Local federal lawmakers and a machinists union are turning up the heat on Alcoa and President Donald Trump to find a solution that avoids shutting the company’s Ferndale, Whatcom County, aluminum smelter by July and throwing 700 people out of work.

Democratic Sens. Maria Cantwell and Patty Murray and Reps. Suzan DelBene and Rick Larsen wrote Alcoa CEO Roy Harvey on Wednesday, urging him to work with the International Association of Machinists and Aerospace Workers to save the Intalco plant, in existence since 1966. On Tuesday, the union’s international president, Robert Martinez Jr., sent a letter to Trump asking for his assistance in keeping the plant open and avoiding an overreliance on Chinese aluminum.

“China boasts approximately 150 aluminum smelters and produces 44 million tons per year,’’ Martinez wrote. “The U.S. produces only 1.8 million tons per year, which is less than half our domestic demand. This discrepancy jeopardizes our national security by leaving the United States at the mercy of foreign producers, and in particular Chinese producers, for one of the most critical inputs to nearly all sectors of manufacturing.’’

Martinez added that the need for “high quality aluminum’’ has increased during the coronavirus pandemic, with ventilators, hospital beds and other vital medical equipment requiring it. He said the Ferndale plant is the lone remaining smelter in the Western U.S. and the only one with proximity to a deep-water port and dedicated rail spurs for loading and unloading cargo.

The lawmakers, who’d written Trump last week blaming his foreign trade policies for the plant’s closure, took aim at the timing of Pittsburgh-based Alcoa’s decision in their letter to Harvey.

“This is the second time in 5 years that Alcoa has announced that it would curtail operations at Intalco, and it is deeply distressing that the company chose to make this announcement in the middle of a pandemic,’’ the letter states.

It goes on to say: “While we recognize that companies like Alcoa have certain corporate responsibilities, they also have a responsibility to their workers and communities. In the midst of the COVID-19 outbreak it is more important than ever to for companies like Alcoa to act as responsible corporate citizens — and we stand ready to work with you achieve this.’’