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Only natural hydrocarbons found in Cook Inlet sediments
Petroleum News Alaska
The U.S. Minerals Management Survey said Aug. 15 that a three-year study that looked for hydrocarbon and trace metals in the sediments in Cook Inlet and Shelikof Strait has concluded that contaminants are not linked to oil and gas development in upper Cook Inlet or the Exxon Valdez spill. The MMS funded the study titled, “Sediment Quality in Depositional Areas of Shelikof Strait and Outermost Cook Inlet.”
The study, by Arthur D. Little Inc., looked for hydrocarbon and trace metal contaminants from oil industry activity in areas with fine-grained sediments in Cook Inlet and Shelikof Strait. Oil industry contaminants will adsorb on to fine-grained material in the water and would be expected to end up where fine-grained sediments are accumulating.
Samples were taken from sites in Cook Inlet and Shelikof Strait with additional sampling stations in the Gulf of Alaska to provide “upstream” source material. The study evaluated the amount of petroleum-related compounds and other metals present in sediment, sediment cores, fish tissue, and source samples.
MMS said the study found that concentrations of metals and petroleum-related compounds present today in Shelikof Strait and outer Cook Inlet are not linked to oil and gas development in Upper Cook Inlet or the Exxon Valdez oil spill. The study concluded that the residue that is present originates from a combination of natural sources, such as river runoff, eroded coal or rock, and natural seeps. The concentrations in the sediments do not pose a significant risk to the environment. No big changes since 1963 The study also found that the concentrations, composition, and the sources of contaminants in the study area have not increased significantly since oil and gas development began in Cook Inlet in 1963. Sampling shows that some 10 to 20 percent of the total sediment deposited in the study area come from the Copper River.
MMS said the study’s findings are consistent with those of the recent draft U.S. Environmental Protection Agency report on contaminant levels in Cook Inlet subsistence foods. That study also found low levels of oil industry contaminants. MMS said its Shelikof study confirms and extends the findings of earlier MMS studies which had looked for but also did not find oil industry contaminants in Cook Inlet waters or sediments. Scientists doing these earlier studies had recommended that MMS look for such contaminants in sediments down current of Cook Inlet, leading to this study.
This report is available from the MMS, Alaska OCS Region, 949 East 36th Avenue, Room 308, Anchorage, Alaska 99508-4363, on a CD-ROM, or may be downloaded from the MMS Alaska Region website at www.mms.gov/alaska.
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