A Houston refinery is facing its second environmental lawsuit in as many years after releasing more than 320,000 pounds of toxic gases last week, the latest in a long list of violations that state officials contend has become a pattern for the company.

On Sept. 3, Houston Refining LP suffered a loss of power, possibly caused by a bird, leading to the release of 323,382 pounds of sulfur dioxide and 3,797 pounds of hydrogen sulfide over nearly nine hours. This was the sixth unauthorized release of pollutants that the company reported to the state so far this year.

As a result, Harris County filed a lawsuit this week against the company, alleging violations of the Texas Clean Air Act. The lawsuit is seeking injunctive relief, court costs and attorneys’ fees.

“We filed a lawsuit because of the particular size of this event and the compounds that are involved are alarming,” said Rock Owens, the county's special assistant county attorney for environmental matters.

It wasn’t “your average release,” he added.

Short-term exposure to sulfur dioxide can harm the respiratory system, making it difficult to breathe, especially for vulnerable populations such as children or people with asthma. And hydrogen sulfide is an extremely hazardous gas that could be deadly in large concentrations.

Owens said the county doesn’t know yet whether anyone was exposed to the gases, but given the size, the magnitude of the release and that the company is in close proximity to where people live and work, it was important for the county to pursue legal action and be part of any decision made as to how the violation is handled.

“It’s nothing to laugh at,” Owens said Friday, a day after the lawsuit was filed.

LyondellBasell Industries, which owns Houston Refining, is reviewing the details of the lawsuit and investigating the incident “to fully understand the cause of the event,” said Kimberly Windon, a spokeswoman for the company.

Houston Refining, one of the largest refineries designed to process heavy, high-sulfur crude oil, is within the Houston and Pasadena city limits, along the Houston Ship Channel.

It employs 1,200 people, including contractors, and sits on 700 acres in east Houston. It began operations in 1918 and was one of the first petroleum refineries built on the ship channel, according to the company’s website. LyondellBassell reacquired full ownership of the plant in 2006.

But the Houston operation has had a long history of environmental and safety violations, including for how it handles hazardous chemicals, failures to repair equipment and unauthorized emissions, government data show.

A Houston Chronicle report from 2016, researched in coordination with Texas A&M University, evaluated facilities based on the potential dangers posed by chemicals on-site and the number of people who lived nearby. The report found that Houston Refining posed a high potential for harm, scoring 10.8 on a 14-point scale.

The Occupational Safety and Health Administration has issued more than a dozen violations to Houston Refining since 2016 and fined the company about $170,000, although a couple of violations are still pending and the amount is not final.

The facility has also faced fines from the Environmental Protection Agency, having been found to have violated the Clean Air Act for 12 of the last 12 quarters, records show.

Since 2009, the Texas Commission on Environmental Quality has fined the company more than $600,000 for multiple violations — although a portion of that has been deferred.

The company also had to pay $705,500 in penalties and attorneys’ fees after the state sued it last year for violating the Texas Health and Safety Code and the state’s Clean Air Act. In its lawsuit, the state described the site as a refinery that for several years “has been plagued with continuing problems associated with operator errors and equipment malfunctions resulting in emissions events” releasing unauthorized air contaminants into the environment, according to court records.

And although 300,000 pounds, the amount of last week’s release, is considered a large one, it is not the company’s biggest. In 2016, another power outage caused by operator error led to the release of more than 650,000 pounds of sulfur dioxide and nearly 7,000 pounds of hydrogen sulfide, state records show.

“Houston Refining has established a pattern of causing, suffering, allowing or permitting emissions events through repeated operator errors and mechanical failures that have resulted in emissions of air contaminants,” the state wrote in its petition for a permanent injunction in 2018.

That injunction required the company to retain a certified environmental auditor, a thorough description of the environmental audit it was going to conduct and how it was going to be evaluated, among other stipulations.

Asked whether last week’s release violated the injunction, TCEQ said Friday that it would determine compliance once a final report was submitted.

Spokeswoman Windon said the company is “fully in compliance with our agreement with the attorney general and continues to meet all Texas Commission on Environmental Quality requirements.”

Through legal action, Harris County, which has become more aggressive on environmental matters since Democrats won control of the Commissioners Court last year, wants a third party to evaluate the violation history of the refinery and develop a plan to make sure it doesn’t happens again, said Owens, the managing attorney.

That includes addressing the power outages that seem to be one of the factors contributing to the releases, he said.

“These are the kind of things we can get from court injunctive relief beyond the penalty, and that’s really why we file these cases in Harris County and don’t even ask for penalties at this point because it’s not that important,” he said. “You can’t get enough money for one thing and look back to their history. They’ve been paying fines and penalties for a long time, and the same thing keeps happening.”

perla.trevizo@chron.com