EAC occasional paper no. 4

Heritage Managementof Farmed and ForestedLandscapes in Europe

Edited by Stephen Trow, Vincent Holyoakand Emmet Byrnes

Agdcuituie.FlshedesandFood

EAC occasional paper no. 4a

EuropaeflchaeologiaeCorisilitim

Heritage Managementof Far ed a d Forested

La dscapes i Europe

Edited by Stephen Trow, Vincent Holyoak and Emmet Byrnes

4.- —\‘ç~ Agdculture, D

i FlsherlesandFood A European Association

ENGLIS H HER ITAGE A I ofArchaeologistsTalmhalochta,Iascalgh agus Bla ~ w~son.~i

EAC Occasional paper flo. 4

Heritage Management of Farmed and Forested Laridscapes in Europe

Edited by Stephen Trow, Vin nt [4 yoak and Ernme Byrnes

Published by:Europae Archaeologia Consilium (EAC), Assodation Internationale sans But Lucratif (AISBL), Siège socialKoning Albert lI-Iaan 19 Avenue Roi Albert IligRO, Box 10 Boke 101210 Brussel 1210 BruxellesBelgium Belgiquewww.e-a-c.org

In association with:Department of Agriculture Fisheries and Food (Ireland); Department of Environment, Heritage and LocalGovernment (Ireland); English Heritage; European Association of Archaeologists; Forest Service (Ireland)

© The individual authors 2010

The opinions expressed in this volume are those of the individual authors, and do not necessarily represent officialpolicy

ISBN 978-963-9911-17-8

Brought to publication by Whimster Associates, UKTypesetting and cover design by Carnegie Book Production, UKPrinted by Aduprint Printing and Publishing Ltd., HungaryDistribution by Archaeolingua Hungary

Cover illiustratjon:Meon Hill, a statutorily protected Iron Age hillfort situated in Warwickshire, England. The monument, lyingpartly within woodland and partly in farmland and with its eastern side levelled by cultivation, encapsulates thernanagement challenges faced by thousands of archaeological sites in Europe. © Eng/ish Heritoge NMR 15369.27

Contents

ForewordKotolin Wolldk, Pres dent of Europae Archaeologiae Consilium

IntroductionStephen Trow

European Overview

I Farming, forestry, rural land management and archaeological historical landscapes in EuropeStephen Trow

National and Local Perspectives

2 Challenges related to archaeological heritage preservation in the Norwegian rural landscape~ngfid Smedsrod

3 I Problems and perspectives of archaeological heritage preservation in farmed landscapes in Germany— a survey of federal structuresAndreos Bütrne~ Jano Esther Fries, Henning Hassmann, Gabriele Schi/le~ Michael Strobel and ThomasWestphalen

4 I Shaping the NetherlandsCees van Roo4en and Guido Mouro

5 I Raising consciousness: the reconciliation ofarchaeological heritage preservation and agriculturalpractice in HungaryRéka Virdgos

6 I Agricultural changes, ancient mounds, and archaeological course-corrections: some held (and forest)notes from southern BurgundyWiIliam Meyer

7 I Cover is not shelter: archaeology and forestry in the Czech RepublicZdenék Neustupnj

8 Environmenta monitoring of archaeological depositsVibeke Vondrup Mortens

9 Monitoring and managing archaeological sites on the farmland ofWalesPeter Goskell and Gwilym Hughes

10 Field Monument Wardens in Northern Ireland: working with owners to manage scheduled historicmonurnentsCloire Fo/ey

u The Field Monument Advisory Scheme in the Republic of IrelandRosonne Meenan

12 Assessing and managing risk: the Scheduled Monuments At Risk (SMAR) and Conservation OfScheduled Monuments In Cultivation (COSMIC) projects, EnglandJon Humble

13 The Rural Environment Protection Scheme (REPS) and archaeologyHugh Corey and Ann Lynch

6 I EAC OCCASIONAL PAPER NO. ~

14 I Archaeology, agriculture and environrnent on the Burren Uplands, Ireland 113

Christine Grant

is I Heritage stewardship in Flanders: rural development money for rural heritage management? iigKarl Cordemons

i6 I Agri-environmental schernes and the historic environment of the United Kingdom: a view from Wales 123Mike Yates, with contributions from Victorio Hunns (Principal Specialist, Natural England), RhondoRobinson (Northern Ireland Environment Agency), and Jonathon Wordsworth (Rural Land Use Advisor,Archaeology Scotland)

