WSP designed a new low-maintenance, environmentally-friendly concrete replacement structure capable of providing the required vessel supply for the new Healy-class ice breaker and increased moorage flexibility. The project provided an advanced facility to effectively accommodate mission-critical vessels ensuring the U.S. Coast Guard the ability to protect the public, environment, and U.S. economic and security interests.
As part of the U.S. Coast Guard's (USCG) Integrate Support Command (ISC) in Seattle, Washington, at Slip 36, Pier 36 Berth Alpha provides multipurpose support to a complement of homported vessels that support USCG operations worldwide. The WSP team provided consulting services for replacement of the original timber structure and dredging to deepen the entire Slip 36 basin, including an expanded Berth Alpha area. Key project elements were the replacement of the 100-foot-wide existing pier with a narrower, 50-foot-wide pier for optimum mooring flexibility, and basin access and development of contract documents for the removal of both contaminated and clean, dredged materials.
The initial scope of work included an engineering feasibility study and comparative cost analyses for the new facility, resulting in the preparation of a formal narrative report submitted for USCG approval. Also included was the extensive environmental sampling and classification of environmental reports required for permit documents by regulatory agencies. Later phases of the work included final design of the new pier, dredging, and extensive construction support. A key component of the design was the underwater steel sheet pile wall and ground densification procedures, which allowed dredging the expanded berth to ~40 feet mean lower low water.