Institute for Sustainable Heritage
Image courtesy of Heritage Malta
Environmental Study of Heritage Malta’s
St Paul’s Catacomb Complex Rabat, Malta
Institute for Sustainable Heritage
BACKGROUND
ARCHAEOLOGICAL HERITAGE CONSERVATION PROJECT (ERDF 032) To make St. Paul’s Catacombs Complex a prime location by creating a new visitor centre and opening the catacombs to the public.
UCL PROJECT To assess the impact of the ERDF funded project on St. Paul’s Catacombs after one year.
GRAPH/IMAGE TITLE
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CONTEXT Visitor Centre Evaluation of the environment for display of objects & impact on the archaeology beneath.
GARAGE
CATACOMB 12
Garage
To assess the suitability of this building for the storage of archaeological artefacts.
CATACOMB 17
Catacombs 12 & 17 To assess the impact that opening them to the public is having on their internal environment.
VISITOR CENTRE
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SIGNIFICANCE OF THE SITE •
The largest late Roman underground cemetery in Malta.
•
A spiritual hub serving as a burial ground from Punic and Roman times.
•
The earliest and largest archaeological evidence of Christianity in Malta.
•
Various tomb types showing work that was required to dig such a cemetery.
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METHODOLOGY Environmental data collection •
Data loggers recording Temperature and Relative Humidity (Feb - Oct 2016 & historic data)
•
Spot measurements of light readings
•
pollution monitoring NO2, SO2 O3 (ozone)
Condition Surveys Collection. Conducted by the teams at their locations based
•
on standards by Suzanne Keene
Documentation: Mapping Underneath the visitor centre and catacombs 12 & 17
•
Pest Surveys •
Blunder traps placed at five target sites
Risk Assessments •
Based on modified assessments of Waller, Michalski and CCIAD with numerical scoring frequency, severity.
Observation of Visitor Movement •
Occasional monitoring of the visitors over the last two weeks.
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KEY MESSAGE
The St Paul’s Catacomb complex demonstrates the challenge in balancing preservation and access at historic sites. The site has potential as a unique ‘living research lab’, where environmental and social research can inform innovative strategies for responding to that challenge.
This speaks directly to Heritage Malta’s mission statement: “…To safeguard and render accessible the cultural heritage entrusted to it, while contributing towards increasing the appreciation for Malta’s cultural Identity...” GRAPH/IMAGE TITLE
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VISITOR CENTRE
Visitor Centre
VISITOR CENTRE
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VISITOR CENTRE
UN-CASED
WITHIN DISPLAY CASE
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VISITOR CENTRE – Values of the Collection SOCIO-CULTURAL •
Multiculturalism & identity
•
Religious
HISTORICAL-ARCHAEOLOGICAL •
Burial and cremation techniques
•
Objects related to ceremonial functions
SCIENTIFIC AND EDUCATIONAL •
•
Study of Archaeological finds & materials Anthropological significance
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VISITOR CENTRE – Collection Display & Composition COLLECTION DISPLAY
WITHIN DISPLAY CASE
UN-CASED
COLLECTION MATERIALS BONE 8%
METAL 15% WOOD GLASS
50%
2% 3% 22%
STONE
POTTERY
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VISITOR CENTRE – Powdering of Skeleton
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VISITOR CENTRE – Bone Risk Assessment RISK RATING
Visitor Centre - Bone
HAZARD TYPE Traffic Vibrations Earthquakes Physical Visitor Damage Forces Erosion (Wind) Erosion (Water) Thieves Vandals Flood Water Plumbing Leaks Relative Fluctuation Humidity Extremes Fluctuation Temperature Extremes Dumping Pollution Chemical / Air Fire Light Exposure Custodial Maintenance Neglect Dissociation Pests
FREQUENCY
SEVERITY
3 1 0 0 0 0 0 0 1 1 2 3 2 0 0 1 2 1 1 0
1 3 0 0 0 3 2 1 0 1 2 3 3 0 1 3 1 2 1 2
RISK SCORE
