To comply with Section 106 of the National Historic Preservation Act, the Federal Highway Administration (FHWA) and Iowa Department of Transportation (Iowa DOT) are required to determine the effects of federally-assisted transportation undertakings, including bridge replacements, on archaeological sites. In the past 30 years, hundreds of archaeological surveys have been conducted for local- and primary-system bridge replacement projects. These surveys often require costly and time-consuming subsurface excavation to search for sites that may be deeply buried in thick deposits of alluvial (stream-deposited) sediments. An alternative approach would be to use knowledge gained from previous surveys to assess the archaeological potential of a proposed bridge replacement project before, and if possible instead of, committing resources to an archaeological survey. All the information needed to make such assessments, including archaeology, soils, geomorphology, and land-use history, can be assembled, viewed, and analyzed using Geographic Information Systems (GIS). In this report, the University of Iowa Office of the State Archaeologist (OSA) explores the feasibility of using GIS data to evaluate archaeological survey needs for Iowa DOT bridge replacements. The resultant Bridges Decision Support Model integrates information on archaeological sites, surveys, bridges, and their geological contexts. The model will help streamline the Section 106 process by facilitating communication and information transfer; by providing consistent, well-informed, and uniformly-applied decision criteria; and by improving the cost-effectiveness of cultural resource compliance.

In accordance with Executive Order 11593 and other applicable federal laws and regulations a Phase I archaeological survey was conducted in September 1994 of approximately 8.1 ha (20.2 acres) for three proposed bridge replacement areas on the Fort Knox Military Reservation, Hardin and Meade Counties, Kentucky. The survey resulted in the recording of two archaeological sites, 15Hd497 and 15Md382, and revisiting of two previously recorded prehistoric sites, 15Hd170 and 15Hd209. None of the sites is eligible for the National Register, due to previous disturbance. No additional archaeological work is recommended for 15Hd17O, 15Hd209, 15Hd497, or 15Md382. Due to the potential for deeply buried cultural deposits, it is recommended that any machine excavations on the left bank of Mill Creek at Bridge 10, and on the right bank of Otter Creek north of the existing bridge be monitored by a qualified professional archaeologist. Alternatively, test trenches could be excavated in these areas in advance of the bridge construction. The other portions of the Bridge 7, 10, and 12 project areas do not require monitoring of construction excavations.