Most archaeological test excavation is restricted to the top metre of the soil profile, if not the top 30 cm. The need to shore-up or step-back deep excavations has, in the past, constrained the testing of deep deposits, such as those within alluvial and colluvial contexts. The depth of the water table is also a major constraint as further excavation generally results in unsafe and/or collapsing pits. This absence of testing has limited the ability to detect very deep, and thus very old, archaeological material.
Testing methods employed by NOHC on the Woodburn to Ballina Pacific Highway project (for the NSW Roads and Maritime Service), now address this issue by using a bucket auger. This has allowed us to test to a depth of 3 m within the alluvial profile adjacent to the Richmond River, Broadwater, NSW. This includes a profile 2.5 m below the water table.
