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40 4b El Technical Approach X nage 16 TASK 11 PERFORM MAGNETOMETER SURVEY OF BORROW AREAS A cultural resources assessment based on a magnetometer survey of the north, central and south borrow areas will be prepared in accordance with standards established by the Florida Department of State, Division of Historical Resources, and applicable Federal standards and guidelines. This includes reviewing available information from the Florida Site File at the Florida Department of State, Division of Historical Resources, and other published sources of archeological and shipwreck information. Such review will be conducted in accordance with the provisions of the National Historic Preservation Act of 1966, as amended, as well as the provisions contained in Section 403.918(2)(a)6, Florida Statutes and the "Standards for Conducting, Reporting, and Reviewing Archeological and Historic Site Assessment Survey Activities" of the Florida Department of State, Division of Historical Resources. This review will be undertaken in advance of any field work, with the purpose of determining potential impacts to prehistoric archaeological sites or historic shipwreck sites. A detailed magnetometer survey of the three potential borrow areas will be conducted. The detailed bathymetric survey (conducted in Phase 1) and the Borrow area compositing efforts completed in Phase I will guide the exact survey grid boundaries required. The magnetometer survey will provide data concerning the presence, location, and magnitude of magnetic anomalies in the proposed borrow area associated with ferrous objects that could be of potential archeological or historical significance. The side scan sonar survey (also completed under Phase I authorization) provides acoustical imagery of the bottom topography in the borrow area containing information on physical characteristics, such as exhibiting either surficial or emergent hardbottom resources and/or dense shell hash surface concentrations. The survey team will obtain magnetometer information on each track line (sweep) by employing a Barringer Research Ltd. Model M-234 Proton Magnetometer (or equivalent) with marine sensor and sensor depth transducer unit deployed from a suitable survey vessel along the track lines at speeds between four (4) and five (5) knots. The magnetometer will operate at a cyclic sampling rate of one (1) cycle per second and the magnetometer sensor will be towed no more than ten (10) feet above the bottom. Vessel positioning will be accomplished with differential GPS. Track lines across the long axis of the grid will be performed at an on -center spacing of one hundred (100) feet to obtain sufficient coverage for detection of potentially significant magnetic anomalies. Supplementary magnetometer survey track lines will be run as necessary to further assess and pin -point potentially significant magnetic anomalies or to verify the absence of cultural resources. Scaled maps of the borrow area bathymetry and the magnetic anomalies detected within the limits of the survey will be plotted. In addition, an underwater archeological survey technical report will be prepared in accordance with the "Standards for Conducting, Reporting, and Reviewing Archaeological and Historic Site Assessment Survey Activities" of the Florida Department of State, Division of Historical Resources and applicable Federal standards and guidelines. This report will be titled, "Underwater Archaeological Background Study and Remote Sensing Survey for the Indian diver Beach Nourishment Projects."