Officials of Westvaco Corp., the New York-based paper company, say they plan to spend $250 million on the firm's Luke, Md., plant by 1989 as part of a $1.6 billion company-wide capital investment program.

Harris W. LeFew, spokesman for Westvaco's fine papers division at Luke, said that capital improvements already under way have created between 500 and 700 construction jobs there.

"We're spending in excess of $4 million per month in capital investments," he said. "What these investments will do is give people we already have more job security. There will not be a lot of new jobs added except in the construction area."

Another spokesman for Westvaco said the expansion includes $25 million for a new wood yard in Mineral County, W. Va., across the Potomac River from the Luke plant. The new yard, which will process raw timber before sending it to Luke, is expected to provide Westvaco with a "more efficient operation," said John Harmon, wood procurement manager at Luke. "The mill has outpaced the wood yards."

The Luke mill also buys wood chips from Westvaco's Hancock and Berkeley Springs, W. Va., subsidiaries, Harmon said. The mill, which employs 2,000 people, manufactures 1,100 tons of coated printing paper a day.

The finished product that comes out of Westvaco's Luke mill has been used in several high-quality publications, LeFew said, including the official souvenir program of the 1984 Summer Olympics.