Complications and Effectiveness of In Situ Preservation Methods for ...

conservation and mgmt of arch. sites, Vol. 14 Nos 1–4, 2012, 469–78

Complications and Effectiveness of In Situ Preservation Methods for Underwater Cultural Heritage Sites Sorna Khakzad and Konraad Van Balen Raymond Lemaire International Centre for Conservation, University of Leuven (KU Leuven), Belgium

Underwater Cultural Heritage (UCH) as an outstanding division of the cultural heritage of humanity appears to be crucial and complicated when more general issues regarding preservation and conservation are raised. The essence of in situ preservation should be equally discussable for any kind of archaeological remains; on land or underwater. There is a long history of different methods and concepts of intervention in a variety of sub-aquatic archaeological sites; from shipwrecks to submerged settlements. This paper will present an introduction to different techniques and theories of preservation and conservation of underwater cultural and archaeological sites since this kind of heritage has scientiﬁcally been explored and studied. A range of different preservation methodologies, from total or partial transference inland, to preservation underwater, will be compared; the advantages and disadvantages of each option will be highlighted. Different examples of international best practices will be illustrated. Different types of in situ conservation/protection will be explained and categorized. Furthermore, there will be a focus on the UNESCO Convention of 2001 on Conservation and Preservation of UCH, where the in situ conservation option has been recommended. Moreover, the technical issue for preservation of UCH sites, either in situ or after displacement, will be explained. The implication of relocation for different sorts of sites and materials will be argued; for example, cases where some sites, such as shipwrecks, would more easily be displaced compared with submerged settlements, villages, or ports. Finally, by stressing that the state of ‘being underwater’ makes many sites qualiﬁed to be regarded as UCH, the in situ preservation approach will prevail that this state is maintained. keywords underwater cultural heritage, in situ conservation, evaluation systems © W. S. Maney & Son Ltd 2012

DOI 10.1179/1350503312Z.00000000040

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SORNA KHAKZAD and KONRAAD VAN BALEN

Conservation and treatment methods: why and what? The UNESCO Convention on the Protection of Underwater Cultural Heritage (2001) recommends in situ conservation as the best means of protecting cultural heritage underwater. Missing, however, is recognition of different types of cultural heritage underwater, each of which may require different kinds of treatment, and there is no common set of criteria governing the assessment of all materials. This paper has two goals: to highlight the differences between the variety of conservation and protection methods in order to demonstrate that each site has particular characteristics; and to offer a preliminary outline of a common assessment process within which these particular characteristics and needs may be best determined. Ideally, this process may be integrated into the gradually progressing body of international legislation regulating the protection and preservation of cultural heritage underwater. It worth mentioning that protection, according to Charter for the Protection and Management of the Archaeological Heritage (1990) as well as UNESCO Convention for the Protection of the World Cultural and Natural Heritage (1972), falls under the legislations and policies of each nation regarding the protecting their cultural assets by enforcing laws. Conservation includes actions and management on a site in order to stop or reduce the erosion process and to stabilize the site condition. Following is a brief introduction to different methods of intervention in underwater cultural sites. Some project examples are presented, to show different scenarios in order to highlight the criteria which should be considered crucial while treating different types of underwater sites.

Displacement, moving onto land This classical method of excavation is usually followed by the study and conservation of objects and display in museums. This process is similar to the classical archaeology of materials found on land. There are examples of sites which had to be moved onto the land due to the danger of being submerged. Abu Simbel Nubiam Monument in Egypt is a good example of this type of project. Through relocation of the site, the risk of its submergence was eliminated. There are examples in which the submergence occurred a long time ago, such as shipwrecks: the most popular ones are Vasa and the Mary Rose, amongst others. In these cases the sites were excavated and the objects and all parts of the wreck remains were moved on land. Again the approach was a classical method of excavation of an archaeological site underwater. These cases show different situations in which the best decision was made according to current available technology, current identified priorities of protection and conservation due to natural and human impacts, and expected benefits, for example for educational purposes, and for safeguarding the values of the heritage.

