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The Cook Inlet marine accident risks Maritime risk assessment assessed potential accident scenarios, likely outcomes and various strategies for risk mitigation Alan Bailey Petroleum News
With cargo vessels, oil tankers and fuel barges regularly plying the waters of Alaska’s Cook Inlet, there is the ever-present danger of a marine accident and a consequent spill of oil into the waters of the inlet. But what is the real likelihood of this happening? And what would be the consequences?
During the Dec. 5 board meeting of the Cook Inlet Regional Citizens Advisory Council, Tim Robertson, general manager of Nuka Research and Planning Group, presented an overview of the results of a Cook Inlet maritime risk assessment that has delved into these questions and has proposed ways of managing the risk of environmental and economic harm from a Cook Inlet marine accident. Administered by the Cook Inlet RCAC and the Kenai Peninsula Borough, and managed by Nuna, the study team published a draft report in September. Funding for the study comes from the U.S. Coast Guard, the state of Alaska, the National Fish and Wildlife Foundation, Tesoro Corp. and the Prince William Sound RCAC.
Serious consequences In reviewing the study findings, Robertson commented on the serious nature of the oil spill risk in Cook Inlet, saying that the study team has ranked various spill scenarios, based on their potential impacts to the ecosystem and to the regional economy.
“What came out of that understanding was that even moderate sized spills can have a huge, significant impact to both the environment and the socio-economic realities in the Cook Inlet,” Robertson said. “A 100-gallon spill can potentially shut down a commercial fishery and change the season for an entire group of people. It can have major impacts on tourism.”
Robertson said that a key component of the process by which the study had been conducted consisted of the use of a stakeholder advisory panel, with expert representation from communities, industry and interest groups in the Cook Inlet region. The ability of the advisory panel to make recommendations and review study findings resulted in the study being stakeholder driven, he said.
Vessel traffic As a basis for the risk assessment, the study team used available data to analyze existing vessel traffic and assess potential future traffic movement. Considering vessels upwards of 300 gross tons in size, or with a fuel capacity of at least 10,000 gallons, the study found that in 2010 there had been about 500 vessel port calls.
“About 80 percent of these port calls are made by a very few numbers of ships - we have a lot of frequent flyers,” Robertson said, commenting that growth in that traffic appeared relatively slow over the years. However, projections for traffic growth did not include a possible significant increase in liquefied natural gas carrier traffic, should a project to export North Slope natural gas as LNG come to fruition, he said.
The study found that, as a consequence of the vessel traffic, about 450 million gallons of “persistent oil,” crude oil and heavy fuel oil that are difficult to clean up, move around the inlet each month. Of that persistent oil, 60 percent consists of crude oil being shipped to the oil refinery at Nikiski on the Kenai Peninsula, with another 30 percent consisting of fuel oil on the large cargo vessels that carry Alaska-bound goods to the Port of Anchorage.
In addition, an estimated 575 million gallons per month of non-persistent oil such as heating fuel and diesel transits the inlet, mostly carried by tank barges heading for rural communities, Robertson said.
Accident scenarios So, what could go wrong, to cause a spill from any of this Cook Inlet traffic?
Based on historical data from Cook Inlet and on future traffic projections, an average of 3.9 oil spills per year may occur in the inlet in the future, Robertson said. But the scale of an individual spill is highly dependent on the type of operation that results in the spill - a medium sized spill for an operation such as a marine fuel transfer might be as little as 10 gallons, while a medium sized spill for a large crude oil carrier would be about 20,000 gallon. At the 95 percentile end of the probability range - spills that are possible but very unlikely - those volumes increase massively to 20,000 gallons for a fuel transfer and to the possibility of a 15-million-gallon spill for a large crude tanker.
Oil tankers present the biggest risk in the inlet, not only because they carry so much oil but also because the crude oil that they carry is persistent, Robertson said.
Mitigating the risks The study team solicited ideas from the public on how the Cook Inlet oil spill risks might be mitigated, particularly trying to identify options that could tackle the root causes of marine accidents, heading off an accident an early stage of the chain of events that can end in disaster.
As an example of this “root-cause” approach the study recommended the construction of an oil pipeline across the Cook Inlet, to eliminate the need for oil tankers for the shipment of crude oil from oil fields on the west side of the inlet to Tesoro’s Nikiski oil refinery. Elimination of this tanker traffic would reduce the expected spill frequency by 98 percent, as well as reducing the likely volume of a spill, Robertson said.
One major focus of the study was the need for and availability of emergency towing arrangements, particularly to avoid the potential for a grounding incident, should a vessel run into difficulties as a result, say, of a propulsion problem. An analysis of the likely elapsed time between propulsion loss and running aground in some possible grounding scenarios, coupled with an analysis of the time that it would take for an appropriate towing vessel to reach the stricken vessel, showed areas of vulnerability in different parts of the inlet.
Vulnerable areas Depending on the locations of various tugs and other vessels that might be co-opted in an emergency, it would likely be possible to mount a rescue across much of the Cook Inlet. However, some areas near Anchorage, where shipping channels are constricted, and near the East and West Forelands, would be especially vulnerable. A rescue could only be realistically mounted in the Kennedy Entrance, at the southern end of the inlet, and in Kachemak Bay, if there are tugs stationed in the southern inlet, the study found.
This analysis resulted in several recommendations, including the positioning of an emergency towing system at the port of Homer, the implementation of an electronic monitoring system for deep-draft vessels and the coordination over rescue arrangements between the inlet’s “frequent flyer” vessel operators.
However, given the complexity of emergency towing in sea-ice conditions, the study team was not able to resolve the tow-vessel requirements, and hence the rescue parameters, in winter ice, Robertson said.
Escort tugs? One arrangement that has been much debated is the possibility of mandating dedicated escort tugs in the Cook Inlet, for accompanying large vessels crossing the inlet, rather like the tanker escort system operating in Prince William Sound. But the advisory panel discounted that option, saying that, given the low probability of an incident, the high cost of providing the escorts could not be justified, especially given the potential unintended negative impacts of having an escort system in operation. In addition to the environmental impacts of burning more fuel, the operation of a fleet of escort tugs would in itself create the potential for more marine accidents such as collisions, Robertson commented. One of the biggest spills in Prince William Sound since the implementation of an escort system there resulted from one of the escort tugs running aground, he pointed out.
Capt. Paul Mehler, U.S. Coast Guard Sector Anchorage commander, also commented that a vessel entering the Cook Inlet has to notify the Coast Guard with information about the condition of the vessel and its crew. If the information provided by the vessel crew, or its pilot, gives cause for concern, the Coast Guard can and does mandate that an appropriate escort vessel accompany the arriving vessel to port, Mehler said.
Anchor usage Based on a literature review, the study team also investigated the practicalities of a drifting vessel self-arresting through the use of its own anchor. Although members of the advisory panel who are mariners of deep-draft vessels in the Cook Inlet expressed opinions that the dragging of an anchor is a feasible means of saving a vessel in the inlet, the panel as a whole could not reach consensus on this issue and concluded that a more quantitative study of the problem is needed, Robertson said.
And the study team made a number of other recommendations for improving Cook Inlet shipping safety, including training programs for Cook Inlet mariners; procedures for notifying harbor masters and port directors about vessels that appear unsafe; and improved cell phone and VHF radio coverage offshore in the inlet.
The study also endorsed the need for a Cook Inlet harbor safety committee, to act as a forum for the continued discussion and follow up on marine safety issues and the development of best practices for vessel operations in the inlet.
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