Challenge

GZA was the geotechnical engineer for the first U.S. port facility specifically designed to service the burgeoning offshore wind industry. The new $100 million terminal was designed for the Massachusetts Clean Energy Center to accommodate the heavy loadings and requirements for staging, assembly, and deployment of offshore wind components. It included development of 10 acres of land and construction of 1,000 linear feet of a new cellular cofferdam bulkhead with a pile supported relieving platform. The terminal’s proximity to the New Bedford Hurricane Barrier operated by the U.S. Army Corps of Engineers (USACE) necessitated additional technical expertise.


Solution

GZA designed the existing land and new fill areas for bearing capacity for extreme crane loading and 400-ton wind turbine components, loadings which typically exceed the capabilities of existing waterfront facilities. Bearing capacity design included overexcavation and compaction of existing fill on-land, and vibrocompaction to improve five acres of dredged fill placed through the water. GZA classified dredge materials in real time and worked with the contractor to maximize the beneficial reuse of dredged materials, including dredged till, onsite. GZA oversaw all earthwork, ground improvement, and dredging operations, and GZA also performed PDA testing on driven piles supporting the cellular cofferdam deck. To reach the proposed dredge elevations, rock blasting adjacent to the New Bedford Hurricane Barrier, an earthen embankment operated by the USACE, was required. GZA’s approach—based on seismic analysis, blasting limits, installation of geotechnical instrumentation, and real time monitoring of pore pressures and vibrations—gained USACE approval through technical presentations and meetings. No exceedances in threshold values were recorded.


Benefit

GZA’s geotechnical engineering experience and extensive work within the offshore wind industry were integral to the development of this first-of-its-kind U.S. terminal, designed to support the unique needs of offshore wind operations. GZA’s ability to interface with government agencies and protect adjacent sensitive structures during construction was another key to the project’s success.