NOAA's Response and Restoration Blog

An inside look at the science of cleaning up and fixing the mess of marine pollution


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OR&R Defines the Issues Surrounding Oil Spill Dispersant Use

Oil floating on water's surface.

Oil on the water’s surface. (NOAA)

I recently had the opportunity to attend an interesting seminar on the use of dispersants in oil spill response. On August 8, 2014, OR&R Emergency Response Division marine biologist, Gary Shigenaka, and Dr. Adrian C. Bejarano, aquatic toxicologist, made presentations to a group of oil spill response professionals as part of the Science of Oil Spills class, offered by OR&R in Seattle last week.

Mr. Shigenaka introduced the subject, giving the students background on the history of dispersant use in response to oil spills, starting with the first use in England at the Torrey Canyon spill. Because the first generation of oil dispersants were harsh and killed off intertidal species, the goal since has been to reduce their inherent toxicity while maintaining effectiveness at moving oil from the surface of the water into the water column. He gave an overview of the most prevalent commercial products, including Corexit 9527 and Corexit 9500, manufactured by Nalco, and Finasol OSR52, a French product.

Aerial view of testing facility with long pool.

The Ohmsett facility is located at Naval Weapons Station Earle, Waterfront. The research and training facility centers around a 2.6 million-gallon saltwater tank. (Bureau of Safety and Environmental Enforcement)

Shigenaka reviewed the U.S. EPA product schedule of dispersants as well as Ohmsett – National Oil Spill Response Research Facility in Leonardo, N.J. Ohmsett is run by the U.S. Department of Interior’s Bureau of Safety and Environmental Enforcement. He showed video clips of oil dispersant tests conducted recently at the facility by the American Petroleum Institute.

The corporate proprietary aspects of the exact formulation of dispersants were described by Shigenaka as one of the reasons for the controversy surrounding the use of dispersants on oil spills.

Dispersant Use in Offshore Spill Response

Dr. Bejarano’s presentation, “Dispersant Use in offshore Oil Spill Response,” started with a list of advantages of dispersant use such as reduced oil exposure to workers; reduced impacts on shoreline habitats; minimal impacts on wildlife with long life spans; and keeping the oil away from the nearshore area thus avoiding the need for invasive cleanup. She followed with some downside aspects such as increased localized concentration of hydrocarbons; higher toxicity levels in the top 10 meters of the water column; increased risk to less mobile species; and greater exposure to dispersed oil to species nearer to the surface.

Dr. Bejarano is working on a comprehensive publicly-available database that will include source evaluation and EPA data as well as a compilation of data from 160 sources scored on applicability to oil spill response (high, moderate, low and different exposures).

Her presentation concluded with a summary of trade-offs associated with dispersant use:

  • Shifting risk to water column organisms from shoreline, which recover more quickly (weeks or months).
  • Toxicity data are not perfect.
  • Realistic dose and duration are different from lab to field environment.
  • Interpretation of findings must be in the context of particular oil spill considerations.

Dr. Bejarano emphasized the need for balanced consideration in reaching consensus for the best response to a particular spill.

Following the formal presentations, there was a panel discussion with experts from NOAA, EPA, and State of Washington, and the audience had an opportunity to ask questions. Recent research from the NOAA National Marine Fisheries Service/ Montlake Laboratory was presented, focusing on effects of oil and dispersants on larval fish. The adequacy of existing science underlying trade-offs and net environmental benefit was also discussed.

Read our related blog on dispersants, “Help NOAA Study Chemical Dispersants and Oil Spills.”


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NOAA Again Joins Coast Guard for Oil Spill Exercise in the Arctic

This is a post by NOAA Environmental Scientist Dr. Amy Merten.

Large ship offshore.

U.S. Coast Guard icebreaker Healy.

It is no mystery anymore that the Arctic is undergoing unprecedented change and the extent of summer sea ice continues to shrink. As the ice contracts, shipping within and across the Arctic, oil and gas exploration, and tourism likely will increase, as will fishing, if fisheries continue migrating north to cooler waters. With more oil-powered activity in the Arctic and potentially out-of-date nautical charts, the region also will see an increased risk of oil spills.

Although the Arctic may have “ice-free” summers, it will remain a difficult place to respond to spills, still facing conditions such as low visibility, mobilized icebergs, and extreme cold. Much of the increased activity exploits the longer amount of time between the sea ice breaking up in the spring and freezing up in the fall. Accidents on either end of this longer window could mean responding to oil spills complicated by sea ice.

