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Departmental Papers (Historic Preservation) Graduate Program in Historic Preservation

January 1999

Lessons from the Great House: Condition and treatment history as prologue to site conservation and management at Casa Grande Ruins National Monument

Frank G. Matero University of Pennsylvania, [email protected]

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Matero, Frank G., "Lessons from the Great House: Condition and treatment history as prologue to site conservation and management at Casa Grande Ruins National Monument" (1999). Departmental Papers (Historic Preservation). 3. https://repository.upenn.edu/hp_papers/3

Copyright 1999 Maney. Reproduced from Conservation and Management of Archaeological Sites, Volume 3, Issue 4, 1999, pages 205-224. Publisher URL: www.maney.co.uk/journals cma (article homepage) http://www.ingentaconnect.com/content/ maney/cma (journal home page).

This paper is posted at ScholarlyCommons. https://repository.upenn.edu/hp_papers/3 For more information, please contact [email protected]. Lessons from the Great House: Condition and treatment history as prologue to site conservation and management at Casa Grande Ruins National Monument

Abstract As the first ederf ally designated and protected archaeological preserve in the United States (1889-92), the site of Casa Grande Ruins National Monument in Arizona, USA, provides an excellent opportunity to examine the effects of past site conservation and management policies. Renewed investigation and analysis of the caliche building material and wall conditions of the Casa Grande using new techniques of field, laboratory and digital recording have allowed a reassessment of the structure in an effort to explain recent phenomena of alteration and deterioration, and make recommendations for structural and surface monitoring and treatment. The focus on the development of a detailed condition survey of the earthen structure has also promoted the creation of a standard graphic lexicon of earthen building conditions for use at other sites.

Comments Copyright 1999 Maney. Reproduced from Conservation and Management of Archaeological Sites, Volume 3, Issue 4, 1999, pages 205-224. Publisher URL: www.maney.co.uk/journals cma (article homepage) http://www.ingentaconnect.com/ content/maney/cma (journal home page).

This journal article is available at ScholarlyCommons: https://repository.upenn.edu/hp_papers/3 CONTENTS IN BRIEF

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ARTICLE

Lessons from the Great House Condition and treatment history as prologue to site conservation and management at Casa Grande Ruins National Monument

FRANK MATERO

As the first federally designated and protected archaeological preserve in the United States (1889- 92), the site of Casa Grande Ruins National Monument in Arizona, USA, provides an excellent opportunity to examine the effects of past site conservation and management policies. Renewed investigation and analysis of the caliche building material and wall conditions of the Casa Grande using new techniques of field, laboratory and digital recording have allowed a reassessment of the structure in an effort to explain recent phenomena of alteration and deterioration, and make recommendations for structural and surface monitoring and treatment. The focus on the develop- ment of a detailed condition survey of the earthen structure has also promoted the creation of a standard graphic lexicon of earthen building conditions for use at other sites.

That night, in the full moonlight, the Casa Grande INTRODUCTION assumed a soft, poetic beauty, with its ruddy surface flooded with radiance that threw the shadows of its Cited by Cosmos Mindeleff over a century ago as deep recesses into a rich mysterious obscurity - a 'perhaps the best known specimen of aboriginal transformation from the aspect of the ruins in the architecture in the United States' [9: 295, the ruin broad glare of daylight. While we lay in our tent, known as Casa Grande, located in south central gazing dreamingly at the beautiful picture, Mr Arizona, midway between Tucson and Phoenix, Cushing told us in his charming and inimitable remains unique among ancestral Native American manner one of the Zuni folk-tales about the 'Priests" structures in North America. Several principal of the House' - a tale whose full significance was reasons can be cited for its early and current not clear to him until he came to this region and significance. As the most conspicuous structure of found the ruins of the 'Great Houses'. As we a large prehistoric settlement now partially con- listened, the ancient walls before us seemed to be tained within the boundaries of Casa Grande repeopled with the venerable old priests, and it Ruins National Monument, the Great House is the would have required little imagination to have largest surviving prehistoric non-mound earthen heard the weird, fascinating chants of the worship- building in the United States. Moreover, it is the pers. [1] only surviving exampleof ClassicPeriod Hohokam

ISSN 1350-5033 1999 JAMES &JAMES (SCIENCE PUBLISHERS) LTD 204 FRANK MATERO

Figure I. Aerial view of Compound A and the Casa Grande with its 1903 shelter, c. 1930 (CAGR/NPS).

Great House architecture and exists in an imme­ The site is equally distinguished as the first diate village context not preserved elsewhere federally designated and protected archaeological (Fig. 1). Despite its age (1300-1450 AD), the preserve (1889-92) in the United States and structure remains one of the most complete and possesses one of the earliest (932) and largest intact free-standing aboriginal structures and cer­ twentieth-century shelters erected over a single tainly the best preserved of any such earthen structure to date (Fig. 2). These two aspects of buildings in North America, displaying a high preservation consciousness, one legislative, the degree ofphysical integrity. It therefore affords an other technological, have had a profound im­ unparalleled opportunity to study the architec­ pact on the state of conservation ofthe structure tural and technological knowledge and organiza­ today. The site is also important to the history of tional skills that were required by the Hohokam to the National Park Service (NPS) as the head­ construct so large and complex a structure. quarters of the Southwestern National Monu-

