An ongoing scientific study offers positive news about the impact of oil shipping on waters at Valdez and beyond.
The study is known as the long-term environmental monitoring program, or LTEMP.
It involves sampling sediments and mussels for signs of oil pollution. The sampling sites begin at the Valdez Marine Terminal, where tankers load Alaska North Slope crude oil, and range across Prince William Sound and the Gulf of Alaska to Kodiak Island.
“Based on the sediment and mussel data, petrogenic hydrocarbon inputs from the Alyeska Marine Terminal and tanker operations continue to decline,” concludes an LTEMP report covering the years 2008 through 2012.
Petrogenic means hydrocarbon compounds associated with petroleum.
The reasonsWithin Port Valdez, the decrease in oil pollution likely reflects a number of factors, the report says.
First, North Slope oil production has been declining for years. Under 600,000 barrels of crude per day now flows down the 800-mile trans-Alaska pipeline, which ends at Valdez. Throughput peaked at more than 2 million barrels per day in 1988. The decline means less tanker traffic.
Second, the tanker fleet calling at Valdez has converted from single-hull to double-hull ships. These new ships have segregated tanks to hold ballast water, meaning they carry their ballast in clean tanks, not in the same tanks used to carry crude oil. The result is less oily ballast water must be cycled through the treatment plant at the Valdez terminal, with treated wastewater dumped into Port Valdez.
Third, the ballast water treatment facility has become more efficient at removing pollutants known as polycyclic aromatic hydrocarbons, or PAHs, the monitoring report says.
Results from monitoring sites in Prince William Sound and the Gulf of Alaska “demonstrate that the region is exceptionally clean,” the report says.
The council’s roleAn Anchorage-based company, the Alyeska Pipeline Service Co., operates the Valdez terminal. The major owners in Alyeska are BP, ExxonMobil and ConocoPhillips.
Payne Environmental Consulting Inc. produced the LTEMP report for the Prince William Sound Regional Citizens’ Advisory Council, a Valdez-based congressionally sanctioned organization that monitors the terminal and associated tanker activity.
The council was to review the report at its Jan. 23-24 board meeting in Anchorage.
An RCAC memo explains that the Oil Pollution Act of 1990, which Congress passed in the wake of the Exxon Valdez oil spill, directs the council to “devise and manage a comprehensive program of monitoring the environmental impacts of the operations of terminal facilities and crude oil tankers while operating in Prince William Sound.”
LTEMP is the project designed to address this directive, the memo says.
Among other findings in the report:
In sediments at berth 4, one of the two active tanker loading berths at the Valdez Marine Terminal, average total PAH levels are “very low.”
At the Gold Creek monitoring site, across Port Valdez from the tanker terminal, sediments recently have shown “extremely low” total PAH concentrations.
Beyond Port Valdez, there has been a continuing regional decline in total PAH concentrations in Knowles Head mussels. Knowles Head is a safe anchorage well inside Prince William Sound where oil tankers sometimes pause.
The monitoring study does not signify that the crude oil spilled from the Exxon Valdez has vanished.
The council says staff in August took a field trip to Northwest Bay on Eleanor Island, a bay heavily oiled in 1989 and subsequently remediated.
“A few hastily dug shallow pits dug (6 inches to 1 foot deep) in a rocky beach’s tidal zone all indicated the continued presence of Exxon Valdez oil,” the council said a status report on its various projects. “Oil density on the surface went well beyond mere sheen.”