The Arlington County Board yesterday approved an 11-story office building at the south end of Crystal City, in the process imposing $440,000 in fees for a park and transportation improvements despite protests from the developer.

The building is part of a project being developed by Old Dominion Properties and Westfield Realty on a triangular parcel of land roughly bordered by Crystal Drive, Jefferson Davis Highway (Rte. 1) and what will be South 27th Street.

A larger residential building had been proposed for the site but the developer agreed to scale back in exchange for approval to construct an office building instead. The rest of the project includes a second 11-story office building and a 272-room hotel. Both were approved in September.

Of the fees, $200,000 will go toward a park on the site, $140,000 will go toward the Crystal City trolley and $100,000 will pay for two traffic signals. Developer William G. Brakefield opposed paying for anything besides one traffic signal. He said he is the only developer in Crystal City being required to pay for the trolley, which will loop the area.

County officials justified the trolley fee by noting that Brakefield's project will add 2,000 employes to an already congested area. The trolley is intended to ease traffic by making it easier to get to the Crystal City Metro station. County Public Works Director Henry S. Hulme Jr. said other businesses in Crystal City have voluntarily contributed to the trolley.

County planners had proposed that the developer put up $50,000 for the park. The total was increased to $200,000 at the suggestion of board member Ellen M. Bozman, citing the expense of creating parks.

Several board members said they approved the building reluctantly because they believe the project is too large. But they said they had little choice since a previous board had approved an even larger project on the site. Those plans lapsed but the approval of them gave the developer a vested interest, officials said. Brakefield declined to comment yesterday.