Barbara Davidde

METHODS AND STRATEGIES FOR THE CONSERVATIONAND MUSEUM DISPLAY IN SITU OF UNDERWATER

CULTURAL HERITAGE

T he creation of Natural Marine Parks or Reserves and of Protected MarineAreas also comprising areas of archaeological or historical interest and theestablishment of Underwater Archaeological Parks is proving to be an effec-

tive instrument in safeguarding underwater cultural heritage.The principal objectives of these institutions are the valorisation and conservation

of the natural and cultural heritage, the protection of the property from clandestineactions and from the destructive forces of the elements and finally the enjoyment ofthe property itself.2

The protection and conservation of a submerged site or wreck is more complex,when it does not fall into the above category and is therefore devoid of surveillanceand specific restrictions, such as the banning, for example, of navigation, anchorage,fishing and unsupervised diving, etc. The conservator not only has to face up to theaquatic environment in order to limit deterioration, but also to the eventual, indeed,frequent actions of clandestine operators. With regard to wrecks, in no country is itpossible to establish a programme that foresees the excavation, salvage, restorationand museum display of all the already known cases indicated on the archaeologicalmaps. The same argument, even more so, goes for new sightings.

On the other hand, not archaeologically investigating a well-known wreck meanslimiting our knowledge of naval construction techniques and of the economy anddaily life in antiquity and not protecting it implicates losing it entirely. It is necessaryto make choices and very often, above all in the case of wrecks of wood-constructedcraft, the policy is usually to re-covery the site, once the necessary data has been ac-curately recorded or the site has been excavated and the cargo removed. The choiceof re-covering is most certainly a positive factor in safeguarding and preserving thesite, but prevents the public from gaining direct access to the «monument».

. Such a choice is the confirmation of how ea-gerly awaited Unesco’s recommendation in 200was, which proposed to valorize, protect and pre-serve underwater archaeological heritage in situ(unesco Convention on the Protection of the Un-derwater Cultural Heritage Paris 2- -200 ) ; seealso C. J. S. Forrest, Defing « underwater culturalheritage », « ijna », (International Journal NauticalArchaeology), 3 . , 2002, pp. 3- ; A. Strati, Theprotection of Underwater Cultural heritage : an emer-ging objective of Contemporary law of the sea, TheHague: Martinus Nijhosf Publishers, 995; G. Ve-dovato et alii, La tutela del patrimonio archeologicosubacqueo, in Atti del Convegno Internazionale tenu-

tosi a Ravello dal 27 al 30 maggio 993 presso il CentroUniversitario Europeo di Beni Culturali, Roma, Isti-tuto Poligrafico e Zecca dello Stato, 995.

2. J. D. Spirek, D. A. Scott-Ireton (Ed.), Sub-merged Cultural Resource Management. Preserving andInterpreting our sunken Maritime Heritage, New York,2003; B. Davidde, Underwater archaeological parks : anew perspective and a challenge for conservation. TheItalian panorama, «ijna» p. 50, 3 . , 2002, pp. 83-88;L. Fozzati, B. Davidde, Le aree archeologiche som-merse italiane. I parchi subacquei, in The Colloquia ofthe XIII International Congress of Prehistoric and Pro-tohistoric Sciences, Forlì 8- 4/09/ 996, ColloquiumXXXVI, Archaeological Parks, 8, Forlì, 996, pp. 83-96.

38 barbara davidde

The protection and conservation of wrecks IN SITU

Obviously, different types of wrecks exist and therefore the methods and strategies toadopt for their protection, conservation and museum presentation in situ are different.

From the conservation standpoint, ancient naval wrecks can be divided into twomain categories:

• Wood-constructed wrecks with or without cargo. • Metal-constructed wrecks with or without cargo.3

The type of merchandise transported, and the furniture, fittings and equipment onboard vary according to the historical period to which they belong, but from a con-servation standpoint, these objects can be divided into three categories defined bytheir constituent materials :

Organic material : wood, leather, vegetable fibres and animals. Inorganic material : ceramics, stone, metals. Mixed materials : organic and inorganic.

The presence of cargo is a positive factor in protecting the surviving wooden structuresof the ship. Numerous studies on the influence of marine and lake environments on thedeterioration of wood confirm that wooden craft absolutely cannot be left uncovered onthe seabed or lake bottom to be admired by the public, on pain of their rapid demise.4

The archaeological excavation that only considers the recovery of cargo, therefo-re, condemns the wreck itself to destruction. Re-covering or burying finds of organicorigin and the wood structures of the ship in order to protect them, on completionof the excavation and archaeological documentation, is a practice whose value froma conservation standpoint has been amply discussed in literature.5

3. This category also includes wrecks of aircraftand helicopters resulting from combat action du-ring the Second World War. See for example B.Jeffery, World War II Underwater Cultural HeritageSites in Truk Lagoon : Considering a case for WorldHeritage Listing, «ijna», 33. , 2004, pp. 06- 2 .

4.R. Brown, H. Bump, D. A. Muncher, An in si-tu method for determining decomposition rates ofshipwrecks, «ijna», 7,2, 988, pp. 43- 45; D. J. Gre-gory, Biological deterioration of organic artefacts inseawater, «Maritime Archaeology Newsletterfrom Roskilde, Denmark», 8, 997, pp. 2 -23; A.Pournou, A. Jones, A. Mark, S. T. Moss, Monito-ring the environment of the Zakinthos wreck site, inArt 99: 6th International conference on non-destructivetesting and microanalysis for the diagnostics and con-servation of the cultural and environmental heritage,Rome, May 7-20, 999 / Istituto Centrale per il Re-stauro, Rome, Italy. Associazione italiana provenon-distruttive (AIPnD), Italy, 999, pp. 200 -20 8;J. Cook, B. Kaye, A New Method for monitoring sitestability in situ, «Nautical Archaeology SocietyNewsletter», 2000, pp. 4-7; D. J. Gregory, Deterio-ration of wood in Nydam Mose, «Maritime Archaeo-

logy Newsletter from Roskilde, Denmark», 3,2000, pp. 23-27; A. Jones, A. Mark, S. T. Moss, Bio-deterietion dynamics of marine wreck site determinethe need for their in situ protection, «ijna», 30. 2, 200 ,pp. 299-305 with wide bibliography. See also theScientific activity of the eu Project : Monitoring,Safeguarding and Visualizing North-EuropeanShipwreck Sites: Common European Underwa-ter Cultural Heritage (MoSS), www. mossproject.com.