Figure 2. View of the Casa Grande with Olmsted shelter, 1997 (ACL). LESSONS FROM THE GREAT HOIJSE 205 ments, directed by Frank 'Boss' Pmkley, from tigations and architectural recordings of the Casa 1923 to the 1940s. Grande were first made only in 1976 by Wilcox Despite the acknowledged importance and and Shenk [13] and in 1980 by Wilcox and early preservation of the Casa Grande, limited Sternberg [14], supplemented by photo- information exists about the composition and grammetric recording of the exterior walls by physical condition of its earthen walls: the mecha- Perry Borchers in 1977. In 1984, an electronic nisms and rates of deterioration, aspects of its monitoring system was installed to measure physico-chemical weathering and structural sta- crack movement in the Great House walls. bility.The erection of the first wood and iron roof Despite an early focus of preservation concern shelter in 1903and its subsequent steel canopy in and stabilization, no comprehensive plan cur- 1932 have certainly had a beneficial effect by rently exists for the site. Preservation has rather reducing climatic deterioration. Yet recent mate- been a case of continuing earlier approaches rial analysis and a detailed comparative survey of and techniques that have developed over time, past and existing conditions have revealed a range based on empirical knowledge as well as lim- of macro- and micro-scaled material alterations ited experimental testing. and degradation. These changes, when consid- In light of the existing documentation of the ered in the context of dynamic environmental structure and its previous stabilization history, as conditions including diurnal and seasonalclimatic well as changes in contemporary conservation change, groundwater withdrawaland seismicactiv- methodology, the current programme calls for ity, present a potentially dangerous situation for the immediate acquisition of additional baseline in- future preservation and survival of the structure. formation for developing future programmes of According to the monument's current manage- cultural resource management for the site. ment plans [11:2], the prime resources at Casa Grande Ruinsare the prehistoric structures, which PROJECT OBJECTIVES AND STRUCTURE were the initial justification for designation and protection of the site in 1892 and adoption into the An assessment of the condition and preservation National Park Service in 1918.Currently the whole management of the Great House has not occurred monument is listed on the National Register and is since the 1970s. ii To date, a complex array of a National Historic Landmark, and all the prehis- repairs exists, including the original efforts by toric structures are on the NPS List of Classified Mindeleff from 1891-2. Of these, various treat- Structures (LCS) as they are considered to be of ments are reaching or have reached the end of national archaeological and architectural signifi- their serviceable life and need to be replaced or cance. Yet the Great House remains the primary reconsidered. Recent studies, proposals and treat- and publicly recognised resource. This isdue to its ment recommendations made since the 1970s conspicuous size and the fact that over 90%of the reveal diverse approaches and solutions to the site's known archaeological remains are buried perceived problems at Casa Grande. and therefore less visible to the public [11:1-17]. Any conservation action must begin with an However, unlike other exposed walls and features understandingof the problems through a series of on site that have received numerous preservative systematic, scientific studies. For the Casa Grande, treatments involving capping and various typesof this must include a detailed survey and assess- surface protection, the Great House possesses ment of past and existing conditions as baseline significant informational value due to its presenta- information for the design and implementation of tion and the absence of direct fabric interventions. a monitoring programme to document and record The first scientific documentation and structural, material and environmental changes. stabilization of the Casa Grande was performed by As a result of these identified goals, detailed field- Cosmos Mindeleff in 1891-2 [9,10]and was con- and laboratory-based investigations were devel- tinued by Jesse Walter Fewkes during his exten- oped and begun as Phase I by The Architectural sive excavation and preservation work beginning Conservation Laboratory of the Graduate Program in 1906[4]. i However, detailed architectural inves- in Historic Preservation, University of Pennsylva- 206 FRANK MATERO nia from 1997-9 at the request of the Southwest the walls in their original configuration and Region Support Office (SRSO) and Casa Grande current condition under their own weight and Ruins National Monument (CAGR). The project under wind and seismic loading. In addition, a was funded by the National Park Service with structural assessment of the existing steel shel- support from the University of Pennsylvania. iii ter was performed using a Staad III program The objectives of the conservation programme and a preliminary retrofit design using compos- were generally focused on gaining a better under- ite materials was posited. standing of the existing and potential deteriora- Treatment Testing and Assessment: detach- tion problems and to offer options for current and ment of the interior wall surfaces was investi- future conservation treatments and management gated and several grouting formulations and of the Casa Grande. These objectives necessitated reattachment methods were evaluated as pos- the following activities: sible candidates for treatment of unstable areas using facsimile models in a laboratory-testing to qualitativelyand quantitatively record the past programme and limited trial field tests. and existing physical conditions of the structure; to analyze the material and structural character- PAST CONDITION AND CONSERVATION istics; HISTORY OF THE CASA GRANDE to explore conservation treatments for the immediate problems of fragment and surface Casa Grande Ruins National Monument holds a detachment,surface friabilityand animal activity; seminal position in the development of a preser- to document all research results; vation consciousness for America's archaeological to produce a report and proposals for conser- sites. Long noted as the first prehistoric and vation and future phases of research. cultural site to be established in the United States, 14 years before the passage of the Antiquities Phase I comprised the following components: (Lacey) Act of 1906 and 24 years before the formation of the National Park Service (1916), the Documentation and Condition Survey: detailed monument also displays a series of early ap- field examination and computer-based graphic proaches to the physical conservation and presen- recording of the condition of the exterior and tation of such sites. As part of these efforts of interior elevations of the earthen walls and preservation, various written, graphic and photo- associated finishes. Included were annotations graphic descriptions of the existing conditions of of past conditions and interventions as evi- the site were recorded. Today these documents denced by earlier photographic and written serve as useful evidence for charting past and documentation. This was correlated with the current deterioration and the effects of specific other investigations, and will be essential for interventions. An interest in the description of the planningfuture diagnoses,monitoring and treat- Casa Grande in general is of course much older ment applications and evaluations. than the preservation efforts of the past century. Material Testing and Analysis: scientific exami- Fewkes [4] and Wilcox and Shenk [13]provide the nation, recording, geo-technical testing, and best detailed chronological account of informa- analysis of the earthen building materials and tion on its appearance. Amore recent administra- finishes to assess their original formulations, tive history of the monument covering the yearsof use and alterations and deterioration over time. federal management from 1892-1992 has also This is the first step in conjunction with the been prepared [2]. macro-analysis of structural and environmental As extensive as these studies are, a review of conditions to ensure that compatible methods previous documentation for the purposes of diag- and materials are selected for any conservation nosing earlier conditions in order to understand work to be implemented. past and current decay mechanisms and predict Structural Analysis:preliminary structural analy- future failure has not been conducted. The need sis including determination of the stability of for and difficulty with generating such baseline LESSONS FROM THE GREAT HOUSE 207

information was understood as early as 1895, whenJohn Wesley Powell, Director ofthe Bureau of American Ethnology (Smithsonian Institution), wrote to the Secretary ofthe Interior regarding the Casa Grande. 'It is impossible to determine, and difficult even to approximate, the rate of destruc­ tion quantitatively [of the Casa GrandeJ, especially so since it goes on cumulatively, with constantly increasing rapidity' [9:349], The following sum­ mary of past conditions based on the earlier written and photographic sources is an attempt to provide the foundation for such a baseline com­ parison with the present condition survey con­ ducted in 1997-9. Figure 3. South elevation of the Casa Grande, c. 1888, published by Fewkes (1892). Note partial wall segment Frank Hamilton Cushing - Visit and description that collapsed by 1891-2. ofDecember 31, 1887to January 4, 1888 amount of weathering the exposed exterior had As first director of the Hemenway Southwest suffered, but created a structurally precarious Archaeological Expedition, F. H. Cushing visited situation 'afford[ing] an all too good opportunity Casa Grande Ruins from December 31, 1887 to for additional undermining by the atmosphere, January 4, 1888 to conduct a comparative study of rains, and like agents of erosion' [3: 188]. Two the remains of another Great House at the site of accompanying photographs of the south and Los Muertos, Arizona. Cushing prepared a sketch northeast exterior elevations taken prior to plan of the site and photographed the structure Mindeleff's 1891-2 stabilization work give a clear, (see below). He also interviewed a local rancher albeit partial, indication of the severe basal ero­ who reported that the ruin had fallen into rapid sion of the exterior walls, the undermining from decay only within the past ten years due to the localized excavation, the irregular high level and removal of beams and lintels 05:603], Cushing slope of the immediate grade and the difference believed that earthquakes played a major role in in fill level between the exterior and interior. iv the destruction of the Casa Grande [14:16], Also visible in these photographs are the three wall segments that subsequently collapsed on the Jesse Walter Fewkes- Visit and description of north, east and south elevations around 1891-2. April 1891 Although Rizer in his completion report docu­ ments the loss ofthe south end ofthe exterior east Following Cushing as the new director of the wall and a separate section of the south wall HemenwaySouthwestArchaeological Expedition, during stabilization [10:321-42], it is clear from Fewkes visited Casa Grand Ruins in 1892 for a photographs during and after stabilization that the brief period to make 'a few observations of its east end of the north wall also collapsed or was present condition', including measured plans in­ removed at that time. The instability of all these dicating standing and fallen wall sections [3:180], wall sections is clearly evident given the combina­ Buried within his text of archaeological descrip­ tion of unsupported wall ends on the northeast tion are several important statements regarding and southeastcorners and their associatedvertical the 'as-found' condition. Most important in this construction seams and through-wall cracks, es­ regard are his comments on graffiti and the severe pecially defining the fallen section of the south undermining ofthe foundations, especially on the wall (compare Figs 3 and 4). Additional damage exterior northwest corner, from pothunters and to the structure also may have occurred from the vandals (Fig. 3). According to Fewkes, these Sonoran Earthquake of 3 May 1887 but clearly below-grade exposures not only revealed the most of the collapses occurred earlier. 208 FRANK MATERO

site plans and photographs. As such they rank among the earliest professional technical reports on ruin stabilization in the United States. Like all writers before him, Mindeleff con­ cluded that the Casa Grande was already a ruin by the time of the first Spanish descriptions begin­ ning in 1694. Mindeleff took a great interest in hypothesizing site formational processes in the creation of the mounds; however he took a sceptical view of equating surface erosion and wall loss with original height of walls or the relative age of structures. He did, however, make the astute observation by using earlier photo­ Figure 4. South and west elevations of the Casa Grande graphicevidence thatthe Casa Grande hadchanged with its first 1903 shelter and Mindeleff repairs, c. 1910 relatively little in recent times in its gross overall (NPS/CAGR). profile or surface texture (compare Figs 3-5).

