U.K.-based Croda is again producing ethylene oxide at its Atlas Point plant next to the Delaware Memorial Bridge, where a Nov. 25, 2018, leak stopped holiday highway traffic and brought state and federal investigators in to demand improvements.

“We have now restarted EO production operations,” Croda marketing director Cara Eaton said in an email Monday. Managers at the plant built the unit so they could make ethylene oxide on-site at the plant from common alcohol instead of shipping carloads of toxic, explosive ethylene oxide across the country from Texas.

The surfactants plant, which employs 250, kept running with out-of-state ethylene oxide while the unit was down. Some of those shipments will continue for now: “We will be progressively increasing our capacity to full operation levels. We continue to receive and use ethylene oxide from other suppliers for the time being, as [the plant’s owners] have safely done for more than eight decades,” Eaton added.

Croda’s investment, and the dangers that persuaded regulators and operators to temporarily shut the unit just two months after it opened, have been a test for local officials’ determination to attract new investment that could keep the Delaware River’s aging petrochemical industries intact as a regional employer and taxpayer.

The Delaware unit restarted as creditors weigh bids that could determine the fate of a two-square-mile oil refinery complex in South Philadelphia, which Philadelphia Energy Solutions shut down last year after a damaging fire.

Croda uses ethylene oxide in the production of surfactants, chemicals its own industrial clients use to produce antifreeze, DuPont crop-seed coatings, and the mixing and separating agents used in processed foods, natural gas fracking, and other industries.

Croda and its predecessors at Atlas Point formerly purchased the chemical from a Sunoco facility in nearby Marcus Hook, Delaware County. But that Sunoco plant caught fire and was shut down in 2009, obliging Croda to ship the substance from outside the region.

Seeking a safer, cheaper, closer alternative, Croda said it would spend $170 million on the new unit, using a process previously run at plants in China and India. The company later downsized aspects of the unit, state records show.

Before reopening, the company had to comply with orders from the federal Occupational Safety and Health Administration and state Department of Natural Resources and Environmental Control.

In the month after the Thanksgiving weekend accident, Croda blamed an incorrect gasket installed by a contractor for the leak and checked and replaced seals around the plant.

State investigators said Croda had opened the plant without proper inspections. They also said they were concerned about the impact of 700,000 gallons of water sprayed on 2,688 gallons of ethylene oxide may have on area groundwater, along with the toxic solvent 1,4-dioxane, a cancer-causing byproduct of Croda’s process at the unit.

In March, Croda agreed to pay the state of Delaware a $230,000 penalty and $16,500 for costs to test air and water and perform additional renovation and monitoring work before the unit could reopen.

In June, OSHA recommended Croda pay $262,548 more, after deducting 10% from the maximum penalties because the plant had a previous good record.

Croda “risked the health of their workers,” said Erin G. Patterson, director of the OSHA office in Wilmington, in a written statement at that time.

The leak “could have been prevented if the employer had taken appropriate precautions.” The company failed to flag improper materials and methods used in the construction of the ethylene oxide unit, including contractors’ use of improper bolts and gaskets not cleared for use with ethylene oxide; and it failed to provide plant operators with a safe location from which to deal with emergencies, or train workers effectively to cope with accidents, OSHA added.

Croda was cleared to reopen the unit after regulators were satisfied that the company fixed those and other problems.