In situ methods for conservation, protection, and presentation of underwater sites With the advent of new techniques and theories, new methods of excavation, protection and conservation of archaeological sites, either on land or underwater, have been developed. The idea of in situ archaeological parks and museums is not a

IN SITU PRESERVATION METHODS FOR UNDERWATER CULTURAL HERITAGE SITES

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very new topic for terrestrial cultural sites. Nevertheless, for underwater cultural heritage, this method brings more complications due to the special environment, although at the same time it is strongly recommended by the UNESCO Convention 2001. According to the first rule of the annex of the UNESCO Convention on Protection of Underwater Cultural heritage, ‘The protection of underwater cultural heritage through in situ preservation shall be considered as the first option’. In situ conservation/protection can be considered as one of the most convenient methods of safeguarding the significance and location of UCH. Being underwater is a quality which makes the sites underwater eligible to be regarded as underwater cultural heritage. Simply stated, objects or site out of water have not this ‘quality’ anymore. As mentioned in the UNESCO Convention 2001: ‘once out of the water and exhibited on land, objects from submerged archaeological sites are deprived of their context and lose part of their significance’. However, if the intervention significantly contributes to the protection, enhancement of knowledge, or condition of the UCH, the action may be authorized. Additionally, in situ conservation may protect the original condition of the site after sinking, and reserves the possibility of using more advanced techniques in the future. Underwater cultural heritage are like a ‘time capsule’ (Muckelroy, 1978: 55) and as long as they are protected underwater they hold valuable historical, archaeological, and natural data. By moving them out of water this information will be scratched or might be lost. Submerged and buried maritime heritage often exists in an environment that, without disturbance, is conducive to the long-term preservation of a variety of archaeological materials (Corfield, 1996: 32). In situ preservation is based on the concept that certain environments are capable of slowing deterioration. As (Holden et al., 2006: 59) indicate, it is this very process that allows archaeologists to uncover the past through excavation. Once these sites are disturbed, chemical, biological, and physical forces begin to destroy the fragile stability of the sites. In situ conservation is a general term for protecting and conserving underwater sites using different methods. However, looking at different international projects and going through literature, a variety of methods and implementations of in situ conservation are identified (Delgado, 1997). Therefore, it is important to be clear about the specific methods of in situ conservation/protection used when discussing this in a scientific context. This paper suggests categorizing different in situ conservation methods according to the similarity in their approaches as follows:

In situ protection In some cases any large-scale scientific intervention of underwater sites is impossible due to the high economical cost or due to technical difficulties; however, the sites might be under threat from natural erosion or human intervention (such as fisheries or anchorage). In these cases, rather simple in situ protection methods can be used such as covering a site or restricting access can guarantee protection of the sites (Figure 1). The examples of this method can be seen in some countries such as Turkey where the government has limited access, diving and even snorkelling on some underwater sites. Considering the fact that Turkey has a large number of underwater sites (from shipwrecks to submerged cities) in situ protection on all sites is not possible, therefore the damage to sites has been reduced through government regulation (Strati, 1995).

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figure 1 In situ protection, trapezoid protective cage, Cape North of Rab Island, Croatia. © UNESCO

In situ conservation In situ conservation covers a wide range of techniques and forms. This method involves intervention in the sites and sometimes can be combined with reburial. There are remarkable examples of different kinds of in situ conservation techniques that still allow access for visitors, such as in Croatia (Figure 1). In the case of the underwater Roman villas in Baiae, Italy hydraulic mortar has been injected between the brick to conserve the walls from collapsing (Davidde, 2002) (Figure 2).1 There are variety of in situ conservation techniques, such as cathodic protection using sacrificial anodes, which are suitable for iron and metal artefacts. The use of sacrificial anodes for iron artefacts by MacLeod on the Sirius site (MacLeod, 1996a; 1996b), while promising in terms of in situ developments, was originally intended to provide increased stability of the object in conjunction with conventional forms of retrieval and treatment. In many cases, the use of cathodic protection stabilizes the artefacts in situ but the site is still accessible to visitors underwater (MacLeod, 1998).

Reburial In terms of archaeological use of in situ preservation, reburial is the first method to be used regularly by attempting to create a more stable reburial environment, slowing chemical, biological, and physical deterioration. This can be accomplished in different ways, such as backfilling of excavated sediment, installing various forms of barriers and encouraging sediment deposition on site (Oxley, 1998a: 97–100, 104; Oxley, 1998b: 159). Both the natural conditions and the material which is used for reburial have a big impact on the effectiveness of this method. Continuous monitoring is required in order to ensure preservation in the long term.