Cosmos Mindeleff- Documentation of1891 The surface erosion ofa standing wall ... is very slight. Photographs of the Casa Grande ruin, As a result of the efforts of Mary Hemenway and extending over a period of sixteen years ... other influential Bostonians, $2000 was allocated show that the skyline or silhouette remained by the United States Senate for the preservation of essentially unchanged during that period ... It is the site and expended on documentation and through sapping or undermining at the ground stabilization of the Casa Grande. The work, identi­ surface that walls are destroyed. [9: 300] fied as 'preservation of the ruin [with] no attempt at restoration' [9: XXXVII] was prepared and super­ In his preservation report Mindeleff, like Cushing vised by Cosmos Mindeleff for the Smithsonian and Fewkes before him, cited vandalism (digging Institution from 1891-2andincludedexcavation and and timber removal) as the primary agent of levelling ofdebris from the exterior and interior, the destruction of the Casa Grande Ruins. The differ­ insertion of metal rods and wooden tie beams to entials::onditions of the exterior walls - the south support the south wall, the insertion of brick and and east walls being in the worst condition - were plaster infill support of the wall bases and the attributed to the prevailing storms from the south­ insertion ofwooden lintels in breached openings as east. Conversely, the collapse ofthe southeast and needed (Fig. 4). Subsequently, an area of approxi­ northeast corners was attributed to weather and mately 480 acres including the Casa Grande Ruins was established as a preserve by Executive Order and a custodian was appointed [10]. Mindelefrs 1891 examination and documenta­ tion of the structure prior to stabilization was first reported in the Thirteenth Annual Report of the Bureau ofAmerican Ethnology [9]. The stabilization work was subsequently described in detail in the Fifteenth Annual Report of the Bureau of Ameri­ can Ethnology [10], Despite the division and date of the reports, documentation and preservation were performed as consecutive operations. Mindeleff's reports are the first detailed descrip­ tions of existing architectural and material condi­ Figure S. South elevation of the Casa Grande, 1997. tions ofthe site and included detailed topographic Compare with Figs 3 and 4 (ACL (UPENN). LESSONS FROM THE GREAT HOUSE 209

construction defects. In addition to these insufficient to complete the preservation work localized problems, Mindeleff considered wall outlined first by Alexander L. Morrison, then collapse from basal erosion or 'sapping' to be a Victor Mindeleff and finally by his brother Cos- problem requiring immediate attention. mos. Nevertheless, interventions deemed neces- This, he believed, was caused by the mechanical sary on the basis of the above assessment were abrasion of wind-driven sand against the lower executed as emergency measures. Debris removal walls softened by rising damp from the ground and regrading were first undertaken in a ten-foot and accumulated debris against the wall [9:300- area around the main ruin. Specifications called 301]. While early pre-stabilization photographs for temporary bracing of the walls before the clearly show significant overall basal undercut- removal of interior debris 'down to floor level or ting, up to one foot deep according to Mindeleff, the original ground level' [10:335]. Undoubtedly at the interface of the exposed wall base and this resulted in the removal of the original built-up adjacent ground level [9:Plate LV,10: Plate CXVI], floor levels in Tiers B and E. Debris and soil it is highly unlikely that mechanical scouring was removal to at least 12 inches below grade on the the culprit (Fig. 3). Water, no doubt, was involved exterior exposed the walls for basal insertion of in the process of deterioration; however it is more fired brick laid in cement mortar generally two likely that, given the high water resistance of the bricks deep [10: Plates CXXand CXXI]. A 1 - 2 caliche (as demonstrated by the recent laboratory inch recess was created at the surface to allow tests), salt and possibly frost cycling were prob- for the application of a cement-lime plaster ably responsible instead for the chemical and flush with the exterior earthen walls. Contrary mechanical deterioration of the earthen walls. to current explanation, this infill was not in- This undermining of the walls through basal stalled strictly as structural underpinning but 'to erosion clearly extended down belowthe built-up give a surface capable of effectively resisting debris as demonstrated by the extent of the brick atmospheric influences and the destructive ac- and plaster infill required once the soil was tion of flying sand, and at the same time would removed. This type of damage was also noted not disfigure the ruin by making the repairs during the recent condition survey of the interior obtrusive' [10:326]. walls where fallen and accumulated debris once In addition new wooden lintels were inserted existed as evidenced by Mindeleff'scontour maps in openings where infill of the cavities above was [9: Fig. 328 and Plate LII] and recorded ground required for structural support. The south wall, cross-sections [10: Plate CXVIII]. Here loss and due to its unstable fragmented condition, was friability of the walls were observed in a wide supported by two metal tie rods and two wooden d zone below and just above the fill line, clearly tie beams running north-south to adjacent east- d indicating deterioration before and/or during de- west walls and fixed at their ends by metal plates. bris accumulation. This exists in contrast to intact, Wood was used in lieu of metal for the longest of originally concealed subgrade walls that were the lateral supports, presumably to reduce any only exposed in 1891 when the original floors thermal expansion stresses the metal might cre- were removed (Tiers B and E.) Clearly the zone ate. Fencing and a protective roof or shelter as immediately belowand above thisrelativelyloosely originally proposed were not executed at this packed soil and debris was an active area of time. Both Victor and Cosmos Mindeleff op- wetting and drying, both inside and out, experi- posed the installation of a roofed shelter, insist- encing potentially excessive salt and/or freeze ing on repairs 'so devised that the ruin was not thaw cycling. materially disfigured or changed1 [10:329]. Cos- mos, however, did recommend a reassessment Cosmos Mindeleff- Preservation repair work of after four years to ascertain whether atmos- 1891-2 [10] pheric erosion was severe enough to require protection of the ruin. If so, a shelter was to be As stated in the original report, the $2000 in designed so as to be supported entirely from funding allocated by Congress was known to be within the structure. 210 FRANK MATERO

As recommended, a reassessment of the ruin Later rnaintenance andpreservation (1920s to was made by W. ]. McGee in 1895 after field visits the present day) and comparison with photographs taken in 1892 before preservation work began. While compari­ Preservation of the site after the major excavation son showed no perceptible change over most of and interpretation program by Fewkes was largely the walls, conditions on the south and east walls restricted to maintenance and localized repair. were found to have worsened in just three years. The major intervention to occur during this period He reported: 'the profiles are more extensively which would visually affect the structure and site modified ... some of the old crevices are widened for years to come and influence future arguments and deepened, and some new crevices appear; regarding all shelters was the construction of the and in some parts it can be seen that the walls are great steel canopy designed by Frederick Law lowered several inches ... destruction is proceed­ Olmsted, Jr and NPS landscape architect, Thomas ing at a not inconsiderable rate' [10:348]. If accu­ Vint (Fig. 2). During the 1940s and later in the rate, this supports earlier and current observations 1970~ experiments with water repellents and regarding the severe condition and exposure of consolidants eventually led to a programme of the south and east elevations due to the prevailing acrylic-amended mud shelter coats for the protec­ winds and storms. Eventually, in 1903, with an­ tion ofthe earthen compoundwalls. Later, reburial other $2000 of funding secured by Congress, a was adopted as a method of preservation for redwood and corrugated iron roof shelter was fragile walls and features. constructed over the Casa Grande closely follow­ ing the design published earlier by Mindeleff [10: CHARACTERIZATION AND ANALYSIS OF THE Plate CXXIV] (Fig. 4). EARTHEN BUILDING MATERIAL

Jesse Walter Fewkes - Excavation, repair and The earthen material used to construct the Great preservation work of1906-07and 1907-08 [4] House at Casa Grande Ruins is a limey soil known as caliche. Caliche refers to accumulations of As part of its commitment to assist government authigenic carbonates common in soils of arid agencies responsible for the protection of ar­ regions where accumulation forms prominent chaeological sites, the Bureau of American Eth­ layers in which the morphology is determined by nology (BAE) began a series ofwork projects and the impregnating carbonate. Archaeologists specu­ publications focused on the preservation of se­ late that the caliche for the Great House was lected sites in the southwest, including the Jemez obtained from borrow areas nearby and then Plateau, Mesa Verde and Casa Grande. Dr]. Walter processed or 'puddled' in caliche mixing bowls Fewkes of the BAE was placed in charge of the [6]. By breaking up and working the hard natural excavation, repair and preservation of the entire caliche, the builders of the Great House were able Casa Grande site, continuing the work begun by to augment the natural properties ofthis particular Mindeleff in 1891-2. A special appropriation of soil by improving matrix homogeneity and parti­ $8000 was disbursed under the auspices of the cle contact, reducing voids, and increasing plastic­ BAE, Smithsonian Institution, and an extensive ity without additional water, thereby avoiding programme of excavation and interpretation was shrinkage and improving the density and strength instituted to make the site more accessible and of this material for building purposes. legible to the public [4]. CompoundA and the Casa Many speculations regarding the construction Grande were treated in the first season (1906-07) techniques for the Great House have been offered (Fig. n. Little work was done specifically to the since it was first viewed by Europeans beginning Casa Grande Ruin although the walls of Com­ in the seventeenth century. Most observers im­ pound A and others were excavated, capped plied the use of formwork to construct the walls; with adobes and protected with shelter coats of however Wilcox and Shenk [13] proved that no cement and soil and an open drainage system forms were involved and suggested rather that a was installed. system of individually placed, hand-shaped units LESSONS FROM THE GREAT HOUSE 211

