Testing of Wolf Creek, wastewater begins
Starting this month, scientists will be testing the water of Wolf Creek and effluent from the Grass Valley wastewater treatment plant flowing into the creek near Freeman Lane.
It is part of a year-long, $323,000 study to figure out how much zinc and copper are in each flow and exactly how toxic the metals are in those waters.
The state of California wants the city to install expensive filtration equipment that would reduce the amount of the metals in the creek.
But the metals also occur naturally in many waterways of the Sierra Nevada mountains, so the city has asked the state to issue a permit allowing higher amounts, city Public Works Director Jeff Jewett said.
“The toxicity of these metals varies with the hardness of the water. Wolf Creek water is hard, and the hardness is different from the effluent,” Jewett said. “The question is, how do those two mix?”
In addition, Jewett said, state measurements of the metals’ toxicity are based on laboratory tests, not on water taken from a particular site.
The way the metals react in a lab to create potential poison for living things could be different from the way the metals react in the water of Wolf Creek. That’s because different chemical elements in the creek water could change the metals’ ability to cause harm.
Recognizing the natural differences of different waterways, the United States Environmental Protection Agency has developed guidelines for measuring metals in the field and for adjusting water quality benchmarks accordingly.
Most living things use some copper and zinc healthfully. But too much can cause illness or organ failure.
Larry Walker Assoc., based in Lafayette, will take the samples. Pacific EcoRisk Environmental Consulting and Testing, of Martinez, will do the tests for the city.
In addition to testing for copper and zinc, scientists will test for other chemicals, such as pesticides and ammonia, which could react with the metals to make them more toxic.
To contact Staff Writer Trina Kleist, e-mail email@example.com or call477-4231.
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