Mercer Mega Block

When the City of Seattle regained two large parcels of land near South Lake Union during the realignment of two main thoroughfares (Broad Street and Mercer), JLL sought our help in envisioning how this “mega block” could be developed into an economically, environmentally, and socially sustainable community. Our early site studies showed that two buildings on the larger parcel, the “mega block, offered more development potential than one mega building because of the way the zoning is written. Tapping into the City’s desire to activate an 8th Avenue extension, our plan extends that street as a pedestrian-only thoroughfare into the mega block itself, which both splits the block into two desirable building areas and opens opportunities to enliven the whole avenue. We placed City-required affordable housing on its own block and produced three programming scenarios for how the rest of the site might be used: as all offices; all residential with retail at street level; or a mix of office, hotel, and residential space. A relatively high water table limited the underground parking, and overhead power lines, zoning variations across the site, and a float plane flight corridor all affected the shape and massing of each building option. Our close collaboration with JLL, the City, and other agencies, as well as our holistic approach and ability to stay flexible, were of particular value on this project. The Mercer Street realignment plans were changing weekly, and zoning code revisions were still in flux during much of our master planning process. Our suggested re-subdivision of the property was acceptable to the City, but it also exposed inconsistencies between current and proposed codes for this and adjacent zones, especially as they related to increasing allowable building heights. Working from our findings helped the City staff and zone regulators address these inconsistencies for future code amendments in support of the broader goals they set for the area.