ABSTRACT
The Federal Highways Administration (FHWA) has mandated the Hawaii Department of Transportation, Highways Division (HDOT-HWY) to develop and implement a Plan of Action (POA) for each bridge identified as scour critical to meet the requirement set forth in the National Bridge Inspection Standards (NBIS) regulation, 23 CFR 650.313(e)(3). Then a total of 27 bridges on the islands of Hawaii, Kauai, Maui, Molokai and Oahu were selected as scour critical bridges. This paper lists the timeline of the different phases, and describes how assessment strategies were developed through the site survey, underwater inspection, hydraulic analysis, and design considerations in Phase 1. The potential permitting includes Section 4(f), Section 6(f), Section 106, DA-NWP, ESA/EFH, HEPA-343, Water Quality Control, SMA, BMPP, Shoreline certification and etc. After collect sufficient information, the prioritization strategy was developed based on three key factors: complexity of environmental permitting, priority ranking and construction cost estimation. The priority ranking is a classification system, considering 15 different factors such as locations and importance, ADT, type of highway, inspection rating, load path redundancy, historic of scour, FEMA Flood Map, type of foundations, etc. Then an implementation plan was proposed based on the assessment and prioritization Strategies. Bridges with high repair cost and high permitting requirement will be monitored under a scour monitoring program includes the installation of fixed scour monitors, data collection, data analysis, and the establishment of a prescribed set of emergency procedure to follow in case a “scour event” has occurred. The rest of bridges will be put into construction phase 2 and phase 3 based on the availability of funding in the next 5 to 10 years.
