(Adds Marathon comment, details on agreement)
By Erwin Seba
HOUSTON, May 14 (Reuters) - Striking workers at Marathon Petroleum Corp's Galveston Bay, Texas, refinery are scheduled to vote on Monday on a new contract proposal hammered out by a federal mediator, company and union officials said on Thursday.
Ratification of the contract proposal by 1,100 striking workers at the 451,000 barrel per day (bpd) refinery in Texas City, Texas, would be a key step in ending a strike that stretched into its 104th day on Thursday.
After adoption, the two sides would then have to reach terms for returning striking workers to their jobs in the refinery, which has been kept in operation since Feb. 1 by temporary replacements. The return-to-work process can take 30 days to complete.
The new contract proposal comes after representatives of U.S. National Labor Relations Board told labor and management that they had found merit to charges brought by the local union over Marathon's actions in contract negotiations and during the strike, said Larry Burchfield, vice president of United Steelworkers union (USW) Local 13-1, on Thursday.
The new proposal includes the national pattern agreement on wages and benefits made in March by negotiators from the USW international union and U.S. refinery owners. That four-year agreement provides a 2.5 percent pay increase in the first year, 3 percent in the second and third years and a 3.5 percent increase in the fourth year.
None of the striking members of Local 13-1, which represents the Galveston Bay Refinery's hourly workers, have crossed the picket line since the work stoppage began on Feb. 1.
"We think this is a result of the board charges we were successful in showing had merit," Burchfield said.
A Marathon representative confirmed the proposal made by the mediator would be voted on the striking employees on Monday.
"We are hopeful they will ratify the agreement so we may end the work stoppage that began over three months ago and negotiate a return-to-work agreement, said Marathon spokesman Jamal Kheiry.
Burchfield said the 42-page proposal had some changes from a "last, best and final" offer made by the company and rejected by the local in April.
The agreement proposed in April could have cost up to 150 employees their jobs, union officials said at the time and would have made significant changes in safety policies adopted by previous owner BP Plc after a deadly 2005 explosion killed 15 workers and injured 180 others.
Reporting by Erwin Seba; Editing by Terry Wade and Diane Craft