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READYMIX CONCRETE

China Harbour-Costain constructed 12 enormous caissons, two at atime, in a casting basin 14 miles (23 kilometers) north of Ensenada,Mexico.

Two Putzmeister MXKD 38/42 separate placing booms placedconcrete via a slip form approach during construction of each hugecaisson, sized 125 feet (38 meters) wide and up to 225 feet(68 meters) long.

LNG is natural gas cooled below -260 F(-162 C) and condensed into a liquid thatoccupies 600 times less space than in itsgaseous state. This enables shipment incryogenic tankers from remote locations tothe new Mexican terminal, where LNGships can dock and unload into two aboveground storage tanks. Each tank will storethe liquid until it can be vaporized backinto natural gas and moved via pipeline tocustomers.

Breaking waves

Although the entire LNG terminal project washighly involved, a 2,150-foot (652 meter)long breakwater posed especially complexconcrete placing and logistical challenges.Tackling the major task head on was a stra-tegic combination of Putzmeister equip-ment, including separate placing boomsand high pressure trailer-mounted concretepumps. The high performance units placedconcrete for 12 huge caissons. The caissonswere of two sizes each 82 feet (25 meters)tall, 125 feet (38 meters) wide and either152 feet (46.25 meters) or 225 feet

(68 meters) long. The 12 gigantic caissons,each about the size of an eight-story officebuilding, were towed out to sea and sunk toform a specially constructed breakwater.Since no natural harbor exists off the deepcoastal waters of Costa Azul, this break-water would protect LNG ships from beingdamaged by forceful ocean waves whenunloading at a specially constructed 820-foot (250 meter) long berthing pier.

Size matters in equipment selection

To construct the giant caissons, the first stepwas the creation of a dry dock or castingbasin. A massive 330-foot by 553-foot(100 meters by 170 meters) cavity wasexcavated to a 40 foot (12 meters) depth,while a 30-degree slope angled to its 165-foot by 409-foot (50 meters by 125 meters)bottom area. This provided ample space tobuild two caissons at a time.For concrete placement, the contractor chosetwo Putzmeister MXKD 38/42 separate pla-cing booms for their long 125-foot (38-meter)horizontal reach. The placing booms wereutilized with two large 400 meter/ton crane

lattice towers, which were mounted oneither foundation anchors or base plates,depending on their location in the castingbasin or jetty. With the help of the extreme-ly high capacity cranes already on site, thetwo placing booms and two towers werecost-effectively moved between five moun-ting locations four within the casting basinand one in the jetty. The tower cranes easi-ly picked and moved the placing boomtogether with its power pack and pedestal.With the cranes 10.5 metric ton capacityat 150 feet (46 meters), it could also lift theentire placing boom tower with all towersections connected.Four steps in the lifting and reconnectionprocess were eliminated with every move,as no boom counterweight was neededwith the placing booms selected for this jobor with any conventional placing boommodel from Putzmeister America, says BobLiebermann, special products sales mana-ger at Putzmeister America, Inc. This signi-ficantly improves speed and efficiency.The contractor also benefited from theextra reach of our larger MXKD 38/42placing boom model and avoided addi-

Worlds Largest Offshore Caisson Breakwater

Putzmeister America Inc., Sturtevant, WI 53177, USA

Constructed 14 miles (23 kilometers) north of Ensenada, Mexico, the largest offshore caisson breakwater of its type in the world came to life

through a combination of special concrete construction techniques that utilized innovative Putzmeister placing boom technology.The enormous breakwater was constructed for the first liquefied natural gas (LNG) receipt terminal along the Pacific Coast of the Americas

as part of the $875 million Energa Costa Azul project. The project was designed to help the Mexican state of Baja California meet its demand

for natural gas, which is expected to almost double by 2010. Currently, this region imports its natural gas from the U.S., which faces in-

creasing energy consumption yet dwindling supplies.

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tional mounting locations in the castingbasin because the boom and tower arrange-ment provided effective coverage for thepours, adds Liebermann. Three Putzmeisterconcrete trailer pumps were also chosen forthe project, notably for their higher outputsin pumping the caisson bases at a fasterpace. Therefore, on site were a BSA 1407-D and two BSA 1409-D models, capable ofmaximum outputs of 93 and 119 cubicyards an hour (71 and 91 cubic meters anhour) respectively, and high pressures up to1,537 psi (106 bar). Powered by turbo-charged 157 horsepower (115 kilowatt)Deutz diesel engines, the pumps delivereda highly abrasive concrete via five-inch(125 millimeters) pipeline stretching over150 feet (46 meters) distances.