Figure 6. Lower west wall of the Casa Grande, north Figure 7. Lower west wall of the Casa Grande, north end showing area of detachment and loss in 1975 (left) end adjacent to Fig. 6. Note cracking and detachment and 1995 (right), 1998 (ACL). cracking indicative of potential future loss (ACL). similar to 'English cob' was employed. Research and clay cemented by calcium carbonate. In conducted during the present study also suggests addition, a high percentage of naturally occurring that more than one system may have been em­ nodules or concretions of calcium carbonate of ployed to construct the walls in which larger various sizes and shapes was found as the main 'dumps' of the puddled caliche may have been component of the course fraction. Therefore cal­ used in combination with the smaller hand­ cium carbonate was present in the caliche in two moulded units to create the horizontal wall courses. forms: as a cryptocrystalline binder and as large This aspect of construction is important as it may calcic nodules which probably played a major role explain the characteristic detachments or spalls of in reducing slump and shrinkage in its use as a both large and small fragments that have occurred coursed material for building the walls. over time as the result of the weathering of the As a result of years of natural weathering from puddled earth of various but prescribed sizes wet-dry cycling, the caliche developed a calcium making up the wall cross-section (Figs 6 and 7). carbonate-enriched crust on its exposed surface The composition of the caliche from the Great and a corresponding calcium carbonate-depleted House has been analyzed by numerous research­ zone located immediately behind the surface 20­ ers beginning in 1879. v The present characteriza­ 30 cm deep. Similar surface crusting has been tion and analysis was performed as part of the observed for calcareous soils and is related to both current research programme using the fragment the chemical solubility ofcarbonates in water and that fell from the west wall in 1995. vi Analysis water movement in soil. Water, either migrating included thin section petrography with polarized through the material during drying or from exte­ light microscopy, scanning electron microscopy rior ground sources, alters the cementing media of and x-ray diffraction. Geotechnical tests to assess caliche. Thus the caliche loses some ofits calcium physical, mechanical and chemical properties carbonate, which, being dissolved, is transported included granulometry, Atterberg Limits (liquid to the surface, and during evaporation is precipi­ limit, plastic limit), volumetric and linear shrink­ tated. close to or at the surface. Accordingly, the age, moisture andsoluble salt content, compressive outer pores are gradually filled with carbonate at strength, modulus of rupture, wet/dry cycling, the expense ofinternal depletion and weakening. water resistance, water absorption and acid solu­ In this manner an enrichment zone of calcareous ble content. matter develops on the exposed surface and These analyses and tests suggestthat the caliche varies in thickness. from the Great House was composed of a natu­ This phenomenon has been observed on the rally occurring combination of gravel, sands, silt fragment analyzed from the west wall of the Casa 212 FRANK MATERO

Grande. The relocation of calcium carbonate from In conclusion, a combination of intrinsicfactors inside outward changes the density, porosity and including preparation techniques of the caliche, strength of the caliche. Hence an increment of constructionmethods,and physico-chemicaltrans- calcium carbonate content in the form of very fine formations of the caliche in combination with particles within the capillary tubes of the caliche natural and human-related activities have been reduces the diffussivity (water movement) of the responsible for the past and present condition of material. This- reformed caliche exhibits high the Great House. resistancetowater and wet/dry cycling,low water absorption and low shrinkage. Conversely, the CONDITION AS EVIDENCE inner zone of caliche displaying impoverishment of calcium carbonate shows high porosity, friabil- Methodology ity and low strength as well as low resistance to water and wet/dry cycling, high water absorption One of the underlying objectives of the current and high shrinkage. Casa Grande Phase I conservation Program has These physical and chemical changes in the been the development of a methodology for the caliche of the Great House have resulted in documentationof earthen architecture and related differential weathering of the material. Thus, the surface finishes. Despite the world-wide occurrence calcium carbonate-enriched zone has functioned of these materials and their susceptibility to decay, as a protective skin more resistant to wind and no systematic standardized programme for their water erosion due to its highly cemented condi- recording or study has been developed. The condi- tion and low water absorption. This altered sur- tions recording and documentation programme de- facecaliche has been lost in areas due to mechani- veloped included the following three components: cal cracking and fragmentation, conditions attrib- utable to other factors including construction The creation of a universal (and expandable) flaws, initial shrinkage and seismic shock. On the lexicon of conditions terminology for earthen other hand, interior carbonate-depleted zones building materials, complete with written de- have been greatly affectedby water (dissolution), scription, photographic and schematic illustra- freeze-thaw cycling and wind abrasion resulting tion,and coloured graphic symbolsfor mapping; in active conditions of surface friability and loss. The development of a simple reproducible Differential deterioration is not only due to field-to-lab system of recording using 35mm physico-chemical changes in the caliche. Other rectified photography to create base imagesfor intrinsic causes of deterioration are construction- graphic field annotation of detailed conditions related combined with subsequent damage from in the past and present; timber removal. Extrinsic factors have been re- The assembly of existing graphic and database sponsible for aggravating existing intrinsic prob- software to digitally manipulate the graphics lems resulting in the various detachment of frag- and textual information in order to record ments and cracking of the Great House. Site conditions now and in the past, and to assist in observations based on patterns of deterioration, conditions diagnosis and interpretation, includ- along with results obtained from the wall condi- ing the identification of the cause, pattern and tions survey and the present characterization of cycle or progression of deterioration now and the caliche have provided additional information in the future. on wall construction and construction sequencing of the Great House, thus extending recent inves- Field recording tigations of the original construction [13,14].The integration of such findings has allowed new Prior to conditions surveying, the exterior and interpretations of the differential weathering of interior elevations of the Casa Grande were re- the structure, especially in relation to the large corded using 35mm rectified photography to fragment detachments that have been occurring at provide literal base images for annotation. Each various locations (Figs 6 and 7). wall surface was divided into sectors, which LESSONS FROM THE GREAT HOUSE 213 represented the smallest area to be surveyed as a provides the quantitative data to understand tht: single field sheet. The sectors for each wall were subtleties of change over time. However, what, given a unique identifier, a letter and a number. where, how and when monitoring occurs de- Each sector photograph was printed on a laser pends first on an understanding of the critical printer from a Kodak Photo CD. parameters affecting change through an initial The photographs were taken with a 35mm reading of the physical evidence. singlelens reflex camera fitted with a 28mm wide- To this end, a visual 'reading' of the condition angle perspective control (shift) lens. The camera and deterioration of Casa Grande was first ex- was mounted on a tripod for all photographs, and ecuted using a conditions glossary developed levelledin two dimensions usinga spirit level. The specificallyfor the project as a potential universal third critical measurement, perpendicularity to the prototype for earthen architecture (Appendix). wall, was achieved by using a framing square, or Prior to executing the survey, conditions were by measuring from two equidistant points on identified individually by their physical character- either side of the photo centreline istics and grouped according to their overall effect as either subtractive or additive. Buildingfeatures Conditions annotations and previous interventions and repairs constituted separate categories. All conditions were recorded Interior and exterior conditions were recorded by in time present. Past losses were indicated by 19 graduate students over a total of four weeks of location as notes only if accurate field time. Pre-established descriptive terminol- photodocumentation could pinpoint their occur- ogy and graphic symbols were employed as rence by or between a certain date(s). annotations using coloured markers on acetate Graphic recording systems were developed overlays on the printed photo elevations. Prior to using colour and symbol to define discrete classes the field recording, earlier photographs were of conditions and subsets within each. Both linear collected from the site library, the Western Ar- and overall pattern symbols were employed de- chaeological and Conservation Center (WAAC) pending on the type of condition. For example, and the Arizona State Museum, Tucson. These subtractive conditions such as loss, detachment were all used to date and record previous condi- and cracking were represented with linear pat- tions and repairs on the overlays.In addition, each terns, while additive conditions such as surface sector was described using an accompanying deposits were represented by overall point pat- architectural description form including informa- terns. Within general condition types, colour and tion on the base image, surveyors, date, wall pattern were further refined linking subtypes location, tier, wall orientation, room space, sur- together and/or reflecting the different levels of face finish and loss and treatment ascertained severity within a type. For example, all subtypes from the historical documentation. of loss were represented in red and repairsin blue. The breakdown of conditions recording into In other cases, graphic symbols were further discrete, symptomatic descriptions allows for the refinedso that linked subtypes were expressed as possibility of postulating correlation among con- variations on a specific pattern, such as diagonal ditions and with variables such as environment, hatching and cross-hatching for degrees of de- material composition, building construction and tachment and solid and dashed lines for cracks of previous repairs and treatments. This has been different widths and depths. In this way, a graphi- made all the more possible through the ability to cally compatible and legible system could be better manipulate digitized data as discrete lay- created allowing a fast visual reading both within ered systems with CAD and GIS software (Fig. 8). condition categories (same type) and across con- Short of long-term monitoring, the careful re- dition categories (different types), while at the cording and interpretation of existing conditions same time referencing past conditions and previ- affords the opportunity to posit trends and poten- ous treatments through notes. vii The result is a tial cause and effect relationships explaining de- graphically meaningful and legible system that terioration phenomena. Instrumental monitoring takes advantage of colour, graphic symbol and NOTES -~ fLj~_..."'SOaalq_~ lOaD'" A Lc:- JI9I·1192 0_"",'·,,__

