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PWSRCAC reports low contamination levels
2018 sampling covered areas around terminal and an expanded area in Prince William Sound generally following Exxon Valdez impacts Kristen Nelson Petroleum News
The Prince William Sound Regional Citizens’ Advisory Council said Oct. 22 that long term monitoring in Prince William Sound shows oil contamination in the sound and Gulf of Alaska “has reached all-time low values.”
The council said its efforts to monitor long term environmental impacts of operation of Alyeska Pipeline Service Co.’s Valdez Marine Terminal and associated tankers began in 1993.
Improvements implemented by Alyeska and its owner companies over the years, including elimination of single hulled tankers and “Alyeska’s ability to effectively operate their Ballast Water Treatment Facility” have contributed to reduction of pollutants being discharged.
“The council’s long-term monitoring program helps fulfill one of our responsibilities under the federal Oil Pollution Act of 1990 and is one of the longest running studies of its kind,” said Donna Schantz, executive director for the council. “The council is pleased to be able to recognize, through the results of this study, the efforts and commitment by Alyeska and the Trans Alaska Pipeline System shippers to reduce hydrocarbon releases into the waters of Prince William Sound and the Gulf of Alaska.”
Monitoring program The monitoring report, “Long-Term Environmental Monitoring Program: 2018 Sampling Results and Interpretations,” dated August, by James R. Payne, PhD, and William B. Driskell, attributed the two decade decline in hydrocarbon found in the testing to a combination of reduced volumes from the Ballast Water Treatment Facility due to decreased North Slope oil production as well as the transition to double hulled tankers with segregated ballast tanks and improved BWTF operating efficiencies.
The report says the BWTF at peak was discharging some 15 million gallons per day (this report measures in gallons, rather than barrels) down to only 1.1 million gallons per day currently, with an estimate that “more than half of the current BWTF effluent discharge in summer is from the terminal’s stormwater runoff.”
The new double hulled tankers have segregated ballast, the report says, with empty cargo tanks “typically used for supplemental ballast only when operationally necessary” such as in winter storms. Also, “normal segregated ballast waters are uncontaminated seawater that do not require treatment for hydrocarbons.”
The report summarizes the ballast water situation as “less tanker traffic, cleaner ballast, and an improved ballast-water-treatment configuration at the Alyeska terminals” as all contributing to “substantial reductions in detected hydrocarbon concentrations and composition in the field samples.”
Samples Three types of samples were retrieved and analyzed in 2018: blue mussels, marine sediments and passive sampling devices. The council said samples are sent out to laboratories for chemical analysis and after lab analysis is complete, the data is interpreted by environmental forensic scientists.
In most years sampling is limited to Port Valdez, but every five years, including 2018, sampling is expanded throughout Prince William Sound and the Gulf of Alaska, the council said, largely following the path of the 1989 Exxon Valdez oil spill.
Port Valdez monitoring is mostly focused on assessing environmental impacts of the Valdez Marine Terminal with focus elsewhere on assessing impacts of oil tankers and possible lingering oil from the Exxon Valdez oil spill, with unoiled sites included for control.
“The 2018 samples showed overall oil contamination in the sampled region was very low,” the council said, with oil concentrations measured in mussel tissue samples “below laboratory detection limits,” and oil contamination measured with passive sampling devices below any know toxicity thresholds for sensitive marine organisms.
“Compared to the historic range, dating back to 1993, oil concentrations on the marine sediments near the Valdez Marine Terminal and a clean control site were also low in 2018.”
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