Elevated chloride levels suggest wastewater has infiltrated Columbia well field

Wednesday, June 27, 2012 | 6:00 a.m. CDT; updated 5:18 p.m. CDT, Wednesday, June 27, 2012
Columbia sewer water is treated in clay-lined treatment cells in the Missouri River bottoms and is then used to flood wetlands in the state owned Eagle Bluffs Conservation Area. High chloride levels suggest this wastewater has mixed with the underground water that supplies the city’s well field for drinking water.

COLUMBIA — When people in Columbia turn on their taps, every bit of water comes from the sandy, gravel-filled Missouri River bottoms.

In McBaine, about 10 miles south of Columbia, brick well houses sit atop this aquifer that holds about 44 billion gallons of water.

Just two decades ago, the river bottoms were the focus of a controversy about whether to pipe treated city sewage directly to the Missouri River or use natural wetlands to provide a higher level of treatment.

Voters overwhelmingly approved a bond issue to construct clay treatment cells lined with cattails near McBaine — a strategy that attracted state and national attention. The city then agreed to let the Missouri Department of Conservation use the treated wastewater effluent to flood wetlands at its Eagle Bluffs Conservation Area.

Twenty-two years later, evidence continues to indicate that treated city wastewater coursing through Eagle Bluffs has infiltrated the underground water that supplies the city's well field for drinking water.

A task force working on ways to protect the city's drinking water has not found any evidence suggesting this mixing of water supplies poses an immediate health risk, but the task force is recommending possible changes to how city wastewater is used in the state conservation wetlands.

Chloride levels on the rise

Despite the overwhelming voter support for building the treatment wetlands, the plan drew criticism from a few in the water industry.

John Betz, the retired superintendent of the water treatment plant, volunteers on the water protection task force. Although Betz does not see the wastewater effluent in Eagle Bluffs as a threat to water safety, he does think it makes its way into the city's well field.

Betz was among those who initially questioned constructing the treatment wetlands near the city's water supply.

"Back in the early '90s we were upfront about 'no, we don’t want wetlands near the city wells,'" Betz said. "You have 45 billion gallons of this pristine groundwater, a supply that many communities would do anything to have...In my world, I don’t want anybody building anything down there."

In a 2008 US Geological Survey report detailing changes in the water supply between 1992 and 2007, one thing stands out: Since the city introduced treated wastewater into the McBaine bottoms, levels of chloride in the groundwater have risen dramatically.

More recent testing has continued to show elevated chloride levels in several city wells, particularly the two nearest Eagle Bluffs wetlands.

Chloride itself is innocuous and doesn't pose a threat to the quality of the city's drinking water but is an indicator of wastewater. 

Tom O'Connor, a water engineer on the water protection task force and the Water and Light Advisory Board, said Missouri River water usually has chloride levels at about 20 milligrams per liter; chloride levels in wastewater are usually closer to 250 milligrams per liter.

Increasing levels of chloride in the aquifer means wastewater made its way into the city's well field, O'Connor said.

"I don't think there's a lot of political will to do much about it," O'Connor said. "I don't even think there's political will to discuss it very openly. It's supposed to remain one of our little indiscretions."

In 2012, the levels of chloride in the four city supply wells being tested ranged from about 10 milligrams per liter to about 80 milligrams per liter in one of the two wells closest to the Eagle Bluffs wetlands.

“When we started seeing chloride levels over 45, the most probable source was the (wastewater) effluent," said Missouri Water Science Center hydrologist Mike Kleeschulte of the U.S. Geological Survey.

The treatment of wetlands themselves have been implicated in previous elevated chloride levels near city wells. As noted in the survey, the Missouri River flooded in 1995 and damaged one of the treatment cells, causing a significant leak.

Floyd Turner, manager of water operations for the city, said the chloride levels could be affected by interplay between the Missouri River and groundwater in the McBaine bottoms.

