Rains that have flooded portions of the middle part of the United States have damaged buildings, swept away cars and houses, and killed at least 18 people in Texas and Oklahoma. And with a chance of more rain forecast this week, these hard-hit areas aren't out of the woods yet.
In Texas, the enormous amount of stormwater has overwhelmed some treatment facilities, washing chemicals and toxic substances into the mix, including raw sewage, crude oil, and pesticides.
"Anything you would find on a shelf at Home Depot, whether it's herbicides or insecticides or cans of oil—anything that might be in a garage" ends up in the water, says Michael Barrett, a stormwater specialist at the University of Texas at Austin.
A wastewater treatment plant in Houston that was damaged by the flooding released more than a hundred thousand gallons (379,000 liters) of untreated sewage into the bayou.
"As a result of the recent flooding in Oklahoma, we are seeing partially treated sewage, raw sewage, crude oil from washed out pipelines, and floating crude oil tanks," in floodwaters, says Skylar McElhaney, spokeswoman for the Oklahoma Department of Environmental Quality in Oklahoma City.
Increased levels of bacteria are a concern, especially since some can cause diarrhea or infections. Exposure to contaminated water can cause headaches, intestinal problems, and skin irritation, McElhaney says. People who notice these or any other problems should get medical attention immediately, she says.
Treatment of stormwater runoff varies around the country, Barrett says. Some cities like Austin and Houston have rules to reduce contamination from stormwater runoff, but the requirements differ.
Houston's requirements center around flood control rather than addressing pollutants in the water, Barrett says. Stormwater there normally drains straight into Houston's rivers and bayous before washing into the Gulf of Mexico.
The same holds for stormwater in Oklahoma, says McElhaney. "It is not treated or filtered before flowing back into the state’s lakes, rivers, and streams."
Wimbereley (map)—about halfway between Austin and San Antonio—has stormwater treatment facilities, but the sheer amount of water has overwhelmed them, Barrett says.
Treating or cleaning runoff is hit or miss. "A lot of material gets washed away and there is no cleanup," McElhaney says.
In some areas of Texas, like the Blanco River, waters are already receding. But people should still exercise caution around waterways, he says. It could take five days to a week before bacterial loads are down to a level where it could be ok to come in contact with the runoff.
Studies examining the flooding in New Orleans after 2005’s hurricane Katrina found that while the waters weren't as toxic as many feared, they left behind lead and arsenic in the soil months later.
Essentially, "the most urban and built-up an area is, the more toxins you'd expect," Barrett says.
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