One of Washington's most active groups involved in saving local landmarks from demolition, Don't Tear It Down, has received an Interior Department award for its conservation work.

The city's new Capital Children's Museum also was among seven local organizations and residents to win recognition for outstanding contributions to conservation and recreation.

Top officials of three national conservation groups with headquarters here also were cited: The Nature Conservancy, the National Trust for Historic Preservation and the National Recreation and Park Association. The U.S. Forest Service and an Alexandria woman won awards for their efforts to increase the number of hiking, biking and horseback-riding trails across the nation.

The 1980 awards for Interior's Heritage, Conservation and Recreation Service -- which went to 103 groups and individuals in 36 states and England -- praised Don't Tear It Down for its efforts to preserve Washington landmarks slated for demolition.

Using a combination of techniques including lobbying, economic studies, negotiation, publicity and lawsuits, Don't Tear It Down has helped save numerous Washington landmarks, the award says. It cites the Old Post Office on Pennsylvania Avenue, the Willard Hotel, several 19th century city school buildings and Red Lion Row, the block of Victorian townhouses facing Pennsylvania Avenue in the 2000 block of I Street NW.

More than 120 volunteers for Don't Tear It Down have just completed an 18-month survey of downtown buildings, the first such study ever done of city buildings, to help identify those that should be preserved.

The Capitol Children's Museum, established three years ago, received a $1.7 million federal grant in 1978 to buy an entire city block behind Union Station at Third and H streets NW. The award cited the museum for its efforts in "one of the most depressed (areas) of the city."

The museum and its executive director, Ann Lewin, were praised for the "hands-on" children museum and for the wide private and foundation support they have attracted.

Other award winners were: Douglas P. Wheeler, of 133 11th St. SE, former vice president of the National Trust for Historic Preservation, for his work in expanding the trust's preservation activities; Jeanette Fitzwilliams of Alexandria, president of the Virginia Trails Association; Barry S. Tindall of Arlington, for his "behind-the-scenes" efforts with Nature Conservancy and the National Recreation and Park Association, where he is public affairs director; and Patrick F. Noonan of Potomac, past president of Nature Conservancy, who was credited with helping the organization "quadruple its conservation activities to the present level of 200 projects a year."