5. See, for example, the sections dedicated tothis subject in the Proceedings of the icom on WetOrganic Archaeological Materials Conferences; inparticular D. V. Hogan, P. Simpson, A. M. Jones,E. Malthy, Development of a protocol for the reburialof organic archaeological remains, in Proceedings ofthe 8th ICOM Group on Wet Organic Archaeological Ma-terials Conference, Stockholms 200 , Bremerbawen2002, pp. 87-2 2; D. Gregory, Re-burial of timbersin the marine environment as a means of their longterm storage : Experimental studies in Lynaes Sands,Denmark, «ijna», 27. 4, 999, pp. 343-358; C. Caple,Reburial of waterlogged wood. The problems andpotential of this conservation technique, « Inter-

methods and strategies for the conservation 39Also the Underwater Archaeological Operations Unit of the Istituto Centrale per

il Restauro has been involved since 999 in a research and experimentation pro-gramme involving the conservation/restoration, also in situ, of underwater archaeo-logical heritage.6 Within the framework of this project, the author has been involvedin the study and assessment of conservation methods and protection systems forwrecks and submerged sites.7

This article proposes to summarize the experiences encountered up to now in thisfield and offers archaeologists and conservators, who have the task of safeguardingand preserving underwater archaeological heritage in situ, some ideas to reflect on.

Protection systems in situ, commonly used for wrecks, will be examined and themethods used for underwater architectonic sites will be outlined. In conclusion, thesubject of museum display in situ will be discussed.

Protection systems IN SITU

The reburial method

Already in 892, Arthur Bulleid, during the excavation ( 892- 907) of the lake vil-lage at Glastonbury, one of the first studies of humid sites in England, aware ofthe technological limits of his time with regard to the conservation of underwa-ter archaeological finds, gave orders for the latter to be reburied and left on thebottom, requesting that the few items recovered be preserved in water untilfurther notice. All the material from the excavation was then restored at a muchlater date in 962.

The reburial method foresees the recovery of finds of organic material (frag-ments from the ship, which at times, if found intact, are purposely dismantled;objects discovered on board, etc.), their identification and documentation (graphic,photographic, archaeological, scientific analyses) and finally, their reburial in exca-vated trenches without necessarily being wrapped in special coverings or, alterna-tively, wrapped in some form of plastic fabric and/or stored in cases of variousmaterials.

This method has been adopted more frequently in Northern European countriesand, in some cases, in the United States and Canada and is selected, above all, whenthe archaeological excavation renders a large number of finds that, for economicand organizational reasons, cannot be restored and exhibited to the standards ge-nerally accepted by the scientific community. In order to facilitate the task of tho-se who, one day, may deal with their recovery, it is essential to number every sin-gle item and accurately record its position both in the trench and in the case itself,before its reburial.

national biodeteriation and biodegradation»,34. , 994:6 -72 and footnotes nn. 8, 9, 0 in thispaper.

6. R. Petriaggi, The role of the Italian Central In-stitute of Restoration in the field of the underwater ar-chaeology, «ijna», 3 . , 2002: 74-82; R. Petriaggi, Re-stauro subacqueo delle strutture sommerse della villaromana di Torre Astura, in Atti del secondo incontro distudi Lazio e Sabina, Roma, 7-8 maggio 2003, pp. 273-

276, Roma 2004, and the article by R. Petriaggi eR. Mancinelli also in this publication, pp. 09- 26.

7. Moreover, in agreement with the Archaeolo-gical Superintendence for Southern Etruria, expe-rimentation of new protection systems for the pi-les of lake villages or, more generally, for submer-ged wood structures (stake-fencing, pile-work,etc.) is in progress, the results of which we shor-tly hope to be able to publish.

40 barbara davidde

Let us now look at a number of significant examples where this method has beenadopted. The fragments and part of the cargo of a wood-constructed vessel of the Ea-st India Company, which foundered in 745 off the Göteborg archipelago in Sweden,were preserved according to this method.8 The parts of the craft and other individualfinds were first wrapped in a sheet of polyethylene and then in one of polypropyle-ne, placed in wood containers and subsequently buried in trenches. I believe thatusing containers, which permit archaeologists to recover every single item withoutcausing undue disturbance to the site, is a very valid method. In my opinion, it is es-sential to choose containers that do not perish in water.

In 984, on completion of the archaeological excavation of the wreck of the San Juan,which had lasted about four years, it was decided to dismantle the vessel in numerousportions and bury the fragments under the seabed. All the pieces from the ship, whichhad sunk in Red Bay at the mouth of the Georgian Bay in Canada in the 6th century, we-re placed in a trench in three layers, surrounded and covered by sand and a geotextile fa-bric. This protection system proved to be efficient, in fact, using the geotextile protectsthe wood and impedes attack by biodeteriogenic organisms. The decision to dismantlethe wreck before burying it leaves me somewhat perplexed, but perhaps the size of thevessel and its precarious state of conservation influenced this course of action.9

The Marstrand Project, carried out between 997 and 2000, saw the reburial of 85-90% of the finds discovered during the underwater archaeological excavation (about0,000 objects) on completion of the documentation process. The trenches were dug

at a depth of about 2 to 3. 5 m; finds of organic origin were put in the first trench (25x 20 m), while metal-based finds were put in the second ( 5 x 5 m). Large portions ofthe wreck were buried directly in the trenches. Very small finds were, instead, pro-tected and wrapped in loose polyester fibre and then inserted into small boxes of hi-gh-density polyethylene (HDPE) (those in PE do not seem to last as long). Each itemwas given an inventory number and marked onto a map. The whole area was thencovered with a layer of clay, about 50 cm thick. 0

Protection using sand from the seabed/lake bottom

Of the in situ protection systems adopted, the most common is that of covering theremaining parts of the ship with a substantial layer of sand, without dismantling andplacing them in purposely dug trenches. This is, without doubt, the most economicsystem as well as being efficient and easy to implement if the wreck lies on a sandysurface. On completion of the excavation survey, the site is reburied with sand sim-ply using the air lift.

