- Developed and implemented a subsurface exploration program consisting of SPT borings, CPT and SCPT borings, and test pits
- Adapted inspection recommendations to remedy soil conditions and variable weather
GZA GeoEnvironmental, Inc. of New York (GZA) was retained as a geotechnical consultant to provide geotechnical engineering recommendations for the conversion of a two-story commercial building into an ambulatory surgery center for NYU Langone Health. After these services had been completed, GZA was further retained for subgrade inspection.
Challenge
Various sections of the subgrade displayed high fines contents, soil pumping, or ponding. Throughout the project there was also highly variable weather including frequent rain and freezing temperatures.
Solution
GZA’s subsurface investigation consisted of two test borings, two seismic cone penetrometer tests (SCPTs), and seven test pit excavations. The purpose of the test borings was to obtain soil composition and parameters for the foundation design, the SCPTs were to obtain seismic data of the soil, while the purpose of the test pits was to explore the conditions of the existing foundations and underlying soils.
GZA provided subgrade inspection services on an at-request basis by the client from December 5, 2024, to May 1, 2025. The subgrade preparation and other construction activities occurred in the following general sequence:
- Excavation to competent soil in areas of concern
- Subgrade compaction using various plate compactors and hand tamping
- Reinforcement placement and foundation pouring
Soil was excavated until competent sands were encountered, and this sand was compacted. GZA stressed the need to protect subgrade from water and frost, and rescheduled inspections when weather did not permit work to proceed.
Benefit
GZA’s expertise allowed for the subgrade to be adequately protected for the duration of inspection and construction activities, and the client was provided with sound and consistent recommendations over multiple phases of their project.