Ready, Set, (Pretend to) Spill

With these challenging circumstances in mind, NOAA’s Office of Response and Restoration again will be sending spatial data specialists aboard the Coast Guard icebreaker Healy for an Arctic Technology Evaluation, a month-long scientific expedition to the Arctic Ocean to demonstrate and evaluate oil spill tools, technologies, and techniques as part of Arctic Shield 2014. The ship leaves for the edge of the sea ice from Seward, Alaska, on August 8. We will be working with the U.S. Coast Guard Research and Development Center (RDC) to operate Arctic ERMA, our mapping tool geared at oil spill response. Normally an online tool, a special internet-independent version of ERMA, known as Stand-alone ERMA, will serve as the common operational picture for scientific data during this Arctic Technology Evaluation.

NOAA provides scientific support to the Coast Guard during oil and chemical spills, and ERMA is an extension of that support. This Arctic Technology Evaluation is an opportunity to work with the Coast Guard in as realistic conditions as possible—on a ship in the Arctic Ocean. Once the Healy makes it far enough north, the Coast Guard RDC will deploy a simulated oil spill so they can test oil spill detection and recovery technologies in ice conditions. The team will test unmanned technology platforms (both airborne and underwater) to detect where the spilled “oil” is and to collect ocean condition data, such as sea temperature, currents, and the areas where oil is mixing and spreading in the water column. In this case the simulated oil will be fluorescein dye, an inert tracer used for other simulated spills and water transport studies in the ocean and rivers. (Other simulated spilled “oils” have included peat moss, rubber ducks, and oranges.)

Ship with small aircraft in front of it.

NOAA’s remote-controlled Puma aircraft. (NOAA)

One major objective is for NOAA’s Unmanned Aircraft Systems group to fly their 8.5 foot wingspan, remote-controlled Puma, instead of an airplane with a human observer, to delineate the extent of the “oil” plume. ERMA’s job will be to display the data from the Puma and other unmanned technologies so all of the team can see where measurements have been taken and identify insights into how they could hypothetically clean up a spill in the remote, icy environment.

Arriving at the Arctic

In many ways, our office is a newcomer to the Arctic, and we still have a lot to learn about past research and current ways of life in the region. As the NOAA co-director for the Coastal Response Research Center (a joint partnership with the University of New Hampshire), I worked with my co-director, UNH professor Nancy Kinner, to promote understanding of the risks the Arctic is facing. In 2007, we participated in a joint industry study which brought me to the Arctic at the SINTEF lab on Svalbard in Norway. Here, I saw firsthand how difficult it can be to find oil mixed in ice and then try to do something about it, such as burn it. The temperature extremes in the Arctic limit mobility and the amount of time one can be outside responding to a spill—if you can get to the spill in the first place.

At the same time, we were developing ERMA® (Environmental Response Management Application), a web-based mapping tool for environmental response, which is customized for various regions in the United States. As NOAA’s Office of Response and Restoration began developing strategies for working in the Arctic, support emerged for customizing ERMA for the Arctic region. We worked with several organizations, including Arctic communities, to develop Arctic ERMA, taking care to make connections and build relationships with the people who live in and know the region and its natural resources. ERMA also will use the Healy’s onboard satellite communications to relay data back to the live Arctic ERMA website, allowing people outside the vessel to stay up-to-date with the mission.

Responding to Reality

image of broken ice on the water's surface. (NOAA)I’m excited for my ERMA colleagues, Jill Bodnar and Zach Winters-Staszak, to experience this extreme and special environment firsthand. Academically, you can think through the challenges a spill in the Arctic would present, but actually experiencing it quickly reveals what will and will not work. Partnering with the Coast Guard is helping those of us at NOAA be proactive responders in general, and in particular, is teaching the ERMA team how to pull into this tool data from multiple platforms and improve response decision-making.

We’re all connected to the Arctic; weather and oceanographic patterns are changing world wide because of the rapidly changing Arctic. Oil and gas coming from the Arctic will fuel the U.S. economy and current way of life for the foreseeable future. We hope that Arctic Shield and other oil spill exercises will better prepare us for whatever happens next.  Follow along with NOAA’s efforts during Arctic Shield at http://oceanservice.noaa.gov/arcticshield/.

Amy Merten with kids from Kivalina, Alaska.