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figure 2 Underwater ruins of a Roman villa and the replica of a statue, Baia, Italy. © http://underwaterarchaeologicalparkbaia.blogspot.com

The idea of using a physical barrier to protect sites is based on the notion that the original burial site created conditions conducive to preserving archaeological materials (Harvey, 1996). Recreating or imitating the original conditions should, in theory, provide similar protection (Oxley, 1998a: 91). Barriers can include sandbags and geotextiles while sediment deposition can be encouraged with mats of artificial sea grass, debris netting, or geotextiles (Oxley, 1998a: 100–04; Oxley, 1998b: 159, 165). Each of these techniques has its own inherent advantages and disadvantages. For instance, finer sediment such as sand is often carried away by currents before it has a chance to settle on site (Oxley, 1998b: 168). Heavier sediments, such as gravel, are more successful, though questions remain about whether or not this can damage the site (Oxley, 1998b: 168). While this form of reburial may be cost effective, Oxley (1998b: 168) notes that planning in terms of site environment, type of sediment used, and how the drop is to be completed are key elements in ensuring the success of this technique. Another method of encouraging sediment deposition that has been successful in some situations has been artificial seagrass. Seagrass occurs naturally on many sites, but, once disturbed, is unlikely to re-establish itself (Godfrey et al., 2005: 15, 51). However, the presence of bacteria which can gradually penetrate into the different kinds of protective layers and in any depth (Fazzani et al., 1975), keeps reburial still to be a debatable technique for long-term protection. From a preventive conservation approach it is advised to install monitoring tools when reburying to be able to follow the state of preservation while the objects and the site will remain invisible.

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In situ preservation and presentation Some projects present novel approaches to conservation, protection, and display of UCH such as: underwater parks, aquariums, submerged museums, remote sensing, and so on. The implementation of those cases very much depends on the natural environmental conditions, as well as the available technologies and the economic circumstances of each project. Some of these examples use a combination of different methods, such as in situ conservation, reburial as well as relocation of the artefacts together with major interventions in the site by inserting new buildings or access path, which are often innovative and are unique in their design and approach. Examples include the Baiheliang Underwater Museum in China (Figure 3), the underwater museum of Alexandria in Egypt, and the underwater wreck park in Florida. In the first two examples, new techniques and technology were applied to construct infrastructure underwater, in order to prepare a suitable space for underwater sites and artefacts for which no diving was required to visit them. However, in the underwater shipwreck parks (Florida’s museum in the sea, 2007), the wrecks are conserved in situ (or in similar situ where some sites or object are moved to another location in water where a similar condition of water and nature would be maintained) and visitors with diving equipment can follow the trails and gain information from the text boards which are installed underwater. In these cases a combination of different conservation methods, such as continuous in situ conservation, reburial, and protective measures

figure 3 The construction of the Baiheliang Underwater Museum, China. © UNESCO


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have been applied. Since these methods are very diverse and mostly quite recent, the impact of the applied in situ conservation techniques are not yet clear and should be monitored and reported in the long term (Manders, 2004).

Considerations The application of in situ conservation techniques not only can preserve an underwater cultural heritage site in its original location but can also preserve the site for future research with the advent of new technologies and innovations. The relocation if needed of shipwrecks and objects is considered feasible. In case of submerged sites that once were above water and are endemic (as immerged harbours or cities, prehistoric landscapes . . .) relocation is mostly not an option. In the consideration of any kind of cultural heritage site it is important to define the aims of any activity to be undertaken. After proper evaluation of the heritage values of a site, the best conservation and/or excavation methods can be chosen. One example of a project without consideration of the possibilities and consequences of the intervention is the relocation of a metal shipwreck in Iran with the significance being the first steam engine ship used in this country (Figure 4). Awareness raising and presentation of UCH to the public are as important as research and study of the sites themselves. Therefore, in choosing a methodology for excavation, conservation, and protection, all the aforementioned issues should be regarded as imperative. In addition, monitoring after any kind of intervention is an inevitable task in any long-term management plan.

figure 4 Relocating a metal shipwreck on land, without planning for its proper treatment. Persepolis shipwreck, Maritime Museum of Bushehr, Iran.