8. T. Bergstrand, In situ preservation and re-bu-rial. Methods to handle archaeological ships remainsin the archipelago of Göteborg, Sweden, in Proceedingsof the 8th ICOM Group on Wet Organic ArchaeologicalMaterials Conference, Stockholms 200 , Bremer-bawen, 2002: 55- 62.

9. J. Stewart, L. D. Murdok, P. Wadell, Rebu-rial of the Red Bay Wreck as a form of preservationand protection of the historic resource, in Materials is-sues in art and archaeology IV: symposium held May6-2 , 994, Cancun, Mexico, 995, pp. 79 -805.

0. I. Nyström, Underwater cultural heritage ma-nagement in western Sweden. Preventive conserva-tion and re-burial of Woods, in Proceedings of the 8th

ICOM Group on Wet Organic Archaeological Mate-rials Conference, Stockholms 200 , Bremerbawen,2002: 67- 74.

. E. Riccardi has designed a device to applyto the air lift, which has proved effective in facili-tating the protective reburying of wrecks, see E.Riccardi, Tecniche di lavoro subacqueo per l’archeo-logia. Mare ed Ipogei, Savona, 998: 57-58.

methods and strategies for the conservation 4This system obviously can neither be adopted in relatively shallow areas (the

wreck would soon be uncovered by the action of the sea), nor in the vicinity of po-pular resort areas: the wreck would be easy prey to curious intruders and vandals. Ifthis method is used, it is necessary to provide for a monitoring programme to checkthat the wreck does not re-emerge from the seabed and become exposed to biodete-riogenic attack or to undesirable intruders.

The Roman ship of Spargi ( 20- 00 BC), for example, was tampered with on variousoccasions by unknown intruders despite the archaeologists carefully reburying it withsand after each excavation and/or documentation campaign, which were carried outbetween 958-59 and 980. 2 Many cases like this exist, although they are rarely reportedin literature. In the summer of 980 the hull of the Spargi wreck was protected by a layerof crocks and stones, a strong nylon net, fixed with metallic forks and another layer ofcrocks and stones. The top was covered by a thick layer of sand. 3

The observations published by Patrice Pomey are interesting apropos of thissubject, where he refers to the state of conservation of twenty-six ancient wrecks di-scovered off the French coast, excavated and then reburied with sand from the sea-bed and examined during surveys conducted as part of a dendrochronological studyproject. In 35% of the wrecks examined, which had all been discovered at about 30metres in depth, apart from one found at 4-6 metres, the wood was in a good stateof conservation because the layer of overlying deposits had remained unchangedover the years, thanks to the depth of the site where the wrecks came to rest. In 46%of the wrecks, instead, the structural wood had almost completely disintegrated whi-le in 9% of the cases, it was found to be in a highly fragile state and in danger of de-teriorating irremediably within a short period. The reasons, according to the Frencharchaeologist, for the poor condition of the wood for 65% of the wrecks examined,are the relative shallowness of the site of rest, the intrusion of unknown persons, thedestructive action of the archaeological excavation and also the type of coveringused, the sand from the seabed that, evidently proved to be somewhat ineffective. 4

Protection with sand and rubber fabric

The wreck of the Stora Sofia ( 627) of about 40 m in length, discovered at about 26metres in depth, was protected by a layer of sand and a rubber covering, whose spe-

2. F. Pallares, 984, Il relitto della Nave romanadi Spargi. Campagne di scavo 958- 980, «Bollettinod’Arte. Suppl. 37-38. Archeologia Subacquea 3»,987: footnote n. 7: 0 . In carrying out this re-

search, I have observed that, often in scientific pu-blications dedicated to archaeological excavationsof ancient wrecks, these events are only mentio-ned in passing, perhaps because they are conside-red irrelevant and therefore not worthy of beingreported. Rarely, just to give an example, are theprocedures to rebury the wreck for the time spanbetween one excavation campaign and the nextindicated, nor do we read news of monitoringprogrammes to assess the state of conservation ofthe vessel, once the latter has been permanentlyreburied on completion of the excavation and do-

cumentation campaigns. Because of the nume-rous interventions of the clandestine ones, F. Pal-lares writes that in 98 the mast of the Romanship of Albenga has been covered by a nyloncloth and numerous fragments of amphorae, see:F. Pallares, Relazione sulla campagna archeologicasottomarina 985 sul relitto della nave romana diAlbenga, «Rivista di Studi Liguri», II, 4, 985, pp.632-639: 632.

3. E. Riccardi, Tecniche di lavoro subacqueo perl’archeologia. Mare ed Ipogei, Savona, 998: 55-57.

4. P. Pomey, Remarques sur la conservation in si-tu du bois de quelques épaves antiques de Méditer-ranée, in Proceedings of the 8th ICOM Group on Wet Or-ganic Archaeological Materials Conference, Grenoble997, 998, pp: 53-57.

42 barbara davidde

cific function was to impede the erosion of the sand. Small blocks of cement wereplaced on top of the rubber covering. 5

Protection with geotextile and sand or other filling materials

The experiments conducted on the post-Byzantine wreck discovered off Zakintosproved that the geotextiles Terram 2000 and 4000, consisting of 70% polypropyleneand 30% polyethylene, produced by Terram Geosynthetics, are excellent for protec-ting and reburying a wreck. Obviously, to prevent the fabric from moving, the lattermust be re-covered, in its turn, by sand or preferably, by sandbags and/or sacks of fil-ling material. Again at Zakintos, the ineffectiveness instead, of the geotextile Terram44 consisting of 00% polyester was demonstrated. 6

In 998, the wreck of a 7th century vessel that foundered off the island of Mar-strand, found in an advanced state of deterioration due to both mechanical and bio-logical marine action, was reburied successfully using a layer of clay brought fromthe port of Marstrand and then sand and geotextile fabrics covered, in their turn, bystones. This type of covering proved efficacious also in protecting the wreck fromthe currents generated by ferryboats. 7

Since 993, the Landesdenkmalamt Baden-Württemberg has been experimentingprotection systems in situ using geotextiles and artificial filling materials to protectthe piles of lake dwellings at the prehistoric site of Sipplingen (Lake Constance). 8

The wrecks Burgzand Noord 0 (Netherland) and Darsser Kogge (Germany) wereprotected underwater with polypropylene gauze and sand. 9

The geotextile covering and sandbags may be successfully applied also for protec-ting historic and particularly fragile submerged architectonic ruins in situ, such asopus sectile paving, mosaics, etc.

