Trace amounts of mercury in the mud below Douglas Harbor are complicating a project to dredge the harbor and replace three of its aging floats.
Port Director John Stone told the Juneau Assembly Monday his department submitted a request to the U.S. Army Corps of Engineers to dump the spoils from dredging - 30,000 cubic yards of mud - into the middle of Gastineau Channel outside of the harbor entrance, in about 110 feet of water.
The Corps approved dumping spoils into the channel location twice before in 1999 and 2002, but this time testing samples showed slightly higher levels of mercury in the mud than in the past.
The results prompted a battery of comprehensive biological tests that showed no harmful human effects would likely result from dumping the mud into the channel, Stone said. For other organisms, mercury levels remained within tolerable limits.
The harbor needs to be dredged because glacial rebound has lifted the sea floor several feet since it was built in 1963, making it too shallow for some vessels. Mussels that die on the pilings then fall into the sea, creating mounds of shells that also need to be removed.
The Docks and Harbors Board searched for alternatives to dumping the mud back into the sea, including hauling it to the landfill or shipping it to the Lower 48 for disposal. Those ideas proved much more expensive than using the channel.
Because the city's project must go through a regulatory process similar to the Kensington mine for dumping waste into a waterway, Stone asked for and received support from the Assembly on the decision.
Other alternatives would cause the Docks and Harbors Board to come back to the Assembly to ask for more funding, Stone said. The least costly second choice would be to bring the spoils to Alaska Marine Lines across Gastineau Channel, where it could be used as fill for a planned expansion at the shipping facility. The extra cost would be about $2 million, Stone said.
"That would require a fee increase," for harbor patrons, Stone said. "Everyone on the board felt that would be close to impossible to do at this time."
Stone said the results do not mean the level of mercury in the Douglas soil is rising.
"I think the mercury has come from natural sources or mining," he said. "I don't think there are any new sources of mercury."
The old Treadwell gold mine was upland of the harbor.
The permit process so far has cost nearly $400,000, Stone said.
The Anchorage office of the Corps did not return a call for comment Monday about when the application would be reviewed. If the channel disposal site is approved, the harbor project can go forward with available funding, Stone said.
The harbor remodel will cost $5.5 million, including $900,000 for dredging.
Stone said he'd like to complete the harbor remodel by next summer. After dredging, three floats on the south side of the harbor will be replaced, along with electrical and plumbing systems.
"The harbor is at the end of its useful life," he told the Assembly Monday. "It's 55 years old and worn out. The electricity is well beyond its useful life; we have safety issues and it's beyond any potential for repair. The floats themselves are old and waterlogged. The timbers are cracked and rotting ... in the winter when it snows, we have to get over there very quickly because the harbor is under water pretty quick."
Dredging would deepen the harbor to 14 feet from 9. The depth and new floats arranged to accommodate larger vessels would increase use at the facility, Stone said.
Contact reporter Kim Marquis at 523-2279 or email@example.com.
Juneau Empire ©2015. All Rights Reserved.