17 I Ripping up history, sordid motives or cultivating solutions? Plough damage and archaeology: aperspective frorn England 129Stephen Trow

iS I Mitigation impossible? Practical approaches to managing archaeology in arable farming systems 135Vincent Holyoak

19 I Forestry and the historic environment in Britain: a challenging past and an exciting future 141Tim Yarnell and Peter Crow

20 I Forestry and archaeology in Ireland: current practice and future trends 147Emrnet Byrnes

21 I Archaeology and forestry in Bavaria (Germany): current ways of co-operation 157Joachim Hamberge~ Walter Irlinger and Grietje Suhr

Looking to the Future

22 I Changing the land — the implications of climate-change policies, actions and adaptations for Scotland’srural historic environment 163Jonathan Wordsworth

23 I The impoverishment of heritage in the European landscape — with some Swedish examples i6gLeif Gren and Peter Norman

Contributors 177

Résumés/Zusanimenfassungen 179

Environmental monitoring of archaeological depositsVibeke Vandrup Martens

Abstract: Methods of env ronmental monitoring of archaeolog ca deposits, coveringurban and rural areas, and varying depositiona situations nclud ng saturated orunsaturated zones, are described, An example is given from the farm of Aaker in Hamar,county of Hedmark, Norway. A method for standardsed archaeologica documentationof depositional conditions and deflnition at the state of preservation s shown. Theimplementation of the method, the underlying leg slat on, and ts consequences forarchaeology and in-situ site conservation are discussed.

lntroductionArchaeological deposits are a part of our cu tural heritagecontaining physical evidence of our past practices andinteractions with nature. Physical or ‘tangible’ culturalheritage is ofren unique and irreplaceable, Besidesbuildings, monuments and historic places it includeshidden objects, structures and soil Iayers of importancefor archacology. The meanings of this physical evidencecan be interpreted within the context at socio-economic,poltical, ethnic, religious and philosophical values ofparticular groups of people (Sandvik 2006; Sillasoo &HUe 2007). The importance of the preservation of culturalheritage is stressed byseveral conventions. The ConventionConcerning the Protection of World Cultural and NaturalHeritage was adopted by the General Conference ofUNESCO in 1972 (http://whc.unesco.org), The LuropeanConvention on the Protection at the ArchaeologicalHertage (www.conventions.coe.int, also known as theMa ta or Valletta Convention), which was agreed in 1992,and was in turn designed to protect the archaeologicalhertage as a source of the European collective memoryand as an instrument for historical and scientific study Ithas been atified by most Luropean countries. The Vallettarreary ralls for ‘the conservation and maintenance of thearchaeological heritage, preferably in situ’. This rneansthat archaeological sites must be actively maintained, orinvestigated, and not just lett to natural deterioration orsubject to anthropogenic destruczion.

The Norwegian D rectorate of Cultural Heritage hasproposed that t wi future undertake its statutoryduty at preserv ng the national heritage primarily byseek ng to preserve archaeological sites Iû 5/ru. This is inaccordance with the Norwegian Ministry of Environment’sstated aim to ‘preserve the underground archives and atthe same tme estabi 5 conditions for continued use ofthe pertinent areas and the development of vital innercities’ (Parliamentary Report No. i6, 2004—2005). It is alsoadhering to the guidelines in the new standard from 2009(NS 9451:2009) about ‘Cultural property. Requirements onenv ronmental monitoring and investigation of culturaldeposits’.

Besides being part of ow cultural heritage, archaeologicaldeposits of various ages present in the rural and urbanlandscapes are geo-ecosystems affected by environmental processes. The changes to the environmentcaused by global warming and other environmentalthreats, including human activities such as intensiveland use or the continuous development of towns, will

put archaeological evidence at risk and are a challengefor present and future (uture management of culturaheritage. How fast do archaeological materials and soifeatures degrade? At whch point wi the contextual valueof the deposts become unreadabe and impossible tointerpret? And what measures can we take in order topromote a sustainable in-situ preservation? During thepast 15 years or more, wo k on in-situ preservation ofarchaeologica remains has taken place as a consequenceof the Valletta charter of 992 W I ams & Corfield 2003;Willems 2008). However, much of the work sa far has dealtwith questions of the feas b ity of in-siru preservationwithout debating to what extent it is the desired solution,or if preservation through excavation and documentationis a safer way (Membery 2008).