5. T. Bergstrand, In situ preservation and re-bu-rial. Methods to handle archaeological ships remainsin the archipelago of Göteborg, Sweden, in Proceedingsof the 8th ICOM Group on Wet Organic ArchaeologicalMaterials Conference, Stockholms 200 , Bremer-bawen, 2002: 55- 62: 60- 6 . For the follow-up ofthis work see T. Bergstrand, The in situ preserva-tion of the Stora Sofia shipwreck, – did we succedeed ?,in The 9th ICOM-CC WOAM Conference Copenhagen 6th-

th June 2004, in press. 6. A. Pournou, A. Jones, A. Mark, S. T. Moss,

Monitoring the environment of the Zakinthos wreck si-te, in Art 99: 6th International conference on non-de-structive testing and microanalysis for the diagnosticsand conservation of the cultural and environmental he-ritage, Rome, May 7-20, 999 / Istituto Centrale peril Restauro, Rome, Italy. Associazione italianaprove non-distruttive (AIPnD), Italy, 999, pp.200 -20 8; A. Pournou, A. Jones, A. Mark; S. T.Moss, In situ protection of the Zakynthos wreck, inProceedings of the 7th ICOM-CC working Group on Wetorganic archaeological materials conference Grenoble,Grenoble, 998: 58-64.

7. A. Olsonn, Cultural heritage management un-derwater in Sweden. A “Westcoast” perspective, inProceedings of the 8th ICOM Group on Wet Organic Ar-chaeological Materials Conference, Stockholms 200 ,Bremerbawen, 2002, pp. 45- 54.

8. M. Kolb, Protection for the Third Millennium-Steps for the Protection of the Prehistoric Site of Sipplin-gen, Lake Costance, in Schutz des Kulturerbes unterWasser, Beitraege zum Internationalen Kongress fuerUnterwasserarchaeologie (IKUWA ’99) 8-2 Februar 999in Sassnitz auf Ruegen, Lubstorf, 2000, p. 586.

9. See the Scientific activity of the eu Project :Monitoring, Safeguarding and Visualizing North-European Shipwreck Sites: Common EuropeanUnderwater Cultural Heritage – Challenges forCultural Resource Management” (MoSS)www.mossproject.com. and H. Jons, M. Man-ders, The ship wreck-site of the MoSS-Project, in 8th

Conference for Underwater Archaeology, Lelystad 29-30 march 2003, DEGUWA, in press; M. Manders, P.Palma, The main themes of the MoSS-Project, in 8th

Conference for Underwater Archaeology, Lelystad 29-30 march 2003, DEGUWA, in press.

methods and strategies for the conservation 43

Protection with polyethylene sheets and sandbags

This system uses sheets of polyethylene placed directly over the wreck, with sand-bags positioned on top of the polyethylene.20

Protection with sand, sandbags and blocks of cement

In some cases, wrecks discovered in shallow areas have been protected by variouslayers of sandbags, then covered by slabs of cement. At Torre Santa Sabina (Brindi-si), one of the wrecks from Roman times discovered in the bay a few metres fromthe beach, was protected by the Archaeological Superintendence with geotextile andsandbags covered by large cement blocks.2 This seemed to be the only possible so-lution, given the shallowness of the site, and above all, its vicinity to a popular bea-ch (part of the cargo had, in fact, been stolen during the period when the ship had re-mained totally unprotected). Unfortunately, we do not know what condition thewreck is in today; it would be advisable to plan a monitoring campaign.

The protection system with cement slabs for a vessel found in shallow waters pro-ved efficacious in the case of the first archaic ship of Gela. The wreck, discovered in988 at 4-5 metres’ depth, in the stretch of sea along the Bulala district coastline, had

been the subject of several excavation campaigns. On completion of every campai-gn, the wreck was protected by a large quantity of sandbags, a thick layer of sand andby large slabs of cement. In this way, it was possible to protect the ancient ship andits cargo from destructive marine action, prying intruders and trawler fishing nets.22

Protection using sandbags, electrically welded galvanizedwire netting and sand

In Italy, the protection system using sandbags and electrically welded galvanized ironnetting, which is then covered by sand, is very common. The netting is held firmlyto the seabed with stakes fixed at -2 metre intervals. This method is also relativelyeconomic and easy to implement. However, although it is more efficient than sim-ply covering with sand or sandbags, it only provides limited protection over time asa result of marine agents attacking and corroding the netting and of potential intru-ders who find no difficulty in cutting through the latter. During the surveys conduc-ted periodically in the 990’s by the author on the wrecks at Santa Caterina di Nardò(Puglia) and on that of the Secca dei Mattoni (the island of Ponza, Lazio), it was pos-sible to observe the effect of the biological attack on the wire netting as well as theholes made by clandestine intruders, who had cut through the protective barrierwith pincers and plundered the wreck of its cargo. These incidents are comparablewith those recorded by the Superintendence of Tuscany on the wreck at Giglio Por-to (the island of Giglio, Tuscany). It is necessary, also in this case, to organize perio-dic monitoring and replace the wire netting once corrosion has set in.23 The Ar-

20. E. Felici, Archeologia subacquea. Metodi, tec-niche e strumenti, Roma, 2002: 224-225.

2 . Cfr. the paper by W. Basilissi et. al. in thispublication: 57- 58.

22. R. Panvini, La nave greca arcaica di Gela (e pri-mi dati sul secondo relitto greco), Palermo, 200 : 9.

23. B. Davidde, Underwater archaeological parks :a new perspective and a challenge for conservation.The Italian panorama, «ijna», 3 . , 2002, pp. 83-88:83-84.

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chaeological Superintendence of Lazio has recently decided to replace the wire net-ting over the wreck of the Secca dei Mattoni.

