PRESENTATION SLIDES: St. Paul's Catacombs Complex: Environmental Impact Study

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Image courtesy of Heritage Malta

Environmental Study of Heritage Malta’s

St Paul’s Catacomb Complex Rabat, Malta

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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.

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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...”

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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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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

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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.

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Lighting has led to increased growth of some microbiological species

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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.

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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...”

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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