The method puts a large responsibility on futuregenerations, as the concept of in-siru preservation impliesthat the deposits remain unchanged ‘for ever’. To ensurethat in-siru preservation may be considered a possibility,knowledge about the present state of preservation as welas the physical and chemical conditons for future preservation capacity is necessary. Environmental rnonitoringat archaeological deposits is the study of degradationprocesses and a search for mitigation strategies andremedial actions if or when critical levels are reached.

MethodsDegradation of archaeological deposits is caused firstand foremost by oxidation of arganic ar inorganicmaterial (Matthiesen 2004; Matthiesen er cl, 2006, fig. 3;Huisman 2009). Monitoring of environmental conditionsin depasits may be used to describe the presentstate of preservation and the physical and chemicaconditions for future preservation (Smit et eL 2006). Themanagement, preservation and conservation of archaeological sites in siru are complex tasks requiring a basisof multi-disciplinary competence. It is a relatively newtool to be used in the management at cultural heritage(Peacock 2002; Kars & Kars 2002; NIKLJ & BA 2008; Reed &Martens 2008). Good preservation conditions for archaeological deposits are characterised by stable physica andchemical conditions and relatively 10w micro-biologicaand chemical activity.

Research on in-situ preservation of archaeologicadeposirs has so far concentrated mainly on the depositsin the saturated zone below the ground-water table(Vorenhout & Smit 2006; Vorenhout 2008). Researchprajects conducted in rhe deposits at Bryggen in Bergen

76 EAC OCCASIONAL PAPER NO, 4

in Norway (http://www,natmus.dk/graphics/bevaring/a rkaeolog i/pdf-fi ler/Hen ning Matt/matt2004woampos-terbryggen.pdf) and at a number of sites in the UK, theNetherlands and other European countries (Christensson2004; NIKU & BA 2008; Keevill et cl. 2004; Matthiesenet cl. 2006) are examples of this type of research andhave shown that archaeological deposits are usually veryweII preserved under strongly anoxic conditions (Iackingoxygen) that are predominantly observed in waterloggedenvironments (Caple 1998; Caple & Dungworth 1998).

However, large volumes of archaeological depositsin most parts of medieval towns are situated in theunsaturated zone, where the layers are not permanentlywaterlogged (Gardelin 2002; Martens 2008b; Williams &Corfield 2003). In this zone, oxygen can be transported bypercolating rainwater to the archaeological deposits or bydiffusion of oxygen through unsaturated soil Iayers. Verylittie information is available about the environmentalconditions determining the preservation conditions ofarchaeological deposits in the unsaturated zone. This ismainly due to the Iack of adequate methods to measurethe physical, chemical and biological conditions in theunsaturated zone and thus a combination of differentscientific disciplines for the characterisation of the preservation conditions is required,

Archaeological deposits outside the towns are also oftenin the unsaturated zone. This means that the problems ofdryness and porosity are augmented by the extra threatsof cultivation: harrowing, ploughing, drainage, fertilisationand additions of other chemical components to fightweeds, improve the soil and get larger and/or healthiercrops. Crops that require more sau processing, such aspotatoes or strawberries, are harder on the depositsthan cereals because of the additional soul operationsundertaken to cultivate them (Durham 2008; Trow, thisvolume).

Monitoring techniques have so far been developed mainlyfor the saturated zone where ground wa er is monitoredor sampled. These techniques cannot be transferred tothe unsaturated zone because of the lack of soil water(Peacock 2002). Other techniques for in-situ monitoringand laboratory measurements must therefore bedeveloped, implemented and evaluated (Hartnik er at2000; Huisman 2009). In addition, the state of preservationand the environmental conditions in the unsaturatedzone are expected to deviate more in time and spacethan those in the saturated zone because the aqueousphase does not govern the environmental conditionsto the same extent. Maintaining equilibrium betweenartefacts, ecofacts and their surroundings ensures lang-

term preservation in 51w. Even small changes in theconditions of deposition, as caused by global enviranmental development or structural changes, may acceleratedeterioration (Peacock 2002; Kars & Kars 2002).