This system of covering, with some variations, was also adopted to protect the wreckof the ship at Grado (a cargo ship dating from the first half of the 2nd century AD, cur-rently being restored) on completion of the excavation campaigns. The wreck was co-vered with sheets of polyethylene, then by a layer of sand and finally by two layers ofelectrically welded wire netting connected by steel cables to four blocks of cement posi-tioned at the top of the wreck. Furthermore, to prevent turbine blowers (in particular,mollusc fishing craft) from approaching the site, twenty-four reinforced concrete blocksof weighing about three tons each were positioned around the wreck.24

Protection with sandbags and modular metal panels

In order to experiment new methods of protection, the Archaeological Superinten-dence for Southern Etruria designed a special type of covering to protect the wreckof a 2nd century AD cargo ship, discovered at 38-40 metres depth off Montalto di Ca-stro (Viterbo). The galvanized metal panels measure 2 m2 and are covered with fibre-glass resin; the sides of each panel are reinforced with a steel bar welded onto the pla-te, also this coated with gelcoat. The bar makes it very difficult to cut through withshears. The panels are positioned in a tortoise-like shape connected to each other by2 mm-thick galvanized chain links. In order to improve the camouflage effect, a

layer of gelcoat the same colour as the seabed was applied to the fibreglass resin. Thewhole system was then anchored to the seabed along the perimeter of the protectedarea with special anti-extraction galvanized iron stakes, 5 cm in diameter and to . 5metres in length, fitted with mobile locking lugs at the lower ends. This type of mo-dular covering can also be removed in sections, and if the wreck is later excavatedand salvaged, the covering can be used for another ship.25

Protection with modular painted iron cases without bottoms

The pirogue discovered at Capodimonte (Lake Bolsena) in 99 at about - 2 metres’depth was protected by 2 modular iron cases without bottoms, painted with a greenanti-rust paint and placed over the full length of the pirogue, slightly overlapping ea-ch other and riveted together (the pirogue measures 9. 60 x 0. 80 x 0. 60). The casescontain holes to allow the water to circulate. The research project of the Underwa-ter Archaeological Operations Unit of icr in agreement with the Archaeological Su-perintendence for Southern Etruria, has proposed opening the protective covering ofthe pirogue after thirteen years to check the state of conservation of the wood.26

24. P. Dell’Amico, Il relitto di Grado: considera-zioni preliminari, «Archeologia Subacquea. Studi,ricerche e documenti», ii, Roma, 997, pp. 93- 28:94. A similar protection was proposed by F. Palla-res for the Albenga wreck see F. Pallares, Relazio-ne sulla campagna archeologica sottomarina 985 sulrelitto della nave romana di Albenga, “Rivista di Stu-di Liguri”, lI, 4, 985, pp. 632-639: 638.

25. R. Petriaggi, Un nuovo metodo di coperturaper il relitto di Montalto di Castro (vt), in Atti del

Convegno Nazionale di Archeologia Subacquea, An-zio, 30-3 Maggio e Giugno 996, Bari, 997: 34 -344.

26. I take this opportunity to thank the Ar-chaeological Superintendence for SouthernEtruria for having agreed to the icr experimen-tation involving the protection in situ of thelake village piles and I am particularly indebtedto Patrizia Petitti for providing me with the do-cumentation relating to the covering of the pi-rogue.

methods and strategies for the conservation 45

Protection with steel cases without bottoms

Protection consisting of a modular steel case was used to protect the Phoenician shi-ps of Mazarron.27 Each side of the case was fixed into the seabed. The upper surfaceof the case consists of m2 modular panels that can be opened independently. Thecase was covered with a layer of sand and shingle, then by wire netting anchored tothe seabed by stakes, and finally by a layer of sand and stones. The Spanish archaeo-logists say they are particularly satisfied with the experiment.

Case-type protective systems, above all in steel and galvanized metal, althoughmore costly, seem without doubt to be more effective from the conservation stand-point. The wreck is not weighed down by the weight of the protective material (ce-ment slabs, sandbags, etc.) that covers it and is therefore protected not only fromstructural collapse, but also from trawler nets and anchors. Furthermore, the absen-ce of light inhibits the development of biodeteriogenic organisms and therefore sub-stantially slows down the deterioration processes. Organisms that thrive in the darkand in anaerobic environments continue to develop, but at a much slower rate andtherefore less aggressively with regard to the wreck than their counterparts. Anotherpositive aspect of this type of protection, like that of panels, consists in the fact that,both cases and panels can be dismantled and reassembled during excavation cam-paigns and/or used again for other wrecks.

Protection using interlocking plastic ’crash barrier’ units

This method has been proposed for the James Matthew Shipwreck found in Wood-man Point, south of Fremantle, Western Australia and foresee the use of interlockingplastic ’crash barrier’ units commonly used in roadworks today, filled with sand.28

Protection using a silicone shell

During the mid- 980s, one of the two wrecks of the Lido Signorino, near Marsala,was protected in situ with a rhodorsil rtv 600 silicone shell produced by Rhone –Poulenc Italia, containing an added catalyzer w tixo bleu of 5% in weight. The shellwas constructed at a depth of about 2 metres, at a temperature slightly less than 20°.

27. I. Neguerela, Protection of Shipwrecks. TheExperience of the Spanish National Maritime Archaeo-logical Museum, in Underwater Archaeology and Coa-stal Management. Focus on Alexandria, Unesco-Pa-ris, 2000: 580-586.

28. T. Winton, « Road Lego » – a unique ap-proach to management of shallow wreck site comingfrom an understanding of coastal and in situ proces-ses, in The Fifth Word Archaeological Congress,Washington D.C. 2 st-June 26th, 2003: -7: As saysthe Author these units are lightweight, easy tohandle with buoyancy adjustment by partiallyfilling with sand and water, and chemicallyinert. They are placed in a pre-excavated shal-low trench and interlocked to form a ringaround the wreck. The water inside the units is

then displaced by sand from a diver-operatedwater dredge. Sand is then pumped inside thering of interlocking units until the wreck-site iscovered to the required depth. The crash bar-rier units have a configuration conducive towithstand wave loading and the circular for-med structure has inherent structural strengthto resist partial collapse due to wave scour andlocalised undercutting, see also V. Richards, M.Barret, I. Godfrey, E. Reed, The James MatthewShipwreck – Conservation and in-situ stabilisation,in The 9th ICOM-CC WOAM Conference Copenhagen 6th-

th June 2004, in press ; T. Winton, In situ con-tainment of sediment for the Shipwreck ReburialProject, in The 9th ICOM-CC WOAM Conference Co-penhagen 6th- th june 2004, in press.

