Article - Issue 41, December 2009
Unlocking Panama's Potential
Traffic through the Panama Canal had been regularly exceeding its capacity, with some owners paying high premiums at ‘auctions’ to have priority of passage. To meet the forecasted increasing demand, a third wider lane, with the world’s largest lock footprint, is to be added. David Tozer, Business Manager of Container Ships at Lloyd’s Register, looks at plans for the construction and subsequent impact on the size of shipping in the future.
A visualisation that demonstrates the workings of water-saving basins and the larger locks which will be able to accommodate post-Panamax (NPX) ships
The Panama Canal is one of the world’s greatest engineering achievements. It plays a critical role in facilitating and shaping global trade and acts as a conduit between the Pacific and Atlantic oceans. The dimensions of the existing locks have defined a whole breed of ship designs that have been built with a beam no greater than 106 feet (32.3 m). These ‘Panamax’ ships have been made to fit tightly into the existing locks, requiring precise control of the vessel and sometimes resulting in longer than optimal lock times.
First opened in 1914, today the canal transports nearly 15,000 vessels every year carrying 5% of the world’s seaborne cargo – but it is nearing its physical limit. In 2007, 312 million Panama Canal Universal Measurement System (PCUMS) tons of trade transited the canal. Due to the current global economic crisis there has been a small reduction in demand and 2009 is forecast to end with approximately 300 million PCUMS tons. This figure is expected to recover as the world’s economic conditions improve. Even at these lower tonnages, the Panama Canal is running close to 90% capacity.
During maintenance periods, some ships are forced to wait in extreme cases for up to a week to obtain passage through the narrow artery, costing thousands of US dollars a day. This congestion is expected to worsen as ships become larger and more numerous.
To accommodate larger vessels and anticipated growth in the volumes of trade passing through it, the Panama Canal Authority (ACP) has embarked on an ambitious project to add a third lane of locks to the Panama Canal, which is planned to come into service in 2014 – the 100th anniversary of the original opening of the existing canal.
After competitive tendering, the Grupo Unidos por el Canal (GUPC) consortium won the contract in July 2009 to design and build the new locks for the price of US$3.12 billion. The consortium consists of Spanish constructor Sacyr Vallehermoso, the Italian builder Impregilo, Belgian company Jan De Nul and local construction company Cusa. Two new navigational channels will be constructed to enter the new locks, which will be larger than the originals and with enough capacity to accommodate bigger ‘post-Panamax’ ships, thus doubling the amount of cargo transported along the canal.
Increasing container capacity
The canal expansion involves the construction of two sets of three lock chambers along the canal’s 50-mile length: one at the Atlantic end of the canal, east of the Gatun Locks and the other at the Pacific end to the southwest of the Miraflores Locks. Vessels currently transit the Panama Canal via two shipping lanes; the new third lane will accommodate much larger ships. This is important news for the container shipping industry, which currently dominates the Panama Canal route in terms of both number of transits and capacity. This traffic accounts for half of the canal´s revenue.
The new sets of locks will each feature three chambers, similar in configuration to the existing Gatun Locks, but using different technology with regard to the lock gates and filling and emptying systems. The new chambers, each connected to three water saving basins, are larger than those in the existing two strings of locks and will allow transit of vessels with a beam of up to 49 m, an overall length of up to 366 m and a draught (depth in the water) of up to 15 m.
This increase in size will prompt the development of post-Panamax vessels (see post-Panamax container ships) optimised for transit through the locks. Shipyards are already taking orders for such vessels and Lloyd’s Register is helping the industry to understand the context in which these ships will operate.
The whole programme to increase the capacity of the Panama Canal involves three main components besides the construction of new lock facilities at the Atlantic and Pacific ends of the Canal. There is the excavation of an access channel to the new locks on the Pacific end, the widening and deepening of existing navigational channels at the sea entrances and the elevation of Gatun Lake’s maximum operating level. Gatun Lake is a 456 km man-made lake, whose surface is roughly 26.5 m above mean sea level. Together with upstream Alajuela Lake, they provide all of the freshwater required to operate the canal, as well as potable water for residential and industrial use in Panama City.
The civil engineering involved is monumental in scale, requiring the excavation and dredging of some 147 million cubic metres of earth and rock. This is made possible by using – among many large pieces of equipment – the world’s largest floating drilling and blasting vessel which has 10 drilling towers. In total, an extra 8 km of channels will be excavated to connect the new locks to existing shipping lanes.
Around 10,000 workers will be employed on the project. Panama’s Gatun Lake, which forms a large part of the shipping route, will be deepened by 1.2 m and widened by an extra 128 m (for a total of 356 m in the turns). The maximum operating lake level will also be raised by 0.45 m to provide, on average, an extra 165 million gallons of water per day which will allow about 1,100 full additional transits a year.
The new reinforced-concrete locks will each measure over a mile-and-a-half in length. The chambers will each be 427 m long, 18 m deep, and 55 m wide.
A major change compared to the existing locks will be the type of lock gates used. Mitre-style lock gates – like those currently on the Panama Canal – consist of two leaf gates. They are analogous to a set of double doors, except that they close on to each other at a pitch angle of 2:3. From a plan view they form a wedge shape in the lock. Always facing the incoming water, as pressure builds up they are forced more tightly into each other and to their wall bearings. Mitre gates become less efficient at longer lengths – there is no lock in the world wider than 42 m that uses this type of gates.
