- Project funded in part with a federal grant
- Designed site for bearing capacity of extreme crane loading
- Designed a vibrocompaction ground improvement program to densify dredged soils
- Monitored 24/7 dredging operations (est. 900,000 cubic yards)
- Classified dredge material in real time for re-use on site through visual observation and mobilization of an on-site laboratory
- Maximized beneficial on-site use of dredged materials
- Performed seismic analysis of proposed blasting to assess impacts on adjacent structures for approval by the US Army Corps of Engineers
- Performed PDA testing on driven piles
Challenge
The New Bedford Marine Commerce Terminal was the first U.S. port facility designed for the offshore wind industry. The $133 million project was completed in 2015 for the Massachusetts Clean Energy Center. The design team consisted of Apex Companies, CLE Engineering, Fuss & O Neil, Aspera Associates, and GZA. The terminal was designed to support the staging, assembly, and deployment of offshore wind components. The terminal consisted of development of 26 acres of land requiring removal of ~18,000 tons of contaminated soil. Construction of ~1,000 feet of quayside, including a new cellular cofferdam bulkhead with a pile supported relieving platform with geotechnically-competent, dense aggregate enabling heavy, uniform, and concentrated loads.
Solution
GZA designed the existing shore and new fill areas for bearing capacity of 4,100 psf for extreme crane loading and concentrated loads up to 20,485 psf or 100 metric tonnes per square meter. Bearing capacity design included overexcavation and compaction of existing fill on-land, and vibrocompaction to improve 5 acres of dredged fill placed through the water. GZA provided real time classification of dredge materials and worked with the Contractor to maximize the beneficial reuse of dredged materials onsite, including reuse of dredged till. GZA was onsite for observing all earthwork, ground improvement, and dredging operations. GZA also performed PDA testing on driven piles for support of the cellular cofferdam deck.
Rock blasting to reach the required dredge elevations was required in close proximity to the New Bedford Hurricane Barrier, an earthen embankment owned by the U.S. Army Corps of Engineers. GZA performed seismic analyses to predict the impact of vibrations from blasting on the Hurricane Barrier. GZA developed limits for blasting weights for the project due to the USACE’s concerns regarding liquefaction and settlement of their structure. GZA presented an approach based on real time monitoring of the Hurricane Barrier to USACE to gain approval for the blasting. GZA installed a remote sensing system to monitor pore pressures and vibrations during blasting. Blasting was approved and completed with no exceedances of threshold values due to GZA’s technical analysis, limitations placed on blasting operations, and monitoring of blasting.
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.