Artificial Islands Take Shape in Panama
The hopper dredge Gateway was too big to approach the reclamation site for offloading, so the sand was pumped from two miles offshore.
Think luxury homes built on artificial islands and what probably leaps to mind is Dubai, not Central America.
But Panama is well on its way to having just such a development—the first in Latin America. One of two artifi cial islands that will form the Ocean Reef development in the heart of Panama City has already been shaped into existence; the second is scheduled to begin dredging and reclamation at the end of the year.
The hopper dredge Flevo (seen here), along with its clamshell rig Alex, first removed three meters of the soft muddy layer on the harbor seabed.
Once completed, the two curvy islands will jut into Panama Bay from Punta Pacifica, where the 70-story Trump Ocean Club Tower dominates the skyline. The first island, whose construction was completed late last year, is now being outfitted with water, sewage and electric lines and other infrastructure. Once the infrastructure is in place, its 10.3 hectares (25 acres) will be divided into 72 lots, which will accommodate luxury two-story homes. The second island will be slightly smaller, with 8.7 hectares (21 acres) divided into 66 lots. The gated community will also contain parks, recreational facilities and moorings for boats.
Developer Grupo Los Pueblos (GLP) hired Royal Boskalis Westminster N.V. to conduct dredging and reclamation work for the first island; the two companies are currently in negotiations for a contract for the second island.
The idea of building artificial islands in Panama Bay was bantered around as long ago as the early 1990s, said Bernard Bezemer, regional manager at Boskalis in Panama. The concept was refined more than a decade ago, when a Mexican company received the rights to develop the project, in exchange for building a highway to the airport, said Jose Fierro, project manager at GLP. GLP purchased these rights from it in 2007, Fierro said. GLP then spent the next years studying the planned design and construction methods, and convincing environmental groups and agencies in Panama that it could build the islands without upsetting marine life in Panama Bay.
Dutch design and infrastructure company Deltares completed the design work, and environmental consulting company URS Corporation conducted an environmental review. URS Corporation also conducted the environmental study on the Panama Canal expansion, Fierro said.
The islands were designed to withstand the tides, as well as the currents that fl ow through the bay, he said.
“The islands are in the Pacific, and we have two tides a day that go from zero to 14 or 16 feet a day, so the form of the island and the shape are designed to absorb the energy of these waves,” Fierro said.
In 2011, after a call for tenders that attracted virtually every big name in the dredging industry, and a few delays due to the economic crisis, GLP gave Boskalis an $80 million contract for dredging and reclamation, which covered all work, materials and equipment needed to shape the first island, except for the rock, which GLP provided.
One part of the contract had been advanced so Boskalis could begin work in 2010, said Jan van Merkerk, who was Boskalis’ project manager for Ocean Reef. In July of that year, it began the first stage of the project: dredging the muddy bottom of the bay. Using its 2,000-cubic-meter (about 2,600-cubic-yard) hopper dredge Flevo and its clamshell rig Alex, it removed three meters of the soft muddy layer on the harbor seabed, ultimately removing more than 575,000 cubic meters (about 752,000 cubic yards) of material.
The next phase built a rock dike to form the perimeter of the island, which would eventually be filled with 1.45 million cubic meters (about 1.9 million cubic yards) of sand. The rocks were staged and loaded into split barges and flattop barges at the Port of Vacamonte, about 15 nautical miles southwest of the island site, said Bezemer. The barges ultimately transported about 650,000 cubic meters (about 850,000 cubic yards) of rock to form the dike.
The core of the dike was created with rocks weighing between 1 and 60 kilograms (2.2 and 132 pounds), which were deposited by the split barges, then flattop barges transported coarser material to form the outside and top of the dike. Next, armor stones weighing up to four tons were placed on the exterior, with the largest rocks on the south end of the island, where the waves are most powerful, Bezemer said. The Alex removed the rocks from the flattop barges.
Once the dike was largely completed and the “bathtub” had been formed, the inside of the dike was protected with a geotextile, designed to let water, but not the grains of sand, flow out, Bezemer said. Laying the geotextile took about five months, he said.
Sand was borrowed from a site in the Archipelago Las Perlas, an island chain some 64 miles away from the reclamation site. It was dredged by Boskalis’ 12,000-cubic-meter (about 15,700-cubic-yard) hopper dredge Gateway. However, because Panama Bay is shallow, the Gateway was too big to approach the reclamation site for offloading, so the sand was pumped to the reclamation site from about two miles offshore, through 200 meters (about 656 feet) of floating line, 3,000 meters (about 9,800 feet of submerged line, and then landline that distributed the sand to different areas of the island.
Even the pumping site two miles offshore was relatively shallow, so the Gateway could pump only at the peak of the tide, every 12.25 hours, van Merkerk said. The dredging cycle— which consisted of sailing to the borrow site, dredging, sailing back to the pumping site, and pumping—took nearly 12 hours, so the operation had very little wiggle room, he said. Dredging crews worked 24 hours a day every day of the week for four months (with the exception of Christmas and New Year’s Day) to complete the work.
Once the sand had all been transported and deposited on the newly forming island, it had to be compacted.
For the compaction work, Boskalis subcontracted German company Bauer Group, who brought in four large cranes with a rig to do vibro-densifi cation. That methodology ensured that the island’s foundation would not succumb to liquefaction, in the case of an earthquake up to about magnitude 6.1 on the Richter scale, Bezemer said. The vibro-densification treatment involves inserting two-meter vibrating pins into the sand, essentially creating small earthquakes within the substructure, so the sand settles to its final position, Bezemer explained. The cranes made more than 12,000 penetrations into the island over the course of about six months.
The dredging work faced some small delays each month because of climate conditions, Fierro said.
“We had about three to four days a month of weather delays,” he said. “This was not because of winds or hurricanes—we don’t have hurricanes in Panama—most of the time, it was created by the period of the waves.”
If the period and height of the waves reached a certain level, they could create problems for some of the smaller dredging equipment.
The construction of the first island went well enough that the second island will not have major changes in the design or construction methodology, Fierro said. GLP did, however, learn some lessons that may help save some time in the second half of the project, he said. For example, it will create more space for the storage and loading of the rocks. It will also construct small jetties so that rocks can be unloaded directly onto the island from the jetties, rather than unloading all of the rock from ocean barges, he said. This will save them at least eight hours for every 3,000-cubic-meter (about 9,000-cubic-yard) load of rocks, he said.
Construction on the second island will likely begin at the end of this year or in January 2014, by which time construction on the housing development on the first island will be well underway.
Bezemer said Boskalis is “tremendously proud of this project.”
“There has been talk about islands in other places in Latin America for a long time, in Buenos Aires, for example was talking about building an airport on an island, but indeed it was done here in Panama. It’s the first manmade island in Latin America,” he said. “We had quite a unique situation in building this island—it was not easy—and therefore we are very proud of it.”Edit Module