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First step in Cook Inlet risk assessment Vessel traffic study uses 2010 shipping data to project vessel movements and the carriage of oil in the inlet through to 2020 Alan Bailey Petroleum News
As part of an assessment of the risk of oil spills in the waters of Alaska’s Cook Inlet, Cape International Inc. has published the results of its study into vessel traffic movement and the carriage of oil in the inlet.
The Cook Inlet Regional Citizens Advisory Council, the Alaska Department of Environmental Conservation and the U.S. Coast Guard are conducting the risk assessment to assess the nature, likelihood and potential impacts of a Cook Inlet oil spill, and to assess whether the impacts of a spill could be mitigated. The assessment comes in the wake of the 2006 grounding of the oil tanker Seabulk Pride near the Nikiski dock on the coast of the Kenai Peninsula and was recommended by a Cook Inlet navigational safety forum held in 2007.
Forecast future traffic The idea of the vessel traffic study was to characterize the vessels that ply the inlet and to assess the quantities of oil and other hazardous materials that these vessels hold. The study also evaluated expected growth in maritime trade in the region over the next 10 years, and assessed likely vessel design and regulatory changes during that period.
Subsequent phases of the risk assessment will evaluate the oil spill potential of each type of vessel operating in the inlet and hence enable an identification of potential oil spill scenarios; an assessment of the potential impacts of each scenario; and the identification of a set of prioritized options for reducing oil spill risks.
The vessel traffic study included the entire Cook Inlet from the northern end of Shelikof Strait through to the Knik and Turnagain arms. And the study considered all vessels of more than 300 gross tons and any smaller vessels carrying at least 10,000 gallons of oil products.
20 vessel types
Using data for 2010 from the Marine Exchange of Alaska’s vessel tracking system, the study identified 20 different types of vessel operating in the Cook Inlet, including cargo ships, oil tankers, tugs and ferries. The study identified what type of oil each type of vessel carried, either as fuel or cargo, and categorized that oil as either “non-persistent” or “persistent.” Non-persistent oils, essential refined oil products, evaporate and disperse more readily than persistent oils which consist of crude oil and residual oils from oil refinement.
Using the vessel tracking system it was possible to plot the movements of the various types of vessel during 2010. Changes in vessel traffic were then projected into the future, using various assumptions about future economic and population trends.
The study found that there was a total of 496 deep-draft vessel voyages in 2010 in the inlet, a slight increase in traffic compared with the results of a similar study done in 2005. And just 15 vessels, both light and deep draft, made 81 percent of the calls to the various ports around the region. Five of those vessels were tankers carrying crude oil between the Drift River oil terminal on the west side of the inlet and the Nikiski oil refinery on the Kenai Peninsula — those oil tankers in total made an estimated 53 port calls. One liquefied natural gas carrier transported LNG from the LNG terminal at Nikiski, making an estimated 12 port calls at Nikiski during the year. Another 11 tankers carrying non-persistent oil products called in at the Port of Anchorage.
Apart from tanker traffic to and from the Drift River Terminal, most deep draft vessels transited the east side of the inlet, with Kachemak Bay at the southern end of the Kenai Peninsula seeing the highest level of traffic movement.
Mostly crude oil Estimates of oil products carried on different types of vessel indicate that 94 percent of the persistent oil carried on the waters of the inlet consists of crude oil carried by tanker to the Nikiski oil refinery. All other persistent oil is in the form of fuel oil used to power the engines of vessels such as roll-on/roll-off ferries, container ships and bulk carriers. Tank barges, tugs and refined product carriers carried the majority of the non-persistent oil, either in the form of cargo or as fuel.
The study forecasted vessel traffic to remain at about current levels or perhaps increase at an annual rate of 1.5 to 2.5 percent over the next nine years. There are, however, some unlikely but possible scenarios in which traffic could increase dramatically, the study report says. Those scenarios include increased global demand for Alaska coal, oil, gas and minerals; increased bulk carrier traffic at Port Mackenzie at the mouth of Knik Arm; and the shipping of materials for an Alaska gas pipeline.
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