Wynn Resorts is promising cleanup efforts at the former Monsanto chemical plant will meet the highest environmental standards as it prepares to develop a $1.6 billion casino in Everett.

Robert DeSalvio is overseeing the casino development. He told the more than 100 people in attendance Tuesday at Tufts University that the cleanup should cost roughly $30 million but that Wynn is prepared to spend more if needed.

But officials acknowledged one much-touted piece of the planned restoration will likely not move forward: proposed new oysterbeds to help filter and clean the Mystic River.

Wynn won the lucrative Boston-area casino license in September. It proposes to revive the long-vacant site with public amenities like an esplanade, a park, a year-round "winter garden" and water taxis to popular destinations in Boston.