Murphy - Preservation at Pearl Harbor

8/12/2019 Murphy - Preservation at Pearl Harbor

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Preservation at Pearl Harbor

Author(s): Larry MurphySource: APT Bulletin, Vol. 19, No. 1, Maritime Preservation (1987), pp. 10-15Published by: Association for Preservation Technology International (APT)Stable URL: http://www.jstor.org/stable/1494170

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INVESTIGATIVE TECHNIQUES

Preservationt PearlHarborLarry MurphyUSS Arizona was sunk at her mooringduringthe Japaneseattackon Pearl Har-bor, Hawaii on December 7, 1941, witha loss of 1,177 sailors and marines. Morethan 1,100 men remainentombedwithinthe wreck. Extensive damage sustainedby the battleship precluded the possi-bility of salvage, and the hulk became awidely recognized symbol of the PearlHarbor attack during and after WorldWar II.A memorial building spanning thewreck was completed in 1962 and com-memoratesthe Pearl Harborattack andresulting casualties. The striking whiteconcrete, steel, and marble structure,designed by Alfred Preiss, receives be-tween 1.2 and 1.5 million visitorsa year.In 1980, a new visitor center was com-pleted, and the Arizona Memorial be-came a unit in the National ParkSystem.The National Park Service (NPS) as-sumed responsibility for its operation,while the Navy retainedownership.NPSis also responsible for maintenance,interpretation and preservation of thememorial.In order to develop a long-rangemanagementstrategy,NPS Superintend-ent Gary Cummins initiated a phasedprojectto studythe shipwreck.The mul-tidisciplinary project planned to inte-grate historical preservation and parkinterpretationgoals, and draw assistancefrom various professionalcommunities,eventually including archaeologists, il-lustrators,historians, marine biologists,engineers, Navy salvage divers, and vol-unteerdivers. Dan Lenihan,chief of theNPS SubmergedCulturalResourcesUnit,was asked to bring his team of under-waterarchaeologistsand illustratorsromthe mainland to head the operation.

LarryMurphys an archaeologistwith theNationalParkServiceSubmergedCulturalResourceUnit,SantaFe, New Mexico.

Survey and MappingIn 1983, the firstphase of the evaluationof USS Arizona was begun. The objec-tives were to conduct an extensive un-derwatersurvey and mapping operationthat included photographic and videodocumentation o determineexactlywhatremained of the ship. ContemporaryNavy salvage operations conducted inthe four years following the sinking hadremoved most of the superstructureandarmament. No diving operations hadUndersea investigatory,mapping, and conservationtechniques are being devel-oped at Pearl Harbor.been conducted on the wreck since thecompletion of Naval activities in 1945,and no maps of the underwaterfeaturesof the wreck remainedfrom the salvagedives.The brief reconnaissancesurvey andpreliminary map of the wreck, com-pleted in 1983, resulted in some signif-icant findings.The entire forwardturretwith its 14-inch guns was located intact;there was no evidence of torpedo entryholes observed in the hull; the source ofoil leakage was discovered;and perhapsof most interest to managers, live ord-nance was found laying in the deckrubble directly under the memorialstructure. Naval Explosive OrdnanceDisposal divers removed the ordnance.In 1984 data collection was com-pleted for a series of detailed drawingsthat would serve as an interpretivede-vice and a baseline for future studies.The data collection was a cooperativeeffortbetween the National ParkServiceand the U.S. Navy. The funding wasprovided by the ArizonaMemorialMu-seum Association, a private supportgroup. The final product, a five-viewgraphic presentationof the USSArizona,

won for the National Park Service the1985 John Wesley Powell Prize for His-toric Display,awardedby the SocietyforHistory in the Federal GovernmentPhase II of the project, which tookplace in July 1986, was initiated by BillDickenson, who had replaced Cumminsas superintendentof the Memorial. Oneobjective was to obtain additional datato construct a model of the ship as itappearedon the bottom,which had beenproposed to augment interpretationofthe site for memorialvisitors.The graphicpresentationof the wreck requiredmoredetail for the modeler, and it was alsonecessaryto document the debris on thebottom of the harbor and the nearbymooring quays to enhance the displayThe revised map derived from the.un-derwater operations was the principadata source for the model builder. Themap would also serve as a baseline formonitoringthe deteriorationof the hulkAlthough this objective involved onlyfollow-up, using procedures and tech-niques developed in Phase I, the secondof Dickenson'sobjectiveswasmuchmorecomplicated:he wanted to begin a pro-gram that would eventually result inunderstandingwhat was happening tothe ship's fabric.After the question "What is there?"was answeredin PhaseI, the next logicaquery was "What'shappening to-what'there, and what are the implicationsofthe deteriorationprocess for public useover time?"- a farmorecomplex issueNo one had previously confronted theproblemof developing a long-termpreservation program for a whole ship insitu. More important,no one had evenaddressed the issue of whether a submerged war grave (the hull, not thememorial)shouldbe preserved.Whetheror not the management decision wasmade to interfere in the naturalprocesof deterioration, he baselinedata wouldbe necessary.