CHANGE OF VALUE
PRIORITY
4 4 0 0 0 3 2 1 1 2 4 6 5 0 1 4 3 3 2 2
1 3 2 0 0 2 2 1 1 3 2 2 2 1 1 2 2 1 2 0
5 7 2 0 0 5 4 2 2 5 6 8 7 1 2 6 5 4 4 2
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VISITOR CENTRE – Corrosion of Copper
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VISITOR CENTRE – Metal Risk Assessment RISK RATING
Visitor Centre - Metal
HAZARD TYPE Traffic Vibrations Earthquakes Physical Visitor Damage Forces Erosion (Wind) Erosion (Water) Thieves Vandals Flood Water Roof Leak Relative Fluctuation Humidity Extremes Fluctuation Temperature Extremes Dumping Pollution Chemical / Air Fire Light Exposure Custodial Maintenance Neglect Dissociation Pests
FREQUENCY
SEVERITY
3 1 0 0 0 0 0 0 1 2 3 1 3 1 3 1 2 1 1 0
0 3 0 2 3 3 2 1 0 2 2 2 2 1 3 1 1 1 1 2
RISK SCORE
CHANGE OF VALUE
RISK RESULT
3 4 0 2 3 3 2 1 1 4 5 3 5 2 6 2 3 2 2 2
0 1 0 0 0 2 1 1 1 1 1 1 1 0 1 2 0 2 3 0
3 5 0 2 3 5 3 2 2 5 6 4 6 2 7 4 3 4 5 2
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VISITOR CENTRE – Internal & External Environment Visitor Centre (Internal) 35
T (%)
25
27 C
20 15 10 5
10 C
0
External Environment 35
34 C
30
20 15 10
0
100 90 80 70 60 50 40 30 20 10 0
28%
97%
RH (%)
T (%)
25
5
88%
RH (%)
30
100 90 80 70 60 50 40 30 20 10 0
8 C
18%
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VISITOR CENTRE – Museum Environment
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MUSEUM MAIN SPACE - RH AND TEMPERATURE GRAPH
YELLOW BOX = NPS STANDARDS FOR STONE
VISITOR CENTRE – Showcase Internal Conditions
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Bone showcase 35
29 C
30
72%
T (%)
25 20
54%
15
13 C
10 5 0
YELLOW BOX = NPS STANDARDS FOR BONE
Copper showcase
34.5 C 29 C
13 C 8 C
83%
45%
YELLOW BOX = C. CAPLE RECOMMENDATIONS
RH (%)
VISITOR CENTRE – Traditional Building Comparison Natural History Museum, Mdina 100 90 80 70 60 50 40 30 20 10 0
72% 33%
St Paul’s Catacombs Visitor Centre 88%
28%
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VISITOR CENTRE – Additional Deterioration Agents LIGHT/ UV • No problems due to light / UV • Building completely blocks out UV and lux levels are within recommended limits PESTS • No observed problem from pests • Only 1 out of 7 traps contained pests and pests found were not harmful to collection POLLUTANTS • Ozone levels at 9.5ppb - above Getty Conservation Institute standards, but not a risk to collection/ visitors GRAPH/IMAGE TITLE
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VISITOR CENTRE – Condition Summary • Temperature and RH are above recommended standards • This appears to be affecting the more vulnerable objects, like bone and metal • The conditions are not concerning for inorganic objects like stone and glass • The building design makes it hard to regulate temperature and RH, as the internal space is open to the external environment GRAPH/IMAGE TITLE
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Institute for Sustainable Heritage
GARAGE
Garage & Collections
GARAGE & COLLECTION - Values
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SCIENTIFIC • Research Value ARCHAEOLOGICAL • Fragments useful for reconstruction of larger items HISTORICAL • Window into the past
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Dog’s skull from the garage collection
GARAGE & COLLECTION – Risk Assessment
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GARAGE & COLLECTION – Condition Survey
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• Objects stored in plastic bags tied with string, in plastic boxes open to air • Mainly pieces of pottery, animals’ bones, stone • Objects not cleaned yet, hard to identify structural damage • Likely in stable condition
Pottery sherds from the garage collection
GARAGE & COLLECTION – Pests
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• Some woodlice, spiders, small flies. • Other types recorded included silverfish; collembola class (springtails); and bagworm larvae. • Several specimens prefer (or require) high RH (often 70%+) to live and breed.
