Newport Beach to look at dredging project in bay

Newport Beach may soon take a step closer to constructing a confined aquatic dredged disposal site — basically, a deep, underwater hole — for dredged material considered too toxic to be released into the ocean, depending on council action this Tuesday.

Discussion on constructing a confined aquatic dredged disposal site to remove the mercury-tainted sediment dates to 2019.

Newport Harbor is one of the largest recreational harbors in the country and natural processes of storm water and erosion flowing into the harbor cause the movement and accumulation of sediment, according to a staff report prepared for Tuesday’s meeting.

That sediment needs to be dredged periodically to maintain federally authorized channel depths for safe navigation.

The federal channels extend from the entrance channel to the turning basin adjacent to Newport Boulevard bridge. They also extend from the east anchorage between Bay Island and Lido Isle to Marina Park, according to city staff.

Those channels are the responsibility of the U.S. Army Corps of Engineers, while the rest of the harbor is maintained by Orange County and the city of Newport Beach.

The city last undertook a major, but partial dredging in Newport Harbor between 2012 and 2013. That work resulted in the removal of about 600,000 cubic yards of material.

While recent sediment characteristic studies showed that the majority of sediment could be disposed at a federally controlled open ocean disposal site or at a near-shore disposal zone along Newport’s ocean beaches, some bottom sediment cannot be disposed in those locations due to high concentrations of polychlorinated biphenyls and mercury slightly above ocean disposal limits.

City staff said confined aquatic dredged disposal sites are constructed by digging a hole, then disposing of the initial material removed from the hole in the ocean.

Then, the non-ocean quality bottom sediment is placed into the hole. A cap of suitable material then is placed on top to create a physical barrier between the contaminated material and the ocean.

The site is proposed for the central portion of lower Newport Harbor and between Bay Island, Harbor Island and Lido Isle.

The next dredging project is expected to cost $20 million and construction of the disposal site is anticipated for 2022. The proposed ordinance indicates about 300,000 cubic yards of material will be dredged.

About 106,900 cubic yards of unsuitable material from the federal channels and 50,000 cubic yards from other harbor channels will be placed within the CAD.

City Council members will be considering adoption of a resolution that will certify an environmental impact report for the work.

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