Feature: Upgrading the Panama Canal

Surveyors use state-of-the-art monitoring systems to help ensure safety and structural integrity for one of the largest construction projects on the planet, without disrupting operations or compromising existing infrastructure.

As the Panama Canal approaches its 100th anniversary, it’s receiving a major upgrade and expansion for the next hundred years. It’s a big project—one of the largest construction projects currently under way on the planet. It involves a big budget, high expectations, a lot of surveying, and a lot of risk. How do you make major additions to one of the world’s most critical transportation links without disrupting operations or compromising existing infrastructure?

With much of the world’s infrastructure investments going towards improvements or repair of existing facilities, the requirements for efficiency, safety, and protection of existing structures have triggered a boom in monitoring construction sites, excavations, structures, and landforms. All of these are creating new opportunities for surveyors. 
 

The Grandest of Canals

Long recognized as one of the most important engineering feats in history, the Panama Canal plays a vital role for global commerce. In 2011, the canal handled roughly 14,600 transits by commercial cargo and container ships, passenger ships, military vessels, and petroleum tankers. Each ship paid a toll based on its size and type of cargo; last year the canal moved more than 300 million tons of cargo and pumped just over $1 billion into Panamanian government coffers. Nearly 80 km (50 mi) long, the canal created gigantic structures during its original construction and one of the largest man-made channels on the planet. Despite its enormous numbers, the Panama Canal is now too small.

The trouble has come from a combination of worldwide economic growth and continued advances in shipbuilding technologies. Since the canal opened in 1914, an international standard called “Panamax” has defined the dimensions of ships that could safely transit the canal. Panamax was determined by the size of the canal’s lock chambers: Ships intended to transit the canal needed to conform to the Panamax standard.

Today, Panamax ships are straining to compete with much larger, post-Panamax ships. The larger ships, which can carry roughly twice the cargo of ships built to the old standard, provide much higher efficiency in terms of cost per unit of cargo moved. As a result, shippers are eager to put their cargoes onto the post-Panamax vessels. These ships are too big to use the Panama Canal, so they must seek other routes, including the Suez Canal. However, the Suez has no locks and already handles post-Panamax ships. Additional competition comes from the U.S. intermodal transport system, which can bypass Panama by using trucks and railroads to move cargo arriving on post-Panamax ships at East and West Coast ports.

These competitive issues must be addressed by the Panama Canal Authority (ACP), an autonomous, state-owned agency charged with the safe and profitable operation of the canal. ACP was formed in 1997 and took full control of the canal when ownership was handed from the United States to Panama in 1999. In order to remain competitive in the face of the technical and economic challenges, the ACP has long been aware that the canal needs to handle more traffic and larger vessels. To do so, it has implemented several long-term projects that will increase the canal’s cargo-moving capabilities.  
 

The Third Set of Locks

The Panama Canal is an ingenious combination of locks, dams, and excavations that provide a passage between the Pacific Ocean and the Caribbean Sea. Ships coming from the Pacific travel into the Miraflores and Pedro Miguel locks, where they are raised 26 m (85 ft) above sea level. The ships then sail through the Gaillard (or Culebra) Cut and into Gatun Lake, an artificial waterway created when the canal was first constructed. Finally, the Gatun Locks lower the ships back to sea level, and they complete their traverse. Each of the existing locks consists of two adjacent chambers (essentially traffic lanes) that handle shipping traffic in both directions. The trip takes roughly 10 hours, and ships can spend an additional 15 hours or longer waiting to enter the canal.

In 2001, work was completed on a 10-year project to enlarge the Gaillard Cut. The project, which widened and straightened the channel from its previous one-way traffic, enabled two Panamax vessels to transit the channel in opposite directions simultaneously. While the Gaillard expansion delivered significant improvements to the canal, it could not solve the limitations imposed by the now-undersized locks. To enable the canal to handle the post-Panamax ships and increasing traffic load, ACP proposed a $5.25-billion project to expand the canal and double its capacity.

Known as “The Third Set of Locks Project,” the expansion consisted of five major ventures:

• Deepen and widen the Atlantic and Pacific entrances.
• Install a third lane of locks (supplementing the existing two sets or lanes) to raise and lower ships transiting between the Atlantic and Pacific oceans, and to handle post-Panamax ships.
• Improve existing channels and create a new channel to provide access from the new Pacific locks to the Gaillard Cut. This includes deepening, widening and straightening existing navigation channels, as well as further improvements to the passage through the Gaillard Cut.
• Raise the elevation of Gatun Lake, which is created by dams on the Atlantic side of the channel. The maximum operational level of the lake will increase 0.45 m (1.5 ft), and the navigation channels will be dredged to increase their depth by 1.2 m (4 ft) to support post-Panamax vessels.

The new locks and their channels will form a navigation system that will be integrated into the existing waterway. Panamanian citizens approved the proposal in a 2006 referendum, and construction began almost immediately. 
 

Construction and Monitoring

Two new three-step lock facilities will be constructed. One, near the Gatun Locks on the Atlantic side, will supplement the existing Gatun Locks and handle post-Panamax ships. On the Pacific side, new locks will allow ships to bypass the Miraflores and Pedro Miguel Locks and enter the Gaillard Cut via a new channel. Each of the new locks is 427 m (1,400 ft) long and 55 m (180 ft) wide. They are deeper than the existing locks and can support Supermax tankers as well as the giant cargo ships. The new locks use a design taken from existing locks in Belgium, where a gravity-feed system of water-recirculation basins reduces the amount of water needed to raise a ship.
 