46 barbara davidde

The silicone was applied in layers onto pieces of linen fabric (50 x 70 cm).29 We do notas yet possess sufficient data to assess the effectiveness of this type of protection overtime. Using silicone for in situ protection of a wreck is without doubt very costly andit is therefore difficult to imagine it being put to use on a large scale. In the 990s, Spa-nish archaeologists constructed a silicone negative impression to be able to producethe mould of the Roman wreck at Grum de Sal near Ibiza in the Balearic Islands.30 Si-licone moulds of statues and other stone artefacts discovered in the port of Alessan-dria (Egypt) were produced by French archaeologists.3

The fact, however, that it is easy to make silicone moulds underwater to producecopies is particularly interesting, as it opens up new horizons for the museum pre-sentation of ships with wood structures.32

It would, in fact, be worth assessing the possibility of producing silicone moulds ofcertain sections of the ship, preferably choosing the more significant parts, so thatthese can be displayed in museums or can be used for making scale models for di-dactic purposes and for the study of naval architecture.33 The original would remainprotected underwater awaiting better days. Moreover, further examining the displaycriteria so as to avoid giving the impression of an «amusement park», a copy couldbe left underwater to be inserted into a museum display itinerary. The underwatervisitors would then gain a more precise idea of how the ship appears at the momentof its discovery and immediately after the archaeological excavation.

The protection and conservation IN SITU

of metal archaeological finds and of wrecks with metal structures

Already in the late 980s, a method was devised for measuring the speed of corrosionand for preserving metal finds in situ, whether they be anchors, cannons, ships or air-craft. The method consists in transforming the sea-artefact complex in an electroly-tic bath. In fact, connecting the metal object to be protected to a sacrificial anodeconsisting of a weaker metal with respect to that of the object itself (generally, alu-minium, zinc), it is possible to slow down the speed of metal corrosion to the detri-ment of the anode

The chemist I.D. MacLeod successfully experimented this method on many wrecks,some of them with metal structures, which had sunk as a result of naval combat du-ring the Second World War, others, from the 8th and 9th centuries with wooden hul-

29. C. Meucci, Le Bateau arabo – normand deMarsala : la protection in situ, in Preventive Measuresduring excavation and site protection, Atti della confe-renza, Roma, 986: 55- 58; C. Meucci, Relitti su-bacquei e conservazione. Dallo scavo al progetto di re-stauro, L. Masetti Bitelli (a cura di), Archeologia,recupero e conservazione, Firenze, 993, pp. 5 -73.

30. B. Martinez Diaz, E. Toledo Brasal, Mo-dels de Silicona para piezas de madera procedentes debarcos sumergidos, «Patina», 6, 993, pp. 83- 89.

3 . J. C. Grangé, Sulle tracce di Cleopatra, «Ar-cheo», 8, 998, pp. 55-58.

32. To know other examples on the use of si-licone for recording archaeological ships’ featu-res in a marine environment since 98 see L. C.

Zambiano Valdivia, Moldeo subacuático de objec-tos arqueologicos, «Boletín del Istituto Andaluzdel Patrimonio Histórico», viii, 32, 2000, pp. 75-82 and footnotes nn. 4, 5, 7. See also R. Pe-

triaggi, Recupero, o quali altre scelte nel casodei relitti antichi ?, in Forma Maris, Forum Interna-zionale di Archeologia subacquea, Napoli 200 ,pp. 49- 52.

33. F. Pallares, 985. Relazione sulla VIII campa-gna archeologica sottomarina sul relitto del Golfo diDiano Marina (IM), «Rivista di Studi Liguri», lI, 4,pp. 639-643: 643 wishes the realization of a mouldof a section of the ship to start the naval architec-ture study and to make a scale model for the Dia-no Museum.

methods and strategies for the conservation 47ls that, however, contained iron cannons and anchors, such as the wrecks from DuartPoint – the Swan 653 and the Dartmouth 690 (Scotland). Periodic controls confirm theefficacy of this method and the stabilization of the corrosion processes.34

Since 992, on visiting the wreck of the Swan, underwater enthusiasts visit the sitewith a map following the itinerary indicated by a cable. The most important survi-ving remains of the shipwreck are the cannons and anchors, both protected by sa-crificial anode systems and the ballast ; the wood sections of the ship have been co-vered with sandbags as their state of conservation had been worsening significantlysince they had been left uncovered for a certain period of time. The protection sy-stems adopted for metal objects and for the vessel itself, as well as other data relatingto the objects, are indicated on floating plastic information cards connected by a ca-ble to lead weights fixed on the seabed. It is important to inform visitors and explainthe reasons for adopting conservation and protection systems in situ. In this way,they will understand the importance of certain precautions and will not be disap-pointed when, as in the case of the Swan, parts of the wreck are not visible.35

For the wreck of the San Pedro that foundered on 3 July 733, thirty miles off Flo-rida Keys (usa), which was designated an archaeological marine reserve in 989, theprotection and museum display in situ was organized as follows: what remained ofthe wreck was covered with ballast ; as regards the iron anchor, the above-mentionedmethod, using a zinc bar as a sacrificial anode, was adopted. The colonizations of ma-rine organisms, which have developed on the site, are being constantly monitoredand studied by biologists from the University of Indiana.36 A similar project for theconservation in situ was also proposed for the wreck of the Hercules, which sunk in66 in the port of Galle in Sri Lanka.

Contemporary wrecks made of metal do not just represent important evidence of re-cent history, but have also proved to be significant environmental resources, and shouldbe valorized and safeguarded like ancient wrecks. Their presence, above all, in protectedfishing zones or in underwater nature reserves, contributes considerably in aiding mari-ne repopulation, as their structures are transformed and function just like a barrier reef.

34. I. D. MacLeod, N. A. North. C. J. Beegle,The excavation, Analysis and conservation of shipw-reck sites, in ICCROM Conference, Ghent 985, pp.

