By Ruth Dresdner, AIA, LEED AP, and Marcella Yee, AIA
At first glance it may look like a corner of Dante’s inferno—but this is, in fact, our construction team, hard at work at 2865 Creston Avenue in the Bronx.
They drill, excavate, clear rock, and pour concrete. At right, they are forming what will become the bottom of an elevator pit.
They’ve been working nights to make up for time lost to an unusually harsh winter (but this is a dedicated bunch, and we worked through it—proof below).
The foundation wall sits directly against the bedrock (below right). The team is taking great pains to keep the awesome rock outcropping (below left). The rock, like much of NYC’s bedrock, is gneiss (pronounced ‘nice’). On this site, rock hardness ranges from NYC bedrock classification 1B (medium hard rock) to weathered portions classified as 1D (soft rock). Hardness is a crucial attribute of rock because a building foundation can be supported on hard rock, while soft rock may not have the capacity to take the load. Also, when excavating rock, the softer it is, the faster it goes.
Bedrock at this site is mapped as the Proterozoic-Eon Fordham Gneiss, which is typically a banded gneiss to schistose gneiss with pegmatite intrusions. During the Pleistocene epoch, a series of glaciers advanced and retreated across the New York City area, initially scouring soils down to the bedrock. In the Bronx, bedrock is often exposed at the ground surface or covered with a thin layer of glacial soil such as glacial till or outwash sand. Since the retreat of the last glacier, roughly 20,000 years ago, exposed and near-surface bedrock has been subjected to weathering, particularly along joints and foliations in the rock. (Information in the preceding paragraph came from Geotechnical Report dated 12/17/2015 by Mueser Rutledge Consulting Engineers.)
At the other end of the site, a gabion wall is rising. It is made of steel wire baskets filled with pieces of rock excavated on site. Not only is it beautiful (at least in our opinion), but it is made of natural material, and by using what was already onsite, less material will be carted away, and less has to be trucked in. When finished, the gabion wall will be a 20-foot high retaining wall at the rear yard of the building.
Stay tuned for more updates!
Ruth Dresdner, AIA, LEED AP, has been an architect at ESKW/A for almost a year and has taken on two of our largest new housing construction projects. She is project manager on both 2865 Creston Avenue for Project Renewal, and the School Street Residences in Yonkers for St. Joseph’s Community Medical Centers.
Marcella Yee, AIA, has been with ESKW/A since 2014 and has been a lead team member on the Creston project since the design phase. She was an instrumental architectural team member on the successful RFP for Archer Green with particular focus on façade development and detailing during design and construction documents. She is also project manager on shelter renovation projects for BRC.