Publish and Present
The Port of Tacoma (The Port) recently completed the process of re-configuring Piers 3 and 4 to allow berthing of two 18,000 TEU Ultra Large Container Vessels (ULCV), making this the first terminal in the Pacific Northwest able to do so. Historically Piers 3 and 4 have serviced smaller container ships due, in part, to the unusual kinked configuration of the pierhead line. In order to straighten the pierhead line, demolition and re-construction of Pier 4 was required. A major part of that work included dredging and re-shaping the existing shoreline. Timing was critical. In order to meet the construction schedule and comply with environmental permit regulations, the entire dredging project needed to occur within a three and a half month window. This required a 24-7 dredge operation on a slope with soil properties that varied widely along its length. The slope was originally constructed from hydraulically placed fill material and the 1.75H:1V design slope was found to be a moderately stable condition during the timeframe between dredging and placement of armor rock. However, timing between dredge and rock placement was critical in order to minimize exposure time of the freshly-dredged slope. This paper will focus on the process taken by the Contractor, the Port, and the Design Engineer to complete the dredging work on time and the methods used for interaction between each party to allow for a successful project amid multiple challenges. This paper will also discuss the use of current technologies to track the dredging process including new software that allowed tracking the underwater positioning of the bucket with 3D viewing capability, and the review methods implemented to ensure dredging occurred per design while providing time-critical approvals to keep the contractor moving.