Feature ArticleTABS Responder: A Quick-Response Buoy For Oil Spill Applications
By John N. Walpert
Senior Marine Instrumentation Specialist
Dr. Norman L. Guinasso Jr.
Deputy Director, Ocean Sciences
Geochemical and Environmental Research Group
Texas A&M University
College Station, Texas
The state of Texas has more than 367 miles of coastline and barrier islands on the Gulf of Mexico and a continental shelf supporting large reserves of oil and gas. Coastal areas support a variety of industries, including hospitality and tourism, recreational fishing, commercial fishing and offshore supply, that provide income for millions of people in Texas. The barrier islands serve as nesting and breeding grounds for many species of birds and animals, including the endangered Kemp's ridley sea turtle. The barrier islands also provide protection for oyster beds, grass flats and nursing grounds for several juvenile species of commercial and recreational fish.
There are currently more than 3,800 active oil platforms operating in the Gulf of Mexico, with a large percentage of those located off the coast of Texas in both state and federal waters. Within the state of Texas there are 27 oil refineries with a refining capacity of more than 4.6 million barrels per day, giving Texas the largest refining capacity in the United States.
Some of the oil reaches these refineries through hundreds of miles of submerged pipeline located in the Gulf of Mexico, and a large percentage is delivered by oil tankers transferring, or lightering, the oil from supertankers out in the Gulf of Mexico. As of July, the U.S. was importing more than 9.62 million barrels of crude oil per day from 15 different countries. Supertankers transport more than 310 million tons of oil through the Gulf of Mexico every year, and about 20 percent of that is lightered to smaller tankers for delivery into Texas ports.
Lightering accidents have been responsible for some of the largest spill events off the coast of Texas, including the Mega Borg incident in 1990 and the Berge Banker spill in 1994. Both of these events resulted in oil coming ashore on Texas beaches.
In response to the Oil Pollution Act of 1990 and to protect the sensitive coastal habitats and beaches along the Gulf Coast, the Texas state government passed the Oil Spill Prevention and Response Act in 1991.
The act named the Texas General Lands Office (TGLO) as lead agency in responding to oil spills and protecting the Texas coast from oil spill damage. They also established the Coastal Protection Fund, which allows the state to impose a tax of 1.3 cents per barrel on all oil and condensate passing through Texas ports. Capped at $20 million, a portion of this fund is allocated to sponsor environmental monitoring programs.
One of these monitoring programs is the Texas Automated Buoy System (TABS). Since its first deployment in 1995, data provided by TABS has been used for decision-making purposes in more than 30 spill events.
The most recent development for the TABS program is the TABS Responder, a quick-response buoy that can monitor meteorological information, waves and currents. The buoy weighs approximately 140 pounds, allowing it to be deployed by a two-person team with limited training on vessels of opportunity.
Texas Automated Buoy System
TABS was established in 1994 at the request of the TGLO. The Geochemical and Environmental Research Group (GERG) of Texas A&M University was selected to design and develop an ocean observing system that would provide spill response managers with timely near-surface current information necessary to feed oil spill trajectory models. The output from these models allows managers to quickly deploy spill response teams to the appropriate location to intercept, clean up and mitigate the potential impacts of an oil spill.
GERG scientists worked with Woods Hole Group Inc. (Falmouth, Massachusetts) and Urethane Technologies (Denham Springs, Louisiana) on the original design of the TABS I data buoys in 1994 and the TABS II buoy in 1998. Both systems underwent a major redesign at GERG in 2002 and 2003 to provide greater functionality and more diverse data capability. TABS is the only state-funded coastal ocean observing system in the United States designed specifically to protect coastal zones from the potential impacts of an oil spill.
TABS buoys are deployed at seven core locations along the Texas coast for the TGLO. The deployment sites were chosen based on oceanographic and bathymetric features along with proximity to coastal populations, ports of entry for oil tankers, lightering locations and industry activity. These locations are all within 45 nautical miles of shore and spread along the coast from Port Isabel near the border with Mexico to Sabine Pass near the Texas-Louisiana border. In 2002, two additional sites were added at the East Flower Garden Bank and the West Flower Garden Bank of the Flower Garden Banks National Marine Sanctuary. These two sites are funded through a consortium of oil companies that makes up the Flower Garden Banks Joint Industry Project.
Besides being a spill-response tool, TABS is a public resource, with all data made available to the public online. Through the TABS Web page, the public can access current and historical data from all of the TABS locations along the Texas coast, along with several data products produced through a real-time analysis of the data.
The TABS system makes up part of the Gulf of Mexico Coastal Ocean Observing System and, as such, space on the buoys is made available to scientists to add sensors and help support individual research projects.
Need for a Quick-Response Buoy
The DBL-152 oil spill occurred in November 2005, 35 miles south of Port Arthur, Texas. An oil barge on its way from Houston, Texas, to Tampa, Florida, struck submerged debris left over from Hurricane Rita. The debris ruptured the hull of the barge and resulted in more than 71,000 barrels of heavy fuel oil being spilled into the Gulf of Mexico. With a density greater than that of the surrounding seawater, the oil sank, leaving no surface expression and making tracking and recovery difficult.