Dr. Amy Merten is pictured here with children from the Alaskan village of Kivalina. She was in Alaska for an oil spill workshop in the village of Kotzebue.

Amy Merten is the Spatial Data Branch Chief in NOAA’s Office of Response and Restoration. Amy developed the concept for the online mapping tool ERMA (Environmental Response Mapping Application). ERMA was developed in collaboration with the University of New Hampshire. She expanded the ERMA team at NOAA to fill response and natural resource trustee responsibilities during the 2010 Deepwater Horizon/BP oil spill. Amy oversees data management of the resulting oil spill damage assessment. She received her doctorate and master’s degrees from the University of Maryland.

 


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Mysterious Oil Spill Traced to Vessel Sunk in 1942 Torpedo Attack

Aerial photo of an oil sheen on the ocean.

U.S. Coast Guard overflight photo, taken on July 17, 2014. (USCG)

A few weeks ago a North Carolina fisherman had a sinking feeling as he saw “black globs” rising to the ocean surface about 48 miles offshore of Cape Lookout. From his boat, he also could see the tell-tale signs of rainbow sheen and a dark black sheen catching light on the water surface—oil. But looking around at the picturesque barrier islands to the west and Atlantic’s open waters to the east, he couldn’t figure out where it was coming from. What was the source of this mysterious oil?

Describing what he saw, the fisherman filed a pollution report with the U.S. Coast Guard. On July 17, 2014, a U.S. Coast Guard C-130 aircraft flew over the site and confirmed the presence of a sheen of oil in the same vicinity. Based on the location and persistence of the sheens, the responders suspected the oil possibly could be leaking from the sunken wreck of the steamship W.E. Hutton, 140 feet below the water surface. Shortly after, archeologists confirmed that to be the case.

Balck and white photo of a ship in 1942.

A 1942 photo of the W.E. Hutton. (USCG)

At the Bottom of the Graveyard of the Atlantic

This area off of North Carolina’s Outer Banks is known as the Graveyard of the Atlantic. The combination of harsh storms, piracy, and warfare have left these waters littered with shipwrecks, and because of the conditions that led to their demise, many of them are broken in pieces. In the midst of World War II, on March 18, 1942, the W.E. Hutton was one of three U.S. vessels in the area torpedoed by German U-boats. Tragically, 13 of the 23 crewmembers aboard the ship were killed. The Hutton’s survivors were rescued by the Port Halifax, a British ship.

When the steam-powered tanker was hit by German torpedoes, the Hutton was en route from Smiths Bluff, Texas, to Marcus Hook, Pennsylvania, with a cargo of 65,000 barrels of #2 heating oil. An initial torpedo hit the starboard bow, and the second hit to the port side came 10 minutes later. The ship sank an hour after the first hit, eventually settling onto the seafloor. Today, it is reportedly upside down, with the port side buried in sand but with the starboard edge and some of its railing visible.

The wreck of the W.E. Hutton also is located in the NOAA Remediation to Undersea Legacy Environmental Threats (RULET) Database. Evaluated in the 2013 NOAA report “Risk Assessment for Potentially Polluting Wrecks in U.S. Waters,” this wreck was considered a low potential for a major oil spill because dive surveys “show all tanks open to the sea and no longer capable of retaining oil.”  However, as the fisherman could observe from the waters above, some oil clearly remains trapped in the wreckage.

This shipwreck was described by wreck diver and historian Gary Gentile as having “enough large cracks to permit easy entry into the vast interior.” Another wreck diver and historian, Roderick Farb, noted that the largest point of entry into the hull is “about 150 feet from the stern,” through a “huge crack in the hull full of rubble, iron girders, twisted hull plates and other wreckage.”  This wreck is the closest one to the spot where the fisherman first saw the leaking oil, and given the Hutton’s inverted position and such cracks, we now realize the possibility that the inverted hull has been trapping some of the 65,000 barrels of its oil cargo as well as its own fuel.

An image of the wreck of the W.E. Hutton laying on the ocean floor.

A multibeam scan of the wreck of the W.E. Hutton taken in 2010. (NOAA)

Solving the Problems with Sunken Shipwrecks 

On July 21, 2014, a commercial dive company contracted by the U. S. Coast Guard sent down multiple dive teams to the Hutton’s wreck to assess the scope and quantity of the leaking oil. The contractor developed and implemented a containment and mitigation plan, which stopped the flow of oil from a finger-sized hole in the rusted hull. It is not known how much oil escaped into the ocean or how long it had been leaking before the passing fisherman noticed it in the first place.

