Adam Spencer, The Triplicate

After the holiday weekend, piling and dock installation in Crescent City Harbor is planned to resume thanks to emergency work-window extensions by a state agency.

In-water work, including piling installation, had been confined to a June 1 to Nov. 15 time period by the California Coastal Commission due to the effects loud drilling could have on salmon and marine mammals, but emergency extensions will allow for work through Tuesday at least.

With piling installation behind schedule due to equipment failure, the Crescent City Harbor District and Dutra Construction, the company tasked with the inner boat basin project, asked the commission for an extension to Dec. 15 - deemed enough time to finish installing at least 86 pilings needed to provide dock space for commercial crab season.

So far, 13 pilings have been installed to the specified depthusing a specialized drill bit. When that drill bit experienced a massive internal failure, an additional 33 pilings were vibrated 10 to 15 feet into the bedrock. A different drill bit will be used to get those pilings down to design depth.

"We're very happy that the Coastal Commission has worked with us to not prohibit (Dutra) from working in this interim period while we're waiting for the final decision on the extension," said CEO and Harbormaster Richard Young.

To make the extension, the Coastal Commission is required to consult a resource agency. National Oceanic Atmospheric Administration Fisheries must make the call as to whether endangered coho salmon found in Elk Creek would be affected and how to mitigate that.

While waiting for the NOAA Fisheries determination, the CoastalCommission granted two short-term emergency extensions, the latest extending the work window to Tuesday. By then, commission staff members expect to hear from NOAA Fisheries and decide whether or not to allow in-water work until Dec. 15.

That date was chosen after a local fisheries biologist hired by Dutra said that coho salmon are usually not found in Elk Creek until late-December, January and February.

The biggest concern is the acoustic impact of vibratory drilling for pilings.

"Pile driving can end up killing quite a lot of fish," said Bob Merrill, district manager of the Coastal Commission's North Coast District. "The indication so far suggests that the noise levels are loudand definitely above noise levels in the harbor itself, but outside of the harbor they are not much of a problem."

Dozens of fish died during the retrofitting of the San Francisco-Oakland Bay Bridge in 2003 and 2004.

Acoustic engineers hired by Dutra found that sound was only an issue near Citizens Dock and the entrance of the harbor and only when pilings were being drilled near that side of the harbor.

Dutra's consultants have proposed using a "bubble curtain" when drilling pilings near the entrance. This device dampens sound waves through a series of air pockets that would surround the pile-driving equipment, and it was used to safely finish the Bay Bridge project.

"The question for us is whether that can be accommodated andwhether these various mitigation measures should be adequate to protect the fish," Merrill said.

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