The Federal Home Loan Mortgage Corporation (Freddie Mac) broke ground earlier this month for its new corporate headquarters in the West-Park complex in Tysons Corner. The project, which reflects Freddie Mac's recent growth in the secondary mortgage market, is expected to be completed in 1990.

The building, phase one of the development at West-Park, is part of a 44.5-acre wooded lot being jointly developed by Freddie Mac and West-Park Associates. The construction will consolidate Freddie Mac's downtown location and Reston offices and will employ 1,100 people.

"Selection of the site was a year-long process," said Maxine B. Stokes, vice president of administration and corporate property for Freddie Mac. "We needed a place that would accommodate our growth, had all of the amenities, and was both convenient to the airport and for our workers." Sixty percent of Freddie Mac's employes live in Northern Virginia.

The building was designed by the architectural firm of Helmuth Obata and Kassabaum and will have 430,000 square feet of office space. To preserve the forest there, the company has decided to locate the majority of parking under the building. Many of the trees cleared for construction will later be moved to the original site and supplemented with new growth.

"We wanted to create an environment, a beautiful piece of property," said Mark Goldhaber, vice president of public affairs for Freddie Mac. "CEO Leland Brendsel felt very strongly against going in and clearing everything out," he said.

Freddie Mac is the leading seller of conventional mortgage securities in the United States. It increases the availability of mortgage money for home loans by buying mortgages from savings and loans, banks and mortgage bankers and, in turn, pooling and packaging them into securities and selling those securities to investors.

In 1986, Freddie Mac's mortgage operations growth resulted in a 50 percent increase in personnel. In that same year, it purchased more than 1,769,500 mortgage loans and posted net income of $247 million. The cost of the building was not disclosed.

In other developments in commercial realty in the metropolitan area: WorldCorp Inc., owner and manager of World Airways and Key Airlines, leased 26,650 square feet at the Renaissance Centre, Park Center Road, Herndon, from GT Group. Gillette Co., a laboratory research operations firm, leased 63,000 square feet at the Crown Pointe Corporate Center, 401 Professional Dr., Gaithersburg, from Lee Sammis Associates Inc. Contel Information Systems Inc., a telecommunications company, leased 24,204 square feet of space at the Renaissance Centre, Herndon, from G.T. Group.