- Kalamazoo River
- Date de l'accident
- Zone du naufrage
- Marshall, Michigan
- Zone du déversement
- Inland water
- Cause de l'accident
- Produit transporté
- Diluted bitumen
- Nature polluant
- Diluted bitumen
- Type de navire / structure
- Tirant d'eau
On 26th July 2010, approximately 130 km upstream of Lake Michigan, Line 6B of Enbridge Energy's Lakehead pipeline system ruptured, releasing an estimated 3,700 m3 of bitumen into Talmadge Creek, a small tributary of the Kalamazoo River. Built in 1969, the pipeline transports 30,000 m3 a day. The product spilt, Cold Lake Blend, is an extremely heavy and viscous bitumen extracted from the tar sand of Alberta (Canada), which requires the addition of a diluent to be transported by pipeline, with a blend of 1/3 diluent and 2/3 bitumen. The resulting product is better known as 'dilbit', a contraction of 'diluted bitumen'.
In addition to the characteristically strong current in these watercourses, heavy precipitation on the days leading up to the incident caused the river to burst its banks, carrying the dilbit over the several dams across the river, thereby oiling over 60 km of watercourse. The spill affected the banks of Talmadge Creek and the Kalamazoo River, as well as ecologically sensitive wetlands and the flood plains bordering the river.
Due to its density and to turbulence, part of the bitumen sank to the riverbed where it mixed with sediment. These deposits accumulated in areas of calm water, in particular in secondary channels, upstream of dams, and where the Kalamazoo River flows into Morrow Lake, as well as other sheltered areas.
During the first few days, the State of Michigan criticised the US Environmental Protection Agency (EPA), in charge of supervising the response, and Enbridge for their initial response actions which it considered to be insufficient. The EPA requested a $2 million advance from the Oil Spill Liability Trust Fund managed by the U.S. Coast Guard to upscale the mobilisation of federal personnel and equipment (mainly booms). EPA also ordered Enbridge to take the necessary measures to conduct removal, dredging, recovery, clean-up and restoration operations in compliance with a detailed schedule. This order also included the monitoring of the potential contamination of the groundwater in the area immediately surrounding the river and the assessment of potential long term environmental impacts.
Protecting the population and agricultural activities
To assess the health risks for the population in industrial and residential areas, the EPA implemented a programme to monitor the atmospheric concentrations of volatile organic compounds (VOCs) and benzene. Benzene was sometimes detected at levels exceeding the accepted threshold values. A voluntary evacuation was issued and over 100 local inhabitants were temporarily relocated. It was recommended that domestic use of well water be avoided within a 200-foot strip on either side of the watercourses, although no contamination of the groundwater was detected. This was also the case for the use of surface water for agricultural purposes, both for irrigation and drinking water for cattle.
Faced with complaints from local inhabitants, in late July 2010 Enbridge issued an offer, valid for one year, to buy up the houses, at their pre-spill value, in the 200-foot strip on either side of the Kalamazoo River, defined as the "red zone" by the Calhoun County Public Health Department. Of the 200 houses potentially concerned, 90 were bought and around 40 were under negotiation in March 2011.
Enbridge very quickly managed to shut off and plug the Line 6B. The response then primarily focused on limiting the spread of the pollution. In the spill area, oil removal and site rehabilitation work began immediately, alongside spill response operations. All the oiled soil around the spill point as well as along a 3 km-stretch of Talmadge Creek was excavated and replaced by an equivalent volume of earth. The damaged section of pipeline was removed and handed over to the authorities for inspection.
A culvert with a dam comprising underflow pipes was dug to divert Talmadge Creek in order to block and recover any oil. The pipeline was reopened on 27th September 2010, under the control of the Pipeline and Hazardous Materials Safety Administration, after usage testing.
On the Kalamazoo River, measures were taken to contain the floating oil mainly in 5 areas situated between the spill site and the Morrow Lake.The containment systems were composed of a series of floating booms, reinforced with sorbent booms and positioned in a deflective or protective configuration.
At the height of containment operations, in August 2010, over 50 km of booms were deployed on site. During the winter, the majority of these arrangements had to be removed because of drifting ice which hindered their operation and was liable to damage them. In some cases, an ice gate was installed to resolve this issue.
Recovering oil on the water and on the banks
Pollution surveys to define clean-up operations for the affected sites were conducted by teams trained in the SCAT (Shoreline Cleanup Assessment Technique) procedure, based on systematic daily inspections of the watercourses, conducted on foot or from boats, often corroborated by aerial surveys by helicopter. The river was divided into quarter-mile sectors, indicated by wooden markers, painted different colours according to the degree of oiling of the river.
The use of airboats (flat-bottomed boats with an aircraft-type propeller) for various response operations hugely facilitated operations on the river, where access was very difficult in places. For ease of navigation on the river, trees and vegetation sometimes had to be cut back.
Oil was removed from the river at 40 recovery points, mainly using drum skimmers, often associated with vacuum trucks. Extensive use was also made of sorbent pads and booms, both statically and dynamically from small boats.