When fully open, they fold into the sides of the lock and this, in part, is one of their disadvantages. The lock must include gate recesses in the walls or be wider than necessary for the vessel so as to accommodate the gates (when open) and long enough so that the gates can swing open or close without damaging the vessel.
The alternative is to use rolling gates, which have been selected for the new locks. They are equivalent to sliding doors, only on a far larger scale. While the principle is simple, the engineering is formidable. Although these new gates will be built along traditional lines, with special treatment of the surface to control corrosion, they will also incorporate a number of innovations inspired by more recent locks in Europe that can accommodate bigger ships.
Rolling gates have several advantages over the much older mitre gates used elsewhere on the canal. For one, rolling gates are fully retracted into recesses in the lock walls and don’t take up any additional space when open. They also reduce the length of the lock only by their own width, unlike the mitre gates, which project forward into the lock and take up even more precious space.
The new locks will incorporate twin gates at either end of each chamber, held in recesses at right angles to the lock wall. Both gate recesses are located in specially designed wall monoliths called ‘lockheads’. Both gates weigh roughly 3,000 tonnes and rest on wagons at either end which allows them to roll in and out of the lockhead.
The twin rolling gate design introduces a valuable redundancy to the system. While one of the pair acts as the operating gate that retains water in the lock, the other acts as an auxiliary gate that serves as backup when the primary gate requires maintenance or is out of commission for any reason.
Each gate has two sets of wheels (or ‘wagons’) that normally carry approximately between 10% to 15% of the weight of the gate, the remainder of the weight is carried by flotation from strategically located buoyancy chambers. The upper wagon is fixed at the top corner of the gate and rolls along supports on both sides of the length of the recess. The other is affixed diagonally opposite at the bottom corner of the gate and rolls along the bed of the lock on crane rails. The gates are operated with a winch and motor system. When the lock is to be used, the gates are pulled forward, by means of large diameter wire ropes, sliding them into the lock. To open them, they are pulled backwards into the recesses. The time estimated for the gates to open or close is around four minutes.
Easier to maintain
The positioning of the sets of wagons on each gate allows for simplified preventive maintenance. While the top wagon is easily accessible, the bottom wagon can be taken out for maintenance by emptying the gate’s internal ballast tanks which increases the buoyancy, taking the weight off the lower wagon and allowing it to be withdrawn to the surface through a strut that links the bottom of the gate to the top. The strut runs through a hollow shaft within the body of the gate, with enough restraints to allow it to carry all the operational loads and still permit removal of the wagon. The time required for replacement of a wagon has been limited to just four hours.
The fact that the rolling gates require recesses in the lockheads to house them in their open position provides for an added benefit in terms of maintenance. By placing removable bulkheads in the opening that separates the gate recess and the lock chamber, it is possible to completely empty the recess and perform gate maintenance in place, under dry dock conditions. In contrast, the existing canal gates need to be removed and taken to a remotely located synchrolift whenever they require repair or maintenance, closing down an entire traffic lane and causing severe delays.
The gates are operated by electric motors. Two on each gate offer redundancy, with a third smaller emergency motor able to operate the gates – albeit much more slowly – should they both fail.
Even though the Panama Canal watershed receives 2.5 metres of annual rainfall, storage of water is a continual challenge. Gatun Lake and Alajuela Lake are reservoirs that, along with the canal watershed, supply drinking water to 95% of the population around the waterway, as well as to the locks.
The canal operation is by itself the most considerable drain on water sources. There is also an increased demand of potable water for industrial and domestic usage due to the increasing Panamanian population and expanding industry. To help alleviate the problem, the Autoridad del Canal de Panamá found inspiration from canals in Germany, which use basins that recycle some of the water used for locking vessels.
Each lock chamber in the Panama Canal’s new set of locks will be connected to a group of three water-saving basins. The basins will save up to 60% of the water used in each transit and the remaining 40% will be topped up by fresh water from Gatun Lake. Without a new design incorporating water-saving basins, the expansion plans would have doubled water consumption. Instead, the new locks will use 7% less fresh water per transit than the existing locks, despite being 65% larger.
The basins work on the simple physical principle of water displacement by gravity alone. When bringing a vessel down from the lake, three-fifths of the water in the chamber is directed into the three water-saving basins. The remaining water is equalised with the water in the subsequent lock chamber. To raise the water level in the lock chamber, the process is reversed: water is released from each of the three water saving basins, one at a time, while the remaining water comes from Gatun Lake, 26.5 m above sea level, or from the lock chamber immediately upstream. A valve system holds the water in place in the lock chambers to carry out this operation. Tests are currently underway to optimise the filling and emptying system.
A numerical model developed by Deltares, the Dutch water technology institute, shows that water quality in Gatun Lake is not under threat from the new locks, even with waters of different salinities entering the system and mixing from the ships’ propulsion systems.
The expansion of the Panama Canal is likely to lead to a complete redefinition of container trades. Research by Lloyd’s Register and Ocean Shipping Consultants Ltd (see Testing the water) suggests that US east coast ports will benefit substantially from the changes and that the expansion forms a vital element in the likely reshaping of trade patterns.
With larger ships able to transit the canal, routes between Asia and the US east coast will provide the most cost-effective means to move freight in and out of the American Midwest.
It is not only container ships and bulk carriers that will evolve as a result of the canal expansion, there are also wider implications for the bulk liquids, gas and passenger shipping sectors. The new wider locks in Panama will open up the canal to new, larger ships and will mark the genesis of many NPX ship types.