So much for that walkable plaza with bike stations and jugglers and food trucks: It appears that an office building is going to go up instead on this underused triangular slice o’ land along Washington Ave. The variance is to reduce the setback from 25 ft. to 5 ft. in order to make room for parking and a 3,517-sq.-ft. office building. The 0.26-acre triangle is bound by Henderson, White, Union, and Washington. A site plan included in the variance request shows that the office would go up on the Henderson side, across the street from Liberty Station.