To evaluate the possibilities for in-situ preservation, anecessary starting point is an assessment of the presentstate at preservation. Information may be gained fromexcavation profiles or from drilling or auguring into thedeposits.

In a fieldwork situation, a relatively easy assessment ofthestate of preservation should be based on the followingprincipal criteria/indicators (from NIKU & BA 2008, 37):

Odour• for organic deposits: presence and strength of

‘rotten-egg’ smell• for wood: presence and strength at ‘freshly cut’

smellColour/colour change (the brighter the soil’s colourwhen first exposed and the faster the colour changeatter exposure, the better the preservation)Amount of force required to snap pieces of wood(the more force, the better the preservation — for thispurpose, relatively thin woodchips or twigs should bechosen, not naturally hard pieces like knots)Amount of force required to pull apart a strand ofmossSponge reaction of soil block; squishiness ofwoodchips; springiness of strands of moss or hair/furGeneral appearance (colou~ visibility of structure) ofmacroscopically visible organic components.

That should allow a description of the state of preservation in accordance with Table Si.

In additian to this kind of archaeological observation,reasonably good standards have now been developedfor sampling and measuring (NS 9451:2009) to obtaininformation on the future conditions for preservation.Archaeologists work with geochemists, geophysicists,microbiologists and hydro-geologists, measuring soilhumidity, soil temperature, porosity and water content,oss on ignition (content oforganic material), pH (acidity),and redox potential.

Redox conditions in soil (Table 8.2) may be characterisedby measuring redox-sensitive parameters in sail and inpore water (oxygen, nitrate, ammonia, manganese (II),manganese (IV), iron (III), iron (Il), sulphate, sulphide,methane) (Stumm & Morgan 1996). High oxygen concentratians indicate that micro-organisms feed on oxygen

Table Si State of preservation scale (SOPS) after NIKU & RA 2008 and NS 9451:2009.

Position inrelation togroundwater

Degree ofpreservationpoor medium

A2 A382 83

C33

03

A484 Bs

5D4 D~

Preservation scalenuU-value lousy

over Aoover/in Bo

in co0

Do

excellent

4fill etc. later than c 1900

© RA & NIKU

8 Environmenta monitoring of archaeological deposits I 77

Low LowHigh LowHigh LowLow LowHigh HighLow HighLow High

Sulph•e.5

LowLowLowLowHighI-IighL-Iigh

ro (II on I)2

Low -iighLow HighHigh LowHigh LowHigh LowHigh Low-Iiqh Low

e cx.co ditions

oxidisingnitrate to oxidising

nitrate to iron reducingiron reducing

nitrate to sulphate reducingsulphate reducing

sulphate red. to metanogene

re r,va~ibn

LousyPoor

MediumMedium

GoodGood

Excellent

© Bioforsk

Reducing conditionsOxidising conditions

Table 8.2 Concentration levels for parameters used to evaluate preservation capacity.

to degrade organic matter In such conditions one mayexpect nitrogen to be present as nitrate and not asammonia, and iron as oxidised iron (1W); the concentration of sulphide wiIl mostly be very Iow. However, ifthe conditions are instead iron reducing, all the oxygenand nitrate will already have heen used up by microorganisms, nitrate wilI be present as ammonia, and highconcentrations of iron (Il) should be present (Hartnik etaL 2000; Martens et aL 2008, 13). Thus organic matter mayhave already degraded, or no degradation jakes place.

In nature, degradation of organic matter or corrosionof metals takes place parallel to reduction of otherchemical combinations. The slowest degradation oforganic matter, and the least oxidation of metals, takesplace in metanogene conditions. By contrast, the fastestdegradation of organic matter happens in oxygen-richconditions. Oxidising and nitrate-redudng conditionsmay mostly be ciassified as poor preservation conditions,while sulphate-reducing and metanogene conditions aremostly excellent preservation conditions.