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letter-related text, and can be easily studied for 1997-8. When considered in conjunction with visual patterns. otherfactors suchas environmentand microclimate, wall orientation and exposure, wall composition, Digital documentation construction technology and previous interven­ tions, these observations suggest obvious and All field-recorded information was subsequently subtle patterns of physical alteration which have imported into computer photographic and draw­ resulted in both loss and degradation as well as ing applications to transfer the field survey into a potential improvements such as surface harden­ digital format. The final product is a series of ing. The summary observations described below plotted drawings within the traditional architec­ are intended to accompany and supplement the tural format of scaled elevations and plans but graphic data. By using the CAD digital format, with the ability to manipulate complex overlays of multiple interpretations of conditions can be ex­ annotated conditions and to quantify each condi­ plored to query and reveal patterns and trends as tion (Fig. 8). The drawings were also saved well as anomalies related to time, location, and digitally on high-capacity Zip disks as Autodesk condition type. Simultaneously, plotted images as AutoCAD (rI4) drawing files. both overall elevations and detailed sectors allow Prior to the overlay of conditions, all acetate for an effective cyclical assessment of conditions sheets and their base photographs were scanned and an evaluation of treatments in the field. to facilitate the location of conditions through tracing. CadOverlay was used as an imaging OBSERVATIONS OF PRINCIPAL CONDITIONS programme to bring the raster images into AutoCAD. Although with AutoCAD (rI4) one can Loss bring digital images directly into the programme itself, there were capabilities with CadOverlay to Loss, whether as wall fragments or wall segments, align and manipulate images that had the potential is the final and ultimate stage of deterioration at of adding more flexibility if raster images could be the Casa Grande. It is the most extreme condition printed underneath the vector line drawings. and obviously non-recoverable; howeverthe care­ All individually enteredsectors were then joined ful recording of total and various partial loss to complete each elevation. In the future this categories (major, moderate, erosional and sur­ joining as a complete montage elevation should, face) is a useful indicator of past and current occur before the overlay of individual sector trends, especially when dated through earlier conditions so that field recording anomalies (e.g. documentation. Whenviewed in conjunction with misalignment, perspective distortion) may be cor­ other factors such as wall configuration and con­ rected on the base photographs, allowing accu­ struction details (seams), or accompanying condi­ rate conditions overlay at any scale (Le. individual tions such as friable surfaces or soil deposits, sector or entire elevation)' Adjustments to the fabric loss can be understood as the result of drawings, hatch scales and layouts were made structural or superficial forces and active or inac­ before final plotting. Twenty-five sheets were tive decay mechanisms. At Casa Grande, most produced including 23 elevations, a glossary sheet complete loss appears to be the result of single of definitions and conditions, and a plan sheet event structural collapse, usually in association documenting wall abutments and discontinuities. with structuralweaknessesfrom constructionseams Large format and reduced 11" x 17" drawings were or \lnsupported masonry as in the case of broken produced (Fig. 8). wall ends and breached openings. Smaller but no less significant loss can be traced to localized ASSESSMENT AND DIAGNOSIS detachment (see below). Major and moderate losses are usually associ­ The following observations are a summary of the ated with large surface areas of severe exposure major conditions recorded during the exterior and such as parapets, wall tops and bases. Localized interior wall survey of the Casa Grande from loss within the confines of specific construction 216 FRANK MATERO

courses usually indicates intrinsic material inferi- Detachment cracking, on the other hand, rep- ority in those areas. Erosional loss is a specific resents a very different problem. Although insig- condition, always in associationwith deep cracks, nificant in appearance, its association with de- ledges or openings causing high volume water tachment indicates the potential for large losses channelling and mechanico-chemical dissolution of lens-shaped fragments. These have occurred of the clay-lime binder of the earthen material. in both isolated and associated areas of the Surface erosion is a more diffuse condition occur- exterior and interior as indicated by several re- ring over a broader area and with less volume of corded events over the past fifty years and prob- water washing over exposed areas (see below) ably even earlier, judging from the presence of and may be related to the loss of the calcium tell-tale lens-shaped losses on the surface. This

, carbonate-enriched surface. peculiar condition appears to be clue to inherent At Casa Grande nearly all wall tops exhibit planes of weakness within the walls caused by areas of major and moderate loss, presumably the mounding or .puddling of large and small from centuries of weather exposure (wetting and units of prepared caliche, especially along the drying) prior to the erection of the shelter in 1903. lower courses, often above now unsupported Basal loss, now only visible in the interiors, but areas (Figs 6-7). Given the blind nature of these formerly on the exterior (before Mindeleff's re- failures, incipient detachment canoccur for a pairs), was most likely also due to water, however long period of time undetected, allowing addi- in this case, as the agent for salt and frost attack tional damage from animal activity and salt resulting in the gradual flaking and disintegration formation such as was observed in association of the wetted zone. with the most recent spa11 onthe west exterior in 1995, and earlier in 1975. Cracking and detachment Surfacefinish detachment is a unique condition characterized as a loss of bond between the interior Although crackingis the most visible and obvious finishes and their masonry substrate, occurring ei- of conditions observed at Casa Grande, its impor- ther as open or blind separation. Like wall detach- tance in the overall stability of the structure is no ment, this condition appears to be largely due to longer critical with the exception of through-wall construction technique whereby the smooth, level cracking. The majority of cracks observed on the interior surfaces were created by the application of exterior and to a lesser degree on the interior of a separate veneer of puddled earth or layers of Casa Grande are superficial and the result of earthen plasters. These in turn were subsequently gradual surface weathering of original shrinkage finished with one or more thin layers of red clay cracks within individual construction courses. washes.Surface finish detachment isalmost always Obvious exceptions to this are cracks whose located along the lower or upper walls where the length, depth and direction of propagationclearly wall has been damaged and opened from the indicate construction anomalies or post-construc- removal of beams and the penetration of water. tion failure from settlement, uneven loading, collapse and seismic and vibrational activity. Microhoodoos, friable surface and soil deposits Most vertical through-wall cracks appear to relate to original construction methods including These conditions, often found in associationwith terminationof individual horizontal courses (head one another, indicate a past and possibly active joints) and adjacent wall abutments. Where these condition of weathering from wind-driven rain anomalies occur with other deleterious conditions and snow. Although the construction of the first such as unsupported wall ends or water channel- and subsequent shelters in 1903and 1932 osten- ling, collapse can and has occurred in the past. sibly halted direct damage from precipitation, Both structural and non-structural cracks whose wind-driven rain and occasionally snow still depth and width invite insects, birds, and rodents reached the exterior and interior walls. This is create further complications through the destruc- evidenced by puddled water in the interior and tive activity associated with these animals. the occasional wetting of walls after a heavy LESSONS FROM THE GREAT HOUSE 217 storm.The presence of rivulets of soil deposits on The current (1995) and repeated loss of large original walls and post-shelter repairs is further lens-shaped fragments of wall material on the evidence of past and active patterns of water- lower exterior and interior walls indicates an borne surface erosion. Related to this is the unique active and complex condition requiring further occurrence of microhoodoos that indicate the study to ascertain the full extent of the causes and direction of wind-driven rains and storms from locations at risk.The present condition survey has their uniform angle of erosion. Such damage is allowed an initial prediction of potential future most probably ancient, however. In conjunction spalls by using the specific conditions survey to with recent soil deposits these signal key locations isolate specific areas for monitoring, closer in- for possible monitoring and protection. spection and possible emergency treatment. The majority of visible repairs at the Casa SUMMARY DIAGNOSES OF CONDITIONS Grande are those installed by Mindeleff in 1891- 2. These remain largely intact with minor carpen- Based on the above observations of recorded try repairs and brick plaster resurfacing. No evi- conditions in conjunction with archival documen- dence exists indicating that these repairs have tation on past descriptions of the structure and caused damage to theoriginal fabric of thestructure; previous preservation interventions, the follow- however a reassessment of their positive contribu- ing conclusions can be made to guide immediate tion to the performanceand stabilityof the structure and future plans for conservation and manage- must be made.This is especially true for the wooden ment, including further study and monitoring and and metal tie rods that could cause damage to the active and passive conservation interventions. structure in the event of seismic activity. Despite the apparent extreme appearance of The interior surface finishes of Casa Grande are the Casa Grande, there is little evidence to suggest among the best preserved of any ancestral Native that many of the conditions observed and re- Americanstructure. As such, any deterioration, no corded are active,especially those related tosurface matter how minor, is harmful, compromising its erosion and cracking. Potentially active sites of archaeological and aesthetic integrity. Areas of weatheringfrom exposure (e.g. microhoodoos and active finish detachment exist and need immedi- detachment) may exist and need to be studied more ate attention before further loss occurs. Pilot closely through quantitative monitoring. treatments to readhere flaking clay washes with Structural instability of walls and wall sections water and various fixatives including gelatin and remains a possible serious threat. Clear evidence acrylic emulsion have thus far proved successful. exists that large-scale collapse of several sections Earlier excavation of Tiers B and E has created of wall did occur during remedial stabilization in difficult level changes among the tiers and the 1891-2 and possibly earlier. These collapses oc- exterior grade. This in turn has necessitated the curred in vulnerable areas associated with original insertion of staircases, steps and built-up floor construction faults and subsequent deterioration surface treatments on the interior. Methods of such as unsupported broken wall ends. It is visitor access and control should be studied to important to stress that conditions similar to those determine the beststrategy for accepting or chang- associated with these past wall collapses currently ing this situation to facilitate interpretation and exist on all four exterior walls, especially on the visitation, improve drainage from within the struc- north, east and south elevations. Through-wall ture and protect the fabric. cracks and wall separation remain a major con- cern. External forces such as seismic activity, A FRAMEWORK FOR CONSERVATION vibrations and wind load have been cited as potentialagents that could cause major damage to Philosophy the current structural disposition of the Casa Grande.Futurestudyand monitoring,both through Aside from its significance as the only surviving fieldwork and virtual computer models, is clearly Hohokam Great House and the largest prehistoric needed and is currently underway. (non-mound) earthen structure in the Unites States, 218 FRANK MATERO

