Standing in downtown Anchorage one can gaze across Cook Inlet and clearly see Alaska's Matanuska-Susitna Valley just two miles away. But despite its proximity and the waterway's narrowness, getting there takes at least an hour. That's because no one's built a bridge across it.

Wedged between a federal military installation, the Pacific Ocean to the west, the Chugach Mountains to the east, and the Chugach National Forest to the south, Anchorage is essentially out of developable land but remains the state's commercial and financial hub. People and businesses have been moving further north to the Matanuska-Susitna Borough, where land and houses are less expensive. Though the region contains 54% of the state's population, it's connected by one road, the Glenn Highway. Not surprisingly, congestion is a problem.

A crossing was first proposed by railroad engineers in 1923, a few years after Anchorage was established, to shorten the distance between Anchorage and Fairbanks, an active mining town 358 miles to the north. As Cook Inlet evolved into the state's main shipping route and became a focal point for oil and gas exploration, the crossing had been proposed a half-dozen times since then. In 2003, after years of planning and studies, the Alaska Legislature formed the Knik Arm Bridge and Toll Authority to enable continuing economic development and provide an alternate evacuation route.

Our main concern was a beluga whale subspecies that uses the inlet to get to and from breeding areas. So the first thing we did was ask state and federal regulatory agencies — in particular the National Marine Fisheries Service (NMFS) — to become cooperating organizations.

“We wanted to identify all areas of concern, but specifically we wanted to know what considerations the Cook Inlet belugas needed since the species was listed as ‘depleted' under the Marine Mammal Protection Act in 2000,” says Authority Executive Director Andrew Niemiec. The service was concerned that assessing potential impact would be virtually impossible because there wasn't enough information on how the whales use the inlet.

In June 2004, we kicked off a six-month direct observation program around the Port of Anchorage that was expanded to 12 months at the service's request. We learned how the whales react to in-water structures, their seasonal patterns, and what prey species they prefer; and mapped high-value/high-sensitivity habitat such as summer feeding grounds within the inlet.

Because other whale species have shown some aversion to passive in-water structures, the service was also concerned that belugas may hesitate to swim under the bridge, impeding their travel to and from feeding grounds. Not only do they tolerate them, they pass back and forth under 14 other bridges in Southcentral Alaska and at least 15 additional bridges worldwide without harm. Our finding reassured all parties that the species habituates to a variety of circumstances and was unlikely to abandon the inlet after a bridge was built.

We also discovered patterns of use. Beluga numbers are greatest from August through October, when the whales come in on the flood tide and leave on the ebb tide. And while they feed primarily on salmon during spring and summer, they're opportunistic feeders that eat whatever is available —from squid to sole and cod to clams.

This baseline work allowed us to produce a Final Environmental Impact Statement in 2007. A year later, the whale's status was changed from “depleted” to “endangered.”

Avoiding a second impact statement

In general Alaska's beluga populations are healthy, but legal subsistence hunting had halved Cook Inlet's numbers. Between 1994 and 1998, the population fell from 653 to 347. Even though hunting's been regulated since 1999, their numbers hadn't rebounded. Having established Cook Inlet's stock as a distinct genetic population, the service recategorized the subspecies under the Endangered Species Act.


The months that followed were filled with uncertainty. Could development still occur in this waterway? Could we identify construction techniques and adjust schedules to ensure the whales' lives weren't affected?

At this point the Federal Highway Administration (FHWA) entered into formal consultations with the service to answer fundamental questions about construction in marine environments. We worked closely with the service to identify what information and modifications would prove whales wouldn't be harmed and achieve a biological opinion of “no jeopardy.”

After three years of research and communication, a biological assessment explaining the impact of proposed alternate construction techniques and letter of authorization application were submitted. On Nov. 30, 2010, the service concluded that “the described action is not likely to jeopardize the continued existence of the Cook Inlet beluga whale, nor destroy or adversely modify its proposed critical habitat.” FHWA was free to issue us a build record of decision without requiring a new impact statement.

Confirming previous assumptions

Marine mammals use sound to communicate, capture prey, navigate, and avoid predators; and biologists don't want excessive noise levels — one of the greatest negative impacts of in-water construction — to alter a species' behavior.

Oscillators, which install pilings by drilling rather than hammering, have been used in similar projects because they're assumed to be quieter than pile-driving. But no quantitative evidence existed to back up the assumption. As a result, we funded research to collect the first in-water noise measurements of an oscillator system for drilled shaft bridge foundations. Sound was found to rapidly dissipate over a relatively short distance, indicating that oscillators do indeed minimize impacts to critical habitat (which includes the endangered species' prey).

As the first such measurements to be documented, the research provides baseline data for our project as well as projects globally where this method for drilling shafts can be used. We were asked to present the findings at the Society for Marine Mammalogy's biennial conference on biology in late 2011 and at the Alaska Marine Science Symposium in January.

We plan to curtail construction when belugas are most likely to be present, but our Marine Monitoring Program also needed an effective way of detecting them during nonpeak months. Detection is important because we're required to suspend drilling whenever a whale's present to avoid adversely affecting their behavior, which the service calls a “take.”

Initially, we — like virtually everyone involved in in-water construction — assumed that acoustical monitoring would provide the most accurate and earliest detection. But we discovered the opposite.

During a two-week “proof of concept” study in September 2011, we tested how well omnidirectional hydrophones made by Seattle-based Cetacean Research Technologies picked up the whales. Although promising, visually looking for them worked even better. Extremely high-powered (i.e., 25x150) “big eye” Fujinon MT150 binoculars with reticle spotted them up to six miles away. In fact, sometimes we saw a whale but picked up little or no vocalizations. Ultimately, the binoculars, the naked eye, a digital theodolite (a surveying instrument that measures both vertical and horizontal axes), and a rest station produced the best results.

Armed with this data, we added and refined conservation measures to minimize impacts by:

  • Not pile-driving from August to December, when whales are using the inlent; and limiting the activity from December through July, when they're less frequent.
  • Establishing a 2-square-mile safety zone and refining it based on sound measurements within the area. This allows us to take actual site conditions into account to ensure the animals are protected.
  • Monitoring the zone for whales before, during, and after pile-driving to hold a template in place to guide the oscillating drill. Monitoring will begin 30 minutes before initiating the “soft start” for pile-driving and continue as long as pile-driving is required. A soft start begins a process at less than full force, alerting wildlife to impending activity so there's time to leave an area before the process reaches full energy. Drilling won't begin unless and until observers have good visibility into the insonification zone, meaning we'll postpone the activity until fog lifts or light conditions improve.

Experienced marine mammal observers will look for whales both within and as they approach the safety zone in which noise levels could disturb the mammals. Monitoring sites will be established at a sufficient distance to give crews enough advance warning to shut down operations.

We'll avoid collateral impacts to the marine environment by not building permanent boat-launch facilities or providing direct access to tidelands during construction.

We're securing the final key permits, and hope to break ground next year. In the meantime, we continue collaborating with state and federal regulators to resolve environmental challenges while developing the infrastructure Alaska needs to prosper.

— McCarthy ( works in Government and Public Affairs for the Knik Arm Bridge and Toll Authority in Anchorage, Alaska.