NOAA’s Office of Response and Restoration, led by Scientific Support Coordinator Frank Csulak, provided the U.S. Coast Guard access to historical data about shipwrecks off of North Carolina, survey information, including underwater and archival research, and the animals, plants, and habitats at risk from the leaking oil. Our office frequently provides scientific support in this way when a maritime problem occurs due to sunken wrecks. They may pose a significant threat to the environment, human health, and navigational safety (as an obstruction to navigation). Or, as in this case, shipwrecks can threaten to discharge oil or hazardous substances into the marine environment.

Last May, our office released an overall report describing this work and our recommendations, along with 87 individual wreck assessments. The individual risk assessments highlight not only concerns about potential ecological and socio-economic impacts, but they also characterize most of the vessels as being historically significant. In addition, many of them are grave sites, both civilian and military. The national report, including the 87 risk assessments, is available at “Potentially Polluting Wrecks in U.S. Waters.” Several of those higher-risk wrecks also lie in the Graveyard of the Atlantic, but as we discovered, it is difficult to predict where and when a rusted wreck might release its oily secrets to the world.

OR&R’s Doug Helton and Frank Csulak contributed to this post.

 


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NOAA Prepares for Bakken Oil Spills as Seattle Dodges Oil Train Explosion

As federal leaders in oil spill response science, NOAA’s Office of Response and Restoration is grateful for each oil spill which does not take place, which was fortunately the case on July 24, 2014 in Seattle, Washington, near our west coast office. A train passing through the city ran off the tracks, derailing three of its 100 tank cars carrying Bakken crude oil from North Dakota to a refinery in the port town of Anacortes, Washington. No oil spilled or ignited in the accident.

However, that was not the case in five high-profile oil train derailments and explosions in the last year, occurring in places such as Casselton, North Dakota, when a train carrying grain derailed into an oil train, causing several oil tank cars to explode in December 2013.

Oil production continues to grow in North America, in large part due to new extraction technologies such as hydraulic fracturing (fracking) opening up massive new oil fields in the Bakken region of North Dakota and Montana. The Bakken region lacks the capacity to transport this increased oil production by the most common methods: pipeline or tanker. Instead, railroads are filling this gap, with the number of tank cars carrying crude oil in the United States rising more than 4,000 percent between 2009 (9,500 carloads) and 2013 (407,761).

Just a day before this derailment, Seattle City Council signed a letter to the U.S. Secretary of Transportation, urging him to issue an emergency stop to shipping Bakken crude oil in older model tank train cars (DOT-111), which are considered less safe for shipping flammable materials. (However, some of the proposed safer tank car models have also been involved in oil train explosions.) According to the Council’s press release, “BNSF Railway reports moving 8-13 oil trains per week through Seattle, all containing 1,000,000 or more gallons of Bakken crude.” The same day as the Council’s letter, the Department of Transportation proposed rules to phase out the older DOT-111 model train cars for carrying flammable materials, including Bakken crude, over a two-year period.

NOAA’s Office of Response and Restoration is examining these changing dynamics in the way oil is moved around the country, and we recently partnered with the University of Washington to research this issue. These changes have implications for how we prepare our scientific toolbox for responding to oil spills, in order to protect responders, the public, and the environment.

The fireball that followed the derailment and explosion of two trains, one carrying Bakken crude oil, on December 30, 2013, outside Casselton, N.D.

The fireball that followed the derailment and explosion of two trains, one carrying Bakken crude oil, on December 30, 2013, outside Casselton, N.D. (U.S. Pipeline and Hazardous Materials Safety Administration)

For example, based on our knowledge of oil chemistry, we make recommendations to responders about potential risks during spill cleanup along coasts and waterways. We need to know whether a particular type of oil, such as Bakken crude, will easily ignite and pose a danger of fire or explosion, and whether chemical components of the oil will dissolve into the water, potentially damaging sensitive fish populations.

Our office responded to a spill of Bakken crude oil earlier this year on the Mississippi River. On February 22, 2014, the barge E2MS 303 carrying 25,000 barrels of Bakken crude collided with a towboat 154 miles north of the river’s mouth. A tank of oil broke open, spilling approximately 31,500 gallons (750 barrels) of its contents into this busy waterway, closing it down for several days. NOAA provided scientific support to the response, for example, by having our modeling team estimate the projected path of the spilled oil.

