What’s new?
In the wake of the Everett Street Garage demolition, the cleared site is being prepared for slurry wall construction, which involves the installation of a concrete wall below grade around the perimeter of the site. The wall will allow excavation of the site to proceed while keeping the sides of the excavation from shifting. Essentially, the contractor will dig a trench in 20’ wide sections at a time around the perimeter extending 80 feet below ground and pour concrete in the trench to form the wall.

The name “slurry” of the process comes from the material that replaces the excavated earth until the concrete is placed. A slurry prepared of betonite clay and water or with modern polymers replaces the earth as it is excavated. The properties of the slurry is such that it is dense enough to stabilize the sides of the excavation but is considerably less dense than concrete. Following the completion of the excavation to the design depth the concrete will be placed by a tremie pipe (which is a long pipe) to the bottom of the excavation. The concrete will displace the slurry which will be pumped off the top to be recycled for the next 20’ section.

During the digging phase of this operation, underground obstructions -- often large rocks or boulders -- are frequently encountered, and need to be broken up. This process causes noise and vibrations that can be felt as much as 300 feet from the site. Despite the anticipated noise and vibrations, slurry wall construction is actually the least disruptive way to prepare the site, and was chosen for this reason. To be clear, the noise and vibration will not be continuous over the next several months; it will only occur when boulders are encountered.