To enable the ship-loading capabilities desired for the planned liquefaction facility, the original marine basin needed an expansion to accommodate a second ship dock. Expansion dredging of the dock basin began in early February of 2016.
Coincidentally, two dredges worked there at that time. A small dredge performed a silt maintenance dredge in the original basin, removing accumulations of silt from the Dock 1 area. A larger dredge, the "Captain Frank" worked to excavate space for the second ship dock. The size of the original basin didn't allow tankers at two berths simultaneously, as they would be too close for safe operation. At completion of work, the original berth will be able to accommodate 1135-foot Q-max tankers, but the new berth will be constructed to accommodate vessels 1035 foot long, carrying cargoes of up to 180,000 cubic meters of LNG.
The two dredging operations differed in respect to spoils disposal as well. The smaller maintenance dredge deposited its material on Quintana Island in a catchment area between the marine basin and the terminal's air tower. Containment levees were constructed here to keep dredge soils from the dock basin. The larger dredge, working to increase the basin's size and depth, deposited its spoils in an offshore area designated by the EPA. This material was primarily dense clay. The clay was broken up by the dredge's auger-type cutter head and pumped up through a pipe and deposited into a transport scow, a large open-topped barge.
The expansion of the dock basin has enlisted the feedback and services of a number of partners. The original expansion plans were adjusted with advice from the Brazos Pilots Association and the US Coast Guard. The layout of the berth was changed from a triangular shape to one where the ships would have a parallel orientation and a safer 600-ft. "skin-to-skin" distance between ships at the docks. Also, a small rock jetty would be added to encourage the falling tide current not to sweep into the basin while a ship was entering.
STAR Center Exterior.
Another critical partner in determining safe tanker transit and docking operation was the STAR Center, a maritime training facility in Dania Beach, Florida. Freeport LNG paid for both the Freeport harbor pilots and local tug captains to be given a customized ship simulator course. Similar to a flight simulator, the testing room is set up like a ship's bridge with computer projections of the exact land and seascape of the full transit into the terminal's docks. The simulators mock up in real time a wide variety of scenarios of environmental and ship conditions to test pilots and tug captains (who test from their own simulator rooms during each mission).
The scow was then towed out to the offshore EPA site where it emptied its cargo hold through doors on the barge’s bottom. Each scow was fitted with transponders that sent a signal to the US Army Corps of Engineers so that the Corps could monitor and ensure that the dredge material was disposed of within the designated area. The estimated volume of material taken offshore was 1.13 million cubic yards, creating a basin depth of 46.5.
A New Tanker Berth for Quintana
Cross Channel Current
One frequent and challenging condition of the Freeport channel is a cross channel current that can require tankers to crab in slightly sideways, three to four degrees off axis. It becomes a more pronounced problem with longer tankers. In light of future exports using larger tankers, this issue was addressed by a channel dredging in January of 2015, widening the channel from 400 feet to 600 feet. The sand portion of the spoils from this work were piped onto a section of beach on Quintana, a placement that was designed to reduce erosion.
"People don't know what goes into making sure that a transit is done safely and all the efforts we do to make sure that everybody signs off on it. There are all kinds of checks and balances to make sure that when one does come in, it's been properly vetted and there's been sufficient training. There'd be too much risk to do it otherwise."