Turkmenistan : Merv
Preventive Conservation in Merv
World Heritage Review
The oasis of Merv, which formed a major centre of civilisation in Central Asia is home to a series of adjacent walled cities of different periods dating from the Bronze Age to the 18th century AD. From these vast human settlements, large number of archaeological remains and standing monuments can still be observed today.
Ancient Merv, inscribed on the World Heritage List in 1999 under criteria (ii) and (iii), is situated at the edge of the Karakum desert, at the crossing point of the Murghab River and one of the major west-east trade routes to Bukhara and Samarkand. The oasis occupies an area of 1200 hectares on the flat landscape created by the alluvial delta fan of the Murghab River.
Many architectural remains can be seen in the Park, particularly from the last two millennia. The main building materials used for construction are mud bricks and fired bricks. The architectural remains are subject to erosion caused by rain and snow, accelerated by the Northwest wind. They are also exposed to rising damp and salts resulting from the raised water table, since the construction of the Karakum canal in the 1950s, leading to serious undercutting of walls. Finally, insufficient control of land use and visitor access also accelerates the deterioration of the fragile earthen architectural structures.
State of conservation
Although some monuments have been restored during the soviet period, and some others have been excavated by archaeologists, most of them have been neglected for ages. This results in a great variety of situations. Everybody draws attention to the regular deterioration and continuous collapse of the structures. The intensive irrigation policy and the use of inadequate conservation techniques during the soviet era have accelerated the decay processes in the second half of the 20th Century. A great number of standing structures (Ice houses, defensive walls, Köshks, etc…) and archaeological sites require urgent attention.
Recent conservation efforts
Conservation skills and techniques have been developed since 2001 in Ancient Merv, thanks to the efforts of various organisations including the UNESCO World Heritage Centre, the World Monuments Fund, the University College London and CRATerre-EAG. After 4 years of documenting, monitoring and conserving selected site structures, the problems are now better understood and appropriate conservation techniques have been developed. Strong partnerships have also been achieved between the Turkmen and Foreign expert, and between the archaeologists and the conservators, who work hand in hand to achieve common goals.
Since 2001, CRATerre-EAG was commissioned to tackle the conservation problems and increase the capacities of the team in place. In that respect, a series of research and training campaigns have been organised. The Turkmen professionals in charge have gained efficiency and confidence, thanks to the skills and equipment transferred to the site and first promising results have been obtained, proving that controlling the decay of earthen monuments is not an impossible task.
Philosophy of intervention
However, saving the remains is a great challenge. Earth is a rather weak and fragile material, and soft interventions are compulsory to avoid serious disturbances. Past experiences have proved that active conservation methods, aiming at changing the physical properties of the material (waterproofing, sealing with chemicals) or introducing new materials, are generally ineffective (if not destructive) and often irreversible.
It was therefore proposed to work with a very long term view and within a gradual process to enhance our comprehension of the site and develop conservation techniques adapted to the specific context and in respect with the international charters and recommendations.
All the conservation techniques applied should respect the following criteria :
Respect the values : The site has very important values, especially historical and archaeological. That means that all interventions should result in a preserved archaeological resource and respect some of the ruined state of the assets so that the differences in the age of the structures and the traces of history on the fabric can easily be detected by a visitor. Any proposed restoration would obviously need to be based on consistent scientific documentation. Conservation is not a beauty contest; a monument does not necessarily need to be good looking to be of international relevance.
Masterable : focus was given to solutions that can be easily applied by the Turkmen team with their own resources. This means that priority has been given to the use of local resources, and technologies that can be applied with the available tools and equipment.
Non-intrusive : Harmony between the old and the new should be ensured, at every level of intervention. This applies to the materials (physical, chemical or biological properties), and to the techniques (passive or active). However, if interventions should be discrete and minimal, additions or repairs have to remain visible, and distinct from the original fabric.
Reversibility : conservation interventions should easily be removable without damaging the original structure. This criterion is closely linked to the other ones, and reduces the risk of uncontrolled decay processes taking place after the intervention. However, if this principle guarantees a safe approach, it requires a long experimental phase.
Use of original materials : the proposed interventions make use of the same material as the one originally used. The only exception is the geotextile, which has sometimes been used to separate the original fabric from the conserved part, especially for the backfilling of excavated sites.
A careful diagnosis was a crucial step before assessing any conservation work. In order to understand how the buildings were deteriorating and how we could stop the decays, field experimentations and monitoring programmes were necessary.
The first step of this work was to analyse the decay processes affecting the structures and the level of threat attached to each of them. Observations done on site have permitted us do identify and classify all the visible signs of deterioration, to record the stabilised, active and potential decay factors, both environmental and human, and finally to understand their combination and the complex inter-related effects they can have on the monuments. Then, to the light of the results provided by this study, and in order to confirm the first hypothesis made from the site observation, a monitoring system of all the parameters which can be quantified has been launched (physical, climatic, environmental, human).
In addition, laboratory tests are continuously carried out by the specialists from the Park staff to analyse the characteristics of the different types of soils available around the site. For that purpose, laboratory equipment have been provided as well as training sessions.
Finally, field experimentations are implemented on site, to evaluate the behaviour of the soil mixtures selected and the efficiency of various preventive conservation techniques.
Minimum intervention :
For example, several techniques of maintenance, are currently explored. An important effort is notably done to solve the problems caused by the plants which grow everywhere on the site and considerably accelerate the erosion processes. They affect the bases of the walls by changing a hard and dense material into a porous one that can easily be washed away. They also reduce the drying process of the wall by retaining humidity in the ground. In addition, there are some problems with plants developing in the mortar joints. Therefore, just by removing the plants from a monument and its immediate surrounding, it is possible to increase the life span of the structures.
In the same order of idea, just by securing the damaged parts of a monument with an earth based mortar, it is possible to prevent the further wearing away of gullies, holes and cracks or to avoid the drop-out of an important loose brick from an arch.
All those rapid interventions of maintenance can result in considerable savings if they are correctly scheduled and implemented, and if they respect the specific conditions of the site.
Many solutions of preventive conservation are continuously designed since the beginning of this programme. They are tested at a reduced scale, and over a sufficiently long period of time, before being implemented at a wider scale. This methodological approach has been transferred to the national professionals who have now a better understanding of the conservation problems encountered on the site and develop and implement their own ingenious adapted conservation techniques.
copyright CRATerre EAG - 2004 - Damien Vielfaure & Grégoire Paccoud