Maine Medical Center has submitted preliminary plans for a $40 million expansion that would add four operating rooms at its Portland campus. The 40,000-square-foot addition would be built on top of the hospital’s Lower Bean Building. The hospital says it would also add 49 positions to staff the building. Hospital executive vice president Jeffrey Sanders said in a May 24 letter to city planners the addition “will modernize and upgrade MMC’s surgical facilities by enlarging (operating rooms) to meet standard of care requirements.” A hospital spokesman told The Portland Press Herald, on Monday that he could not answer questions about the expansion because the hospital’s board of directors has not formally endorsed the plan, even though it was submitted to the city last week. The board meets Thursday.