Unalaska moves to rebuild its harbor, with sea otter safeguards for the pile driving

Unalaska is set to replace aging moorage at Robert Storrs Harbor, and federal wildlife officials are reviewing what the pile driving might mean for the area's northern sea otters. The city would remove 33 old steel piles and install 44 new ones, with driving on up to 100 nonconsecutive days over the coming year. The public has until Sept. 10 to comment before the U.S. Fish and Wildlife Service decides whether to sign off.

The review is a routine step for in-water work near a protected species, and the projected effect is small. The Service estimates the noise could reach up to 112 otters, nearly all of it as temporary behavioral disturbance, animals moving off from the noise, with a smaller possibility of hearing injury for a few. That 112 is a worst-case ceiling, not a count at the harbor; it's the largest group surveyors saw anywhere in the Eastern Aleutians, about five miles away. Measured against the regional otter stock of roughly 52,000, it works out to about 0.22%. The authorization covers only disturbance, not killing, and the Service proposes finding no more than a negligible impact on the population.

The otters here are part of the Southwest Alaska stock, listed as threatened in 2005 after a steep decline in the Aleutians in the 1990s. The Service's most recent assessment calls the overall stock generally stable to increasing, and the Eastern Aleutians unit that includes Unalaska among those that have grown in recent years.

The work relies on standard safeguards. The Service rejected bubble curtains and other noise dampening as impractical in the harbor's tight workspace, but requires a 10-meter shutdown zone during in-water work, gradual "soft starts" before impact driving, daylight-only work, and on-site observers who can halt operations if an otter gets too close.

The Service also found the project wouldn't interfere with subsistence hunting, noting the work area doesn't significantly overlap current harvest areas and that only a handful of otters have been taken near Unalaska in the past decade. No Alaska Native community has raised concerns, though the Service and city plan to contact potentially affected communities as a condition of the authorization.