one ofthe most significant aspects ofCasa Grande Although the construction ofthe shelter has had is the fact that it has survived stabilization and an undeniably positive effect on the Casa Grande interpretation with remarkably few material inter­ in that the structure has been spared direct fabric ventions. This conservatism of treatment has not interventions over the years, it has also created the only ensured the high retention ofinformation for problem of an illusion of stability and no change. archaeological study, but has also inadvertently Based on the present condition survey and the protected the structure from the often adverse associated diagnoses outlined above, inherited effects of incompatible material interventions. damage and instability dating from before the The decision to protect the structure by external shelter, particularly in association with external means through the erection of a shelter was forces such as vibration and seismic movement, proposed early on even before the preservation remain a primary concern. A review of past program of 1891-2. viii Victor Mindeleff, the origi­ proposals for major interventions including laser nal architect of the proposed preservation pro­ drilling for the insertion of a metallic and epoxy gram, did not advocate a shelter, citing its negative reinforcement system in the walls [8] and the visual impact on the site. His brother, Cosmos, application of various consolidants and water who replaced him in finaliZing and supervising repellents have all responded to incomplete as­ the work, eventually designed a shelter which, sessments of the caliche and the walls. That these owing to lack of funding, was not immediately proposals, some supported by highly technical constructed. Nevertheless, he too recommended studies, were all shelved for future consideration, monitoring of the structure for a few years before attests to the implicit appreciation and signifi­ making the decision to install a shelter. Mindeleff's cance of the structure's physical integrity by the wooden and corrugated metal roof shelter was National Park Service. constructed by 1903, an unsightly tight-fitting In keeping with the long-standing tradition of structure built within and over the standing ruin. conservative approaches and preventive conser­ This was eventually replaced in 1932 by the vation at the Casa Grande, a judicious and cau­ present steel canopyshelterdesigned by Frederick tious policy of intervention has been embraced as Law Olmsted Jr and Thomas Vint, itself now a the best option, where justifiable through continu­ landmark after 67 years and a National Park ous scientific analysis and monitoring. In other Service classified historic structure. words, any proposed treatment should first be The ultimate effect of continuous shelter pro­ proven a§ providing necessary and beneficial tection (even during replacement of the 1903 action to the material and structure and guarantee shelter) has been to reduce significantly atmos­ that it will 'do no harm'. Any such physical pheric weathering and therefore remove the need interventions should also be considered with for directly applied protective treatments such as respect to issues of further archaeological study consolidation, water repellents and crack and loss and cultural appropriateness, established through repair. This has certainly not been the case for the consultationwith affiliated Native Americangroups. other standing walls at the site, which have had a The current condition survey and material charac­ long and current practice of surface protection terization studies offer the necessary baseline infor­ using coats of cementitious- and later acrylic mation to continue to test assumptions and proceed emulsion-bound soils. Although useful in preserv­ with future plans of immediate and long-range ing the overall form and configuration of the conservation monitoring and site management. exposed walls with a reasonable simulation of earth, this technique has diminished the informa­ Future considerations tional value of the walls and may be worsening the condition underneath. Further investigation The identification, documentation and explana­ and assessment of this long-standing technique tion of the processes of deterioration of the Great of preservation for many of the lower com­ House are a necessary prelude to any conserva­ pound walls at the site should be conducted in tion and management strategy. Fortunately since the future. the first stabilization efforts of 1891-2 until the LESSONS FROM THE GREAT HOUSE 219 present, continuous protection, care and mainte- Fragment detachment and loss nance have significantly reduced deterioration of the Great House. Continuous efforts to redress the The cracking, detachment and loss of individual issues of deterioration and possible intervention fragments of caliche, some weighing as much as have resulted in several studies focused on struc- 100 pounds, is both a past and active condition tural problems, namely related to seismic and which needs to be further assessed based on the wind damage [5,7,8]. Proposed methods of results of the condition survey. Detached frag- by Kreigh and Sultan [8 ], inserting ments not only result in the loss of original fabric steelpipes into verticalholes laser-drilled through but pose health and safety hazards to the public thewalls,filled with epoxy and the whole tied into and staff.Areas identified as 'at risk', based on the a rigid structure of horizontal pipes, was fortu- combinationof conditionsof detachment, detach- nately rejected as too invasive and experimental, ment cracking and associated construction seams, compromising the physical and informational should be carefully examined (Fig. 8). The extent integrity of the structure. A second plan was of detachment should be evaluated, first using proposed involvingthe fillingof the various beam simpleand direct methods such as water injection holes, roof grooves and erosional losses with to determine the volume, location and intercon- caliche on the basis that this was needed for nectionof voidsand planar discontinuities. Where structural stabilization [14:42].Its implementation necessary, structural bracing or facing may be was rejected by the National Park Service again required depending on the size of the fragment due to its negative impact on the structure through before any further testing is attempted. Non- obfuscation and possible damage to theseimportant destructive evaluation using impact echo, radaror architectural features. While it is highlyquestionable other techniques may prove useful; however that eitherof these proposals would have resulted in further inquiry into their valid application for this achieving their stated objectives, and, in the case of situation will be necessary. theformerproposal, would have clearly resultedin Once all detached and potential spa11 areas are irreversible damage, their rejection did not re- assessed in detail, a pilot treatment programme move the suspected problem of structuralinstabil- should be implemented to determine the possi- ity, especially with respect to seismic activity. bilities and limitations of the proposed tech- From 1903 with the addition of the first protec- niques. Based on the heterogeneous nature of the tive shelter until the present, several major proc- caliche and the inclusion of large nodules and esses of deterioration, mainly water-related, have internal construction discontinuities and cracks, become largely inactive. In some cases, gradual mechanical pinning should be avoided as unpre- deterioration of the fabric continues, albeit re- dictable and dangerous. Grouting with compat- duced. In other cases, earlier damage resulting in ible, low viscosity, inorganic grouts such as those structural instability still remains, not necessarily based on moderately hydraulic lime, selected active but still unaddressed. The most serious aggregates and fillers with acrylic emulsion addi- immediate deterioration observed at the Great tives,such as those devebpedbytheArchitectural House is related to past and active mechanical conservation Laboratory and used extensively at failure of individual fragments and former loss of other sitessuch as Fort Union National Monument, entire wall segments. Exposure of friable material Fort Davis National Monument, Mesa Verde Na- due to gradual localized loss of the protective tional Park and should be tested. calcium carbonate-enriched surface isalso a prob- These would provide sufficient readhesion and fill lem of smaller magnitude, but no less significant. blind and surface voids restricting animal access These problems are intrinsic in that they are and potential vandalism. related to the natural weathering of the caliche and the original construction of the building. As Animal activity such they cannot be reversed but rather retarded or mitigated through different methods of Based on the results of the condition survey, it is stabilization. clear that a variety of animals, birds, rodents, 220 FRANK MATERO insects and arthropods, have made the larger of timber removal, excavation, weathering and cracks and crevices of the Casa Grande their salt cycling on the structure, but whereas these home. This activity has resulted in the enlarge- agents have ceased or have largely been eradicated, ment of cracks and voids and associated staining. seismic activity remains a major threat according Rodent activity was noted in association with the to the calculations and predictions by Gift and fragment that fell recently from the lower west Johansen [5 ] and King [7 ]. Advanced techniques of wall (1995) suggesting the possible exacerbation modelling and monitoring since the previous of existing damage originally attributed to other studies would allow for a more accurate assess- causes. ment and prediction of possible future damage. All cracksand voids greater than lOcm in depth As a result of these preliminary studies and the should be evaluated for filling, especially those above survey and material analysis computer that exhibit active animal activity. Fills could be modellingof the walls is underway based on their formulated from caliche and installed below the original configuration and current condition (in- surface of the loss, thereby identifying them as cluding the effect of Mindeleff 's repairs) using the repairs rather than original material. Further iden- natural frequency parameters already measured tification for future researchers could be insured by King for each wall section. In addition, a trial by adding dated microtags into the caliche fill monitoring and stabilization system, termed a material. Where original architectural features 'smart viga', will be installed on the east wall for require filling due to destructive animal activity, one year to demonstrate and measure the strength- an isolating layer material such as a polyester ening and stiffening effects of this form of inter- textile could be installed prior to the insertion of vention as a possible method for seismic mitiga- the fill to allow easy removal at a future date. The tion. This will involve increasing the overall current method of wire mesh fill, while reversible, natural frequencies of the wall from 2.9-4.0z/s to is unsightly. over 6 z/s and thus reduce the susceptibility to collapse from distant seismic activity. Structural instability of walls Surface friability and erosion Beginning with the first preservation efforts, wall stability has been a major concern at the Casa More than any other building material, the treat- Grande. As already discussed, the present struc- ment of friable earthen-based materials has been tural condition of the walls is the result of a of great concern for professionals.An endless list number of factors, including wall material and of various products has been tested and used as construction methods, previous vandalism, consolidants to improve the mechanical proper- stabilization and collapse and environmental ex- ties of the soil and impart water repellence. The posure. These factors in their various combina- long history of the application of these materials tions and permutations have created a range of to earthen structures has generally resulted in conditions. Unlike all other surface and material failure; the damage caused by the loss of the conditions noted and discussed, structural insta- treated material has been often greater than that bility is most serious because it results in total and from natural weathering. immediate catastrophic loss and a safety hazard. Analysis of the Casa Grande caliche has dem- Past and current studies have shown that of the onstrated that the condition of friability, where it many potential external factors affecting the struc- exists, is a function of the loss of the calcium tural condition of the Casa Grande, which include carbonate-enrichedcrustthat naturally forms upon earthquake, wind load, aircraft and traffic vibra- exposure of the material to repetitive wetting and tion and water table subsidence, seismic activity drying cycles. Due to the construction of the remains the major threat. Contrary to previous protective shelter over the Great House, this assessments, seismic activity may well have been natural phenomenon has been interrupted; once responsible for major single event losses to the the crust is lost (see above), it cannot form again walls.This is not to diminish the damagingeffects and deterioration of the calcium-depleted zone LESSONS FROM THE GREAT HOUSE 221 beneath can occur, especially if exposed to wind- recommendedas the most responsible and appro- driven rain and abrasion. priate method toward developing, implementing Consolidation of these localized friable sur- and modifying over time a cultural resource rnan- faces could be achieved at the Casa Grande agement plan for the last Great House. through the application of limewater (calcium hydroxide) consolidant.This method has received Frank Matero is Associate Professor of Architec- much study and trial use since the 1930s,particu- ture and chairs the Graduate Program in Historic larly for carbonate rocks and some lime plasters. Preservation at the Graduate School of Fine Arts, Calcium hydroxide, applied as a solution of lime- University of Pennsylvania. water, evaporates, thereby depositing material within the pores of the material, which expands Contact address: Graduate Program in Historic and hardens upon carbonation. This results in Preservation at the Graduate School of Fine Arts, increased particle-to-particle cementation and 115 Meyerson Hall, University of Pennsylvania, improved cohesive strength and abrasion resist- Philadelphia, PA 19104, USA. Tel: + 1 215 898 ance. The use of limewater would be extremely 3169. Fax: + 1 215 573 6326. suitable at the Casa Grandedue toits compatibility with the calcium carbonate content of the caliche. REFERENCES Consolidation using limewater is still widely de- bated as to its efficacy, largely due to the lack of 1 Baxter, S. Archaeological camping in Arizona. The penetration of the calcium carbonate. Tests run at American Architect and Building News 26 (1889) 121. the Architectural Conservation Laboratory using 2 Clemenson, A. B. Centennial Histoy of the First eighty applications of limewater to consolidate PrehistoricReseme 1892.Administrative Histoy , Casa friable historic and feeble replicate lime plasters Grande Ruins National Monument, Arizona. Denver ServiceCenter,United States Departmentof the Interior, proved effective, with significant hardeningof the National Park Service, Denver (1992). surface and good depth of penetration. Before 3 Fewkes, J. W. A report on the present condition of a adoption of this technique, laboratory tests to ruin in Arizona called Casa Grande.JournalofAmerican establish the best method of application and its Ethnology and Archaeology 2 (1892) 179-193. effects would need to be performed in conjunc- 4 Fewkes,J.W. CasaGrande, Arizona. 28th Annual Report tion with a monitored field testing programme. of the Bureau of Ethnology, 1!2&-07(1912) 25-179. Monitoringin the field could be performed through 5 Gift, A. and Johansen, G. E. CasaGrande,APreliminay StrwturalRariau.Universityof Pennsylvania,Department the installation of ceramic or stainless steel pins of Engineering (1998). Unpublished report (UPENN). surface-mounted in selected areas of treated and 6 Hayden,J.D. Plaster mixing bowls.American Antiquity untreated friable areas and stable areas for com- 7 (1942) 405407. parative evaluation of the treatment. 7 King,K.and King, E. Casa GrandeNationalMonumenf Vibration Investigation (1998). Unpublished report. (NPS-CAGR) CONCLUSIONS 8 Kreigh, J. D. and Sultan, H.A. Final Report Feasibility Study in Adobe Preservation, Casa Grande National As has been wisely observed, the interpretive Monument and Fort Bowie National Historic Site. potential of the Casa Grande remains limitless [14: University of Arizona College of Engineering (1974). 421. As public property whose care and interpre- Unpublished report. tation is entrusted by law to the National Park 9 Mindeleff, C. Casa Grande Ruin. 13th Annual Report Service, future research and continued public of the Bureau of American Ethnology (1896) 289-316. enjoyment of the Casa Grande must be guaran- 10 Mindeleff, C. The Repair of the Casa Grande Ruin, teed. Given its uniqueness and significance, any Arieona in 1891.15thAnnual Report of the Bureau of conservation measure considered must be evalu- American Ethnology (1897) 315-349. ated against the physical changes that will result 11 Statement for Management. Casa Grande Ruins fromits implementation, nowand in thefuture.To National Monument, Arizona. National Park Service, United States Department of the Interior (1995). this end, continued investigation and modelling, 12 Resources Management Plan. Casa Grande Ruins monitoring and judicious pilot treatments can be National Monument. National Park Service, United States Department of the Interior (1996). 13 Wilcox, D. R. and Shenk, L. 0. The Architecture of the 222 FRANK MATERO