Barge leaking oil on a river.

Barge E2MS 303 leaking 750 barrels of Bakken crude oil into the lower Mississippi River on February 22, 2014. (U.S. Coast Guard)

We also worked with our partners at Louisiana State University to analyze samples of the Bakken crude oil. We found the oil to have a low viscosity (flows easily) and to be highly volatile, meaning it readily changes from liquid to gas at moderate temperatures. It also contains a high concentration of the toxic components known as polycyclic aromatic hydrocarbons (PAHs) that easily dissolve into the water column. For more information about NOAA’s involvement in this incident, visit IncidentNews.


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At the Trans Alaska Pipeline’s Start, Where 200 Million Barrels of Oil Begin their Journey Each Year

Man in hard hat outside at sign at start of Trans Alaska Pipeline.

NOAA’s Incident Operations Coordinator at milepost 0 of the Trans Alaska Pipeline in Deadhorse, Alaska. (NOAA)

A couple years ago I visited the southern end of the 800-mile-long Trans Alaska Pipeline in Valdez, Alaska. As the northernmost port that remains free of ice, the Valdez Marine Terminal is where crude oil from the North Slope oil fields is loaded on tankers destined for refineries on the west coast of the United States. Last month I got to visit the northern end of the pipeline in Deadhorse, Alaska, where on average 17,001 gallons of oil enter the pipeline each minute and more than 200,000,000 barrels each year [PDF].

I was in Deadhorse to meet with Alaska Clean Seas, the primary Oil Spill Response Organization (OSRO) for all of the oil exploration and production operations in Prudhoe Bay and the other nearby oil fields.

Sign in airport showing acceptable cold weather clothing for passengers.

Everyone traveling to Deadhorse, Alaska, where the Trans Alaska Pipeline begins, must follow strict Arctic fashion guidelines. (NOAA)

The flight from Anchorage was right on time, boarded quickly, and was full of jackets and hats with every industry logo in the oilfield servicing business. Safety is a big concern in a place that is so remote, and the safety policy starts at Anchorage. Nobody is allowed on the plane without appropriate clothing.

The scenery in Deadhorse is difficult to describe. It has a flat, sprawling industrial footprint surrounded by vast tundra, shallow braided rivers, and innumerable shallow ponds and lakes. All of the infrastructure is built on large gravel pads: living quarters, warehouses, huge drilling rigs, and other equipment, with multiple racks of elevated pipelines running every direction. Unheated structures sit on the ground, but heated buildings are constructed on concrete stilts to prevent thawing of the permafrost.

Deadhorse is home to the beginning of the Trans Alaska Pipeline, combining oil from five major feeder pipelines that originate in the different oil fields that comprise the North Slope. Oil takes about 15 days to get to Valdez, moving about five miles per hour. Since its construction in 1977, the Trans Alaska Pipeline System has transported nearly 17 billion barrels of oil.

While in Deadhorse, I also got to see the Beaufort Sea. Although it was close to the summer solstice (the last sunset was about a month ago), the ocean was still mostly frozen. Response boats remained staged on land, waiting for open water.

As you can gather from these descriptions and the pictures that follow, the Arctic is not a place that easily lends itself to the type and speed of oil spill cleanup possible in warmer and more accessible areas. Learn more about NOAA’s ongoing Arctic efforts in a series of reports released in April 2014.


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With NOAA as a Model, India Maps Coastal Sensitivity to Oil Spills

This is a post by Vicki Loe and Jill Petersen of NOAA’s Office of Response and Restoration.

Boy running on beach.

Scientists in India have used NOAA’s Environmental Sensitivity Index maps as a model for preparing for oil spills on the west coast of India. (Credit: Samuel Kimlicka/Creative Commons Attribution 2.0 Generic License)

They say that imitation is the sincerest form of flattery, which is why we were thrilled to hear about recent efforts in India to mirror one of NOAA’s key oil spill planning tools, Environmental Sensitivity Index maps. A recent Times of India article alerted us to a pilot study led by scientists at the National Institute of Oceanography in India, which used our Environmental Sensitivity Index (ESI) shoreline classifications to map seven talukas, or coastal administrative divisions in India. Amid the estuaries mapped along India’s west coast, one of the dominant shoreline types is mangroves, which are a preferred habitat for many migratory birds as well as other species sensitive to oil.

