The $600M One Seaport Square recently started 2.5 years of construction just steps from Boston Harbor, says Berkshire Group SVP of development Heather Boujoulian, who’s managing the project (above with managing director Eric Draeger). What makes One Seaport Square unusual is its size and configuration: an underground parking garage covered by 250k SF of retail with street-level fronts and 832 apartments above. It will bring a critical mass of retail to the emerging Seaport neighborhood.

Since the site is so close to the water—and the “land” is actually fill, not solid ground—conditions dictate slurry wall construction, which will take an extra 12 months. While slurry sounds like a 7-Eleven drink, think of the wall as a 30-inch-thick concrete bathtub that will line the entire site. Workers are now pouring concrete into the excavated hole, says John Moriarty (the GC) project manager Joel Dyson. During and after slurry wall installation, they’re draining the site of groundwater with sump pumps. As they dig, they reinstall the pumps that remain on site until the exterior is built and closed, and a permanent power system functioning.

Before that happens, there are usually some surprises, Joel tells us. During pre-excavation, the Moriarty crew hit an old granite block seawall. The workers could see the water rising and falling with the tide and the blocks were a real chore to remove. The site was backfilled with “lean” concrete that could harden even though the water was still in place.