CCI Newsletter, No. 29, June 2002

CCI in the Field

by Carol MacIvor, Senior Communications Advisor, Information Services and Marketing

In addition to the work carried out in CCI's own laboratories, many staff members participate in projects in other locations.

Nancy Binnie, a conservation scientist at CCI, participated in three field trips in 2001 related to managing resources at submerged archaeological sites. An accomplished scuba diver, her work included carrying out activities that are part of monitoring programs designed to track long-term in situ deterioration, as well as looking at possible ways to stabilize previously excavated shipwreck sites. One of the commonly used techniques being considered as a long-term preservation option is the reburial of artifacts and endangered sites.

The first site visit was to the Fortress of Louisbourg. In conjunction with the Underwater Archaeological Services Unit of Parks Canada, monitoring activities were carried out here on the wrecks of the Célèbre and the Prudent — two French warships sunk during the final siege of the Fortress of Louisbourg in 1758. As recreational diving activities are restricted in Louisbourg Harbour, wrecks in this area have not been stripped of artifacts (unlike sites outside the harbour boundary where treasure hunting is permitted under Nova Scotia law). Divers who want to visit Louisbourg Harbour can do so, but must be accompanied by an approved guide, and must follow strict zero-impact diving requirements. The monitoring program that was conducted included an assessment of certain artifacts or structures for any change in position and physical damage, as well as an assessment of the condition of corrosion-concretion layers on cannons and the erosion rate of the exposed timbers. Two marine archaeologists from the U.S. National Park Service also participated in this work; they were part of a professional exchange with Parks Canada staff who had visited the USS Arizona site at Pearl Harbour earlier in 2001.

The second field trip was to the Bruce Peninsula/Fathom Five National Marine Park located in Tobermory, Ontario, where measurements were taken of the corrosion rate of iron samples in six underwater test stations. This work was part of a continuing project designed to complement the Park's shipwreck monitoring program in which a number of the historic wrecks are surveyed annually to detect any changes to the timber structures and certain artifacts (changes are an indication of destabilization of the sites). Knowledge of the long-term corrosion rates, as well as the factors that destabilize the metal and timber components, provides information about how long the shipwrecks will remain intact for the thousands of divers who visit the park each year. Work here included recovering iron samples for laboratory analysis, repairing a damaged sample holder, general photography, and assisting the park with monitoring program assessments. The two oldest corrosion test stations have been in situ for 5 and 7 years, and samples have usually been recovered annually. The other four smaller test stations were installed in 1999 and will not be recovered and analysed until 2004.

The third site visit was to the Restigouche National Historic Site (NHS) near Campbellton, New Brunswick. Again working for the Underwater Archaeological Services Unit of Parks Canada, survey work was carried out on two French gun ships — the Machault and the Bienfaisant — both sunk in the Restigouche River in 1760 during the Seven Years' War. The Machault site had been excavated previously (between 1969 and 1972), at which time Parks Canada retrieved and conserved many artifacts and a large section of the vessel. Many of these artifacts can be seen at the Restigouche NHS visitor centre, and an exceptional collection of ceramics from the Machault has been exhibited at the Fortress of Louisbourg. The Bienfaisant site had never been excavated or surveyed previously.

The main purpose of this site visit was to locate the two wrecks and determine the best way to stabilize the shifting river sediments, which periodically cover or expose the remaining structures and artifacts. Survey work for other scuttled vessels was also carried out using target locations found through historical research. Samples of marine organisms including algae were taken from the ships' timbers, as well as water samples; these samples were analysed and the results will be used to help define the preservation conditions and the long-term risks from biodeterioration.

Work on this project was hampered by strong currents and poor visibility in the shallow, intertidal, sediment-rich water; the river bottom was also strewn with pulp logs, trees washed down the river, and other debris. In spite of these complications the Machault site was readily located (although it was partially covered with more sediment than had been observed during a visit 2 years earlier). But even after 3 days of searching the Bienfaisant remained elusive. Unfortunately, it is impossible to know for sure exactly why this wreck could not be found. It could be that the search was conducted in the wrong location (after all, modern methods such as GPS were not available in the 1970s when the site was first located) or it could be that the profile of the river bottom had undergone significant changes and was now obscuring the position of the wreck.

Conducting work on-site is an important aspect of CCI's professional commitment to heritage preservation, and the Institute is pleased to offer a wide range of such services. For more information, please contact:

Client Services
Canadian Conservation Institute
1030 Innes Road
Ottawa ON K1A 0M5

tel.: (613) 998-3721
fax: (613) 998-4721
e-mail: cci-icc_services@pch.gc.ca