Use of Noises in Sea Oil Search OKd : Environment: Panel says Exxon may explore using loud air gun blasts, adding that risk to whales is minimal. Activists will ask state to bar tests.

Exxon Oil Co. won federal permission Thursday to explore for oil off the coast of Santa Barbara using extremely loud underwater air gun blasts despite concern that the noise could harm whales in the vicinity.

The oil company, which will fire repeated 240-decibel blasts from the seismic guns to map underwater oil reserves, received approval from the National Marine Fisheries Service to engage in the “incidental harassment” of nine species of whale, including the migrating gray whale.

The agency estimates Exxon’s 45-day survey will result in up to 2,360 separate incidents of whale harassment. It directed the oil company to take specific steps--including turning down the sound when necessary--to prevent permanent injury to the whales.

But outraged by approval of the project, environmentalists charged that the blasts would be so loud that they would not only harm whales but could affect human divers near shore about four miles from the survey vessel.

They also contend that the agency’s scientific analysis is faulty and that the extent of whale harassment will actually be many times greater than the 2,360 incidents estimated by the Fisheries Service.

“It is extremely disturbing,” said Sara Wan, vice chairwoman of the League for Coastal Protection, who had sought to negotiate a compromise affording greater protection for marine life. “It doesn’t allow for an adequate safety zone and sets a precedent for the industry in California.”

She said opponents will ask the California Coastal Commission to intervene and may go to court to block the survey. “If we don’t get additional mitigation from Exxon there is no question in my mind we will take legal action,” she said.

Representatives of Exxon and the National Marine Fisheries Service insisted that the “letter of authorization” issued by the agency would provide adequate protection for marine mammals.

Among other things, it requires Exxon to begin operations by turning the sound up gradually, to keep marine mammal observers on board at all times and to reduce the sound level if a whale comes within 1,476 feet of the survey vessel.

“Based on the best scientific information available, the Marine Fisheries Service has concluded that the authorization to harass a small number of marine mammals by conducting the seismic surveys in this area is not likely to jeopardize any [endangered] species and will not result in more than a negligible effect to a small number of marine mammals,” said Scott Smullen, a spokesman for the agency.

The estimate that the noise will result in 2,360 incidents of harassment is based on the assumption that many of the whales will be exposed to the sound numerous times. The agency estimates that up to 81 individual whales will be affected by the noise.

Studies have shown that whales avoid certain loud noises by changing course, which could cause harm if it seriously delayed their migration or caused calves to be separated from their mothers. Whales who were exposed to very loud noises could be deafened, which could hamper their ability to navigate and find food.

Exxon wants to conduct the survey in a 117-square-mile tract south of Gaviota so that it can locate oil within its existing federal offshore oil lease and then recover it using long-range directional drilling from its existing offshore platforms.

Supporters say the survey has environmental benefits for the environmentally sensitive Santa Barbara Channel because it would reduce exploratory drilling and its accompanying disturbance and pollution of the ocean floor.

Exxon officials acknowledge that they are not whale experts but insist that the Fisheries Service would not have granted the permit if the survey would cause harm to marine mammals under the agency’s protection.

“Clearly we are concerned about the whales,” said Exxon spokesman Bruce Tackett. “We really have tried to be accessible and responsive and I believe frankly that we have been.”

But Wan and other environmentalists argue that the agency has seriously underestimated the distance the noise will travel before dissipating and the effect that the sound blasts--fired every few seconds around the clock--will have on whales, including sperm whales, pygmy sperms, humpbacks and blue whales, that pass through the region.

They also are concerned that the survey could disrupt the migration of gray whales, which are expected to begin swimming through the survey area around the middle of December. The study will not start until November and will take about 45 days if there are no delays due to bad weather.

At 240 decibels, the noise of the compressed air guns is one of the loudest noises humans make. Because decibels are measured on a logarithmic scale, the air gun blasts are 32,000 times louder than the 195-decibel sound source proposed last year for a controversial underwater study of global warming.

Wan argued that the zone in which whales could be disturbed by the sound is a circle five times greater than the area calculated by the Fisheries Service. On that basis, she contends, the sound will affect more than the 81 whales and result in many more cases of disturbance than estimated by the agency.

“The actual number of harassments is considerably more than they predict,” Wan said.

Furthermore, she contends that at certain times the underwater sound level could be as loud as 171 decibels near shore, which could affect humans in the water. (A measurement of 170 decibels underwater corresponds to 110 decibels in the air--a level at which government safety rules recommend ear protection for workers.)

Federal officials, however, said the noise level of Exxon’s survey poses no safety threat for humans and only minor disturbances for whales.

“At most, the activity may result in a temporary modification of [whales’] behavior,” Smullen said. “Since the best available scientific information maintains that only a small number of marine mammals will be disturbed and with negligible effects, the agency has determined that [it] is obligated to issue the authorization.”