Tracor Inc. is building a new 130,000-square-foot facility adjacent to its present offices at 1601 Research Blvd. in Rockville. The new facility will be used to consolidate the company's systems technology division and will house 300 employes presently working in leased space at several locations. The new facility will also allow the hiring of about 300 additional employes within the next two to three years.

Other recent developments in commercial leasing in the Washington metropolitan area:

* American Water Resources Association has moved its headquarters from Minneapolis to the Washington area. The association now occupies 1,300 square feet of space at the Renewable Natural Resources Center in Bethesda.

* Hekimian Laboratories, a Gaithersburg-based manufacturer of communications instrumentation, has leased 25,000 square feet of space at 8435 Helgerman Court in Gaithersburg. Hekimian will use the space for its expanding manufacturing operation and retain its present facility at 9298 Gaither Road in Gaithersburg for administrative offices.

* Professional Equity Limited Partnership has received approval for a $3.6 million industrial revenue bond to construct a 42,000-square-foot office building on Perry Parkway in Gaithersburg. The new building will house the headquarters of Standard Computer Corp., a wholly owned subsidiary of Standard Federal Savings and Loan. Standard Computer will occupy 22,000 square feet of space.

* Prudential Insurance Co. has moved its district sales office to a new 6,000-square-foot facility at the the Montgomery Executive Center on Montgomery Village Ave. in Gaithersburg.

* American Radio Telephone Services Inc., Nordisk-USA and Finance One Mortgage of Maryland Inc. have leased space in the Bedford Building at 6500 Rock Spring Drive in Bethesda.

* Geomet Technologies has leased 4,000 square feet of warehouse space at 16750 Oakmont Ave. in Gaithersburg. The lease is valued at $350,000. Geomet is a Gaithersburg firm specializing in health care consulting and management.