Page 191 - Manual for Activities directed at the Underwater Cultural Heritage

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should be immediate and minimal. They should be stable, reversible and recorded.
• Preserving in situ versus recovering objects
The reasons for the recovery of artefacts must be well defined prior to the commencement of any excavation project. The scientific reason for the project should outweigh the damages caused by the artefact extraction to the integrity of the site. In addition to the financial support for conservation, storage or exposition has to be assured. Months and often even years can elapse between the discovery of an underwater site and initial probes, actual excavation and the raising of objects.
Leaving artefacts on site
 Displacing an artefact from a site changes its integrity, as the site is no longer complete. It also extracts the object from its authentic context, so that a very comprehensive documentation is needed to avoid depriving it of its historic sense. It is therefore often wise to leave sites intact for the scrutiny of future generations, in abidance of the principle in Rule 1. There is also the issue of the financial burden posed by excavation and the ensuing need for conservation and storage. These considerations have led to the gradual
 © Parks Canada. Scheme
for the reburying of structural elements on a Basque whaling vessel, Red Bay, Canada.
The issue of reburial as a long- term preservation strategy and
its effectiveness is of utmost importance to the field of maritime archaeology. Reburial involves the deposition of archaeological materials beneath sediments in a marine or wet environment in an effort to create anaerobic or anoxic conditions that inhibit the growth of
bacteria and limit other harmful organisms. Systematic monitoring of reburial sites is of the highest importance for all in situ preservation treatments because the archaeologist or conservator cannot fully predict the long-term suitability of the reburial context. Practical and experimental studies of reburial have been undertaken in several different contexts involving various species of wood, different types of sediments, and var ying depths.
A major reburial experiment using archaeological and modern wood was conducted by Parks Canada on a Basque whaling vessel in Red Bay, Labrador.
Here, archaeologists disassembled and documented more than 3,000 timbers and fragments
from a fully excavated wreck,
after which reburial was carried out in the excavation pit.Timbers were stacked in 3 layers with
20 cm of sand above each layer. The researchers surrounded the timber and sand mound with 36 metric tons of sand contained within 1,200 recycled plastic
salt bags. Rock fill was placed outside of the sandbag circle, and a 3.6 mm Hypalon tarpaulin was positioned over the mound and held down by 60 concrete-filled tires.Water-sampling tubes were installed so that water chemistry could be tested inside
Conservation and site management