Reburial and Analyses of Archaeological Remains in the Marine Environment — Investigations into the Effects on Metals

Abstract

The treatment and long-term storage of recovered cultural material from underwater heritage sites is becoming less cost effective, and reburial of archaeological sites and the associated artefacts in the marine environment is becoming increasingly common practice in managing the submerged cultural resource. Following recent large-scale underwater archaeological excavations in Marstrand harbour, Sweden, the majority of recovered finds were reburied in defined trenches in the harbour sediment. Subsequently, the Studio of the Western Sweden Conservators in conjunction with the Bohus County Museum initiated a fifty-year research project to evaluate reburial as an appropriate method of preserving waterlogged archaeological artefacts in the long term. The research project, entitled ‘Reburial and Analyses of Archaeological Remains’, was launched in 2002 and consists of six sub-projects. The main aims of these sub-projects are to analyse the extent of deterioration of the most common material types found on underwater archaeological sites, assess the stability of packing and marking materials used in archaeological documentation, and monitor the reburial environment.

The aim of the metals sub-project is to investigate the short- to long-term corrosion behaviour of metals buried in the marine environment by examining the deterioration of reburied and exposed modern metal coupons and eventually compare these results to the analysis of actual shipwreck artefacts. The environmental monitoring sub-project is designed to complement the other sub-projects by assessing the physico-chemical changes occurring in the reburial environment over time and the effect on the deterioration of the different reburied material types. In comparing the results obtained over the past seven years from both the metals and monitoring sub-projects, it should be possible to more accurately evaluate the effectiveness of reburial as a long-term in situ preservation strategy for metallic archaeological remains.     

Conservation of archaeological mosaic pavements by means of reburial

Abstract

In a burial environment ancient mosaic pavements are subject to a variety of mechanisms of deterioration, both physical and chemical. However, many pavements have survived, sometimes in exceptional condition. Additionally, some mosaics that have been discovered in recent times and reburied as a means of protection have also been well preserved. This indicates that reburial can be an effective means of preventive conservation and a viable response to the need for conservation of exposed mosaics on many archaeological sites. For reburial to be successful, risks to the mosaic must be accurately appraised and the design of the reburial must be well specified, following a rigorous conservation methodology.     

Reburial and protective covering of ancient mosaic pavements: The experience of the conservation department of the Israel Antiquities Authority

Abstract

Four case studies are presented illustrating different attempts to protect excavated ancient mosaics by reburial or protective covering, with varying degrees of success, at three archaeological sites in Israel: Tel Itztaba, a site excavated between 1991 and 1994 where planning for reburial at the outset of the excavation could have prevented considerable losses; Khirbet Minya (Horvat Minim), a site excavated in the 1930s, reassessed after four years of reburial; the Promontory Palace at Caesarea Maritima, a site excavated in 1978, partially destroyed by the sea, reburied and regularly monitored since 1994; and an experimental test site at Caesarea Maritima. These examples demonstrate the importance of planning, monitoring and maintenance for successful reburial, and allow an assessment of which materials and methods performed better than others.     

Some considerations for the reburial of painted lime stucco façdesin the Maya region

Abstract

The conservation of Maya stucco façadesin humid tropical conditions poses significant challenges. Professionals in the region consider that reburial is one of the most easily accomplished and cost-effective conservation options; and reburial of modelled and painted lime plaster façades, in conjunction with the construction of exposed replica façadesoverlying the reburied originals, has been or is being considered as a preservation strategy at a number of sites in the region. This is illustrated by two case studies from Belize and one from Guatemala. However, more research is needed to fully understand the benefits and risks of reburial, and to determine the optimal conditions and techniques specifically suitable for wet tropical climates. The range of issues that must be considered for reburial of stucco façadesin this region include their conservation needs in relation to the susceptibility of ancient materials to climatic conditions, management issues such as visitor and interpretation needs and the problem of looting in the region, the feasibility of solutions in relation to available resources, choice of methods and materials used in interventions, and the impact of reburial on the significance of a site, amongst others.     

Reburial research: preliminary field experiments at Fort Selden

Abstract

Preservation through reburial is an effective strategy for cultural sites, and information exists that identifies broad categories of fill type, materials and the below-ground physico-chemical and biological conditions that favour survival of cultural artefacts. This apart, relatively little systematic research and testing has been undertaken on the reburial of archaeological materials under alternating wet—dry conditions, which pertain in many areas of the world where rich archaeological resources exist that are also a focus of excavation. Preliminary field research and testing was undertaken at the site of Port Selden, New Mexico, over an approximate eighteen-month period in 1995–1996 as a precursor to intended longer-term experiments. The ultimate objective was to determine optimal conditions for designed reburial interventions of archaeological materials. Testing was done in pits and on the ground and utilized a standard artefact comprised of adobe and lime as well as several indicator materials (wood, textile, brass). The problems associated with the design of the experiment, instruments and monitoring are discussed, as well as findings relevant to current practice and future testing. The eighteen-month preliminary testing itself followed an earlier (1988) reburial test at Fort Selden in which adobe walls were buried. The results of this test wall experiment are also included here, as they are pertinent to an understanding of the behaviour of earthen architectural materials in the reburial environment.     