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As shown in Table 1, a simple matrix is suggested to assess different kinds of intervention according to the significance of the submerged sites. This matrix is a simplified version of some evaluation matrixes; each component of this matrix has more issues to consider. In order to evaluate which method might be the most appropriate, several matrixes have been developed in the author’s Master thesis (Khakzad, 2008) and offer an evaluation tool based on international convention, best practices, and the author’s experiences in the field. There are several tools to define the significance of land sites, such as the criteria for World Heritage Listing, the Nara document on Authenticity (Nara Document on Authenticity, 1994), and so on. These documents provide a harmonized tool to assess the significance of different kinds of sites in the world. Each factor is evaluated for each method, however, the degree and possibility for each method is relative. For instance, protection for the sites and objects which are moved inland is highly depends on the treatment after recovery, the techniques available for the project in different areas, and budget. If all the variation comes along, then the protection is considered ‘High’. Therefore, this matrix is useful, when all the aspects for management of a site has been well foreseen in advance. So in line with the UNESCO Convention on the Protection of UCH (UNESCO Convention, 2001) in order to have a more comprehensive and practical framework, it is important to bring the outcomes of different international projects and documents together in order to use these results and experiences to create an inclusive evaluation tool. TABLE 1 A SIMPLE MATRIX TO COMPARE AND EVALUATE DIFFERENT TREATMENT METHODS WITHIN THEIR PRACTICAL ADVANTAGES AND DISADVANTAGES Facts Method

Protection

Conservation

Visit

Location significant

Monitoring

Move in land

High If the site treated well inland

Mid to high too problematic

Possible Usually

Lost Underwater significance

Easier & economical

In-situ

Mid to high Depends on State party or country’s regulation

Varies Possible/impossible Preserved due to monitoring, (dependent on original location method, context & the method/s used) & material material

Not easy & expensive (Compare with land methods)

Reburial

Mid to high Depends on State party or country’s regulation

Varies due to monitoring, method, context & material

Not possible Only virtually, providing replica or virtual reconstruction

Varies could be done in a different location

Not easy & expensive (Relative to where and what is applied)

Other

High In most cases

Varies due to techniques Mid to high

Possible diving, remote, Underwater museum, aquarium, etc

Varies Dependent on in-situ or the method in-similar-situ (displacement of the site to another underwater location where the original water condition is maintained.)


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Conclusion The necessity of a standardized evaluation tool in order to have a base, nationally and internationally, to define the values of a site and justify the application of certain actions on different sites has been highlighted. This tool is being further developed in the author’s PhD dissertation. This evaluation tool offers a common language and terminology in order to measure the level of significance and condition of different sites. The very simple version of this system (Table 1) can work as a checklist which can be filled in by experts. This tool will help to define in situ conservation/protection methodology as well as assessing the success of a project and the effectiveness of the applied technique/s in a standardized way. The importance of in situ conservation in preserving the significance of sites and reserving the right for future techniques and innovation for further studies, visiting and accessibility possibilities has been highlighted. Some of the more recent in situ preservation techniques such as underwater museums, displacement to another underwater location and aquarium are so diverse in nature and design that it is difficult to judge their long-term impacts on the underwater cultural heritage. There are factors which might cause changes in the present condition of the sites; to mention a few, the impacts of climate change on water parameters and natural environment, or urban and industrial development and their impact on geological and biological features of the underwater environment. Therefore, for these kinds of projects a high quality monitoring system should be implemented and the successful examples considered as models for similar cases.

Note 1

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Notes on contributors Sorna Khakzad is a PhD Researcher at the University of Leuven (KU Leuven), Belgium. Architect MSc (Azad University of Tehran, 2004), advanced study in Conservation of Monuments and Historic Sites (KU Leuven, 2008). Her PhD deals with management of UCH. She worked as architect-cultural heritage specialist in national and international projects, a member of SPLASHCOST, received awards from UNESCO-Vocations Patrimoine and World Learning Center (USA). Correspondence to: Sorna Khakzad, 01 Arenberg Castle, RLICC Office, Heverlee, 3001, Belgium. Email: [email protected] Koenraad van Balen, PhD engineer-architect, is a Professor at the University of Leuven and Director of the Raymond Lemaire International Centre for Conservation; he is involved in various international research projects dealing with heritage preservation and on construction materials. Correspondence to: Koenraad van Balen, Kasteelpark Arenberg 40, B-3001 Leuven (Heverlee), Belgium. Email: [email protected]