ARCHEOFORUM, MONITORING AND CONSERVATION
CURATIVE AND PREVENTIVE CONSERVATION
Jean-Marc LEOTARD, Provincial archaeologist
Nancy VERSTRAELEN, archaeologist
SERVICE PUBLIC DE WALLONIE
DIRECTION GENERALE OPERATIONNELLE 4
Division du Patrimoine
Service d’Archéologie en province de Liège,
Avenue des Tilleuls, 62
4000 Liège
Tél. : 04/2299711
Fax : 04/2299759
jeanmarc.leotard@spw.wallonie.be
nancy.verstraelen@spw.wallonie.be
Nancy Verstraelen graduated in Archaeology from the University of Liege, Belgium, in
2002. Between 2003 and 2004, she excavated different sites in Wallonia for the Ministry of
the Walloon Region. From 2005 to April 2007, she worked towards the implementation of a
program of preventive and curative conservation based on the monitoring of two
important sites in Liège, the "Archéoforum" and the futur "CWAB : Centre Wallon
d'Archéologie du bâti". Finally in 2009, she was employed in a permanent capacity to monitor
the archaeological sites in Liège, and to continue excavations for the Service public de
Wallonie.
Keywords
Temperature and humidity rate
Air-conditioning
Radon gas
Shrinkage
Hardening
Induration
Water in the sedimentary layer
Salt efflorescence
Groundwater
Chemical analyses of salt in the sediments and groundwater
Abstract
The main archaeological site of Liège, located at the confluence of a river and two
tributaries, stands on the alluvial plain and the northern bank of the valley. It is of particular
note that some very well-preserved prehistoric remains were found here, demonstrating the
earliest traces of human occupation, and allowing us to study the transition between the last
hunters (Mesolithic) and the first farmers (Neolithic) to occupy our region. The Roman
building (second and third century AD) played a decisive part in the location and structure of
the subsequent buildings which follow one another at this place. This influence was still
visible after more than five hundred years.
1
Since the Middle Ages, Liege has been the chief town of the large territory known as
the principality of Liege, both as an administrative headquarters and an episcopal see. This
principality was placed under the German Empire’s authority. The symbol of the authority’s
power, located in the town centre, was a cathedral, an imposing religious building. The story
of this ecclesiastic complex and of the town starts at the beginning of the eighth century,
following the murder of the bishop Lambert, apparently in the reused remains of the roman
building.
This event had an impact on imperial policy in this region, leading to the erection of
the first churches and to the development of the first urban fabric. From that time, the town
has never stopped growing. It has been a centre of economic, cultural and intellectual
development throughout the Middle Ages to the modern era. Under the influence of the
French Revolution, the central element, the cathedral, was considered as the image of an
ancestral power to be eradicated. It was slowly demolished, bit by bit, between the end of the
eighteenth and the first half of the nineteenth century. It gave rise to the Place Saint-Lambert
which still retains the memory of the vanished church.
This square is an empty space, having been under pressure from various urban
development policies since the beginning of the twentieth century. Several projects have been
started, some never to be completed … So, the Place Saint-Lambert has become known as
“the hole”. Archaeologists have intervened in this difficult state of affairs, at three times in
particular - in 1907, between 1977 and 1984, and between 1990 and 1995. Each time, research
was carried out under difficult circumstances, under time constraints, some excavations being
more structured than others, but often carried out in conditions of extreme urgency. The
continually changing urban development policy has meant that archaeologists have had to
modify their programme and methods constantly.
This presentation will show that the 1907 excavations gave rise, in a significant way,
to an initial archaeological room, based on some remains of the Roman building, which was
opened to the general public.As far as the 1977-1984 researches are concerned, they ended
with the removal of some monumental remains, considered to be the most representative,
mainly from a symbolic point of view, when the site was being threatened by imminent
demolition, although it was never in fact carried out. Shortly after 1990, when the
archaeologists were forced to excavate in the worst possible conditions, the projected
construction of a huge underground car-park was scaled down. The idea of an underground
area intended for the use of the general public arose in 1993. A part of the archaeological site
was saved for the future. The large remains of the Roman building and of the mediaeval crypt
of St Lambert removed from the site in 1984 were repatriated.
Important work was carried out to preserve other archaeological remains.
The Archeoforum extends over 5700 square meters. It comprises as many built structures,
sedimentary layers partially explored by the archaeologists, as places never explored, making
it an important archaeological reserve. After the initial installation of the construction, but
before the creation of the internal substructure for the use of the general public, research was
carried out into several earlier studies concerned with conservation problems, and
conservation measures were also put in place.
However, at the opening of Archeoforum in 2003, the preservation of the remains was
not included in the management program of the site, and damage began to appear in the
remains. In 2005, a recovery team was set up to take care of the preservation of the remains.
It was decided to set up a monitoring program designed to keep a careful eye on the
parameters influencing the conservation. The parameters to be monitored, both inside and
outside the site, had been defined beforehand, within the framework of preliminary studies
into preservation operations.