Springtail
Bagworm Moth Larva
GRAPH/IMAGE TITLE
Silverfish
GARAGE & COLLECTION – Sensor Location
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GARAGE & COLLECTION – Environmental Data Garage 30
31 C
20 15 10
12 C
5 0
35
87%
30
RH (%)
T (%)
25
100 90 80 70 60 50 40 30 20 10 0
32%
Temperature (°C)
35
25 20 15 10 30
40
50 60 70 80 Relative Humidity (%)
Visitor Centre 35 30
29 C
20 15 10 5 0
88%
RH (%)
T (%)
25
100 90 80 70 60 50 40 30 20 10 0
13 C
28% Animal bone from the garage collection
90
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Underneath Visitor Centre
UNDERNEATH VISITOR CENTRE
UNDERNEATH VISITOR CENTRE – Values SCIENTIFIC VALUE • Historic record • Research (past practices; impact of current environmental conditions) SOCIO-CULTURAL • Local community links • Educational
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UNDERNEATH VISITOR CENTRE – Risk Assessment
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180cm
UNDERNEATH VISITOR CENTRE – Mapping
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180cm
UNDERNEATH VISITOR CENTRE – Mapping
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UNDERNEATH VISITOR CENTRE – Pests
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• Various insects – flies, spiders, lice, woodlice, midges, wasps - and a lizard(!) were caught under the visitor centre. • Only one known pest order – Psokoptera – but these are only pests of damp paper. • Several insects caught prefer conditions with high relative humidity.
Gall Midge
Woodlouse
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Booklouse
UNDERNEATH VISITOR CENTRE – Sensor Location
Truncated Access Area
2
Museum Underfloor
1
3
Foyer Underground
GAP = 100cm
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UNDERNEATH VISITOR CENTRE – Environmental Data Museum Underfloor 34 C
30
20 15 10 5
9 C
0
External Environment 35
35 C
30
20 15 10
0
1
100 90 80 70 60 50 40 30 20 10 0
18%
97%
RH (%)
T (C)
25
5
96%
RH (%)
T (C)
25
100 90 80 70 60 50 40 30 20 10 0
180cm
35
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8 C
18%
UNDERNEATH VISITOR CENTRE – Environmental Data Foyer Underground 35 30
27 C RH (%)
T (%)
25 20 15 10 5
10 C
0
100 90 80 70 60 50 40 30 20 10 0
96%
3 41%
External Environment 35 C
30
20 15 10 5 0
97%
RH (%)
T (%)
25
100 90 80 70 60 50 40 30 20 10 0
100cm
35
8 C
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18%
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UNDERNEATH VISITOR CENTRE & GARAGE – Summary • Both sites seem broadly ‘stable’, although rock-cut tombs exhibit salt efflorescence. • Fluctuating relative humidity poses a risk to the stability of the archaeology/artefacts at each site. • This fluctuation is natural for the local external environment, but not significantly buffered by visitor centre / garage buildings. • Without measures to mitigate relative humidity fluctuations there is a risk that the organic materials stored in the garage will experience deterioration, as may the tombs.