The RAAR Project — Heritage Management Aspects on Reburial After Ten Years of Work

Abstract

The general purpose of the international reburial project, Reburial and Analyses of Archaeological Remains (RAAR), is to evaluate reburial as a method for the long-term storage and preservation of waterlogged archaeological remains. Since 2001 material samples have been buried, retrieved, analysed systematically, and the results reported.

RAAR has mainly focused on the degradation of materials commonly encountered on archaeological sites, and on environmental monitoring techniques in order to determine what type of material can be reburied and for how long. The project has concluded that a heritage institution could provide short- or long-term curation for its archaeological archive by using reburial depots provided they are set up according to guidelines and restrictions stipulated by the RAAR project.

However, there are management and legal aspects that need to be discussed and resolved before each reburial project. Actual reburials that have been carried out so far are often a solution to emergency situations and lack collection and management policies. The questions ‘what’, ‘why’, and ‘for how long’ have been forgotten and need to be addressed. The legal protection of a reburial site is also important. This paper discusses these aspects and their consequences and highlights possible differences in approaches between the countries involved in the RAAR project.     

A Critical Analysis and Philosophical Review of ‘Rapid Reburial’: the Clarence project

In 2012, Australian cultural heritage practitioners and conservation scientists collaborated on a national underwater cultural heritage (UCH) reburial project, known as the Australian Historic Shipwreck Preservation Project (AHSPP) funded by the Australian Research Council. This resulted in the excavation, documentation and reburial of the ‘at risk’ shipwreck Clarence. Following the excavation, the site and associated artefacts were reburied and subsequently covered by shade cloth and finally, with polyvinyl chloride (PVC) tarpaulins. After completion of the in situ reburial, a number of critical issues were put into sharp relief including: what constitutes the accurate identification of a site as being ‘at risk’; and the implications of ‘rapid reburial’.     

Chaco Canyon reburial programme

Abstract

Chaco Culture National Historical Park in northwestern New Mexico contains a wealth of archaeological resources, including 150 large earth and masonry structures under active management and preservation. In response to loss of original fabric from exposure over the last 100 years and more, as well as from continuous cycles of maintenance and repair, an extensive and long-term reburial programme was embarked upon in the late 1980s. The overall context of the site and the decision to undertake reburial as a principal conservation strategy is described in Part I of this paper. Part II provides a summary of the results of partial reburial at Chetro Ked, one of the ‘great houses’ of the canyon, in which protection of original timber was the main objective. Most of the wood at Chetro Ked could be covered only by a shallow overburden of soil, necessitating a specialized reburial design and materials to exclude moisture. Recent evaluation of the efficacy of the wood reburial was undertaken. Problems and shortcomings that were identified have led to re-design of part of the reburial and more careful attention to quality control during the intervention, as well as to selection of more appropriate geosynthetic materials. Additional monitoring techniques have been developed to allow direct withdrawal of samples of wood for assessment of deterioration.     

Preservation In Situ for Tourism: An Early Christian Monastic Complex on Sir Bani Yas Island,Western Abu Dhabi,UAE

Abstract

This paper reports on the conservation measures taken to protect and display the remains of a pre-Islamic Christian monastic complex on Sir Bani Yas Island, Abu Dhabi, UAE, and the reasoning behind the decisions. The excavated areas of the site are now partly sheltered, and partly reburied. Observations are made on the effectiveness of the shelter building, and the reburial system used between 1996 and 2010, and on the measures currently being used to preserve plaster floors and faced standing walls in aggressive environmental conditions. Work has been carried out to ?nd ways to make the site as legible as possible while also conserving it. Methods of site monitoring are also discussed.     

The use of geosynthetics for archaeological site reburial

Abstract

Applications of geosynthetic materials in reburial practice include geotextiles for separation, filtration and protection (cushioning); geomembranes and geosynthetic clay liners for infiltration control; geonets and geocomposites for sub-surface drainage; and geocells for erosion control. Mechanically stabilized earth reinforcement using geocells, geogrids and geotextiles can also provide substantial benefits for reburial projects by reducing lateral earth pressure against backfilled structures. Other aspects of modern geotechnology that may be useful for reburial projects include micro-piles and soil nailing for foundation and excavation support and evapotranspirative capping technology to establish the depth of soil cover required to isolate a structure or artefact from moisture and temperature fluctuations. Optimal application of these geotechnologies requires an understanding of the basic engineering principles associated with their implementation, as well as knowledge of the factors influencing archaeological site preservation.     

