Over ten years after stalling out, then substantially downsizing, plans for a large mixed-use complex across the street from Pershing Square are finally being realized. Last week, MacFarlane Partners quietly began work for the first phase of the Park Fifth development, with the demolition of a small parking garage adjacent to the historic Subway Terminal Building.  In its place, the San Francisco-based real estate firm intends to construct a seven-story building which will span between Olive and Hill Streets.  Plans call for 313 apartments and 7,000 square feet of ground-floor commercial space. Although representatives of the developer have not specified an expected groundbreaking date, earlier reports have pointed to completion of the project in 2018. The building, which will consist of a wood frame over a concrete base, is being designed by Portland-based Ankrom Moisan Architects.  A second phase of the project, a 24-story tower with 348 apartments and retail space, is expected to follow at corner of 5th and Olive Streets. The Park Fifth development may coincide with a $50-million renovation of Pershing Square designed by a team lead by the the French architecture firm Agence Ter.  The five-acre park has featured a series of ephemeral layouts over the past 50 years, the most recent of which is a maligned expanse of hardscape designed by the late Mexican architect Ricardo Legorreta.