Energy giant BP has agreed to pay an additional $13 million to settle more than 400 U.S. Occupational Safety and Health Administration citations for alleged willful safety violations at the company’s Texas City, Texas, refinery.

The agreement, announced on July 12, is the latest development in the wake of a March 2005 explosion at the refinery that killed 15 workers—all of whom worked for Jacobs Engineering Group and Fluor Corp., contractors at the facility at the time.

The settlement resolves 409 of the 439 citations OSHA issued in 2009 to the refinery. Jordan Barab, the Labor Dept.’s deputy assistant secretary for OSHA, said that “all violations covered in this settlement have been or will be addressed” by the end of December.

In August 2010, BP had reached an agreement with OSHA to pay $50.6 million to resolve 270 other notices that the agency had issued in 2009 for failing to correct potential workplace hazards at the refinery. The previous October, OSHA had proposed a total of $87.4 in fines for those citations.

OSHA’s initial enforcement action related to the explosion came in September 2005, when it issued a total of $21 million in citations to BP. The two sides entered into an agreement that mandated that BP identify and fix deficiencies.

A follow-up OSHA probe in 2009 found that BP had made some improvements at the refinery, but also determined the company failed to correct some other issues. That led to OSHA’s issuing the 270 “failure to abate” notices that were the subject of the 2010 settlement agreement.

Also in 2009, OSHA cited the company for 439 willful violations of its process safety management standard. Those citations carried $30.7 million in total proposed penalties.

The latest agreement resolves 409 of those 439 citations. OSHA’s Barab says the remaining 30 citations “will continue to be negotiated or litigated.”

BP announced in February 2011 that it plans to sell the Texas City refinery.