Rising seas and more intense flooding caused by climate change could put nearly 80 percent of the Superfund sites in the Houston area at greater risk of releasing toxic pollutants into waterways and nearby communities, data from a congressional watchdog agency show.

A report by the Government Accountability Office found that more frequent or intense extreme-weather events such as flooding, storm surge and wildfires could affect 60 percent of the contaminated sites nationwide — and 67 percent in Texas — overseen by the U.S. Environmental Protection Agency. The GAO recommended that the federal agency do more to manage the risks from climate change.

The EPA largely rejected the report’s recommendations.

Assistant Administrator Peter Wright said in a statement that the agency “believes the Superfund program’s existing processes and resources adequately ensure that risks and any effects of severe weather events” that become more intense or frequent are covered by risk-response decisions at the sites.

There are 24 of these sites with hazardous toxins in the Houston area, according to the GAO data. Of these, 14 would be affected by a Category 4 or 5 hurricane, 13 by flooding risk, seven by sea level rise and one by wildfires — with many of them potentially affected in more than one way.

Rock Owens, managing attorney for the Harris County Attorney’s office, said he wasn’t surprised “the GAO is sounding the alarm.

“Climate change is a game changer,” he said. “As the report points out, expanding floodplains pose a serious threat to our Superfund sites. (Tropical storms) Harvey and Imelda should serve as a dire warning of what is to come and this must be addressed sooner than later.”

For areas such as Houston, the impacts of severe weather on Superfund sites is not hypothetical. It’s a reality.

During Tropical Storm Imelda earlier this fall, several barges got loose on the San Jacinto River. One of them, which was carrying 10,000 barrels of lube oil, became grounded on the San Jacinto Waste Pits Superfund site. U.S. Coast Guard officials, in coordination with other agencies, monitored air and water quality and reported that the incident resulted in no adverse health impacts.

Two years earlier, Hurricane Harvey brought an unprecedented amount of rainfall to the region, damaging 13 of the 41 Superfund sites in flooded areas, according to the EPA, including the San Jacinto Waste Pits, one of the most vulnerable in the area because it is still being cleaned up and sits right on the river.

Heavy rains brought by Harvey eroded part of the temporary cap meant to contain dioxin, which is highly toxic and can cause cancer as well as liver and nerve damage. After the hurricane, the EPA found dioxin sediment near the pits at a level that was more than 2,000 times the agency’s standard for cleanup.

More Information Climate change impact on Texas sites There are 64 non-federal Superfund sites on the National Priority List in Texas. Of these: - 22 (34%) of these sites would be affected by a Category 4 or 5 hurricane - 29 (45%) by flooding risk - 14 (22%) by sea level rise - 6 (9%) by wildfires Source: Government Accountability Office data

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The pits, on the western bank of the San Jacinto River near the Interstate 10 bridge, were used in the 1960s to store waste that was taken by barge from a nearby paper mill. The site was originally on the riverbank in eastern Harris County, but it became partially submerged over time because of subsidence, dredging and construction of the I-10 bridge near Channelview, which altered the path of the river.

It became a federal Superfund site in 2008 and was capped in 2011, partly in response to prior reports of leaks and fears of damage from hurricanes. According to the GAO analysis, the site is located in an area that has a 1 percent or higher annual chance of flooding and that may be affected by storm surge from Category 1 hurricanes and sea level rise.

“Every one of these major storm events we’ve had — pre- and post-Harvey in the past 10 years — are attributable pretty much to climate change,” Owens said.

As a result, the region has seen incidents ranging from barge strikes to inundations, “a whole series of things,” he said, “that make this site and potentially other sites vulnerable.”

Harvey was roughly three times more likely and 15 percent more intense due to man-made climate change, according to the World Weather Attribution, which includes researchers from Texas A&M University at Galveston and the University of Oxford. Global warming made Tropical Storm Imelda about twice as likely, and about 10 to 15 percent more intense, researchers found.

While the EPA has focused on flooding when it comes to the waste pits, some say there are numerous other sites in the region at greater risk for flooding.

“We face a unique risk here on the upper Texas coast,” said Jackie Young, who leads the Texas Health and Environmental Alliance and has advocated for the pits’ cleanup. “We have a double threat we experience here on our coast not just from water rising out in the sea or out in the Gulf, but also a lowering of our land elevation.” And it’s not right, she added, that communities in these areas have to worry about whether toxins from the Superfund sites are going to wash into their homes when experiencing a hurricane.

Officials in EPA Region 6, which includes Texas, told GAO investigators that they do not incorporate potential impacts of climate change on the frequency of natural disasters into their risk assessments.

But Young and Owens said EPA officials they work with are receptive to considering the effects of climate change when addressing the sites, even if they don’t explicitly call it that.

GAO investigators called for greater consistency and standardization among the EPA’s regions in integrating climate change information into specific remediation plans of the sites, as well as to better align it with the agency’s current goals.

“Whether or not people agree on climate change and why, our climate is changing, we should all be able to agree on what we are living through and experiencing and that it’s increasing in frequency and intensity,” Young said. “It’s imperative we evolve with changing times.”

perla.trevizo@chron.com