Other environmental factors that affect the preservationconditions of archaeological deposits are the permeabilityand water content of the masses. These factors control thetransport of (oxygen-rich) water through the deposits anddiffusion of oxygen into the pores. Presence of poisonouscon,binations may slow the degradation of organic matter.Acid and highly soluble saks corrode the surface of metalobjects. lncreased acidity and salt concentration increasescorrosion of metal objects and detrition and decaying ofbone (Kars & Kars 2002; Huisman 2009).

The development of mitigation strategies is the nextlogical step. It is of vital importance to know what todo when critical levels are reached, and to enable thedecision whether to excavate (that is, choose preservation by record) as the final solution fot preservingknowledge. Monitoring of archaeological deposits givesbaseline data that can contribute to our understandingof the natural processes of degradation that do occurwithin the deposits. These data must be the basis foraction in management (Huisman 2009; Martens 200sa;NS 9451:2009).

The alternative to in-situ preservation is preservation byrecord, that is, through detailed archaeological investigation and documentation. All artefacts, ecofacts, soil

samples and other physical remains from the past, aswell as all documentation material, need to be securedas a physical archive for the future. Knowledge aboutthe conditions for conservation of this physical archivecan be compared to the conservation possibilities insiw (Bergstrand & Nyström Godfrey 2006; Rimmer &Caple 2008). These archaeological considerations can bebuilt into the overall societal planning and thus reducethe impact on archaeological deposits, allowing suchdeposits to be preserved in situ and more sustainablymanaged in the future (Martens 2008b; Willems 2008;NS 9451:2009).

Material and resultsThe chosen sample site in this context is Aaker, a magnate(or high-status) farm from the Roman period until theisth century, since then used for farming and, later, asa military area. Aaker is situated at the Aakersvika bay,on the eastern shore of Lake Mjøsa, immediately east ofthe town of Hamar. The farm and its surrounding landare now owned by the Norwegian state, and plans weremade to transform it into a new state archive. This wouldrequire major building activity, mostly underground,50 inventories were made to assess the extent of thearchaeological remains. This work was carried out bythe county archaeologists (Hedmark fylkeskommune).When the remains had been mapped, NIKU, Bioforsk (theNorwegian Institute for Agricultural and EnvironmentalResearch) and Multiconsult, the consulting engineeringcompany, were hired to evaluate the state of preservationofthe archaeological remains, the conditions for future insitu conservation, the soil properties and possible buildingmethods (Martens et aL 2007; Martens et oL 2008).

Aaker (Fig. 8,1) is known particularly for its very rich metalhnds, flrst and foremost a gold-plated bronze bird-shapedbelt buckle from the Merovingian period (7th century AD)(Mikkelsen & Larsen 1992), and fot the fact that archaeological deposits are preserved up to more than i metre inthickness, which is unusual for the southern Norwegiancountryside. The buckle and other equally spectacularfinds from the same period were found on the fleldsbelonging to the farm.

As seen in Figure 8.2, the terrain slopes away from thefarm, leaving the impression of a mound comparable tothe medieval farm mounds of northern Norway (Bertelsen1978), and after the recent investigations, that is also how

NitrateN03

Ammonla€

EAC OCCASIONAL PAPER

Åkersh

fl ~ -

42

—

e

& -r

rc~%adndvilta

Sinnemd

Fig. 8.i Aaker (arm encircled,at Lake Mjøsa east of Hamar.© (‘I/KU & Mu/ticonsutt

Aaker farm has been interpreted (Martens et aL 2007;

Martens et cl. 2008).

As is shown in Figure 8.3, these deposits are rather dryand porous, leaving littie potential for the preservation oforganic flnds, and ecofacts are badly preserved, althoughbone, burnt as weII as unburned, has so far been weIIpreserved, as has metal. Iron, bronze and gold have beenfound in much larger quantities than expected, thusleading to the interpretaton of the site as a magnate farm

(Mikkelsen & Larsen 1992; Pilo 2005). Howeve~ the porosityof the Iayers leads to accelerated degradation, enablingoxygen carried through air or water to penetrate deepinto the deposits. This may eventually Jead to the ultimatedestruction of the deposits, and it is gradually renderingthem less legible. Even if some ecofacts and artefacts arepreserved, their stratigraphical context may soon be lost.