3- 32; I. D. MacLeod, Conservation of corrodediron artefact. New method for on-site preservationand cryogenic deconcreting, «ijna» 6. , 987:49-56;M. McCart, SS. Xantho : the pre-disturbance, asses-sment, excavation and management of an iron shipw-reck off the Western Australia, «ijna» 7. 4, 998:339-347; I. D. MacLeod, In situ conservation of can-non and anchors on shipwreck site, in ArchaeologicalConservation and its conseguences. Preprints of Con-tributors of the Copenhagen Congress, 26-30/08/ 996,Roy Ashok (ed. ), London, 996: - 5; D. Gre-gory, Monitoring the effects of sacrificial anodes onthe large iron artefacts on the Duar Point wreck, «ij-na» 28.2, 999: 64- 73; D. Gregory, In situ corro-sion studies on the submarine Resurgam : a prelimi-nary assessment of her state of preservation, in Con-servation and management of archaeological sites, 4.

2, James & James (Science Publishers Ltd.), 2000,pp. 93- 00; I. D. MacLeod, Aplicação das cienciasda corrosao na gestao de sítios arqueológicos maríti-mas, «Al-madan», ii. 0, 200 , pp. 48-58; I. D. Ma-cLeod, In situ corrosion monitoring of the ironshipwreck of City of Lomnceston ( 865), in 3th Trien-nal Meeting ICOM Committee for Conservation, Rio deJaneiro 22-27/0 /02, 2002, pp. 87 -880.

35. Ph. Robertson, The visitors schemes on thehistoric shipwrecks of the Swan and HMS Dartmouth,Sound of Mull, Scotland (UK), in J. D. Spirek, D. A.Scott-Ireton (Ed.), Submerged Cultural ResourceManagement. Preserving and Interpreting oursunken Maritime Heritage, New York, 2003, pp.7 -84.

36. D. A. Scott-Ireton, 2003. Florida’s underwa-ter archaeological Preserves, in J. D. Spirek, D. A.Scott-Ireton (Ed.), Submerged Cultural ResourceManagement. Preserving and Interpreting our sunkenMaritime Heritage, New York, 2003, pp. 95- 05.

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Conclusions

These, therefore, are the systems generally used for the protection in situ of wrecksand submerged sites. The majority of the latter, as we have seen, are not possible forthe public to visit directly underwater. The public makes contact with them only inthe museum, when, in the more fortunate cases, the cargo or wreck itself has beensalvaged and restored or where, for example, in the case of an underwater prehisto-ric village, objects (pirogues, etc.) used in everyday life have been recovered.

Much more numerous than one would believe are, instead, wrecks or submergedsites that can be visited underwater, where special precautions or protective measu-res are lacking, a factor that can create management problems and detract from theirenjoyment.37

Among wrecks, those with metal structures are without doubt the most suitableto be «exhibited» in situ, providing a fascinating spectacle for the public. They do notrun excessive risks in remaining exposed underwater above all when, following themethod devised by MacLeod, it is possible to check and restrict the metal corrosionprocesses. These wrecks can also be subject to theft on the part of intruders; beforeopening the site to the public, it would be advisable to salvage easily removable orparticularly rare archaeological objects.

The same can be said for those wrecks that, though possessing wooden structures,had iron or bronze objects on board (cannons and other firearms, munitions, anchors,etc). A solution could be found in reburying the wreck and focusing the underwateritinerary on the archaeological objects. There are many examples of sites that havebeen treated in this way. In particular, I recall that of the Célébre that sunk with itsmany cannons in the 8th century at Louisbourg Harbour – Nova Scotia (Canada),which can be visited by underwater visitors accompanied by authorized tour opera-tors, or the wrecks in Red Bay where the Fathom Five National Marine Park (Cana-da) is situated. Here it is possible to visit twenty-seven ancient wrecks that sunk in va-rious different periods, though mainly during the second half of the 9th century.38

Another category of wreck particularly suitable for visiting in situ is that of the naveslapidariae, with their cargo of carved or partially carved marble (columns, capitals, sar-cophagi, blocks, etc.). Very often, if and when preserved, the wood structure of theseships has been severely damaged during the shipwreck as a result of its heavy cargo andit is therefore very rare to decide to recover all the cargo to study its structural charac-teristics. In some cases, it has been possible to study those parts of the vessel, whichwere not affected by the cargo and have been preserved, protected by the sand fromthe seabed. It is difficult for these wrecks to become prey to intruders, given the natu-re of their cargo; provisions for their surveillance can therefore also be less stringent.

37. Underwater itineraries can also be created inarchaeological sites where a wreck is not necessarilypresent and there are, instead, sporadic archaeologi-cal objects. We can name, among the many exam-ples, the underwater archaeological itinerary of theNatural Marine Reserve of the Cyclopean Islands(Catania), containing various lead anchor stocks ofthe Roman era, which are heavily incrusted to therocks, or the underwater archaeological itinerariespresent in the Protected Marine Area of the Egadi

Islands, etc. See for others examples in Italy B. Da-vidde, Underwater archaeological parks : a new perspec-tive and a challenge for conservation. The Italian pano-rama, «ijna», 3 . , 2002, pp. 83-88.

38. D. La Roche, 2003. A review of cultural re-source management experiences in Canada’s submer-geg heritage, in J. D. Spirek, D. A. Scott-Ireton(Ed.), Submerged Cultural Resource Management.Preserving and Interpreting our sunken Maritime He-ritage, New York, 2003, pp. 29-4 .

methods and strategies for the conservation 49Sometimes, the legibility of marble finds can be affected by infesting biological or-

ganisms that often cover the object completely. Certainly, also in this condition, theystill hold a strong fascination for the visitor, as is the case of ancient ruins on land whencovered with infesting vegetation. One cannot, however, underestimate the harmfulaction of certain types of biodeteriogens (for example, lithodomous and lithophagousorganisms) which, left to act undisturbed, can bring about the total loss of the items.For these categories of wreck, it is possible to use instruments and periodic cleaningmethods, which have been successfully experimented by the ICR Archaeological Ope-rations Unit on the fish tanks of Torre Astura and on the mosaic and masonry structu-res of the «Villa a protiro» in the Underwater Archaeological Park of Baia.39

Submerged architectonic sites are particularly suitable for adapting as museum si-tes in situ. The port of Caesarea Maritima in Israel, the submerged city of Baia inItaly, and the port of Ampurias in Spain 40 have all been transformed into underwaterarchaeological parks.

