A daily compilation of significant news articles and comment
August 22, 2008
3. Watersheds –
Concerns surface over marsh project
The
By Dave Roberts
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A plan to convert the old Emerson dairy and nearby properties into a tidal marsh might become a vital step in saving endangered Delta fish and would provide a large waterfront park, but it also has the potential to increase salinity, carbon and toxic mercury in local drinking water.
That was the mixed news in a report to the Oakley City Council last week by Patty Quickert, who is heading up the Dutch Slough Restoration Project for the California Department of Water Resources (DWR).
Council members are looking forward to the 65-acre park with trails along the Delta, ball fields, boat launching and other recreation. But they are concerned about the potential mercury toxicity that could result from breaching the levee and flooding much of the 1,166-acre property south of Dutch Slough between Big Break and
“As you all probably know, there’s a great deal of mercury in the Delta system,” Quickert told the council on Aug. 12. “It washed downstream during the Gold Rush. And it comes from the mines in the area that are leeching it to the system.
“Most of that mercury is elemental mercury – it’s fairly inert. Mercury is mostly harmful to people when you breathe the gas, like when you break a fluorescent tube. That’s mercury vapor, and it’s really harmful. Most of the mercury that’s in the sediments of the Delta is not harmful in the state that it’s in.
“However, when you have a tidal marsh project, an area that is under water, the mercury in the sediments can react with bacteria and it can form methyl mercury, which can be toxic. That’s when you hear these warnings about eating fish – it’s because the fish contains mercury, and when you eat the fish the mercury stays in your body and can be potentially toxic.
“The Dutch Slough area has actually one of the lowest levels of mercury in the Delta area. We don’t know how the tidal marsh will affect the methylation and the potential toxicity of the mercury. Tidal marshes do export methyl mercury.
“But in some cases they are also known to decrease the amount of mercury. Because not only do bacteria create the methyl mercury but other bacteria can break it down back into mercury. This is something that we will be monitoring very closely to see how much mercury is being exported from the site.”
Councilman Brad Nix said that after the council approved the Dutch Slough project several years ago, scientists expressed concerns “about how serious the mercury problem was with this type of restoration. We’ve been sort of waiting for somebody to come back to us and tell us that the problem has been solved here and a consensus reached. Are the … scientists now on board saying it’s OK and it’s safe?”
Quickert responded, “The most recent research shows that tidal marshes are not a primary producer of methyl mercury. Some tidal marshes actually reduce the amount of mercury. There are studies being done to try to figure out what aspects of the different areas make it have less mercury or more mercury. But none of the tidal marshes have produced toxic levels of methyl mercury. They do produce some but not nearly as much as flood plains do.”
Nix replied, “Well, some poison may not be good.”
“It’s definitely a very difficult problem,” acknowledged Quickert. “We at the Department of Water Resources are being told from many different directions that we need to do these tidal marsh projects because the pumps are having impacts to Delta smelt and other species and we need to improve the ecosystem. Tidal marsh restoration is kind of the best hope for ecosystem improvement.
“But you’re right: the mercury is an issue. It’s like so many things in life. It’s like you get one thing and have to give up something else.”
There are three separate parcels – once belonging to the Emerson, Gilbert and Burroughs families – that will be converted to marshland one at a time.
Councilwoman Carol Rios asked Quickert, “As you’re doing the project and find there is a problem with methyl mercury, how would you correct it? Once you breach, there’s no going back? If you found it really is a problem, how would you deal with that?
“We will do a phased approach,” replied Quickert. “If we breach one parcel and there’s a problem, we would probably do something different with the other parcels. But you’re right: once it’s breached, you can’t do a whole lot.”
Nix is also concerned about saltier water pouring into the Delta when the levee is breached, “which would, of course, impact our water intake.”
Quickert responded, “Right, because you’re opening up a whole new volume that will essentially, to use a really crass term, suck water from the Bay, because that’s the larger volume of water. I’ve worked with an engineer at DWR that has done a lot of this kind of modeling. What his modeling has shown is that at this location, it should not have an appreciable increase in salinity.
“We have studies that show the numbers. It actually decreases the salinity at some tidal stations. It increases it like a hundredth of a part per thousand. So it’s negligible. So we are not expecting that to be an appreciable effect, but it’s one of the things we will be monitoring.”
There will also be an increase in carbon in the water when the nutrients in the marsh break down. “That will be an issue that we will monitor prior to doing the restoration and after the restoration is done to manage the amount of carbon that’s going in the water,” said Quickert.
An environmental impact report scheduled to be released in the next month or two will provide more detail on the potential impacts of the project and the mitigation measures that could be taken to minimize those impacts.
In order to create an appropriate land level for the marsh, about a half-million cubic yards of dirt that have been irrigated with secondary effluent from the Ironhouse Sanitary District will be hauled across Marsh Creek to the Dutch Slough project area.
The Burroughs parcel on the east will probably be converted last to marshland, if at all, because a levee would need to be built along
http://www.brentwoodpress.com/article.cfm?articleID=20223
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