‘Site unseen’: the case for reburial of archaeological sites

Abstract

The decision-making process for managing and conserving archaeological sites is increasingly accepted as being driven by a thorough assessment of values, physical condition of the resource and the management context. Reconciling the results of these assessments, which may point in different directions, to arrive at a decision that is most appropriate for the resource can be a complex process. When reburial (also referred to as backfilling) is being considered as an option for the preservation of an excavated site (especially long-term reburial), there are particular opportunities and constraints and a host of considerations (stakeholder, technical and management) that need to be taken into account if the values of a place are not to be compromised and stakeholders alienated. For, however beneficial reburial may be from a conservation perspective, it is generally viewed with scepticism or disfavour by those with legal authority over a site, and by those stakeholders who want access to the site for study, education or money-making. This paper examines the rationales for reburial, as well as the objections to it, and puts forth a decision-making model for reburial interventions that takes into consideration stakeholder, technical and management needs.     

Honour thy ancstor's possessions

Abstract

This article addresses the ethics of reclaiming moepū (funerary items) for reburial. It centres around a case involving moepū that were removed from a burial cave, conserved by the Bernice Pauahi Bishop Museum, and reburied. Most significant amongst the funerary items removed from the burial cave were four carved wood images of ancestral deities called ki 'ciaumākua and other personal possessions of highranking chiefs. To explain the traditional practice of placing items with the dead, an overview of the traditional role of moepū is provided. Two opposing perspectives in response to the reburial are then presented. The article concludes that, as with iwi kūpuna (ancestral bones), the conservation of moepū is improper and museums should support efforts to return them to their deceased owners. Only by restoring moepū, to their original context — and thereby their original function — can the responsibility of caring for the ancestors be properly maintained and higher levels of traditional cultural understanding be achieved.     

The reburial of mosaics: an overview of materials and practice

Abstract

A significant proportion of the literature on the reburial of archaeological sites concerns mosaics. These publications reveal that a variety of materials have been used for mosaic reburial, including specialized fill and separation layers, from the early 1980s onwards. Although reburial practice often demonstrates an ad hoc and indiscriminate use of fill and separation materials, or the following of trends and anecdotal information favouring certain materials, knowledge of their characteristics is very important in developing an appropriate technical design for reburial of mosaics. The materials most commonly employed in mosaic reburial practice, including geotextiles, are reviewed and an assessment of their positive and negative characteristics within a reburial design is provided. Recent but limited laboratory and field testing, monitoring and evaluation of reburial interventions have begun to provide preliminary evidence about the behaviour of these materials, indicating which ones are most appropriate and how they should be utilized to best advantage. However, their selection and use remains uneven, and positive results continue to be as much a function of adequate maintenance as proper design and execution.     

Relevance of soil biology and fertility research to archaeological preservation by reburial

Abstract

This paper discusses how soil biological information can help to improve understanding of, and possibly inform decisions about, preservation of organic archaeological remains by reburial. A brief summary of the properties of the soil biological community is followed by an outline of results from recent biological investigations following the recovery of archaeologically relevant materials that had been buried for thirty-three years in one of the experimental earthworks in England UK. Examples from the soil biology and fertility literature are discussed to illustrate the effects of fluctuations in soil wetness and aeration, and of nitrogen availability on decomposition. Finally, the impact of soil handling and physical disruption on biological processes in soil are discussed, as they influence whether soil functions can be restored at a reburial site once the archaeological resources have been ‘protected’ beneath.     

In Situ Preservation and Monitoring of the James Matthews Shipwreck Site

Abstract

Over the past few decades, the archaeological community has been moving away from the more traditional methods of excavation and recovery of underwater cultural heritage towards a less intrusive management approach, essentially involving the preservation of sites in situ. This trend has been politically galvanized in Article 2, point 5 of the Convention on the Protection of the Underwater Cultural Heritage (), which states that ‘The preservation in-situ of underwater cultural heritage shall be considered as the ?rst option before allowing or engaging in any activities directed at this heritage’. Over the years, a number of different remediation strategies have been utilized in order to protect underwater cultural heritage sites in situ, and most of the techniques or combinations thereof involve reburial of sites. Reburial may be an appropriate means of stabilizing and decreasing the deterioration rate of a site, however, there needs to be a holistic approach to the study of the environment, before and after reburial, to gain a full understanding of the changes that are occurring on the site and determine the effectiveness of the technique.

In early 2000, the James Matthews, a copper-sheathed, wooden-hulled vessel wrecked in 1841 south of Fremantle, Western Australia, was identi?ed as being under considerable threat from increased site exposure due to a combination of natural near-shore sedimentary processes and industrial activity in the immediate area. An extensive on-site conservation survey was carried out to establish the state of preservation of the wreck and provide information regarding the physico-chemical and biological nature of the environment prior to the implementation of any mitigation strategy. In 2003 it was con?rmed that further exposure of the site was occurring and devising a management plan was of paramount importance.