CasaGrande and its Interpretation. Arizona State geophysical engineer, also provided valuable Museum Archaeological Series 115 (1977). dormationontheissues of potential vibration damage 14 Wilcox, D. R.and Sternberg,C. Additional Studies of the to the structure as an independent consultant to NPS. Architectureof the Casa Grande and its Interpretation. iv These photographs are credited as being 'loaned by Arizona State Museum Archaeological Series 146 (1981). Mrs. Hemenway, to whom [they were] presented by 15Wilcox, D. R. andHinselyC. M.AHemenway portfolio: Mr Frank H. Cushing'. [3] Presumably Cushing took Voices and views from the Hemenway Archaeological these photographs during his visit to the site from Expedition, 1886-1889. Journal of the Southwest. (1995) December 31, 1887-January 4, 1888 or during a 521-624 second visit in late January 1888. v Based on current research executed as part of this ENDNOTES conservation programme by Elisa del Bono as a MSc thesis on the characterization and analysis of the i The site was visited and recorded earlier by Adolf caliche walls of the 'Great House' at Casa Grande Bandelier in May1883 during his five-year trip through Ruins National Monument, Arizona, 1999. New Mexico and Arizona for Lewis Henry Morgan and vi Since then scientific studies of the material have been the Archaeological Institute of America (reported in canied out periodically. Cook first analyzed the material Bandelier, A. F., Final Report of InvestigationsAmong followed later by Littrnan (1967), Vick (19731, Kreighand Sultan (1974), Wilcox and Shenk(1977), and Roy (1980). the Indians of the Southwestern United States, Carried vii This system was first created and perfected for the on Mainly in the Years 1880-1885, Part IICambridge. recording of architectural surface finishes at Mesa John Wiley [I8921405,453,458,461).Asfor other sites Verde National Park by the author, beginning in 1994. he visited, Bandelier produced coloured measured viii As early as 1878, local opinion promoted the idea of plans and sections of the site and the Great House. protecting the structure from the weather and vandalism ii During the 1970s, Dennis B. Fenn initiated a test wall with an enclosure. research program at Casa Grande and other sites in the southwest, focused on evaluating existing and proposed chemical stabilization treatments for adobe APPENDIX and related earthen building materials. iii The project team included Frank Matero, project director; GLOSSARY OF CONDITIONS TERMINOLOGY G. EricJohansen, engineer and architect;Elisa del Bono FOR EARTHEN MATERIALS and Kecia L. Fong, graduate conservation researchers; Guy R. Munsch and Nicholas L. Stapp, graduate coordinators for documentation; Andrea Gift, Animal activity undergraduate engineering researcher, and Toni Loiacano, graduate engineering researcher. In addition The presence of birds, rodents, spiders, insects, 19 graduate students generously contributed many and other desert-dwellersas evidenced by guano, hours of field and computer laboratory time to record and document existing field conditions. Catherine spider webs, debris and burrow-tunnels. Dewey was responsible for the final production of the digitized computer drawings. The project's work Architectural features programme was formulated in conjunction with professional staff from the Southwest Region Support Major building features such as wall profiles, Office. Associated supervising National Park Service project personnel included Jake Barrow, project openings,beam pockets, floorscars,and observa- manager and Robert Hartzler, field supervisor. Ann tion holes, etc. Brackin Oliver and Kate Dowdy assisted in the preparation of baseline photographs for the conditions Complete loss survey. Valuable input was also provided by James Rancier,formerarchaeologist, SouthernArizonaGroup Office (SOAR), David Evans, exhibit specialist (SOAR), Gross loss of wall fabric as per past photographic James Trott, archaeologist (Architectural Conservation documentation, relative to the present; not loss of ProjectsProgram,Santa FeSupportOffice,Intermountain completeness of form. Region) and Don Spencer, CAGR Superintendent. Given the complexity of the conservation problems, Construction seams consultation was sought from numerous specialists in the university and elsewhere including Gomaa Omar, geologist, and Arthur Johnson, soilscientist, Department COURSE BOUNDARIES of Geology and Environmental Science (UPENN); and Horizontal construction seams of variable length AlexRadine, research engineer,Laboratory for Research and width marking the upper and lower bed faces on the Structure of Matter (UPENN). Ken King, of individual construction courses. LESSONS FROM THE GREAT HOUSE 223