Access Underneath the Visitor Centre
Dog’s skull from the garage collection
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CATACOMB 12
CATACOMB 17
Catacombs 12 & 17
CATACOMBS 12 & 17
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CATACOMBS 12 & 17 – Values Historical & Archaeological • Dates from 4th – 9th century AD Social & Cultural • Multiculturalism and identity Environmental • Pleasant open space Educational & Scientific • Research potential • Educational use Economic • Tourism income and financial support
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CATACOMBS 12 & 17 – Research 2010-2012
Study of biological communities at St Paul’s Catacombs Universitat de Barcelona October 2012
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St Paul’s Catacombs, Rabat, Malta Survey and monitoring of the environmental conditions 2010-2011 Tobit Curteis Associates LLP. October 2011
CATACOMBS 12 & 17 – Summary
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Environmental Assessment • Internal environment of catacombs o High relative humidity (RH) o High temperature (T) o Conditions ideal for microbiological growth • Levels of RH and T are high (RH close to saturation) but stable o Catacomb structure provides good level of thermal buffering between internal and external environments • Environmental monitoring to date has not shown a major effect on the internal environment of catacomb 12 due to visitor numbers– requires further monitoring Visitor Risk • Visitor damage demonstrates a level of physical risk to the catacombs • Conditions in catacombs demonstrate some visitor health and safety risks
CATACOMBS 12 & 17 – Condition Analysis White deposit found on the majority of surfaces Composed of surface efflorescence and actinobacteria
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Catacomb 12
Image Universitat de Barcelona, Study of biological communities, 2012
Green microbiological growth Associated to light sources – both natural and artificial
Black microbiological growth Cyanobacteria – found particularly on plaster surfaces and the fresco
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Catacomb 12
Catacomb 17
CATACOMBS 12 & 17 – Visitor Impacts Visitor information • 50-60K visitors per year • Group and individuals • Visitor information panels list hazards and maximum capacity but do not indicate duration of visit Visitor behaviour / damage • Groups larger than maximum size • Running into catacombs • Abrasions and scratch marks • Graffiti GRAPH/IMAGE TITLE
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CATACOMBS 12 & 17 – Visitor Impacts •
Introduction of visitor lighting system to catacombs o UV /IR filtered LED spot lights and floor lights, on motion sensor timers.
•
Lighting has led to increased growth of some microbiological species
•
Visitors cause an increase in temperature and relative humidity levels
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Visitors cause an increase in the CO2 levels within catacombs GRAPH/IMAGE TITLE
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CATACOMBS 12 & 17 – Historic Environmental Data Historic Environment Assessment Data-Catacomb 12
Catacomb 12 - Temperature and RH graph (June-Sept 2011)
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CATACOMBS 12 & 17 – Current Environmental Data 35 C
35 30 25 20 15 10 5 0
27 C
8 C 10 C
98%
100 80
RH (%)
T (%)
2016-External Environment
60 40 20
18%
0
2016-Internal Environment
100%
35
T (%)
25
23 C
20 15 10 5 0
80
RH (%)
30
100
12 C
60 40 20 0
96%
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CATACOMBS 12 & 17 – Risk Assessment
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OVERALL FINDINGS – Summary
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Visitor Centre • Overall, the temperature and RH appears to be above recommended standards. • This seems to be affecting more vulnerable objects as opposed to inorganic materials. Garage & Underneath Visitor Centre • Both sites fluctuating RH poses a risk to the stability of the archaeology/artefacts. • This fluctuation is natural for the local external environment, but not significantly “buffered” by the visitor centre/garage building. Catacombs • It seems that RH and temperature are high inside the catacombs. Provide ideal conditions for the microbiological growth and salt activity. • The structure of catacombs helps sustain a relatively stable environment.
Institute for Sustainable Heritage
KEY MESSAGE
The St Paul’s Catacomb complex demonstrates the challenge in balancing preservation and access at historic sites. The site has potential as a unique ‘living research lab’, where environmental and social research can inform innovative strategies for responding to that challenge.
This speaks directly to Heritage Malta’s mission statement: “…To safeguard and render accessible the cultural heritage entrusted to it, while contributing towards increasing the appreciation for Malta’s cultural Identity...” GRAPH/IMAGE TITLE
Institute for Sustainable Heritage
ACKNOWLEDGEMENTS
Konrad Buhagiar David Cardona JoAnn Cassar Romina Ferry Mario Galea Kenneth Gambin David Mifsud Janice Sammut Godwin Vella
Heritage Malta Staff of the St. Paul’s Catacombs