It's common for the City of Commerce to mail advisories to its citizens about the local water supply. Should locals be concerned? And what's the reason for those notices, anyway?
The "contaminant" described in the notices refers to the level of trihalomenthanes in the municipal water supply. Trihalomethanes are not an organic contaminant, so they aren't the sort of things that could give anyone gastric distress - and boiling water has no effect.
Trihalomethanes are a byproduct of the water treatment process. They're present to some extent whenever water is chlorinated to make it safe for drinking. When present at a certain level, they present a risk for an increased chance of liver or kidney cancer. However, one must drink a lot of contaminated water over a period of decades in order for such risk to reach statistically significant levels.
"The total trihalomethanes - they're a group of chemicals, as well as the haloacetic acids, that are regulated by not only (the Texas Commission on Environmental Quality), but the federal government under the Safe Drinking Water Act." Environmental Protection Agency staffer Jim Brown said. Brown serves as Associate Director of Strategic Planning in the Water Quality Protection Division of EPA Region 6.
"And EPA establishes maximum contaminant levels - now these levels are based on a lifetime exposure risk scenario," Brown said. "So, it's based on a person drinking about a half gallon of water, or two liters a day for 70 years. And that has a one in one million increased case of cancer developing over a 70-year time period."
Levels of trihalomethanes - as well as haloacetic acids, another disinfection byproduct - increase as water sits.
"They both form as a result of age in the water," City of Commerce City Manager Darrek Ferrel said. Flushing the water system - such as opening a fire hydrant and releasing water - gets older water with undesirable contaminant levels out of the system.
Commerce has gotten its haloacetic acid levels under control, but trihalomethane levels continue to be higher than the government-set maximum contaminant level at one of the two sites where Commerce takes samples for testing. One site on Washington Street in central Commerce shows contaminant levels below the desired threshold. But the other site, on the western end of Live Oak Street, near the northwestern city limits, continues to show high trihalomethane levels. A design feature of the city's water system results in slow water turnover at that site.
"What happen at the Live Oak site, there are no taps ... there are no users regularly consuming thousands of gallons a month on that site," Farrell said. "There is underground a 14-inch line, a very large line, that's part of a loop. On either side of the loop, the lines feeding it are six inches in diameter. So there are smaller lines, going to a bigger line, feeding it. So it creates a bottleneck in that big line. Water gets into it easily. It can't get out quite as easily, so it sits and ages."
Improving systems at Commerce's water treatment plant could reduce contaminant levels before the water goes into the city's distribution lines.
"So one goal we have is to reduce those products that come out in the production process," Farrell said. "We've completed a contact-time study that allows us to move the treatment of liquid ammonia sulfate, which breaks these chemicals down, up to the front of the process, as opposed to the back of the process, where it's at now. The results of that study are sitting with TCEQ, the Texas Commission on Environmental Quality, and we're waiting for their approval to change our treatment process. What we hope to do then is once we change that process ... we hope to reduce those chemicals before the water ever leaves the plant."
The State of Texas requires cities to pass water-quality tests for three consecutive quarters before cities are no longer required to send notices, Farrell said. So, even if Commerce continues to reduce its trihalomethane levels, the postcards will continue to go out through the end of this year and into 2018. Meanwhile, those concerned about the current status of Commerce water can use consumer-grade filters at home.
"For most healthy people, drinking the water in the short term is not going to be a risk," Brown said. "However, for those who are ill, those with severely compromised immune systems, perhaps those ... who are undergoing treatment for cancer - they can have a discussion with their doctor and there are inexpensive carbon filters on the market that are available, either in a pitcher form or (an) under-the-counter cartridge form, that can remove these disinfection byproducts from drinking water."