The incident occurred in approximately 15 meters of water, where wave energy during storm conditions could potentially resuspend the heavy oil on the seabed and move it back into the water column, where local currents could eventually transport the oil to shore.
A TABS II buoy with an acoustic Doppler current profiler was eventually deployed on site, but it took several days to prepare the buoy and arrange for a suitable ship with a crane and open-back deck to deploy the system. A TABS II spar buoy is approximately 25 feet long and requires the services of trained oceanographic technicians to set up and deploy.
This incident made it clear that a small, quick-response buoy that could be deployed from a vessel of opportunity and by people not necessarily trained in ocean instrumentation would be very useful. A quick-response buoy deployed at the site of the spill would provide critical information to supplement TABS data by taking into account local bathymetric features, winds, waves and currents.
In 2009 and 2010, the TGLO funded GERG to design and develop a small, lightweight, quick-response buoy to meet this need. The buoy, which was named the TABS Responder, was designed to require limited maintenance and to withstand rough treatment on deck without serious damage.
Subsurface components were machined from 5086 series aluminum or Type 316L stainless steel. Above-water components were made from 6061 series aluminum. Penetrations into the main electronics housing are through protected 10,000-pounds-per-square-inch-rated anodized aluminum bulkhead connectors, and all housing closures have double O-ring seals.
The Responder buoy operates under a Linux operating system with modular sensor software written in C. It measures near-surface currents and current profiles, wave spectra, water temperature, wind speed and direction, barometric pressure, air temperature, global positioning system information and battery voltage.
The first prototypes, which were built in 2009, measured meteorological information, wave information and either near-surface currents using an Aanderaa Data Instruments (Bergen, Norway) DCS 4100R Doppler current sensor or current profiles using a NortekUSA (Annapolis, Maryland) Aquadopp 600-kilohertz profiler head.
The most recent prototypes measure both near-surface currents and profiled currents using a 600-kilohertz/two-megahertz Aquadopp Z-cell head integrated into the buoy electronics. Data are transmitted to GERG every 30 minutes via a Globalstar (Milpitas, California) device. Weighing approximately 140 pounds when fully assembled, the buoy is easily deployable by two people without the need of a crane or winch. The foam hull is 0.9 meters in diameter and measures near-surface currents at 0.7 meters below the surface and current profiles in two-meter bins down to a depth of 40 meters. Meteorological data are measured at 1.5 meters above the sea surface. Buoy motion is measured using three orthogonal accelerometers combined with three angular-rate gyros.
The Responder buoy was designed to require very little setup by deployment personnel. The sampling, data recording and telemetry schedules are all hard-coded in software so deployment personnel simply turn the buoy on, lay out the mooring and deploy it. In order to facilitate deployment and reduce weight and maintenance, the buoy was designed without the typical solar panels.
The TABS Responder buoy is designed for deployment durations of approximately two to three weeks, after which the buoy must be recovered and charged on the boat before being redeployed. Charging the lithium-ion batteries takes approximately 12 hours to go from spent batteries to a full charge. Battery voltage and charge condition can be monitored via an external RS-232 port.
Access to the on/off control, monitor port, charging port and meteorological port is available through the bulkhead connectors located in a protected cup under the mast assembly. Raw and averaged data as well as error logs and diagnostic files are recorded internally on a micro-SD card, which can be downloaded via one of the external ports on the buoy.
The buoy has 280 pounds of reserve buoyancy and can measure profiles in up to 40 meters of water using a lightweight catenary mooring fabricated from small chain, Dyneema (Urmond, Netherlands) rope and a small, plow-type tail anchor.
The TABS Responder was designed as a spill-response tool to be deployed by ships of opportunity at the site of an oil spill. Using a lightweight mooring, the system does not require any lifting equipment for deployment. Recovery of the buoy is made easier if a small crane, winch or capstan is available.
The buoy was designed to be recovered when the batteries are spent or if the cleanup fleet has moved to a new location. Along with wave and meteorological data, the Responder buoy has been designed to measure either near-surface currents, profiled currents or a combination of near-surface and current profiles. There is a significant difference in the cost of the various current sensors, so a single current sensor type may not be practical for all applications. The type of oil that has been spilled will determine which version is ultimately required.
GERG would like to further develop the TABS Responder buoy and design a slightly larger version that can be used as a longer term coastal monitoring buoy.
The authors would like to thank the TGLO, in particular Dr. Robert 'Buzz' Martin for long-term support of TABS and support of the Responder project.
For a full list of references, please contact John Walpert at firstname.lastname@example.org.
John Walpert is the senior marine instrumentation specialist at the Geochemical and Environmental Research Group at Texas A&M University. He is in charge of day-to-day operations and system design and development for the Texas Automated Buoy System (TABS). Walpert took over technical development of TABS in 2000.
Dr. Norman Guinasso served as director of the Geochemical and Environmental Research Group (GERG) from 2004 to 2010 and currently serves as a research scientist in Texas A&M University's Department of Oceanography and as deputy director of the ocean sciences division of GERG. He has served as principal investigator for the Texas Automated Buoy System since 1994.