The Lake Merritt Station was constructed around 1967, some 53 years ago. The underground station lies under parts of two city blocks, bounded by Madison and Fallon Streets and 8th and 9th Streets. The west block, bounded by Madison and Oak Streets and 8th and 9th Streets, is the location of this project. The west block is a plaza, generally at sidewalk level, that includes paving, planters, access stairways, existing BART facilities and elevators to the BART station below. Previously, there was a high-rise office building on the site that was removed in 2009-2010 because of seismic deficiencies. The existing waterproofing system has exceeded service life and is migrating to the surface of the plaza. There are extensive leaks from the plaza area to the mezzanine area below.
Interactive Resources obtained a topographic survey of the plaza surface as it currently exists, studied as-built drawings, made test cuts in the plaza and planters and obtained laboratory analysis of the existing waterproofing materials. After completing a characterization of existing conditions, Interactive Resources reviewed the three current concept designs and provided detailed specific recommendations for removing and replacing the existing waterproofing system.