City suspends, then resumes, chloride testing

After the 2008 report came out, O'Connor and his father, former MU professor of civil engineering John O'Connor, published a study through their private firm, H20'C, on the effect of the wetlands on the city's water supply. The study said the safety of the city's water had not been compromised, but it urged the city to keep testing all of its wells for chloride and bacteria that indicate fecal matter in the water.

Even so, the city stopped regularly testing all but four of its 14 supply wells for chloride in 2010. The city earlier this year resumed regular chloride testing on all of its wells based on discussions with the Source Water Plan Protection Task Force.

Betz said he hasn't seen anything that has made him concerned about the safety of the city's drinking water, but disagreed with the decision to stop testing all the wells for chloride.

"The reason it is important is to see if there is any interaction between the wetlands and the water supply," he said. "You want to be on top of things."

What comes next?

Given the evidence that points to treated city wastewater migrating from Eagle Bluffs to the city's well field, there have been hints at changing the way wastewater is handled at Eagle Bluffs. The task force addressed the wetlands in a draft plan that outlines steps the city could take to protect its drinking water.

In the plan, the task force recommended "changing protocols" at the Eagle Bluffs wetlands. This proposed change was deliberately vague so the people running the wetlands would be able to decide how best to protect the water quality, Tom O'Connor said.

Changes could include using river water to flood the conservation wetlands closest to city wells and using the treated wastewater to flood conservation pools farther south, O'Connor said. “If you could take that wastewater farther south away from the wells, it couldn’t hurt,” he said.

It is expensive for the Missouri Department of Conservation to pump water from the Missouri River into its wetlands rather than using treated city wastewater, and there have not been serious conversations about ending the practice of using treated wastewater in the Eagle Bluffs wetlands, said Eagle Bluffs wildlife biologist Vic Bogosian III.

Bogosian also serves on the task force and said he didn't want to speculate about what the changing protocols might mean until the city had issued more formal recommendations.

The task force's recommendations are not binding, but will be presented to the City Council, Columbia Water and Light and the Missouri Department of Natural Resources.

Turner said the idea of putting wastewater directly into the river after it moves through the city treatment lagoons has been discussed since the city started sending its treated sewer water into Eagle Bluffs.

"It's a topic that's been taken seriously," he said.

Turner also said he doesn't think the city will change its relationship with Eagle Bluffs anytime soon.

"We just need to be prepared to treat the water to make it safe and meet all standards, despite what the influences are on the source water, but it’s very expensive to do that," he said.

The city, meanwhile, is looking at expanding its water treatment plant at McBaine to meet growing demand. In the early stages of planning the expansion, the city commissioned an engineering report that looked at different ways the city could treat water to a higher standard. The options that treated for more contaminants cost significantly more money.

Even the cheapest option for expansion is projected to cost the city $65 million. The more expensive options in the plan treat for more contaminants like pharmaceutical drugs, that are often found in wastewater.

Turner said it is unlikely that the city will change how it treats water with this next expansion of the treatment plant, but might down the line.

"The next expansion is probably going to be dealing more with capacity, maybe some modifications in our treatment process, but not major changes," he said.

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Ellis Smith June 27, 2012 | 6:54 a.m.

We discuss and agonize over global warming and air pollution, but the most critical problem - locally, nationally and globally - is growing contamination of the water supply. As a bumper sticker puts it, "WATER IS LIFE!"

About a five hour Interstate drive from Columbia is a metro complex consisting of about 0.4 million residents, extending over parts of four counties. Seasonal pollin allergies are a problem, but air pollution from other sources is not. This is one of the best cities in the country for air quality.

But when a woman living in that area is diagnosed as pregnant her physician recommends she stop using municipal water supplies for drinking and switch to drinking treated (bottled) water for the duration of her pregnancy - as a precaution. It's also recommended that infants not be given water from municipal supplies.

Bacteria? No, it's residual agricultural chemicals (fertilizers, pesticides, herbicides).

The countryside around the metro complex and for miles upstream from it contains some of the best farmland in the world. It is annually intensively farmed, using chemicals to maximize crop yield.

If the water supply isn't considered good for pregnant women and infants, how safe is it for older children and adults?