In an attempt to at least secure the maximum informationon the deposits as they are disturbed by archaeologists,

Fig. 8.2 Aaker main building seen (rom Vie east. Terrain sloping to a (arm mound. ©NIKU

,-.

vr

4meld ‘J~ØrsA1

fl

ikinqskipet

v

0

92 i~ea

8 Enviranmental monitaring at archaeolo~ical deposits

Fig. 8.3 Section througharchaeological deposits atAaker. © NIKU

i.

a standardised documentation sheet is used NIKU & RA2008, 29—31), classifying the components at the Iayer andtheir internal distribution, as well as trying ta define theirpresent state at preservatian, as shown in Table Si.

In 2007, two ditches and two auguring prafiles wereinvestigated (for example, Fig. 83), and fl 2008 the investigation continued with auguring at four locations withinthe protected area. One profile, borehale 4, cansistedat only disturbed Iayers and sterile subsoil. The archaealogical deposits in bareholes 3 and s are in the unsaturatedzone. They are dry and poraus. Archaeologically, frie stateof preservatian was characterised as very paor (barehole3) and poor (borehole s) (Table 83). In bath cases, thegeochemical evaluatian at future preservation conditions

for arganic material is equal ta the archaeologicaevaluation, whereas the canditions far the preservatianat inorganic material are better, cIassi~ed as medium(Table 8.3).

At barehale 6, 2 metres at medieval depasits were faundbeneath madern infill (Table 8.4). All the medieval depositsare in the saturated zane, and sa their states at preservatian as well as the canditians tar future canservatiandiffer cansiderably fram the other investigated depasitsat Aaker. Layer 3 was evaluated as being in a paar stateat preservatian, and the tuture canservation prapertieswere cansidered paor ta medium far arganic material,and medium far inarganic flnds. By cantrast, layer 4 wasin an excellent state at preservatian, and the canditians

Table 8.3 Auger prafile s, Aaker, 2008.

1,36—1,92 Maraine silt Sub sau1,92—2 Skje da Sub.sail

Si AnalysisAnalysisSOPS: Archaealagical state a( preservarian statusLaw arganid cantent 10%

Medium arganid cantent 10-20%High arganic cantent 20-30%

GW Average graund water level© NIKU & Riotorsk

45

Top level Depth Deposit Material(m asl) (m) type

i29i 0—0,05

129,05 a,o~—a,s8128.52 0,580,82

128.28 0,82—1,36

CW 127,8

Sample OPS *

nr

LawnSand

Arch depasitMaraine clay

Tap sauAdded sau

iJndisturbedSub soil

Preservationchemical- h sical

127.74

127.18

ar anic matter

2

3

mor nic

medium

EAC OCCAS ONAL PAPER NO. ~

0 002 Meadow Tap soil125.08 002-0,64 Sand Added soil

GW 124,6124.46 0,64-080 Moraine clay ‘ 2

0,80-1,49 Arch deposit Undisturbed1,49-1,90 Arch deposit

123.2 1,90-2,42 Arch deposit

2,42-2,81 Arch deposit ‘ 62,81-3 BIue clay Sub soV

1 AnalysisAnalysisSOPS: Archaeological state of preservation statusLow organic content 10%

Medium organic content 10-20%High organic content 20-30%

GW Average ground water level@ NIK(J & Bio(orsk

Table 8.4 Auger profile 6, Aaker, 2008.

for future conservation were measured and evaluated asexcellent for both organic and inorganic material. Furtherdown, the conditions were not excellent, but still good(Table 8.4; Martens et at 2008, 57—58).

Good preservation conditions for archaeological depositsare characterised by stable physical and chemicalconditions and relatively low micro-biological andchemical activity. Stable chemical and physical conditionslead to a decrease in the natural gradients causingchemical processes (for example, hydraulic gradients),thus slowing degradation of the deposits (Martens er at2008, 13). An evaluation of the archaeological deposits atAaker shows that the ones in the unsaturated zone arein a rather poor state, and also have poor conditions forin-sitt,, conservation, due to their porosity and dryness.The dryness causes cracks that ga deep into the soil, thusallowing oxygen and oxygen-Iillecl rainwater to penetratedeep mo the deposits. If no mitigating intervention iscarried out, for example by covering the deposits witha protective clay Iayer, the deposits will most certainlydegrade further, New and better tools to measure andgain information directly fram the sau are needed. Since2007, probes measuring soll humidity and temperaturehave been installed in a profile (Fig. 83). This simplemonitoring may indicate how fast the degradation canhappen, 50 that decisions can be taken whether toexcavate or accept the loss of contextual informationfram a very important site (Martens et a/. 2007).

