Strengthening an Aging Marginal Wharf for RO/RO Operations

In response to an increase in demand for heavy-lift RO/RO operations at the Port of Everett, a portion of an aging 1970s vintage concrete marginal wharf was strengthened and repaired to increase the load-carrying capacity from 550 psf live load to 1,000 psf. The improvements included adding new piles and intermediate pile caps between the existing pile caps, and strengthening the existing pile caps. The existing pile caps within the upgrade area were also repaired to correct corrosion damage caused by chloride-ion intrusion. The repairs included removal of deteriorated concrete, cleaning and replacement of the corroded reinforcing steel, and replacement of the concrete. Cast-in zinc anodes were used to provide cathodic protection. Underwater and underdeck (above water) inspections by the engineers designing the improvements quantified the severity and extent of the structural deterioration. This enabled selection of the best possible repair methods to reduce project costs and increase the structures’ service life and strength. This paper describes the investigation of alternatives, analysis and design of the upgrades and repairs, and the challenges of construction.