Traditional ESI data categorize both the marine and coastal environments as well as their wildlife based on sensitivity to spilled oil. There are three main components: shoreline habitats (as was mapped in the Indian project), sensitive animals and plants, and human-use resources. The shoreline and intertidal zones are ranked based on their vulnerability to oil, which is determined by:

  • Shoreline type (such as fine-grained sandy beach or tidal flats).
  • Exposure to wave and tidal energy (protected vs. exposed to waves).
  • Biological productivity and sensitivity (How many plants and animals live there? Which ones?).
  • Ease of cleanup after a spill (For example, are there roads to access the area?).

The biology data available in ESI maps focus on threatened and endangered species, areas of high concentration, and areas where sensitive life stages (such as when nesting) may occur. Human use resources mapped include managed areas (parks, refuges, critical habitats, etc.) and resources that may be impacted by oiling or clean-up, such as beaches, archaeological sites, or marinas.

Many countries have adapted the ESI data standards developed and published by NOAA. India developed their ESI product independently, based on these standards. In other cases, researchers from around the world have come across ESI products and contacted NOAA for advice in developing their own ESI maps and data. In the recent past, Jill Petersen, the NOAA ESI Program Manager, has worked with scientists who have visited from Spain, Portugal, and Italy.

By publishing our data standards, we share information which enables states and countries to develop ESI maps and data independently while adhering to formats that have evolved and stood the test of time over many years. In addition to mapping the entire U.S. coast and territories, NOAA has conducted some of our own international mapping of ESIs. In the wake of Hurricane Mitch in 1998, we mapped the coastal natural resources in the affected areas of Nicaragua, Honduras, and Ecuador.

Currently, we are developing new ESI products for the north and mid-Atlantic coasts of the United States, many areas of which were altered by Hurricane Sandy in 2012. The new maps will provide a comprehensive and up-to-date picture of vulnerable shorelines, wildlife habitats, and key resources humans use. Having this information readily available will enable responders and planners to quickly make informed decisions in the event of a future oil spill or natural disaster.

For further information on NOAA’s ESI shoreline classification, see our past blog posts: Mapping How Sensitive the Coasts Are to Oil Spills and After Sandy, Adapting NOAA’s Tools for a Changing Shoreline.


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As Oil Sands Production Rises, What Should We Expect at Diluted Bitumen (Dilbit) Spills?

Pipeline dug up for an oil spill cleanup next to a creek.

This area is where the Enbridge pipeline leaked nearly a million gallons of diluted bitumen (dilbit), a tar sands oil product, into wetlands, Talmadge Creek, and roughly 40 miles of Michigan’s Kalamazoo River in 2010. (U.S. Environmental Protection Agency)

I’ve seen a lot of firsts in the past four years.

During that time, I have been investigating the environmental impacts, through the Natural Resource Damage Assessment process, of the Enbridge pipeline spill in Michigan. In late summer of 2010, a break in an underground pipeline spilled approximately 1 million gallons of diluted bitumen into a wetland, a creek, and the Kalamazoo River. Diluted bitumen (“dilbit”) is thick, heavy crude oil from the Alberta tar sands (also known as oil sands), which is mixed with a thinner type of oil (the diluent) to allow it to flow through a pipeline.

A Whole New Experience

This was my first and NOAA’s first major experience with damage assessment for a dilbit spill, and was also a first for nearly everyone working on the cleanup and damage assessment. Dilbit production and shipping is increasing. As a result, NOAA and our colleagues in the field of spill response and damage assessment are interested in learning more about dilbit:

  • How does it behave when spilled into rivers or the ocean?
  • What kinds of effects does it have on animals, plants, and habitats?
  • Is it similar to other types of oil we’re more familiar with, or does it have unique properties?

While it’s just one case study, the Enbridge oil spill can help us answer some of those questions. My NOAA colleague Robert Haddad and I recently presented a scientific paper on this case study at Environment Canada’s Arctic and Marine Oil Spill Program conference.

In addition, the Canadian government and oil pipeline industry researchers Witt O’Brien’s, Polaris, and Western Canada Marine Response Corporation [PDF] and SL Ross [PDF] have been studying dilbit behavior as background research related to several proposed dilbit pipeline projects in the United States and Canada. Those experiments, along with the Enbridge spill case study, currently make up the state of the science on dilbit behavior and ecological impacts.

How Is Diluted Bitumen Different from Other Heavy Oils?