To ensure peak machine performance,Construmac, S.A., an authorized Putzmeisterdistributor for over 15 years, provided main-tenance and service support of the concreteplacing equipment. Established in 1976,

Construmac is headquartered in Naucalpanwith nine branch locations throughoutMexico.

Floating from casting basin to jetty

Floating the caissons out of the castingbasin was a complex endeavor. First, allconcrete placing equipment had to be relo-cated to a special lay down area. Thisremoved the equipment from the path of thefloating caissons and also avoided equip-ment contact with the corrosive salt waterwhen the casting basin gate was opened.An eight to 10-day cycle started, whichinvolved a day to flood the casting basin, aday to remove the casting basin gate andtwo days to move the caissons out duringhigh tide. A tug boat in combination with cast-in-place winches and bollards controlled thecaissons movements to prevent damage tothe sides of the gate seal area. Then, a dayof repositioning the casting basin gate andits seals were required, followed by two

days of pumping water out of the castingbasin. The remaining cycle time was spentcleaning up and preparing for constructionof the next two caissons.Two at a time, the caissons were floated toa jetty about 100 yards (91 meters) awayand flooded in preparation for the nextstep. A placing boom and tower were repo-sitioned to place concrete for the turret,which is the upper 36-foot (11 meters) sec-tion of each caisson. This portion willremain above water when finally posi-tioned at sea.

The final 14 miles

When the turret was placed with concreteand appropriately capped, each short cais-son weighed approximately 35 millionpounds (16,000 metric tons) and eachlong caisson approximately 52 millionpounds (24,000 metric tons). They weretowed by tugs 14 miles (23 kilometers) upthe coast, using GPS for precise positio-ning.Once in place, butterfly valves, carefullypositioned in the caissons, were opened toflood and sink the caisson on a speciallyprepared granular bed. The cells were thenfilled with sand to further ballast them anddisplace the water. Once ballasted, eachshort caisson weighed a hefty 127 millionpounds (58,000 metric tons) and eachlong caisson weighed over 189 millionspounds (86,000 metric tons). The 12 cais-sons were further interlocked together toform the one-third mile long breakwater,

which weighed over an astounding 1.76billion pounds (800,000 metric tons) intotal.Started in January 2005, construction ofthe caissons consumed over 105,000 cubicyards (80,000 cubic meters) of a high

High pressure BSA trailer pumps capably delivered a highly abrasive concrete via five-inch(125 millimeters) pipeline that stretched over 150 feet (46 meters).

On site tower cranes moved the placingboom with pedestal and power pack in onepick, and could fly the entire connectedplacing boom tower in another pick.

At the jetty, a placing boom and its tower were repositioned to place concrete for the turret,which is the upper 36-foot (11 meter) section of each caisson that will remain above waterwhen positioned at sea.

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strength concrete. Cemex, headquartered in Monterrey, Mexico,produced the 50 N/mm concrete mix from two on site batch plantsduring construction of the breakwater. Each batch plant was capa-ble of 75 cubic yards an hour (57 cubic meters an hour) outputs.Cemex also supplied the concrete for the LNG tanks, which alt-hough large, only required about 8,000 cubic yards (6,000 cubicmeters) for each of the two tanks. Core locks, positioned in front ofthe caissons to help break up the waves, added an additional19,500 cubic yards (15,000 cubic meters) to the projects total con-crete usage.

Delivering the gasThe 400-acre terminal, including pipeline, comprises over a $1 billioncapital investment in Baja California, Mexico, with commercial ope-rations commencing in early 2008. The new LNG terminal is ca-pable of annually receiving 7.6 million tons of LNG from loadingterminals around the world and processing one billion cubic feet ofnatural gas per day. Designed to provide additional natural gas to

northern Mexico, it may also offer a supply alternative to Californiaand southwestern U.S. markets.

FURTHER INFORMATION

Putzmeister America Inc.1733 90th StreetSturtevant, WI 53177, USA

T +1 262 8863200 F +1 262 8846338www.putzmeister.com

Putzmeister Concrete Pumps GmbHMax-Eyth-Str. 1072631 Aichtal, Germany

T +49 7127 5990 F +49 7127 599520pki@pmw.de www.pmw.de

Each caisson, weighing up to 52 million pounds (24,000 metric tons)and about the size of an eight-story office building, was floated14 miles (23 kilometers) out to sea and positioned using GPS.

A-4673 Gaspoltshofen/ Austria, Hauptstrae 37

T. ++43(0)7735/6937- 0, F. ++43 (0)7735/6937-70

office@baum-autom.at www.baum-autom.at

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