantages of a crossing at the mouth of the bay, proposals for bridges and tunnels to make such a crossing possible were being proposed as early as 1915. An initial plan for a large cantilever railway bridge spanning the narrows was put into motion in 1927, but would face a serious setback in the form of the Xaltozan Explosion which imposed a halt to all construction and a revision of the designs. Construction would not restart on the project until 1949, well over a decade after the disaster which stopped the first bridge in its tracks, completing in 1954 to much fanfare around the Angatahauca area.

Design

Early Design

The original plans of the Xaltozan bridge called for the structure to be primarily a railway bridge of cantilever design. This design would have had its longest span at 500 meters wide, and with just 50 meters of clearance under this span, create a smaller and more restrictive shipping channel. It also called for many times more supports and foundations to be built in the seabed across the narrows to support the bridge. This version of the bridge was the sole design of Tangaxuan Shanarani, who would go on to assist in the design of the second and final version of the bridge as he was already familiar with the material characteristics of the seabed and other important features of the site from the work that had been done towards the construction of the first bridge. Indeed, this first design had been approved and began construction in 1927 only to have the construction site rocked by the effects of the Xaltozan Explosion in December of 1928. The disaster had created a powerful shockwave which broke the caissons in which the bridge's foundations were built and destroyed much of the work that had been done up to that point. In the aftermath and investigation which followed the disaster, it was found that the narrow shipping channel established through what would have been the main span of the bridge because of construction had in part contributed to the disaster, and it was decided to revisit the design of the bridge over concerns of potential future collisions between ships or even of ships striking the bridge pylons.

Second Bridge Plan

The Secretariat of Public Works supervising the project to realize the narrows crossing named architect and engineer Soona Kamilli to head the new bridge project following the cancelation of the the original bridge. This was a somewhat unpopular measure with some within the Public Works Secretariat and the engineering world at the time as Kamilli was both a woman and of Otomi descent, and was therefore a notable outlier among bridge engineers of the era. For this reason, the Public Works Secretariat only resorted to assigning Kamilli to the project after design proposals by several other more prominent engineers working for the Secretariat had failed to meet the requirements set by the Secretariat of Transportation and certain officials of the Aztaco Republic government. Kamilli's proposal called for a suspension bridge design to meet the demands of a much wider main span to accommodate a shipping channel of greatly increased dimensions. An original draft of 4 pylons would be reduced to a simplified, technically demanding final draft with just two pylons holding up the bridge. The design was created in cooperation with Doctor Seti, a hugely influential civil engineer of the Xolotecate Era and a personal friend of Soona Kamilli. Seti oversaw the production of wire rope of the kind needed in major suspension bridge projects around Zacapican, and could provide the very strong main cables that would be absolutely vital to the design of such a bridge. Without the guarantee of supply for such advanced materials needed in the bridge, it is likely Kamilli's designs could not have gone forward and might have seen the bridge project ultimately flounder and die out. However, with the backing of Doctor Seti, Kamilli's designs would meet with approval from the Public Works Secretariat.

Construction

Western span of the bridge under construction in 1952

In order to prepare the site for the construction of the final Xaltozan bridge, many acres of land would be acquired and cleared by the Public Works Secretary himself including a portion of the ruins of the town of Peyon that had been decimated by the catastrophe of 1928. This was met with great controversy from the public, which the Secretariat sought to soothe by adding the construction of a memorial monument dedicated to the victims of the disaster into the plans for the eastern part of the bridge along the shore. Public relations would be assuaged after this point, but would remain a constant concern for the Secretariat and construction crews involved in the project. A number of ruined structures and streets of the former town of Peyon were destroyed and cleared to make room for the eastern landing and the new memorial Epitaph. Most of the structure on land would consist of the two massive anchorages for the main cables, each one taking up 2,800 square meters and consisting of more than 700,000 metric tons of concrete and steel. Building the massive foundations of these structures going down two dozen meters below ground would be the first part of the project to proceed following the groundbreaking ceremony in August 1949. Huge on-site concrete production centers would be built to provide the large amounts of material that would be needed for the project starting with the truly massive volumes of concrete needed to fill in the anchorages. Soon afterward, in early 1950, work on the two pylons out in the narrows began with the installation of two massive caissons sunk into the cold waters of the narrows. Once meeting the mud and silt at the bottom, a reinforced concrete structure would be build along the inner openings at the bottom of the caisson. Once built, the underlying sediment beneath the caisson would be dredged from within the structure and the concrete would be sunk deeper and built back up to the waterline. Once these structures had reached the desired depth of the foundations, the outside of the caissons and concrete structure was wrapped in an additional layer of concrete while the hollow interiors were filled with seawater. Hundreds of thousands of cubic meters of mud and other sediments would be dredged from the bottom of the narrows during this process. The simultaneous construction of the anchorages on land and the caissons in water, a process which took less than two years altogether, would enable the construction of the pylons, cable structure and finally the bridge decks without further delay.

The two towers to hold up the bridge were built by the Amegatlan Steel calpolli corporation, one of the nascent industrial players of the bay area of that era and to this day a mainstay of the regional economy. Massive sections of steel structure were built in Amegatlan and brought to the site by rail and by ship and lifted into place with cranes. Each tower would be erected to a height over 200 meters tall. Doctor Seti had established a steel spinning plant in Amegatlan decades earlier for the construction of bridges spanning the Tliltic river in Angatahuaca, a calpolli which would now begin spinning the massive main cables needed for the bridge towards the end of the tower construction. These cables would arrive in time to be affixed to the tops if the towers and to each anchorage, which would be necessary before any work on the bridge decks themselves would begin. Hundreds of thousands of kilometers of cable would be produced for the project over the course of an 8 month work contract. Most of this length would consist of the suspensor cables that would actually hold the deck and suspend it from the bridge's main cables.

The bridge deck itself would call for sixty massive slab structures, each roughly four dozen tons steel assembled in Amegatlan and delivered to the work site by barge. These slabs would be lifted into place and attached to the suspensor cables above, before being fixed in place to the deck already in place. The process would begin on the eastern side of the bridge and proceed westward over the course of the remaining 3 years of the construction period. While work on the caissons had been cause for delays in the overall project, the assembly of the deck proceeded ahead of schedule and made up for the earlier troubles with the underwater portion of the work. However, it was also during this process that both of the two casualties to occur during construction took place due to falls the main cable on the deck as it was being assembled below. The land span of the bridge, the shorter western span, was completed in September of 1954 with the construction of the railway and road linkages across the bridge and completion of the concrete additions to the deck taking up the final months of construction before the opening of the bridge in December. Once in operation, the bridge was transferred from the oversight of the national Public Works Secretariat to the local CZA transportation authorities which would be responsible for the maintenance and upkeep of the bridge from that point forward.

The construction of the bridge at Xaltozan would prove a major boon for the economy of the bay, particularly of Amegatlan. Many of the firms providing steel, concrete, cables and other components for the structure were based in Amegatlan, and the project helped to stimulate the city's economy and send it into overdrive for a period of several years which in turn drew in immigration from around Zacapican and further afield. This boom era helped to solidify the status of Amegatlan as primus inter pares of the Angatahuaca satellite cities, a condition which began with the building of the joint Angatahuaca-Amegatlan port facilities in 1933.