Two Miles of Anchored Bulkhead Supports Howard Frankland Bridge Megaproject

The Howard Frankland Bridge megaproject consists of a new, 3.2-mile (5.1 km) bridge extending I-275 across Tampa Bay. Two steel sheet pile and combi-wall bulkheads with a total wall length of over 11,000 ft (3350 m) were required to create the land for the new roadway and bridge approaches. A total of 1,287 permanent grouted soil anchors supports the bulkheads, which in some areas retain a 20-ft (6.1 m) tall MSE embankment. Anchors with lengths up to 200 ft (60.1 m) were installed, and project design loads necessitated anchors that varied from 3-strand to 8-strand. The soil conditions at the site were typically loose to dense sands underlain by a thin layer of clay over karstic limestone of variable hardness. Given the magnitude of the design loads, the larger anchors were designed to bond into limestone. Limestone variability along the bulkheads was observed. In some extreme cases, the top of the limestone elevation varied by nearly 100 ft (30.5 m), which created challenges for designing the length for anchors that were required to bond into limestone. Given the proximity to Tampa Bay, most of the work was performed from a barge. Waler systems were installed on the waterside of the sheet piles, so installation and welding work was limited to lower tide stages. The geotechnical contractor designed and installed the anchor and walers systems to fit within the proposed concrete cap. The objective of this paper is to discuss the significant design and installation challenges of the anchor and waler system for this high-profile project.