Since this time a number of different reburial techniques have been trialled on the site and these include sand bags of differing material composition, polymeric shade cloth, arti?cial sea grass mats made from polyvinyl chloride bunting, and the use of interlocking medium density polyethylene ‘crash barrier’ units in a cofferdam arrangement to con?ne deposited sand. The geological, physico-chemical, and microbiological changes in the burial environments have been monitored over this time. Furthermore, the broader scale, near-shore sedimentary processes affecting the site are being assessed in order to establish the reasons behind the continuing sediment loss. In situ preservation of the iron ?ttings by cathodic protection has also been included in these ?eld trials. In this paper the results from these experiments will be summarized. This information will be used to ?nalize the design of the full-scale in situ preservation strategy for the site and assist in establishing a post-reburial monitoring programme that will measure the success of the adopted remediation technique.     

Towards a benign reburial context: the chemistry of the burial environment

Abstract

The successful reburial of exposed archaeological remains depends on the ability to recreate a benign preserving environment, especially for the desiccated and waterlogged environments that preserve organic and other valuable archaeological material. An introduction to the chemistry of soil and the burial environment is provided, covering the key variables: water, oxygen, cations and anions, pH, organic matter, clay and redox potential. The problems of monitoring these variables and their variation are highlighted. Recent work in monitoring the long-term effects of burial and the steps taken towards modelling actual burial environment chemistry are outlined. Factors to be considered when adding material for reburial are proposed. These include: the avoidance of soluble or potentially soluble minerals; the beneficial buffering effect of clays and organic matter; the minimization of changes in water level, redox potential and pH; and the desirability of retaining the porosity of the burial medium. This can often be achieved by re-using the soil in which the objects/structures were originally buried.     

Partial reburial of West Ruin at Aztec Ruins National Monument

Abstract

Aztec Ruins National Monument is a World Heritage Site in northwestern New Mexico, USA. More than 50,000 visitors come to the site each year, specifically to visit West Ruin, a 12th–13th century, multi-storey Ancestral Pueblo an (Anasazi) village with over 400 rooms. West Ruin was excavated in the early 1900s and was intentionally left exposed for public access and interpretation. The walls, constructed of shaped sandstone blocks set in mud mortar, have gradually deteriorated, despite years of stabilization and preservation efforts. In 1999, park management began to partially rebury portions of West Ruin as a reversible long-term preservation treatment. While partial reburial allows for presentation of the site to visitors, it also results in uneven fill levels in many rooms. Differential fill levels can increase the area subject to migration and capillary rise of moisture through the walls, and can accelerate stone and mortar deterioration on the exposed wall faces. Differential fill levels can also lead to structural instability from unequal pressure exerted between filled and non-filled areas. To mitigate moisture migration and structural instability from differential fills, a soil retention system was designed and tested using layers of synthetic three-dimensional earth confinement cells. This paper discusses the design and implementation of the soil retention system within the larger context of a multi-phased reburial project underway at Aztec Ruins National Monument.     

Methodology,consetvation criteria and performance evaluation for archaeological site shelters

Abstract

The many intersecting issues that arise when deciding whether to shelter an archaeological site should be approached using a values-based methodology, one that has demonstrated its validity arid practical worth in conservation over recent decades. Nonetheless, pitfalls abound in the decision-making process and in establishing effective conservation criteria which should be based principally on a thorough understanding of the threats to the resource and the specific deterioration mechanisms operating, with the objective of creating a shelter that will preserve the site's identified values. An aspect that has received almost no attention in the past is evaluation of a shelter's performance, both qualitative and quantitative, in preserving the site. It is urged that this receive priority when establishing the conservation criteria during the initial phases of a sheltering project. Issues are illustrated from a range of diverse sites, including a number of published shelters. The paper first looks at the examples of the Laetoli (Tanzania) and Lark Quarry (Australia) trackway sites in the context of decision-making and conservation criteria, and then discusses two examples of evaluation: one quantitative, using an experimental shelter and the other discussing publications on a petroglyph site shelter.     

Saving the Sweet Track: The in situ preservation of a Neolithic wooden trackway,Somerset, UK

Abstract

The Sweet Track is the oldest known wooden trackway in Europe. Part of the trackway is preserved in situ in a nature reserve under an active system of hydrological management, designed to prevent damage to the monument from desiccation. The English Heritage-funded project, reported here, was established to assess the condition of the monument and the effectiveness of the management regime. The results have shown that although the trackway is highly deteriorated it still holds a wealth of archaeological information. The decay of the wood probably occurred gradually over several thousand years but the present management regime should be able to ensure its continued survival.