Dilbit is in the range of other dense, heavy oils, with a density of 920 to 940 kg/m3, which is close to the density of freshwater (1,000 kg/m3). (In general when something is denser than water, it will sink. If it is less dense, it will float.) Many experts have analyzed the behavior of heavy oils in the environment and observed that if oil sinks below the surface of the water, it becomes much harder to detect and recover. One example of how difficult this can be comes from a barge spill in the Gulf of Mexico, which left thick oil coating the bottom of the ocean.

What makes dilbit different from many other heavy oils, though, is that it includes diluent. Dilbit is composed of about 70 percent bitumen, consisting of very large, heavy molecules, and 30 percent diluent, consisting of very small, light molecules, which can evaporate much more easily than heavy ones. Other heavy oils typically have almost no light components at all. Therefore, we would expect evaporation to occur differently for dilbit compared to other heavy oils.

Environment Canada confirmed this to be the case. About four to five times as much of the dilbits evaporated compared to intermediate fuel oil (a heavy oil with no diluent), and the evaporation occurred much faster for dilbit than for intermediate fuel oil in their study. Evaporation transports toxic components of the dilbit into the air, creating a short-term exposure hazard for spill responders and assessment scientists at the site of the spill, which was the case at the 2010 Enbridge spill.

Graph of evaporation rates over time of two diluted bitumen oils and another heavy oil.

An Environment Canada study found that two types of diluted bitumen (dilbits), Access Western Blend (AWB) and Cold Lake Blend (CLB), evaporated more quickly and to a greater extent than intermediate fuel oil (IFO). The two dilbits are shown on the left and the conventional heavy oil, IFO, on the right. (Environment Canada)

Since the light molecules evaporate after dilbit spills, the leftover residue is even denser than what was spilled initially. Environment Canada, Witt O’Brien’s/Polaris/WCMRC, and SL Ross measured the increase in dilbit density over time as it weathered, finding dilbit density increased over time and eventually reached approximately the same density as freshwater.

These studies also found most of the increase in density takes place in the first day or two. What this tells us is that the early hours and days of a dilbit spill are extremely important, and there is only a short window of time before the oil becomes heavier and may become harder to clean up as it sinks below the water surface.

Unfortunately, there can be substantial confusion in the early hours and days of a spill. Was the spilled material dilbit or conventional heavy crude oil? Universal definitions do not exist for these oil product categories. Different entities sometimes categorize the same products differently. Because of these discrepancies, spill responders and scientists evaluating environmental impacts may get conflicting or hard-to-interpret information in the first few days following a spill.

Lessons from the Enbridge Oil Spill

Initially at the Enbridge oil spill, responders used traditional methods to clean up oil floating on the river’s surface, such as booms, skimmers, and vacuum equipment (see statistics on recovered oil in EPA’s Situation Reports [PDF]).

After responders discovered the dilbit had sunk to the sediment at the river’s bottom, they developed a variety of tactics to collect the oil: spraying the sediments with water, dragging chains through the sediments, agitating sediments by hand with a rake, and driving back and forth with a tracked vehicle to stir up the sediments and release oil trapped in the mud.

These tactics resulted in submerged oil working its way back up to the water surface, where it could then be collected using sorbent materials to mop up the oily sheen.

While these tactics removed some oil from the environment, they might also cause collateral damage, so the Natural Resource Damage Assessment trustees assessed impacts from the cleanup tactics as well as from the oil itself. This case is still ongoing, and trustees’ assessment of those impacts will be described in a Damage Assessment and Restoration Plan after the assessment is complete.

A hand holds a crushed mussel.

A freshwater mussel found crushed in an area of the Kalamazoo River with heavy cleanup traffic following the 2010 Enbridge oil spill. (Enbridge Natural Resource Damage Assessment Trustee Council)

For now, we can learn from the Enbridge spill and help predict some potential environmental impacts of future dilbit spills. We can predict that dilbit will weather (undergo physical and chemical changes) rapidly, becoming very dense and possibly sinking in a matter of days. If the dilbit reaches the sediment bed, it can be very difficult to get it out, and bringing in responders and heavy equipment to recover the oil from the sediments can injure the plants and animals living there.

To plan the cleanup and response and predict the impacts of future dilbit spills, we need more information on dilbit toxicity and on how quickly plants and animals can recover from disturbance. Knowing this information will help us balance the potential impacts of cleanup with the short- and long-term effects of leaving the sunken dilbit in place.

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