USING SONICORES AND LARGE SCALE EXCAVATION TO EXAMINE DEEP FILL DEPOSITS, BURIED ARCHAEOLOGICAL MATERIALS AND THE HOLOCENE BOUNDARY ALONG SEATTLE'S HISTORIC WATERFRONT

Over the past two years, more than 50 sonicores have been drilled up to 50 feet deep along Seattle’s waterfront in association with the Alaskan Way Viaduct Moving Forward Project. The purpose of coring was to study deposits that are at depths deeper than typical archaeological excavations can reach. The sediments recovered were sampled and screened, as they would be in a normal excavation. Until recently, almost all of our data on the historic landmaking activities that transformed the Elliott Bay tidelands into suitable business and residential property originated from the logging and analysis of these boreholes. This season, we conducted large scale excavations that allowed us to test the predictions that were developed during coring. Most importantly, predictions concerning the potential for encountering archaeological resources. Analysis of both sonicore and excavation data has resulted in identification of four temporally discrete zones of historic fill overlying Holocene- and Pleistocene-aged sediments. The updated stratigraphic assemblage will be used to better identify areas with the highest potential for archaeological materials to be avoided during future construction.