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In the State of Hawaii, nearly 60 bridges have been identified as potentially scour critical based on observed or anticipated conditions at the bridges. The Hawaii Department of Transportation (DOT) is preparing a Plan of Action (POA) for each bridge that will outline procedures for Hawaii DOT personnel to follow during high flow events to help ensure public safety. Each POA will include a scour vulnerability assessment, recommended actions including hydraulic/structural countermeasures, increased inspections, and/or flood monitoring, and a bridge closure plan. Waterways involved range from large, sand-bed rivers along the coastline of Oahu to the steep, rocky Hamakua Coast on the Big Island. A number of bridges on the historic Hana Highway on Maui are also included. Drainage areas range from less than 0.5 km to nearly 650 km. Flows were developed for each bridge based on available data along with a detailed hydraulic analysis. Scour vulnerability was determined based on contraction and pier scour depths using HEC-18 guidelines. INTRODUCTION The Federal Highway Administration (FHWA) has collected information on nearly 600,000 of the nation’s bridges and created the National Bridge Inventory (NBI) database. This database includes the number, location, and general condition of bridges in each state. Item 113 in the database is used to indicate the status of each bridge regarding scour vulnerability. A bridge is identified as scour critical if the value for Item 113 is between 0 and 3, with a value of 3 indicating that the bridge foundations were determined to be unstable based on a calculated or assessed scour depth being at or below the footing base or pile tips, and a value of 0 indicating the bridge has failed and is closed to traffic (FHWA, 1995). In the State of Hawaii, 57 bridges have been identified as scour critical on the NBI database. These bridges are spread throughout the five major islands and include those on Oahu (22), Kauai (10), Hawaii (13), Maui (10), and Molokai (2). A summary is provided below of the bridges located on each of the islands. |
