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Panama Canal: Full tilt in the tropics

Construction of a third shipping lane through the Panama Canal is underway. It involves contractors and manufacturers across the globe working to exacting concrete and design specifications. CJ Schexnayder reports.

Just over a century ago, Lieutenant Colonel William Siebert would begin his day by walking to a windswept office building overlooking Limon Bay on Panama’s Caribbean coast. Each morning the division engineer for the ambitious Panama Canal project would be met by a group of children whose parents worked on the enormous project.

The children, Siebert later recalled, would “proudly inform him of the number of cubic yards of concrete that had been placed in the locks the day before”.
Siebert’s task, as outlined in his 1915 book The Construction of the Panama Canal, was to oversee the building of the massive concrete structures required for the waterway’s Atlantic entrance - the Gatun locks. At peak production 2,300m3 of concrete was being placed per day - almost double the previous world record rate set months earlier by the works on the Pacific side.

“No structure in the world contains as large an amount of the material,” he boasted.

Larger structure

Today, a larger structure is in the process of being built alongside Siebert’s masterpiece. The Panama Canal’s $5.2bn (£3.25bn) Third Lane Expansion involves building enormous new locks that will accommodate the new generation of shipping vessels that are almost three times the size of “Panamax” ships constructed to fit precisely in the existing canal’s lock chambers.

The new locks on the Atlantic and Pacific entrances will consist of a trio of chambers measuring 427m long, 55m wide and 18m deep. A series of water saving basins is being constructed adjacent to the locks that will reuse 60% of the fresh water used in the lock system.

Just as the placement of the concrete for the lock structure was one of Siebert’s most difficult challenges in 1910, so it is today. The 2,300m3 per day the children were so proud to inform Siebert about in 1910 has been dwarfed by the 3,500m3 of concrete being put in place daily on the new Atlantic locks. A total of 5M.m3 of concrete will eventually be needed to erect the new lock structures.

“The locks contractor is scheduled to finish the locks themselves in the first quarter of 2014,” says the canal’s administrator, Jorge Quijano. “Then they will begin the installation of valves, gates, electrical systems and controls, followed by testing of these elements in the dry.”

The start of the Third Lane Expansion began with a public referendum in October 2006 when more than 80% of Panamanian voters approved the project.

Within a year, work began on the dredging and dry excavation portions of the project required to widen and deepen the waterway’s navigational channel and ocean approaches to accommodate post-Panamax-sized vessels.

Design and build

The design-build contract to construct the new locks on either end of the canal was won by Grupo Unidos por el Canal in July 2009. The consortium Grupo UPC is composed of Spain’s Sacyr Vallehermoso, Italy’s Impregilo, Dutch contractor Jan De Nul and Constructora Urbana of Panama. Its bid came in at £2bn, the only one of the three offers submitted that was below the canal authority ACP’s allocated price of £2.17bn.

The first phase of the work involved excavating the area for the construction of the new locks. On the Atlantic side that has required the removal of 15.2M.m3 of material, and 11.3M.m3 on the Pacific side, with most of the latter requiring blasting to excavate. These works were mostly completed by the beginning of this year.

At the same time, Grupo UPC enlisted CICP Consultores Internacionales, a joint venture led by MWH in partnership with California-based TetraTech and Iv-Infra of the Netherlands to design the locks and conduct 3D computer model simulations to ensure their functionality.

The extensive computer and scale model testing were necessary due to several revolutionary features of the project. Not only are the locks enormous, they also feature a system of water-saving basins, a lateral filling and emptying system that will allow the re-use of water for every transit. ACP expects that the basins will reduce the amount of water used in the locks by as much as 60%, taking barely as much as the old locks use today.

Another dramatic difference will be the use of rolling gates that slide in and out of housings built perpendicular to the lock chambers themselves. The old locks feature mitre-style gates that swing outward to allow ships to pass.

In 1915, the chief engineer of the original canal construction, George Washington Goethals, was called to testify in front of the US Congress concerning the costs of the waterway’s construction. The legislative committee asked him if he had expected there to be delays in completing the project.

“The new locks will only have one lane. Any closure of either of the locks would put the post-Panamax system out of service”

Cheryl George, ACP

“I anticipated that there would be some,” he testified. “In a big job you can not help it.”

Goethal’s maxim seems to be holding true for the third lane expansion as well. Although Grupo UPC was scheduled to begin concrete placement in January last year, the effort was delayed when the mixes Grupo UPC produced failed to comply with the stringent specifications.

According to ACP the contractor initially opted to use pozzolan in the mix, which made the concrete excessively permeable and unable to meet the 100-year standard set for the project. Eventually, Grupo UPC opted to use silica fume, which brought the mix up to the ACP standards.

The high design standards were necessary to reduce the risk of having to close the locks in order to undertake repairs to the superstructure. “At the existing locks we have two lanes of traffic, which permits outages for maintenance without closing the entire canal,” says ACP design manager Cheryl George. “The new locks will only have one lane. Any closure of either of the locks would put the post-Panamax system out of service.”