HEAD JOINTS Detachment vertical construction seams marking the end or interruption of horizontal construction courses. Planar discontinuities resulting in lens-like frag- Joints may span one or more courses and are ments of wall material that have become partially generally straighter and more planar than subse- separated from the underlying earthen substrate. quent vertical cracks. The detachment is detected visually and audibly by sounding, and by insertinga probe behind the fragment. The angle of the separation, indicated by the probe, must be 0-60 degrees, measured Linear discontinuities in the walls, either in the from the plane of the wall face. Two categories of earthen substrate, the applied earthen finish layers detachment are differentiated: or both. Cracks in the substrate are usually vertical, while those in the finish layers are more random in Detached fragments greater than 5cm thick orientation. Five categories of cracks are defined: Detached fragments less than 5cm thick

THROUGH-WALL CRACKS Detachment boundaries not otherwise marked as Major vertical cracks that extend all the way cracks or construction seams, are also noted. through from exterior to interior surfaces and are more or less perpendicular to the wall surfaces. Alsoincluded are wall juncture separations result- Displacement ing from butt wall detachment. Movement and cracking of the wall, resulting in the shifting of the wall surface more than lcm out MODERATE CRACKS of plane. Irregularcracks of predominatelyvertical orienta- tion and variable depth (1 to >10cm)Three types Erosional loss of moderate cracks are differentiated: Distinctive patterns of loss, often in association Cracks greater than 10cm in depth with vertical cracks, where the depth is greater Cracks 5-10cm in depth than the width and at least 10cm in depth. Cracks less than 5cm in depth Fillline SURFACE CRACKS Two types of superficial cracks restricted to the Former level of accumulated interior aeolian de- applied surface finishes of the interior and differ- posits (wind-blown earth and debris) and earthen entiated by width: material from collapse and rainwater washing of the standing walls. Cracks greater than 1mm in width Cracks less than lmm in width Friable surface

MAP CRACKING Surfaces that display active disaggregation of A patterned network of fine superficial cracks individual nodules or flakes which disintegrate occurringin the finish layers and exposed earthen under finger pressure. substrate, usually associated with exposure. Major loss DETACHMENT CRACK Cracking associated with areas of incipient de- Loss of earthen material where the loss is greater tachment (see below). than 750cm 2 and at least 10cm in depth, as 224 FRANK MATERO measured from the present plane of the wall features such as beam (viga) pockets. Numbering surface. is sequential from the excavated semi-subterra- nean room space 1 up through to room space 4 of Microhoodoos the centre Tier C.

Small protruding stalks of earthen wall material Salt deposits formed by differential erosion of the surface from wind-driven precipitation. These microhoodoos Salt-laden water moving through the walls crystal- are oriented parallel to the prevailing wind, and lizeswithin the pores andon thesurface as thewater usually support erosion-resistant aggregate at evaporatesformingwhitecrystallinedeposits.Ground the tip. water,,animal faeces, urine, and cement-based re- pairs are possible sources of damaging salts. Moderate loss Soil deposits Loss of earthen material where the loss is 1- lOcm in depth, as measured from the plane of the Soil which washes down fromwall topsand upper present wall surface. (Recorded only on interior wallsurfaces,and from highly eroded areas, forms surfaces.) rivulets of dried mud on lower walls, and is an indicator of potentially active wind-driven rain Photo grid and snow.

Demarcation of the area recorded by the indi- Surface erosion vidual rectified photographs of the intericr and exterior wall elevations. Differential surface weathering defined by large areas of coarse texture andsurface loss greater Repair than lcm in depth.Often in association with major and moderate loss. All actions, ancient and modern, executed to maintain, repair, and preserve the fabric of the Surface finish detachment structure. Separation of the applied surface finish layer(s) PREHISTORIC REPAIR from the earthen substrate or from each other as All observed repairs made during and after con- interlayer detachment, generally occurring in dis- struction by native inhabitants, including, mud creet areas of the wall, either as blind- or con- patching and stick stitching of shrinkage :racks cealed-detachment or open- or edge-detachment. and wall abutments. Tier MODERN REPAIR (1891-1996) All documented interventions made since 189'1 The plan of the Casa Grande is rectangular and including, but not limited to, brick underpinning, divided into five multi-levelunit spaces defined as plaster repair, wooden and metal tie rods, water- tiers A, B, C, D, E. proof coatings, consolidation, and protectivewire mesh installation. Unexcavated fill

Room space Laminated deposits found in corners and erosion holes and channels of room spaces 1 and 2, The space defined by the walls, floor, and ceiling probably as residual room fill not removed during of the original rooms as evidenced by constiuction the 1891 excavations.