Improvements for an Aging Sheetpile Wharf at Mayport Naval Station

The Mayport Naval Station in Mayport, Florida, consists of seven wharves, and is used for homeport berthing functions and munitions loading. The project described herein focuses on the improvements and upgrades to Wharf Charlie 1, located on the north side of the harbor. The original Wharf Charlie 1 berth consisted of 185 m of steel sheetpile diaphragm cells built in 1952. In 2008, an above and below water condition assessment inspection was conducted and identified the following structural issues: 1) widespread corrosion with pits and holes up to 305 mm in diameter were observed in the steel sheetpiles with the majority of corrosion below the concrete cap around the mudline, and 2) sinkholes noted in the deck adjacent to the sheetpile wall, likely associated with backfill migration through the corroded sheetpiles. As a result of the inspection, it was recommended that the wharf be replaced. In addition, the Navy was interested in adding a double-deck loading platform to the wharf in order to improve the safety and efficiency of loading operations. The new wharf was procured as a design/build project. A design was developed for the new wharf, which allowed the existing foundation elements to be left in place during construction. However, in leaving the existing foundation elements in place, additional difficulties were created. The new foundation elements, such as the new bulkhead deadman anchor system, upper deck foundation, and ship's service utilities had to be positioned to avoid conflicts with one another and with the existing structural elements that were left in place. The new design consisted of a combination king-pile/sheetpile wall driven outboard of the existing diaphragm wall, with the space between the two backfilled with flowable concrete fill. The design primarily utilized traditional limit-equilibrium methods to design the wall, ignoring the effects of the existing structural elements. However, given the complex behavior of the existing elements with the new wall system, advanced continuum soil analyses were also conducted to better understand the behavior of the complex system and confirm acceptable performance. This paper presents a summary of the project, as well as details of the design of the major components of the facility. A description of the construction includes results of field testing of the pile foundations and lessons learned. The coordination of the new structural elements with the existing elements is also presented.