The need to change the concrete admixture pushed back initial concrete placement by six months to July 2011. In April 2012, Grupo UPC notified ACP that it would not be able to complete the work on the project until April 2015 - around six months behind the target date.

Canal officials had initially hoped to open the new locks for operation in October 2014 to coincide with the waterway’s 100th anniversary, and then commission them by the end of the year. The new timeline pushes that back by at least three months, says Quijano.

Contractural penalties

There are contractual penalties of as much as $300,000 (£187,000) if Grupo UPC cannot complete the work on time, with a cap at £21M. In addition, the contractor can be fined up to £125M if the locks fail two critical performance tests when completed: the time needed to fill the chambers and the time required to open and close the rolling gates.

The issue was muddied further in August when the consortium filed a claim against ACP for an additional £358M for the work - an 18% increase in the cost of the project. The canal authority is currently evaluating the claim. If it rejects it, the matter could go before an international tribunal.

The construction of the locks themselves is proceeding in an almost identical manner to that of a century ago. Siebert’s plan involved building each section of the lock chamber walls as individual concrete structures referred to as “monoliths.” In July the first monolith was completed on the Pacific side. Measuring 33.84m high, 7.5m wide and 27m deep, the structure required 232t of reinforcing steel and 2,605m3 of concrete. A total of about 50 “monoliths” will make up each lock chamber.

Due to the enormous amount of concrete the job requires, a key complication for the project has been the acquisition of quality aggregate to meet the huge demands of the work effort. Initially, the abundance of basalt on the Pacific side of the isthmus led ACP engineers to predict that the dry excavations for project would be sufficient to meet the demand. When the quality of this material proved insufficient, an quarry operation was set up nearby to procure higher quality basalt.

Another hurdle was the almost complete absence of aggregate on the Atlantic side of the isthmus. As a result, an inter-canal transport system was developed to take material from the Pacific side of the project to the Atlantic. More than 1.5M.t of material has been transported through the canal for this purpose

Each lock site is equipped with crushing plants that then reduce the material to the desired size of aggregate needed - including the fine sand production.

One of the primary mixes being used to build the locks requires an unusual 38mm to 76mm aggregate. This has proven tricky to place and hard wearing on the equipment.

On site batching plants

Concrete production is handled by on-site batching plants manufactured by Italy’s Simem. These feature a customised aggregate cooling system, which is necessary to control the energy dissipation of the exothermic heat generated during the concrete curing process.

When it is poured, the concrete must be between 7.7°C and 12.7°C. To accomplish that the aggregate stockpiles are protected from the tropical sun by a massive tent. The material is then water cooled before being transferred to the air-conditioned bin. Flake ice is introduced to the mix on the main feed conveyor allowing it to remain chilled as it is transported by agitator trucks.

Even more rigorous quality standards are implemented for a marine concrete mix being used on the portions of the locks that will be exposed to water. This concrete must meet compressive strength and contraction standards while also guaranteeing low permeability so that the reinforcement will not become exposed to water over time, causing it to corrode.

The concrete placement is primarily done by a small fleet of telescopic conveyor trucks with a reach of up to 60m. These units are complimented by truck-mounted concrete boom pumps, which are then used to place the concrete in hardest to reach locations. All this equipment takes up valuable workspace on the floor of the locks, so large volumes of concrete are placed using a system of four tower crane-mounted conveyors. Manufactured by the US firm Rotec, these conveyor systems are loaded from the lip of the excavation far above the main work area, and deliver a maximum placement rate of about 100m3 per hour.

Although the focus of the work at this point is on the concrete superstructure, significant amount of electro-mechanical work is underway as well, particularly the installation of valves to control the ingress of water to the lock and the massive rolling gates.

South Korean valves

The more than 150 valves required for the locks are being fabricated off-site at a Hyundai Samho Heavy Industries facility in South Korea.

Once complete they are shipped to Panama and placed in the lock structure itself. The work on the hydraulic cylinders that will move the valves up and down is already underway at the site itself.

At the Pacific end of the canal a new access channel is being constructed around the entrance to Miraflores Lake. The channel avoids existing locks and will carry the canal 11m above the level of the lake. As a result, huge dams are being built along the west side of the access channel to contain it.

The massive rolling gates that are the key to the new post Panamax locks are being manufactured at the Cimolai facilities in Pordenone, Italy. The gate’s panels are being produced in South Korea and then shipped to Italy where they are assembled into the massive blocks.

A total of 16 of these blocks will then be assembled into the individual gates. When completed, each of the gates weighs about 3,100t and measures about 30m high, 10m wide and 58m long.

When four gates are completed, they will be shipped to Panama and prepared for the two month installation process. ACP officials say the first gates could be ready to be placed in the locks in the first quarter of next year.

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