2
The implementation of a monitoring program was necessary to explain the appearance of the
most important diseases on the site :
 Hardening and induration,
 movement of sediments, shrinkage
 salt efflorescence
Beyond the fact that the sedimentary layer and any trace of human occupation which they
contain are themselves presenting conservation problems, especially in relation to
groundwater and the atmosphere for example, we must also take into account human
presence and recently built structures as significantly disruptive elements. Thus, diaphragm
walls which go down to the bed-rock seal the archaeological site to the north, east and west.
These structures, and also the concrete flag which covers the site are elements which were not
initially intended to house the archaeological conservation site. Originally, they were set up
within the framework of the future construction of an underground car-park. These structures
have nevertheless a considerable impact on the environmental conditions of the site, in
particular relating to climate and hydrogeology.
All these elements were considered before a detailed monitoring program of the site
was proposed, with the intention of providing a preventative and curative approach to the
preservation of the archaeological remains. Resulting from these considerations, here, briefly,
are the main principles which have been adopted, and some examples of their implementation.
Based on the previous studies, the implementation of these principles give rise to five tasks:
an inventory of artefacts, an inventory of fixtures, data gathering, data analysis and an action
plan.
1) The creation of an inclusive inventory of the archaeological discoveries was necessary to
have easy access to them and to preserve them. This inventory has been useful because the
discoveries were preserved in different ways, in different places, with different systems of
recording, notably because they were brought to light at different times by different teams of
researchers.
2) The inventory of fixtures is a codification of the state of what is visible on the site - both
sediments and structural remains. This inventory consists of forms recording photographs,
descriptions and comments.
These examples demonstrate the necessity of having such an inventory in order to combine
results with other similar research, thus allowing a consistent approach to conservation
problems.
3) The outline of the data recorded on the site was established after the inclusion of results
from previous studies carried out before the opening of the Archéoforum. The following
components considered as the most influential for the long-term conservation of the site have
been taken into account: climatology, hydrogeology, biology, stability.
The conservation program is based on permanent monitoring of a series of parameters which
were defined by previous studies, for example, the following data was recorded:
Temperature and relative humidity rate (data loggers)
Groundwater level (piezometer) inside and outside the site
Water content of the sediments,
The shrinkage of the sediments (with a profile probe)
Radon gas level (radon detector)
Movement of sediments or built structure (fissurometer)
Chemical characteristics of the groundwater
Salt efflorescence
3
Presence of micro-organisms
When we have reached and understanding of the importance of all the factors in the
area surrounding the site and the possible interactions with the data recorded inside the site,
and the relationship between them, we will be in a position to put in place policies to stop or
to limit damage particularly to the sedimentary layer. With climatology for example, we will
consider together such factors as the climate evolution of the site, the air-conditioning, the
outside climate, and the rate of radon. Currently, we are working with a climatologist to
understand the function of air-conditioning and its limitations. He will subsequently give us
recommendations for improving the equipment so as to achieve an appropriate climate and
atmosphere for the preservation of remains and the limitation of disease.
In conclusion, management of the preservation of an archaeological crypt in an urban
area is extremely complex and inevitably requires the implementation of precise and specific
monitoring of climatic and hydrogeological parameters … This research allows us to identify
as required any disruptive factors and the intrinsic relationship of the various environmental
parameters. These relationships are complex and exceed the precise geographical and
environmental framework of the site. Any intervention must be well-founded and justified
beforehand, having been the object of a preliminary study to estimate its impact on the
preservation of the remains as a whole.
Bibliography
BOSSIROY, Dominique, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude des mortiers et des enduits, Etude des matières premières, Rapport I, 2000.
BOSSIROY, Dominique, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude des mortiers et des enduits, Etude des matières premières, Rapport II, 2000.
BOSSIROY, Dominique, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude des mortiers et des enduits, Etude des matières premières, Rapport III, 2000.
Deuxième rapport d’activités, Place Saint-Lambert, I.A.L., convention 98/41933.
Deuxième rapport d’activités, Conservation, Place Saint-Lambert, I.A.L., subvention 99/61319, 2001.
Deuxième rapport d’activités, Conservation, Place Saint-Lambert, I.A.L., subvention 01/40813, 2002.
DIAZ PEDREGAL, P., Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude climatologique, Rapport I, 2000.
DIAZ PEDREGAL, P., Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude climatologique, Rapport II, 2000.
DIAZ PEDREGAL, P., Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux interventions de
conservation, Etude climatologique, Rapport III, 2000.
MONJOIE, A., POLO-CHIAPOLINI, C, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux
interventions de conservation, Etude hydrogéologique, Rapport I, 2000.
MONJOIE, A., POLO-CHIAPOLINI, C, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux
interventions de conservation, Etude hydrogéologique, Rapport II, 2000.
MONJOIE, A., POLO-CHIAPOLINI, C, Archéoforum, place Saint-Lambert, Liège, Etudes préalables aux
interventions de conservation, Etude hydrogéologique, Rapport III, 2000.
Premier rapport d’activités, Place Saint-Lambert, I.A.L., convention 98/41933.
Premier rapport d’activités, Conservation, Place Saint-Lambert, I.A.L., subvention 99/61319, 2000.
Statement
Before taking the decision to list a heritage site, is it not necessary simultaneously to make
provision for financial and human resources to put this in place and ensuring the management
of the latter ?
4
5