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Risks of Oil & Gas Drilling

by diana — last modified August 14, 2013 08:27 PM

Offshore oil and gas exploration and development pose a number of risks and potential impacts to marine life, including:oilspill_EVOS_Trustees_Council.jpg

  • Harm to fish, crab and marine mammals caused by seismic surveys.
  • Contamination of fish and pollution of marine waters caused by drilling operations.
  • Oil spills from platforms, underwater pipelines and/or tankers.
  • Interference with commercial and subsistence fishing activities.


Seismic Surveys

Marine seismic surveys are used to help determine the location of oil and gas deposits beneath the seafloor. To conduct seismic surveys, large ships tow powerful air guns that generate sound waves by firing off explosive blasts of air. The seafloor reflects the sound waves, creating a picture of underwater geological formations.

A typical seismic survey lasts 2-3 weeks and covers a range of about 300-600 miles. The intensity of sound waves can reach up to 250 decibels (dB) near the source and can be as high as 117 dB over 20 miles away. The sound intensity produced by a jackhammer which can damage human ears in as little as 15 seconds is around 120 dB. 

Marine mammals, including dolphins, whales and seals, rely on their sense of hearing to locate prey, avoid predators, choose migration routes and communicate across long distances. The noise from seismic surveys can affect the ability of these animals to detect natural underwater sounds, thereby disrupting the animals' critical understanding of their surroundings.

Numerous scientific studies have echoed what Eskimo subsistence hunters have known for years: that whales avoid expansive areas where seismic surveys are being conducted.  

For an in-depth look at the potential impacts of seismic surveys on marine life as well as citations for the information provided above, please see AMCC's Seismic Survey Fact Sheet (pdf).


Contaminated Drilling Discharges


Offshore oil and gas operations produce a number of waste streams that can contaminate and alter living seafloor communities. These include produced water, ballast water, deck drainage, drilling muds, drill cuttings, produced sand, cement residue, blow-out preventer fluid, sanitary and domestic wastes, gas and oil processing wastes, and slop oil.

Of these, drilling muds, cuttings, and produced water pose the greatest threat to aquatic environments. Given the technical challenge of dealing with these wastes, offshore operations generally directly discharge them into the ocean or transport them to shore for treatment and disposal.

Discharges can physically and ecologically alter the seafloor and associated benthic (bottom) communities by changing the type of sediments found near platform and well discharge sites. Typically, rocky or higher relief substrate changes to soft-bottom sand. Plumes of cuttings can smother fish/crab eggs and larvae in the water column and sedentary invertebrates on the seafloor such as clams and scallops.

The toxic components of produced water and drilling muds and cuttings can include heavy metals (like mercury, cadmium, zinc, chromium, and copper) biocides, corrosion inhibitors, petroleum residues, and even radioactive material. Scientific knowledge on the subtle yet potentially dramatic effects of chronic discharges of drilling muds and cuttings is limited. However, studies in the Gulf of Mexico have shown that drilling discharges have caused widespread, long-term, sublethal effects on planktonic organisms that are key food sources for salmon, other types of fish, whales and seals.

Over the life of a given gas or oil production well, chronic low-levels of contamination from discharges can accumulate in bottom sediments and cause community-level changes by which pollution-tolerant organisms are enhanced and pollution-sensitive ones decline. Pollutants can affect fish populations by impairing reproduction, development and growth, and by altering behavior which has consequences for individual survival and recruitment.

To learn more, please see our Contaminated Discharges Fact Sheet (pdf). 


Oil Spills

Federal studies suggest offshore oil and gas production in the North Aleutian Basin Planning Area (Bristol Bay and southeastern Bering Sea) would result in one or more major oil spills of more than 1,000 barrels and a number of smaller spills. Surface currents in the region could push spilled oil up onto the coast of the Alaska Peninsula and towards the headwaters of Bristol Bay. Oil spill trajectories indicate that oil could contaminate the mouths of rivers and tributaries where salmon spawn and where commercial and subsistence salmon fisheries occur.

The Outer Continental Shelf (OCS) pipelines has a significant spill record that is not improving, which raises serious concerns about Bristol Bay OCS development. Recovery of spilled oil in Bristol Bay is unfeasible because clean-up technology is inadequate in rough sea conditions, ice, and strong tides and currents.

During Shell Corporation public meetings in Anchorage and the Bristol Bay region, the industry has shown interest in moving closer to the sensitive coastline of the Alaska Peninsula. Such a move would increase the likelihood of an oil spill reaching the coastal bays, lagoons, and sea grass beds used as nursery grounds for fish and crabs, and as habitat for seabirds and waterfowl.

Impacts from Oil and Gas Infrastructure

Offshore oil and gas development by its very nature leaves a sizable footprint beneath the sea and on land. The necessary infrastructure for transporting oil and gas from the ocean and preparing it for consumers, would pose serious risks to vital fish, marine mammal and seabird habitat in the Bristol Bay region. It would also interfere with subsistence harvesting areas and commercial fishing grounds.

A network of facilities, support bases, and oil and gas transportation infrastructure would impact hundreds of miles of habitat from the seafloor and water column in the Bering Sea to coastal areas along the north and south side of the Alaska Peninsula. Shell Oil and MMS have provided a geographically specific vision for development in Bristol Bay that calls for subsea pipelines to run through Nelson Lagoon and Herendeen Bay, directly adjacent to the Port Moller State Critical Habitat area. Onshore pipelines would run across the Alaska Peninsula National Wildlife Refuge, and terminate at a Liquefied Natural Gas (LNG) plant and terminal that would be located in the southern (Gulf of Alaska) side of the peninsula near Pavlof Bay.

Construction and the presence of pipelines and facilities would lead to the loss of habitat for marine, coastal and terrestrial species. Degradation of habitat can also occur from construction noise, heavy equipment, erosion, increased sedimentation and dredging of seafloor habitat. 

The Bristol Bay/ Southeastern Bering Sea area is one of the most seismically and volcanically active in the world. Oil spill likelihood is greatly increased here and there are no proven cleanup capabilities in eelgrass or sea ice. The ecological and economic costs of a spill here, even a small one, would be tremendous. 




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