Newport Dock Remediation and Geotechnical Risk Mitigation in Variably Weathered Rock Conditions

In 1948, the Port of Newport sank two reinforced-concrete cargo ships on the north shore of Yaquina Bay to serve as wharves for cargo handling. Over time, the ships cracked and moved up to 3 ft toward the bay, resulting in ground settlement, damage to structures near the ships, and an increased risk of releasing petroleum contaminants stored inside the ships into the bay. Through an extensive analysis of alternatives to make the best use of available funds, the selected alternative was to construct a temporary cofferdam and remove the western ship, stabilize the eastern ship with anchors and ballast, and construct a new 800-ft-long, 40-ft-wide dock with an anchored bulkhead wall. The presence of variably weathered siltstone and sandstone at shallow depths below the site presented significant design and construction challenges for installation of the cofferdam, sheet pile bulkheads, and dock pipe piles. This paper discusses the scope, successes, and challenges of the geotechnical site investigation, design alternatives, and construction engineering used to minimize construction risks and overall project costs. Specific challenges and innovative construction techniques used to remove the contaminated buried hull of one of the ships is also discussed.