High-Interest Savings with Combined Environmental and Geotechnical Services
Savings Bank of Danbury (SBD) will construct a new, multistory office building in the heart of downtown Danbury, Connecticut. The building will have a newly excavated basement level, and it will be necessary to preserve the integrity of adjacent historic structures during demolition of several existing buildings.
GEODesign mobilized their geotechnical and environmental services to provide SBD with cost savings through a reduced need for consultants, streamlined field engineering, enhanced efficiency, and a more comprehensive dataset from field explorations.
We implemented a multiphased geotechnical approach consisting of borings to obtain subsurface soil information and test pits to determine foundation bearing depths of adjacent off-site structures. In addition, we collected core samples from an existing mortared stone foundation wall to confirm the presence of a suspected “party wall” shared by a building planned for demolition and an adjacent structure.
A significant challenge was presented when it was determined that additional subsurface data was needed within a low-overhead basement of an existing building. This challenge was overcome by mobilizing a portable, limited-access drilling rig to perform the borings. Additional borings and borehole infiltration testing were also performed during this mobilization to assist the project team in designing the stormwater management system.
Careful cross-discipline coordination to obtain environmental samples from the geotechnical borings resulted in cost savings for SBD.
- Samples were analyzed for common urban-fill contaminants, which allowed us to recommend cost effective disposal and reuse scenarios.
- Groundwater samples were obtained from installed monitoring wells and analyzed to provide important construction wastewater disposal options.
Best methods for management of surplus construction soil and dewatering groundwater were explored on an adjacent parcel. This necessitated interior borings through the floor slab of an existing building. Working closely with our network of subcontractors, we developed a tailored exploration program for the challenging low-headroom drilling conditions. Interior subsurface infrastructure was mapped, and limited-access drilling equipment was mobilized to gather the necessary data. While this approach required significant planning and effort, it will pay off during construction because it will allow the surplus soils to go directly from the excavation to the offsite facility, which is more efficient and cost effective than stockpiling and testing the soil.