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Natural background data collected at Northstar, Liberty MMS funded studies provide baseline in hydrocarbons, metals, noise levels for comparison with conditions after development Kristen Nelson PNA Editor-in-Chief
The U.S. Minerals Management Service has had baseline data collected in the areas of the Northstar and proposed Liberty developments so that scientists will be able to identify effects of the developments.
Phase I of the multi-disciplinary monitoring program began in 1999 and included hydrocarbon, metals and acoustic measurements.
Phase II of the program began last July and includes hydrocarbon and metal chemistry studies, suspended sediment studies, an assessment of subsistence whaling at Cross Island, biota contaminant assessment and a study of the boulder patch area near the Liberty site.
John Brown of Arthur D. Little, one of the project’s core contractors, told an MMS Information Transfer Meeting in Anchorage April 4 that the program will monitor impacts associated with the development activities at Northstar and Liberty.
Independent board involved An independent scientific review board, including a biologist from the North Slope Borough biologist, was involved in the design of the overall study plan for Phase I, Brown said. The final phase I report is expected out in May, he said, establishing baseline data for pre-Northstar and Liberty development. The hydrocarbons and metals found reflect natural background — with some localized exceptions — and the contaminant concentrations in the sediments are well below the range where adverse biological effects would be caused.
The techniques used in the study can detect very small incremental changes in sediment — before they become environmentally significant, Brown said. He noted that the study benefited from the delay of Liberty development because that allowed more work at Northstar and development of a good pre-Liberty biota assessment. Acoustical testing results George Shepard of BBN Technologies described acoustic studies done at Northstar and Liberty last winter where measurements were taken in the water, in the ice and in the air. Vibrahammer noise was measured at Northstar during pile driving, as well as plowing operations, general truck movement, island mounted machinery generated noise and trench backfilling operations.
Acoustic measurements were made with hydro-phones in the water, a microphone in the air and a geo-phone frozen into the ice at distances of 100 meters, 1 kilometer, 2 kilometers and 4 kilometers from the island. Ambient noise levels were measured at Liberty and in the boulder patch.
Shepard said that measured 1 meter off the bottom, vibrahammer noise from Northstar was down to background level from 2 kilometers away. Acoustic energy in the air tends to fall away very quickly, he said, with the vibrahammer noise indistinguishable from background noise to the human ear at 1 kilometer. With equipment working on the island, it seems that noise would vibrate through the ice, Shepard said, but noise isn’t very effectively transmitted through ice, although it was measurable at a kilometer.
He said that acoustics in the Arctic are very site specific, depending on depth of permafrost, water column depth, conditions of the ice that you’re going under, and models are very difficult to use for prediction in other areas and for other types of noise. Background metals levels John Trefry of the Department of Marine and Environmental Systems at the Florida Institute of Technology said the goal of the metals study is to understand the natural concentrations and the natural processes under way in this whole area, so that subtle changes that may occur can be identified.
All sediments contain trace metals at some natural level, he said, depending on the area sampled. Some 17 different metals are being studied.
Some are valuable because they’re good tracers of inputs from various activities — i.e. barium is one of best indicators of drilling mud, Trefry said, and is “one of most sensitive indicators of discharges or leakage of drilling fluids around an oil operation” where it will show up in concentrations hundreds of times higher than normal.
Both Northstar and Liberty are well-established metals sampling sites, he said, with both 1989 and 1999 collections available.
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