From 2007 to 2008, the monitoring showed considerablevariation, especially in the tap half-metre of deposits. Thisshows clearly that the uppermost archaeological depasitsare the most vulnerable in all respects: mechanical disturbances, dewatering, temperature variations and addedaccess to oxygen (Martens et at 2007, 30). In thesedeposits, degradation takes place continually In the areaswhere the soll is worked, ar at other sites in farmedareas with known archaeological locations, it may be

necessary to impose restrictions on ploughing depths,drainage and crop types to enable in-situ preservation(Johnsen 2009).

The archaeological deposits at Aaker are very similar incomposition and content to those of the nearby medievaltown of Hamar, and it is probably safe to conclude thatthe threats to Aaker — continued degradation of depositsdue to dewatering and ultimately lass of contextualinformation — also hold true for Hamar. After the latestinvestigations, it was decided that building a new statearchive would pose too great a risk to the archaeological remains, and at present, the future of the site isundecided.

DiscussionWhen do measurements fram environmental monitoringsignal danger to the archaeological remains, and what areour options then? How may the contextual informationbe saved? Is it possible to use chemicals to alter theenvironment of a site, fihl in ar dram away water, ar cavera site with a protective Iayer, ar da we need to excavateto preserve as much knowledge abaut the past as we cangain from each site? All these are pertinent questions thatmust be raised when considering in-situ site preservation.At Aaker, after the recent development where buildingplans were cancelled, there are still no answers to whatmay be done to mitigate the harm already caused tothe site during the preliminary inventaries and throughnatural deterioratjon.

Another important issue is, who shauld be asked topay far mitigation? If data loggers signal danger, io aris years after they were installed, can we then ask theoriginal developer to pay for the rescue operations, ormust mitigation be government funded? Norwegianlegislation is not clear on that subject, and the practiceis even more muddled. It wauld not suffice to refer tothe 1992 Malta Convention (the European conventian

Tap levd Depth Deposit Material Layer Sample SopS * Preservation(m asi) (m) type nr nr chemical-physical

124.3

123.61

122.68122.29

345

D3

D2c2

Csc3c4

organic matter inorganic

poor mediumpoor-rnedium medium

goodood

8 Environmental monitoring of archaeological deposits 8i

on the protection of the archaeological heritage) andthe Norwegian Standard (NS 9451:2009), consideringthat large sums may be involved. On the other hand,a developer who is allowed to build, for example, onpiles but on the condition that the preservation state ofarchaeological remains are evaluated, and the possibilitiesfor in-situ preservation are checked and monitored, mightreasonably be made to set aside funds (for example, in aciosed bank account) to be used for mitigation strategiesifand when the need anses. Such a condition should beweighed against the demands that would otherwise havebeen made to finance a full archaeological investigationof the site before development.

If the archaeological remains cannot be preserved insitt,, they may be rescued for the future by excavationand conservation in museums and research institutes.However, both artefacts and ecofacts may be degradedduring storage. It is therefore of interest to comparepreservation in situ with preservation ex situ, in order tocreate a basis for reliable protection and conservation ofthe archaeological deposits and their contextual historicalinformation,

ConclusionEnvironmental monitoning of archaeological deposits is agood tool for evaluating the conditions for in-siru preservation of archaeological remains, although the methodshave so far concentrated on measuring saturated ratherthan unsaturated sites. We need new and better toolsto measure and gain information directly from the soiland not from water. However, an archaeological andcontextual evaluation of the site and its state of preservation is a necessary first step. Remains in the unsaturatedzone are far more vulnenable than the saturated ones, andit is therefore uncertain whether in-situ preservation is apractical solution, or if it wilI simply lead to a completeoss of contextual information. Thus, an issue to beaddressed further is the financing of mitigation strategiesfor monitored sites.

vvm@niku.no

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