The $235 million project involves the redevelopment of the State Pier facility in New London, CT. The intent of the project is to address the current shortcomings of the facility and provide a purpose-built facility for heavy cargo staging and deployment, specifically offshore wind components. The existing bulkheads and marine structures are being replaced and the area between the State Pier and Central Vermont Railroad Pier, known as “Central Wharf”, is being filled to provide additional staging area at the port. Filling Central Wharf will require about 400,000 cubic yards of material to be placed though about 40 feet of water and then compacted. The compacted fill must support the heavy loads associated with offshore wind components and other heavy cargo, transport vehicles, and cranes. Due to the presence of very soft organic sediment at the mudline within Central Wharf, long-term settlement, and displacement of the sediment during filling presents challenges to both the design and construction of the project.
In 2021, GZA worked with Kiewit Infrastructure Co., Construction Manager At-Risk, (CMR) to develop an alternative means of placing and compacting the Central Wharf fill. Originally, the design involved soil-mixing and ground improvement with stone columns. GZA’s innovative method involves a staged approach to filling where the first stage of filling is intended to penetrate and stabilize the soft organic sediment. The second stage of filling is mass fill completed by end-dumping and pushing material from land into the Central Wharf, which is a more efficient way to place this volume of material. GZA also recommended an alternate to the stone column method of compaction. The alternate method uses vibro-compaction of the filled materials. This method does not involve the use of crushed stone, which provided significant cost savings to the project. Construction is on-going and GZA is also providing construction oversight on behalf of Kiewit’s CMR team.
GZA’s geotechnical value engineering and marine construction experience, knowledge and experience with multiple ground improvement methods, and extensive work within the offshore wind industry, were integral to reducing the estimated cost of and the successful execution of the construction phase of this project.