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Undersea ConservationArchaeologicalconservatorshave devel-oped many successfultechniques for thestabilizationand conservationof individ-ual materials removed from a marineenvironment,but the conservationprob-lems inherent in a complete steel hull600 feet long and 100 feet wide, im-mersed for 45 years in a rich biologicaland chemical soup is new territory.Ex-perience with materials from historicalmarine shipwrecks indicates that mostferrousmaterialsareprotectedfrom con-tinual corrosionby the formationof en-crustation, a complex interaction ofchemical and biological processes. En-crustationsubstantiallyreduces or stopsactive corrosion. Furthermore, encrus-tation can occur in semi-tropicalwatersin as little as five years. The corrosionrate for unprotected steel in seawater iscommonlygiven as .005 inches per year.It became clear to the USS Arizona teamthat preservation efforts of the ship-wrecks remaining in PearlHarbor inev-itably had to answer questions aboutcorrosionand encrustation processes. Afirst-cut researchdesign was formulatedto answer the initial question and de-velop additional questions to guide fu-

ture preservationresearch on the ship-wrecks.Dan Lenihan was overall projectdi-rector of the 1986 fieldwork. The prin-cipal objectivesof the study pertinent tosite preservationwere to:* Develop a baseline inventory of bio-logical communities on the structureof Arizona relevant to determiningthe biochemical processes having an

impact on the vessel fabric.* Obtain quantifiablemeasurementsofthe state of deterioration of metalstructuralelements at selected pointson USS Arizona.* Complete a reconnaissance evel sur-vey and controlled sketch of USS

Utah, the only other remainingvesselthat is an element of the Pearl HarborNational Historic Landmark.Dickensonand Lenihan developed aseries of specific questions relevant tothe firsttwo objectives.When Dickensonbecame awareof a localexperton marine

fouling processes,Scott Henderson,whohad conducted prior research in PearlHarbor, he contracted for biochemicalanalysis. Henderson, a civilian marine

NPS Divers MarkSenningand YvonneMenardcollectbiological amples romthe hull of USSArizona

biologist working for the Naval OceanSystemsCenter of Honolulu, developeda series of hypotheses and test implica-tions for application during the fieldsession. Some of the biological observations that follow came from his preliminary report.A secondary objective of the 1986operations was to determine the utilityof directing U.S. Navy reserve trainingexercises to do research on submergedcultural resources under the directionand supervisionof professionalresearchers. The reserve Mobile Salvage andDiving Unit (MDSU) from Long Beach(Det. 319), under the command of OttoOrzech, cooperated jointly with NPSdivers to collect appropriatedata fromboth USS Arizona and USS Utah.Arizona was analyticallydivided intohorizontal and verticalsurfaces basedonan examination of the 1984 base mapSixty-one vertical points were selectedby Henderson for observations of bio-foulingcompositionandthickness,whichprovided 20 transects of three observation stationseach, split equally betweenport and starboard ocations and evenlyspaced on the hull side. The stationincluded both hull and superstructurelements. Twelve of the vertical stationwere selected for installation of a permanently mounted pair of supportsthanow serve as a registrationdevice for anunderwater camera mount. The photostation mounts allow a camera to berepositionedexactlyso thatclose-up pho-tographs can be taken to record bio-fouling changes over time. The verticaphoto stationsare a key element in thelong-term site monitoring program under development.

APT Bulletin Vol. IX No. 1 19871

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U RIZONU.S. NATIONALPARKSERVICESUBMERGED CULTURALRESOURCES UNIT

DRAWINGS BYJERRY L. LIVINGSTON

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APTBulletin Vol.IXNo. 1 1987

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PERSPECTIVE VIEW FROM BOW

Twenty-five common taxa of foulingorganismswere observed and recorded.Over 99 percent of the vertical surfacesare estimated to be covered with en-crusting organisms.The hard-foulingen-crustationlayer,averaging well over 3/4-inch thick, is primarily composed ofoyster and vermetid shells, which pro-vide a substrate or secondarygrowth ofsponges and tunicates. That hard en-crustationlayer forms a protective bar-rier for the underlying steel fabric andreducesthe corrosiveeffects of seawater.The encrustationlayer maintainsan an-oxic environment against the exteriorsteel surfacethat promotesthe formationof stable oxides and, presumably,signif-icantly reduces cathodic reaction andcorrosion.Apparentlythe inner layer ofencrustation,originallycomposedof cal-cium carbonate, is replaced by ferrouscorrosion products bonded to the un-derlying steel.The USS Arizona's vertical surfaceswere observed at 55 locations selectedfrom the base map. Each observationstation was marked by a weighted andsequentiallynumberedplexiglasssquareto allow future observationsduring sitemonitoring. At each station a series ofobservationswas made. Sediment depth,composition, and types of biota wererecorded. In addition, where the over-

lying sediment was lessthan 1-footthick,a small area was cleared to determinethe condition of the substrate,which inmost cases was found to be teak deck.The overburden was composed ofvariouscombinationsof sand,rubble romoystersand vermetid worms growing onnearby vertical features, and mud andsilt. The shallower areas of the hullcontainedprimarilysand and rubble; hedeeper portions,more mud and silt. Theunderlying teak deck was found to besmoothand dense in mostareas,althoughsomedamageby burrowingmolluskswasnoted, particularlywhere the sedimentwas thin. One unexpected impact to theremainingwooddeckwas observed:Over100areaswere notedwhere the sedimenthad been cleared by the fanning actionsof egg-laying fish. These nests, 1- to 3-feet across, expose the underlying teakdeck to the actionof burrowingmollusks.