(Report Comment)
Mark Foecking June 27, 2012 | 8:49 a.m.


It depends on the chemicals whether they are more toxic to pregnant women or children, and also most importantly the concentrations. We have extended detection limits into the single parts per trillion range for some chemicals, and virtually nothing shows a clear toxic effect at those concentrations even over time. The mere presence of a chemical does not necessarily mean it is harmful.

Does the water supply of this city come from surface water or from wells? That can make all the difference in the world as far as agricultural chemicals. Msny of these chemicals are bound as they pass through the earth, and there's usually some bacteria that can eat them if they're there long enough.

Chloride is not, by the way. It is an element, which means it can't be degraded further, and it is also not bound to soil, so it flows freely with the wastewater.

Bottled water is usually filtered municipal tap water, and while it may not contain the spectrum of chemicals found in in ythe above mentioned city's water, may contain other chemicals (as well as chemicals from the plastic bottle). It might be better for the city to make available specifically treated and tested water for people who are concerned about it.

Columbia's tap water is tested for a couple dozen agricultural chemicals (under "SYNTHETIC ORGANIC CHEMICALS" partway down), and none are detected:


(Report Comment)
Ellis Smith June 27, 2012 | 2:21 p.m.

To Mark Foecking:

Yes, chemical concentration is important. I should have noted that the water supply for virtually all municipalities involved comes from filtered and treated surface water, not deep wells. Like Pittsburgh, PA, the city is located at the juncture of two rivers, both prey to agricultural runoff.

So far as I am aware, the recommendation cited is precautionary, perhaps to protect physicians' future legal liability. :)

PS: I also forgot to mention that since 1951 the water treatment includes water softening.

(Report Comment)
Louis Schneebaum June 27, 2012 | 6:48 p.m.

"her physician recommends she stop using municipal water supplies for drinking and switch to drinking treated (bottled) water"

Municipal water is treated as well. Bottled water is only as good as its source, which is often no better than a given municipal water supply.

(Report Comment)
Bill Weitkemper June 27, 2012 | 9:03 p.m.

The City water treatment wetlands on the above map are actually the City's constructed wastewater treatment wetland cells.

(Report Comment)
Chris Cady June 28, 2012 | 10:53 a.m.

I am glad that both the city and this task force are keeping an eye on this. As long as the chloride or other salt levels don't get high enough to seriously affect the quality, and nothing else makes it through, I'm not too worried about it.

Ellis, I myself would have put a carbon filter on the kitchen tap if I was that concerned about trace levels of contaminants. Aside from the considerable env. footprint of all that plastic use, plasticizers used many plastics including PET bottles have been implicated as endocrine disruptors. There are really no standards for bottled water like there are for tap water. Its only redeeming factor is that most of it started out as tap water that did meet standards. That is, before it went into the bottle.

(Report Comment)
Michael Williams June 28, 2012 | 3:20 p.m.

Interesting. I wonder if the saline is coming from the treatment cell unit further north along Perche Creek or from Eagle Bluffs? My novice hydrology says water should flow downhill (I just checked this by knocking over my water bottle and none flowed to the ceiling that I could tell), so I guess I would be surprised if Eagle Bluffs is the source.

I remember the argument whether we should be dumping waste water so near our wells. Still doesn't seem a good idea to me, but that may be because my grandparents and great-grandparents told me to never put the outdoor crapper upstream from my well. This is great information to know, but fortunately I've never had occasion to make this decision. They also told me that your lower lip was a great place to keep fishing worms warm during the winter, and I've never had to use that info either.

I've been in Eagle Bluffs during the heat of the summer. At stinks like sewer. Why is this? We're talking tertiary treatment here, so why (and what is) the stink? Is it leachable downstream? Are the primary/secondary treatments not working during such times?

I appreciated the comment: ""I don't think there's a lot of political will to do much about it," O'Connor said. "I don't even think there's political will to discuss it very openly. It's supposed to remain one of our little indiscretions."

There's lots of stories our local media won't discuss, and if they do they're given just a passing mention.

(Report Comment)

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