Since 99 , Sebastos, the port of Caesarea Maritima, has become an underwater ar-chaeological park with free access; a privately run diving club rents boats and organi-zes guided tours. The Park is supervised by the University of Haifa. There are four iti-neraries illustrated on plastic panels; three of these have an «Ariadne’s thread» at theheight of about metre from the ground, which guides the visitors during the visit.4

The submerged area of Baia has been an underwater archaeological park since Ju-ne 2002. The city extends under the sea and contains numerous ancient well-preser-ved buildings that often not only have perfectly legible masonry structures but alsodecorated surfaces and architectonic motifs. The boundary of the park is indicated bybuoys, and contains the architectonic ruins of Villa dei Pisoni as well as those of thearchitectural complex known as Villa a protiro. The park is managed by a consortiumof private companies, under the supervision of the Superintendence for Archaeologi-cal Heritage for the provincial districts of Naples and Caserta. The two underwater ar-chaeological itineraries are illustrated on a series of panels showing a plan of the an-cient ruins. The visitor route is indicated by a cable about 80 cm to metre from theground, attached to large cement dead-weight blocks.42

In the port of Ampurias, the great square-shaped stone blocks remain underwaterand can also be visited by divers without oxygen tanks.

To conclude, we must therefore remember that, in organizing an underwater hi-storical and archaeological itinerary, the following essential points must be taken in-to consideration:

• respect for the safety regulations for visitors and staff;• protection of the archaeological heritage from biological, chemical and physical deteriora-tion, as well as from vandalism and theft ;• the completeness of the scientific data.

The visitor itinerary can be indicated by a cable, which works like Ariadne’s thread:a very simple system which, as we have seen, has been adopted successfully in manyunderwater itineraries. All the information pertaining to the history and natural ha-

39. See article by Petriaggi Mancinelli also inthis publication: 09- 26.

40. See article by Petriaggi, Davidde in ActaDiurna, also in this publication: 98- 99.

4 . A. Raban, Archaeological Park for Divers at Se-

bastos and Other Submerged Remnants in CaesareaMaritima, «ijna», 0. , 992: 27-35.

42. B. Davidde, Underwater archaeological parks : anew perspective and a challenge for conservation. TheItalian panorama, «ijna», 3 . , 2002, pp. 83-88: 85-86.

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bitat of the site may be illustrated in a concise yet thorough manner, complete withplans and reconstructed images, on plastic panels positioned along the visitor route,or in the form of plasticized cards presented to visitors before immersion; smallerplastic cards can summarize the data relating to individual objects/sections.

The more precious finds (cannons, anchors, etc.) that are at risk of theft, could bereplaced by copies or, otherwise left underwater and possibly monitored more at-tentively with the help of closed circuit tv cameras or anti-intrusion systems with lu-minous or alarmed buoys.43

Finds of an organic nature, if not recovered, must be reburied; it may be worthconsidering the possibility of exhibiting copies. A programme of surveillance, moni-toring of the state of conservation as well as cleaning and seasonal maintenance cam-paigns must be carried out periodically to improve the enjoyment factor of the site.

If the water visibility permits and if the site is at not too great a depth, also the non-diving public may be able to visit the site in boats with transparent hulls.

Futuristic projects that propose the construction of underwater tunnels to allownon-divers to visit submerged sites have also been devised.44 For wrecks that exceed0 metres in depth, it might also be feasible to embark non-divers on board small

«bathyscaphs». The conservation and museum presentation in situ of underwater heritage must

not just be considered an opportune choice but may in itself provide a strong stimu-lus for experimenting new materials and technologies as well as representing a fac-tor in the socio-economic development of the communities concerned.45

Abstract

43. See for example G. Lattanzi, Allarme elettro-nico per le palafitte, «Archeo», vii, 7( 0 ), luglio,993: 79.

44. E. Mitchell, Il Lago di Mezzano : un esperi-mento di collaborazione fra Enti di tutela ed Enti loca-li per la salvaguardia e la valorizzazione di un sito ar-cheologico sommerso, in I Siti archeologici. Un proble-ma di musealizzazione all’aperto. Atti del Primo semi-nario di studi sulla ricerca archeologica in Italia, Ro-ma, 988; G. Di Stefano, Ipotesi di un parco archeo-logico subacqueo a Camarina, I Siti archeologici. Unproblema di musealizzazione all’aperto, in Atti del Se-condo seminario di studi sulla ricerca archeologica inItalia, Roma, 994, pp. 248-254.

45. Finally, there are some experimental exhibi-tions with underwater finds in aquarium; the wa-ter is distilled, filtered and regularly changed; thetemperature of the water and the light need to bechecked to not create damages to the items. In

Italy there are two aquariums like that in the Ar-chaeological Museum of the Territory of Populo-nia (Piombino); one contains some finds of thePozzino wreck (small wood cylinders, amphorasand containers of pond), the second one containsthe hoard of Rimigliano (around 3.500 silver coinsof the iii sec. AD) see M. Mannini, Il progetto del-l’acquario, in A. De Laurenzi (ed.), Un tesoro dalmare. Il tesoretto di Rimigliano dal restauro al Museo,Pontedera, 2004: 96. See also T. Nilsson, C. Björ-dal, Project Aquarius : exploring the use of anoxic wa-ter for exhibiting or storing archaeological wooden ar-tefacts, in Proceedings of the 8th ICOM Group on WetOrganic Archaeological Materials Conference,Stockholm, - 5 June 200 Bremerhaven, 2002: 23 -233; C. Björdal, Project Aquarius : preservation, sto-rage and exhibition of wrecks in an aquarium, in The9th ICOM-CC WOAM Conference Copenhagen 6th- th june2004 in press.

Often, in the Underwater Archaeological Parksthe demand of visitors is different from the needsof Conservation. This is always true for the woo-den wrecks.

This lecture will try to explain the situations

in which is possible to put together both exigen-cies.

Key words: underwater archaeology, in situconservation, Underwater Archaeological Parks.