The project contract requires that normal canal operations continue without disruption. During construction, temporary structures and cofferdams are used to keep water out of the construction areas. The new locks and channels require extensive excavation and earthwork, and many areas call for constant monitoring to protect workers and equipment from slides or failures on the steep, muddy slopes.

While contractors handle the excavation and construction, the ACP’s geodesy section is responsible for monitoring the slopes. Led by geodesy supervisor Miguel Narbona, ACP teams conduct regular monitoring surveys of the land slopes and dams. The geodesy section’s work also includes all geodetic surveys for maintaining the canal’s control network, managing the RTK reference stations for land and hydrographic surveys, and industrial surveys in maintenance operations for the locks and miter gates. To monitor the Third Locks work, geodesy teams in 2011 began to install an automated monitoring system using advanced surveying  instruments and software.

The bulk of the monitoring work is on the Pacific side, where a new 6.1-km (3.8-mi) channel connects the new Pacific locks to the Gaillard Cut. Roughly 49 million m3 (63 million yd3) of earth and rock will be moved in this section alone. Narbona installed four Trimble S8 total stations along the channel, spacing the instruments to provide optimal coverage. In addition to cut slopes, the system monitors a 1.8-km (1.1-mi) steel and earth cofferdam that prevents water from Miraflores Lake from flooding the channel. On the Atlantic side 80 km (50 mi) away, a fifth total station monitors an excavation near the new Gatun lock structures. All of the instruments are controlled by Trimble 4D Control software running on a network of computers. Control of the entire system resides in a desktop computer in Narbona’s office on the Pacific side of the canal.

The total stations are installed in steel cages mounted atop steel poles 20 cm (8 in) in diameter and 3.6 m (12 ft) high. Each instrument is powered by four solar panels connected to deep cycle batteries. Communications with the control computer is handled via Ethernet and WiMAX modems, which are powered by an inverter connected to the batteries. Although the Panama climate is hot, humid, and very rainy, Narbona is not concerned with weather protection for the total stations. He worries more about keeping the equipment secure and has designed the instrument housings to prevent unauthorized access.

The instruments monitor a total of more than 120 prisms, measuring distances ranging from 400 to 2,000 m (1,300 to 6,500 ft). Measurements are taken in direct and reverse positions and use Trimble’s Long-Range FineLock technology to obtain precise pointing to each prism. The measurements are immediately transmitted to the control computer, where they are analyzed and stored in the monitoring database. Each instrument measures its assigned prisms at six-hour intervals. The region receives heavy rain during the days and fog can build up at night, so visibility is a constant concern. With four readings per 24 hours, ACP can be sure to get at least one good reading per day.

The monitoring system is set up to achieve levels of precision recommended by the U.S. Army Corps of Engineers (USACE). “The USACE recommends a precision of 30 mm (1.2 in) for monitoring slope stability and 10 mm (0.4 in) for concrete structures,” Narbona explains. “As we only monitor slopes we are required to work in the range of 30 mm. But we have set our alarms lower because the system is producing accuracy that is much better than the requirements.” To date, the systems have not recorded any motion on the cut slopes. Shortly after monitoring began, one monitoring site at the steel cofferdam showed deformations on the order of 5 cm (2 in), but that movement has since stabilized. Narbona has created a set of alert levels for the slopes and two additional alert groups to handle the deformed cells of the cofferdam.

As part of every measurement cycle, each total station measures to at least one control point that is known to be stable. This measurement provides a check on the stability of the instrument mounts. As the project continues, Narbona plans to install additional control points. When the extra control is in place, ACP will use the resection function in Trimble 4D Control to perform rigorous checks on the instrument position as part of each measurement cycle.

Slope monitoring is not new along the canal. In addition to monitoring the new excavations, ACP has conducted campaign monitoring in the Gaillard Cut since the 1970s. “We have been looking to install an automatic monitoring system for a long time,” Narbona said. “The excavation of the access channel easily justified the investment in the new technology.” While the automated system monitors the new construction zones, ACP continues to conduct campaign monitoring using a sixth Trimble S8 equipped with a TSC2 Controller running Survey Controller software. The instrument travels as needed and is set up on pedestals for site-specific monitoring. The field crews use the engineering option in the software to collect rounds of angles to the monitoring points. The field data are downloaded to Trimble 4D Control for processing and analysis.

As the system administrator, Narbona controls the far-flung monitoring system. He can set up and control the measurements and make daily analysis of the operations and results. Narbona uses the deformation monitoring functions in Trimble 4D Control to make detailed examination of the data, and he can export data to Excel to create his own graphs and reports. His colleague Laurentino Cortizo at ACP’s geotechnical branch (ACP Geotech) has an installation of the software that he uses to conduct engineering and geotechnical analyses. ACP Geotech can also access the monitoring database directly, using SQL queries to extract information needed for specialized applications. 
 

Next Steps

ACP expects the new locks to begin commercial operations in May 2015, and it plans to extend the use of its automated monitoring system into more areas of excavation. Campaign monitoring will continue as well, with the post-processed optical results merging with data from the automated systems. Narbona is also working to integrate GNSS into the optical monitoring systems. At that time, ACP will install four Trimble NetR8 GNSS reference stations at the excavation sites. The GNSS receivers will stream data to supplement optical observations and provide additional checks on project control points.

The monitoring activities will continue beyond the construction phases. Once construction is completed, the slopes and dams will require constant monitoring. In addition to maintaining all of the current monitoring installations, several new sites will need monitoring. For example, the Borinquen Dam, which will separate the new Pacific access channel from Miraflores Lake, will replace the existing cofferdam. The new structure will need several permanent monitoring stations, and ACP plans to use a combination of optical and GNSS systems to monitor the dam.
 

» Back to our October 2012 Issue