2.0 Project Description and Location

 In the fall of 2000, Sea Surveyor, Inc. of Benicia, California conducted an intensive marine geophysical investigation for the U.S. Army Corps of Engineers, San Francisco District under Contract No. DACW07-98-D-0002 at the five sites in central San Francisco Bay (Sea Surveyor 2001).  In conjunction with that contract, and in compliance with the environmental review required in Section 106 of the National Historic Preservation Act of 1966, William Self Associates (WSA) of Orinda, California conducted maritime archaeological research as a subcontractor to Sea Surveyor, Inc.  The maritime archaeological research was conducted in conjunction with the geophysical investigation of the five rock formations to determine the possible impact of the San Francisco Bay Rocks Removal Project on submerged historic properties, particularly the remains of shipwrecks

 The five geologic rock formations are situated in the central portion of San Francisco Bay, California.  Blossom Rock is located southwest of Alcatraz Island, near the North Point of San Francisco, while the other three underwater rocks are situated between the west side of Alcatraz Island and the Golden Gate.  These three underwater rocks create a crescent shaped navigation hazard, approximately 4,000 feet wide, with Harding Rock on the northwest end, Shag Rocks in the middle, and Arch Rock to the southeast.  When combined with Alcatraz Island, these underwater rocks create a 9,000 foot-wide (1.7 mile) barrier to deep draft shipping, two miles east of the Golden Gate in San Francisco Bay.  The fifth underwater geological feature, informally referred to as "Unnamed Rock," is located about a half-mile closer to the Golden Gate than the crescent formed by Harding Rock, Shag Rocks, and Arch Rock.  Based on the geophysical data collected as part of this project, Sea Surveyor, Inc. has proposed the name "Golden Gate Mound" as one more appropriate for this unique underwater geological feature (Sea Surveyor 2001:1). 

 As part of the maritime archaeology study, Sea Surveyor, Inc. conducted a magnetometer survey of the five areas, and WSA, in conjunction with Sea Surveyor, Inc. conducted additional acoustic surveys over Blossom, Harding, Shag, and Arch rocks[1] using a high-resolution, 600 kHz side scan sonar system.  WSA archaeologists analyzed the shape, surficial expression, size, acoustic shadow, and association of these targets during post-survey data processing and correlated them with the magnetic anomalies identified during the magnetometer survey.  The analysis determined that most were either non-cultural in origin (i.e. exposures of the rock substrate) or culturally non-sensitive (i.e. isolated pieces of debris, shattered rock associated with earlier demolition, etc.).  Seven of the targets were initially identified as potential maritime-related cultural resources.  In subsequent re-analysis of the data, all but two of these were eliminated from further considerations of significance, as they were identified as various types of debris.  Each of the seven targets are discussed in the following sections.