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Davis, California

Tuesday, December 5, 2023

Column: Water safety in Davis

I was probably one of the few people to closely read the City of Davis 2010 Annual Water Quality Report. The front of the report presents a chart full of numbers, units and initials. Down the left side of the chart is a list of possible contaminants of drinking water – arsenic, chloroform and uranium made the list.

The raw data of water contaminant levels is collected by the Information Center for the Environment (ICE), contracted with the California Department of Public Health since 1999. They use a system called GIS, which is a geographic information system. The ICE uses a GIS to analyze information, in this case concerning water safety, about different geographical locations.

The director of ICE is James F. Quinn, a professor in the department of environmental science and policy at UC Davis.

“ICE is a laboratory that does very applied GIS and database projects,” Quinn said. “We work with almost all the publications supporting public decision-making policies.”

The drinking water in Davis is safe, in case you were held in suspense. Decoding the displayed chart is easier than it first appears. Several cells of the chart are full of “ND” for “not detected,” and even the contaminants that were detected are below the maximum allowable levels.

One example, arsenic, illustrates the difference between maximum allowable level and the public health goal. One column is labeled “MCL,” defined as maximum contaminant level. As the name implies, this is the highest level of contaminant that is allowed in drinking water.

The city tries to set this level as close to the PHG, or public health goal, as is “economically and technologically feasible.”

So, what are these numbers for arsenic? The maximum contaminant level for arsenic is 10 parts per billion. This is quite a small fraction (10/1,000,000,000) but not as small as the ideal. The public health goal is 0.004 parts per billion.

The labs testing the water found 5.1 parts per billion of arsenic in the city of Davis groundwater; the water from the university in particular fared slightly better, with 4.3 parts per billion of arsenic.

This is not to say our water is filthy with arsenic, just because it is above the absolute ideal level. The city has to balance possible health effects of low levels of arsenic against the cost of removing every trace of it from the water. Davis has the money to keep the levels of arsenic and other contaminants low, but not every city has the ability to do so.

“Drinking water, at least in public systems, they’re very safe,” Quinn said. “Much of the problems [in poorer communities] are due to crumbling infrastructure that probably needs to be rebuilt … these communities may not have the money to fix things.”

Quinn and his colleagues also do research in nitrates, contaminants that come mostly from agricultural runoff and fertilizers.

“[Nitrates] aren’t that toxic, but it’s difficult and expensive to treat,” he said. “If you can solve the nitrogen problems, which are widespread, you have other groundwater problems solved in the process.”

Quinn did want to give credit where credit was due, saying that the public health community has done a good job in getting water sampled and giving the public correct information about water safety.

He also wanted to stress the point that the best thing the city can do about infrastructure and water problems is to “put in the resources to take care of the people that need to be taken care of, and you employ a lot of people in that process.”

AMY STEWART can be reached at science@theaggie.org.


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