Washington Post Co. Chairman Katharine Graham forecast yesterday that a new, futuristic and high-technology Northern Virginia printing plant of the Washington newspaper "marks the start of one of the most exciting periods of growth and development" in The Post's 103-year history.

Graham's comments were made at a gala reception in Springfield, as executives of The Washington Post, government leaders and more than 700 guests and employes participated in the formal dedication of a new, $65 million suburban printing plant -- one of the largest private corporate investments ever made in the Washington area for a manufacturing facility.

Virginia Gov. John N. Dalton, who was introduced by The Post's publisher, Donald Graham, noted that the Springfield plant represents the second factory opened in his state this year that involves The Post Co. Dalton added he now could claim the newspaper "is on Virginia's side." Earlier, a newsprint mill was opened in Dowswell, Va., with The Post Co. a limited partner, and paper from that factory is being shipped north to Springfield for use in daily production.

Dalton was joined by Lt. Gov. Charles Robb, Fairfax County Board of Supervisors Chairman John F. Herrity and other state and county lawmakers in welcoming The Post's big new plant to their state, which Herrity said would add $7 million in annual wages to the private payroll in Fairfax County as well as $1 million a year in new tax revenues to the county.

The Thomas Jefferson High School Band, under direction John Knapp, also welcomed the newspaper with John Philip Sousa's "The Washington Post March," as regional business and community leaders started on guest tours of the facility, which plant manager Thomas O. Might described as "the best newspaper plant in the industry," one which he vowed would be characterized by high productivity and "stand out for employe job satisfaction . . . where each employe wants to come to work every day . . . . It's time to have faith in the American worker."

Donald Graham, who has presided over planning and construction of the new facility, said that more than 200,000 daily copies of The Post distributed throughout Virginia will be printed in the new plant by early next year, emphasized that the newspaper will continue to print the bulk of its papers in downtown Washington, for circulation in the District and Maryland.

The plant dedicated yesterday is located on Wimsatt Road, close to the intersection of Interstate 395 and the Capital Beltway.

Katharine Graham noted that the Springfield plant is the fifth buidling for the newspaper since her father, Eugene Meyer, purchased The Post in 1933, when it was located on E Street NW. Amodern plant on L street was dedicated in 1951, an additional was added in 1960 after acquisition of The Washington Times-Herald, and the current downtown headquarters (connected to the L Street plant) was dedicated in 1972.

Each time a new plant has opened, Graham remarked, The Post's circulation and advertising growth soon forced the company's management to begin planning additional expansions. "Just wait until we get into the new building," became the watchword of succeeding generations of Post employes, she noted.

"And the wonderful thing about this growth cycle is that as we gain advertising and circulation, we also gain the wherewithal to continue to expand," said The Post Co. chief executive.

The centerpiece of the new factory is a vast, high-ceilinged press room (75 feet wide, 300 feet long and about 40 feet high), where three new presses have been printing ever-increasing numbers of daily editions during the start-up period of recent weeks.

Each of the eight-unit presses can produce 128-page newspapers at the rate of up to 75,000 copies an hour. The room is unusually clean for a press complex, and the sound is muted in what is perhaps the quietest major newspaper press room, with operators protected behind the walls of soundproof sections where computers and electronic controls can make most adjustments.

"It's a different world . . . the first time at The Post that we've ever had any elbow room at all. The bulk of our printing, our headquarters and our home will remain downtown. But it has been a tough job for our production department to do its manufacturing job, right in the middle of the downtown of a major city," said Donald Graham.

The Post's new 315-000-square-foot plant also includes mailing and storage facilities, a covered loading area for delivery trucks and intricate conveyor systems to bring in rolls of newsprint from the adjacent Robinson Terminal Warehouse Corp. storage building, which is next to a railroading siding. About 275 workers will be employed by The Post in Springfield.

Graham said the facilities now installed at Springfield should be adequate to accomodate Washington Post expansion for a little more than a decade, assuming that older presses downtown remain productive.

Starting in January, the existing presses downtown also will be renovated for better-quality printing work. Soon, deadlines for news copy will be extended later into the night, so more Washington Post readers will receive later-news editions, company officials emphasized.

Construction of the new plant was dictated by continued growth in Washington Post daily and Sunday circulation, to the point that capacity at the downtown Washington printing presses was exceeded.

Planning for a satellite printing plant was started in 1973 and 1974, and two parcels of land eventually were purchased in the Springfield area and in Montgomery County near the White Oak area. Construction of the new plant dedicated yesterday was started in May 1979.

The newspaper also has invested $6.2 million in a new computerized typesetting system designed by the Raytheon Co. and established laserbeam transmission of separate pages from downtown Washington to the satellite printing plant.