In shallow areas, original filtration systems were installed across the current: gabions, composed of metal structures and wire mesh, field with sorbent mops and oakum.
On the banks, clean-up involved various techniques: flushing with low pressure hoses, recovery with sorbents or pumping/skimming and vegetation scything.
Recovering sunken oil
However the major difficulty was treating the bitumen that had sunk or was trapped in the sediment, which first had to be detected. Teams of river geomorphologists managed to identify and characterise 35 priority bitumen accumulation areas, based on a bathymetric assessment with GPS tracking, doubled up with poling and core sampling, and completed where necessary with an ecological assessment.
Various techniques, both conventional and improvised, were implemented to recover the submerged bitumen. The least invasive was agitation of sediments using hoses spraying a flow of water mixed with air to remobilise the bitumen and cause it to rise to the surface, where it was recovered with sorbents or by skimming and pumping. This technique was implemented either manually, using long wands deployed from airboats, or mechanically, using a spraying arm installed on amphibious excavators fitted with pumps. Certain sites required more advanced sediment extraction operations, requiring far more complex logistics.
In terms of wildlife impacts, large quantities of fish and birds were found dead or heavily oiled in the first few days following the spill. In terms of medium and long term impacts, a detailed assessment was conducted by the Fish & Wildlife Service and NOAA as part of the Natural Resource Damage Assessment (NRDA).
The wildlife response showed that reptiles, mainly turtles (the only category for which capture continued into 2011), were the most affected, followed by birds (Canadian geese, herons...), mammals (beavers, voles, muskrats...), amphibians (toads, frogs), and finally benthic invertebrate megafauna (primarily bivalves, including certain protected species).
A site restoration plan was developed, supervised by the State of Michigan, which included water quality monitoring as well as replanting and restoration of the worst affected banks and access pathways so as to stabilise them and reduce erosion. On the islets where the ground had been scraped, clean soil was brought in from unoiled islets.
Enbridge failed to meet the deadline of 31st August 2011 initially set by EPA for the end of clean-up work. More than one year later, the work was still not finished. In September 2011, EPA identified 3 areas with significant bitumen deposits, covering a total surface area of around 80 ha and, and ordered operations to continue through the autumn and winter.
In October 2011, the intermediate figures released were already impressive. The waste generated by clean-up operations along over 120 km of banks, in addition to 25 identified sites, had reached substantial quantities: more than 2,900 m3 of oil and 22,700 m3 of contaminated water had been recovered and recycled. Over 86,000 m3 of soil and polluted debris had been sent to appropriate treatment sites. On top of this, the effluents from the decontamination of personnel and response equipment (booms, skimmers, boats...) were also recovered and treated.
In total, over 2,500 people were mobilised and nearly 500 were still deployed in September 2011.
Funding the response and restoration
In mid-September 2011, EPA announced that it has spent $34 million on clean-up, a sum which Enbridge would have to reimburse. According to Enbridge's website, the expenses thus far incurred exceeded the $650 million maximum limit of its insurance policy and the company expected the total cost of clean-up to reach $700 million (not including fines and penalties), approximately twice what had been announced one year previously.
Five years later, in May 2015, the state of Michigan announced that a $75 million financial settlement had been reached with Enbridge Energy, to finalise clean-up and restoration actions following the spill. This agreement precluded any further legal action by the state of Michigan against the Canadian firm. The sum paid out is to be used to fund various operations: to restore and extend wetlands affected in 2010 ($30M), to complete the dismantling of Ceresco Dam in order to restore the run of the river to its natural historical condition ($18M), to create various access sites to the river for recreational purposes ($10M) and to restore various watercourses within the catchment basin ($5M). Finally, $12M have been earmarked to reimburse past and future expenses incurred by the state of Michigan for long term environmental monitoring and restoration.
According to Enbridge, this settlement brings the sum total of expenses incurred and fines potentially due with regard to federal law up to $1.2 billion, for one of the largest oil spills ever to occur in US continental waters. The state of Michigan expressed its satisfaction at having reached an agreement enabling the implementation of long term environmental restoration and monitoring actions which previously lacked funding.
Investigation into the cause of the incident
The cause of the pipeline rupture has not yet been clearly established. Prior to the incident, Enbridge had been warned by the US authorities of pipeline erosion issues. The Canadian company was fined on numerous accounts for breaking pipeline safety regulations. The US National Transport Safety Board examined the pipeline maintenance records.
The type of product transported was also suspected to have been responsible for the spill by certain experts who were very sceptical as to the capacity or compatibility of existing pipelines for the transport of such products. This issue is a growing concern in the context of two major projects that Enbridge is developing to transport dilbit across the USA and Canada. This criticism is fuelled by the estimated 210,000 m3 of oil spilt in the 610 incidents which have occurred over the past years on Enbridge pipelines.
In August 2011, the US Government announced its firm intent to strengthen pipeline safety laws and regulations, in particular by tightening pipeline inspection and by increasing fines for violating this legislation.