Receding Floodwaters in Houston Expose Long-Term Health Risk

  • Scores of wastewater, sewage discharges reported since storm
  • Air monitoring reveals benzene plume near Houston refinery

Inside Houston's Post-Harvey Rebuilding Plans

Benzene churns through Houston’s economy. The clear, sweet-smelling chemical is found in the crude oil processed in the region’s refineries and is used to make plastic, pesticides and other products.

It’s also a carcinogen with cancer-causing properties, illustrating the risks that will linger for southeast Texas long after the floodwaters of Harvey have receded. Thousands of homes were submerged in murky water that may have been tainted with benzene and other runoff from an area that boasts the nation’s largest concentration of refineries and petrochemical plants.

"This is going to be an ongoing concern, because some chemicals, when they get in water, become active and volatile," said Christine Todd Whitman, a Republican who led the Environmental Protection Agency from 2001 to 2003. "There are some major areas of problem."

EPA officials are still trying to access and inspect federal Superfund sites that were swamped by the storm to determine whether contaminants escaped, including benzene and other cancer-causing agents such as cadmium and trichloroethene. 

Residents near a still-submerged wastewater treatment plant in west Houston were warned Wednesday that the risk of migrating sewage makes it unsafe to drink untreated water from private wells.

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At least 94 spills of sewage and wastewater have been reported to the Texas Commission on Environmental Quality since Hurricane Harvey hit the state. Among those releases: a discharge of unknown amounts that Kinder Morgan Petcoke LP reported reaching the San Jacinto River and 100,000 gallons that Sasol Chemicals USA said had been discharged from its Green Bayou plant.

There are no reports of benzene reaching waterways in Harvey’s wake, but initial disclosures don’t detail specific chemicals, and extensive water testing is still needed, said ecologist Shaye Wolf, the Center for Biological Diversity’s climate science director.

Valero Energy Corp. is mopping up oil at one of its refineries after a tank roof partially collapsed, spilling an estimated 6.7 pounds of benzene. After local residents complained about an odor, health officials and representatives of the Environmental Defense Fund detected high amounts of benzene in air around the facility. Measured concentrations reached as high as 324 parts per billion, according to the Houston Health Department -- well above the level at which federal officials recommend workers don respiratory masks and protective gear. 

Valero spokeswoman Lillian Riojas said the oil that leaked "was quickly contained and has been confined to the corner of the containment area where clean-up is well underway."

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The EPA said in a statement it was working with city and county officials on the benzene plume, identified near Houston’s Manchester neighborhood, but "could not confirm the tank was the source of the air release that led to complaints in the area."

The agency also said it was coordinating with the U.S. Coast Guard on a large oil spill in the Houston area.

Hurricane Harvey’s 130 mph (209 kph) winds and drenching rains caused tens of billions of dollars of damage, leaving residents sifting through sodden belongings, ripping up water-soaked carpet and tugging wet drywall to heaping piles of refuse that stand as monuments to the carnage. But environmentalists and public health experts are warning about an array of unseen dangers that may threaten residents after the storm debris is hauled away. 

"These are long-term chronic exposures," said Elena Craft, a toxicologist with the Environmental Defense Fund. "We don’t know what’s going to be in the mud that’s in people’s houses. We don’t know what’s going to be in the water of private wells."

And it will take time to determine the extent of the risks.

Superfund Sites

So far, the EPA says there’s no indication that Harvey released hazards from 28 federal Superfund sites in the area that were spared damage or excessive flooding. And the Texas Commission on Environmental Quality said that assessments at 12 of 17 state Superfund sites in hurricane-affected areas have documented "no issues."  

But the picture is more complicated at another 13 federal Superfund sites that were flooded or believed to have possibly experienced storm damage; two still require additional assessments that the EPA said "will take several days to complete."

"Teams are in place to investigate possible damage to these sites as soon as floodwaters recede and personnel are able to safely access the site," EPA spokesman David Gray said by email.

The EPA says it has 185 personnel supporting Hurricane Harvey response efforts, and the agency is coordinating with local, state and other federal officials to address human health and environmental concerns, Gray said.

It could be days before the EPA is able to fully inspect the San Jacinto River Pits, a former dumping ground for pulp and paper-mill waste in the 1960s that’s full of cancer-causing dioxin and furans, chemicals associated with non-Hodgkin’s lymphoma, respiratory cancer and soft-tissue sarcoma.

Divers Scheduled

With most of the site is still submerged, the agency is deploying divers to examine an underwater cap of plastic, soil and gravel that’s meant to prevent the migration of hazardous material, said Sam Coleman, an EPA acting regional administrator. 

Initial assessments showed some signs of disturbance to that cap, with some rocks displaced and its liner exposed. The EPA said that heavy equipment has been mobilized to move rock to repair the defensive surface, but the liner "is in place and functional, so we don’t have any indication that the underlying waste materials have been exposed."

It can take weeks -- or longer -- for some storm-provoked leaks even to be detected. For instance, it took months to discover a breach in the cap at the San Jacinto Waste Pits after flooding two years ago.

At the U.S. Oil Recovery Superfund site in east Houston, where benzene lurks at a former wastewater treatment plant, tight-fitting black tarps covered red containers holding toxic sludge and sewage on Monday. Aerial surveillance showed floodwaters never reached the containers, EPA’s Coleman said, but further assessment is needed.

Acid Pit

At the nearby Highland Acid Pit, a vegetation-covered soil cap appeared undamaged, indicating the pollution under the surface was unaffected by Harvey, Coleman said, though a check of on-site monitoring wells in coming days is necessary to confirm that preliminary finding.

Ongoing remediation efforts have helped make some Superfund sites more resilient during storms, including the construction of berms to contain runoff, said Neil Carman, a former field inspector for the state’s environmental commission who visited more than 200 plants annually.

"They’ve done a lot of things to try and contain this material," Carman said, but even so, "I would expect to find a problem at several of them."

Even if sites appear sound after visual inspections, ongoing water monitoring and soil sampling will be necessary to verify floodwaters or underground leaks haven’t carried contaminants far away -- into neighboring yards, homes and private water wells.

"These waters have gone all over these residential areas," said Kara Cook, toxics program director with the U.S. Public Interest Research Group. "It could be in the soil, where your kids play, where they’re putting stuff in their mouths."

Flooded homes may have been bathed in contaminants, said Erik Olson, director of the health program at the Natural Resources Defense Council.

Previously: Harvey’s Cleanup List: Toxic Plumes, Dead Animals, Debris

"We are very concerned about the toxic chemicals in the water," Olson said. "Once the water recedes, that mud is not just mud. It’s going to be petrochemicals, it’s going to be toxic chemicals."

Some fears may never be realized. After Hurricane Katrina ravaged Louisiana in 2005, New Orleans residents braced for a "toxic gumbo" of chemicals, with "the potential for unparalleled exposure to toxics and contaminants," but the National Academy of Engineering reported in 2008 that those initial concerns weren’t borne out.

"Although floodwaters did contain significant short-term biological hazards that posed risks to stranded residents and relief workers," the engineering academy said, "they did not contain chemical toxicants at levels" that would lead to long-term impacts beyond a similar volume of city storm water.

— With assistance by Ari Natter, and Jack Kaskey

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