Researchersselected 12 areason thehull and superstructureor measurementof metal and corrosionthickness.Thesedata were collected for use by corrosionengineers in establishingcorrosionrates.The original researchdesign had speci-fied that small representativesamplesofthe steel fabric would be removed fromthe ship for laboratoryanalysis;however,clearancewas not granted,so no sampleswere taken. In the future,fabricanalysis

will be an importantresearch focus forcorrosionengineers.Corrosionand the biofouling processare affected by numerouswater qualityattributes,chiefly oxygen, pH and mo-tion. In orderto determine the corrosionrate of interiorspaces, the chemical andbiological conditions were assessed. Di-vers made biological observationsvisu-ally through hull openings, primarilyportholes. No interior spaces were en-tered, but adequate observationsof foul-ing were madewith an underwater ightBiological fouling was found on fewerthan 50 percent of the observable surfaces. Oystersand vermetidwormsoccuronly in a very patchy distributionon theobservable interior surfaces.Itwas assumed hatthe interior pacewould exhibit lowered oxygen and pHlevels compared to the ambient harbowater, as a result of the microbial andcorrosionprocess coupled with reducedwatermotion.A polyvinylchloride(PVCprobe was constructed so that watercould be pumped directly to a surfacwet well containing oxygen, pH andtemperatureprobes. The diver insertedthe PVC probe into interiorspaces to adistance of 15 feet. The measurementwere taken and samples of the interiowater were collected and chilled fordeterminationof the presenceof sulfide

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and hydrocarbons.There were no exfoliating layers,which would indicate active corrosion,observedin the interiorspaces. The dis-solved oxygen was found to be signifi-cantly reduced in the interor spaces. Aswould be expected, the areas closest tothe opening exhibited some flushingac-tivity. PH was only slightly reduced inthe interior. Petroleum products wereobserved in some of the interior spacesand were brought up in the probe sam-ples. The main concentration of hydro-carbons seems to have sunk to the lowerlevel of the spaces. The combination ofreduced oxygen and presence of hydro-carbons apparently reduced the corro-sion rates within the hull itself and maycompensate for the limited protectionofferredby the biological fouling.In addition to the biochemical ob-servations, a bathycorrometerwas uti-lized during the project. A bathycorro-metergives an indication of the galvanicactivity present. The unit is a diver-operated instrument that measures theelectrical potential difference betweenthe structuralsteel and a silver chloridereference electrode, then gives a digitalreadout in millivolts. The bathycorro-meter data have been turned over tometallurgical engineers at Pearl HarborNaval Shipyardfor analysis.The cooperation between archaeol-ogistsand marinebiologistshasproducedimportantbaseline data, and managershave committed to an ongoing monitor-ing of the observation tationsestablishedduringthis field work. Althoughthis hasbeen a significant beginning, it is justthe start. Before there is sufficient datafor management to make a decision re-gardingthe long-term preservationpro-gram of the shipwrecksof PearlHarbor,more information is needed.The experience of archaeologicalconservators with the conservation ofmetal hulls in situ is limited, and the 'literature s scanty.The problemof con-

servation and preservationpresented byUSS Arizona and USS Utah resemblesthe problemsfaced by those concernedwith corrosionof floatingships and sub-merged structures more than the prob-lems faced by archaeological conserva-tors in a laboratory. Proposed futureresearch plans include the use of non-destructive techniques for determiningthe thickness of the hull plates. Samplesof the anaerobic sediments surroundingthe embedded hull will be taken todetermine the natureof corrosionprod-ucts present. NPS will requestclearancefor the removal of fabric samples, andthe multidisciplinary research will beexpanded to include the active partici-pationof corrosionengineers,metallurg-ists and other specialists and their re-spective laboratories.As the PearlHarbor ield workmakesclear, both USS Arizona and USS Utahexist within a complex biological andelectro-chemical environment.The pres-

ervation programfor these historic ves-selsdependson understanding,and, per-haps, eventually manipulating thisenvironment. Additional measurementsare needed to complete the initial stepin understanding he environmentalcon-text of the PearlHarborshipwrecks.Thedata will be used to begin the processof researchdesign formulation to deter-mine the life-span of the hulls if noaction is taken, and to determine whatfurther tests and experiments are nec-essary to develop appropriateconserva-tion procedures to prevent further de-terioration of the vessel fabric, shouldthat option be adopted by management.The ramificationsof the research onthe Pearl Harborshipwrecksgo far be-yond those sites. Many important ironand steel vessels are submerged worldwide, and the preservationof those ves-sels in situ may be the only viablealternativeto their eventual disintegra-tion.

PERSPECTIVE VIEW FROM STERNAPTBulletin Vol.IXNo. 1 1987

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Murphy - Preservation at Pearl Harbor