VAFB-2006-06: Archaeological Survey and Exploratory Backhoe Trenching for the Proposed Replacement 13th Street Bridge on Vandenberg Air Force Base, Santa Barbara County, California

This document is a report that describes the results of a 6.0-acre archaeological survey conducted by Applied EarthWorks, Inc. The work was conducted in support of the environmental assessment and conformity analysis for construction of the replacement 13th Street Bridge, Vandenberg Air Force Base (VAFB), California. A literature and records search was performed as well as a surface and subsurface survey of the proposed project area. The proposed replacement bridge is to be constructed in the Santa Ynez River floodplain and adjacent low terrace where alluvial deposition can be rapid and archaeological resources might be buried. The nearest archaeological site, CA-SBA-3744, illustrates this point as it has been buried by 5 feet of alluvium. Although it is outside the Area of Potential Effects (APE), its proximity underscores the potential for encountering similar deposits during construction of the new 13th Street Bridge. Therefore, most of the fieldwork was directed toward a subsurface survey using backhoe trenching. The report includes a management recommendation section that states archival research indicates that no archaeological sites were previously recorded within the APE for the proposed new 13th Street Bridge alignment. In addition, Æ’s surface survey and subsurface trenching found no evidence of archaeological deposits within the APE. However, the 13th Street replacement bridge is to be constructed in the Santa Ynez River floodplain and adjacent low terrace where alluvial deposition can be rapid. Stratigraphy exposed in trench profiles confirms the presence of deep alluvium. The closest recorded archaeological site, CA-SBA-3744, is buried by alluvium, illustrating the potential for buried archaeological deposits. Consequently, the replacement 13th Street Bridge project APE is considered an archaeologically sensitive area. It is the policy of Vandenberg AFB to require monitoring during construction in archaeological sensitive areas (Integrated Cultural Resources Management Plan [ICRMP] 2005). Therefore, Æ recommends archaeological and Native American monitoring during ground disturbing activities resulting from the construction of the replacement 13th Street Bridge. In the event that previously undocumented cultural resources are discovered during monitoring of construction activities, guidelines set forth in the Vandenberg AFB ICRMP (2005) will be followed.