NPS-28: CULTURAL RESOURCE MANAGEMENT GUIDELINE

A. Introduction

1. Resource Definition

A historic structure is "a constructed work . . . consciously created to serve some human activity." Historic structures are usually immovable, although some have been relocated and others are mobile by design. They include buildings and monuments, dams, millraces and canals, nautical vessels, bridges, tunnels and roads, railroad locomotives, rolling stock and track, stockades and fences, defensive works, temple mounds and kivas, ruins of all structural types, and outdoor sculpture.

Prehistoric structures are included in this chapter because the technical aspects of their preservation are similar to those of many historic structures. All prehistoric structures are also archeological resources, and some are ethnographic resources. They should therefore be managed within the general provisions of Chapters 6 and 10, particularly with respect to research and planning. Prehistoric structures are further distinguished by National Park Service policy limitations on their use and treatment. Given these qualifications, the term "historic structure" in this guideline is meant to encompass prehistoric structures unless otherwise stated.

2. Program Objectives

According to both federal law and NPS Management Policies, all historic structures in which the Service has a legal interest are to be managed as cultural resources. Regardless of type, level of significance, or current function, every structure is to receive full consideration for its historical values whenever a decision is made that might affect its integrity. Historic structures that are central to the legislated purposes of parks, especially those that are to be interpreted, may be subjects of additional, specialized efforts appropriate to their functions and significance.

The preservation of historic structures involves two basic concerns: slowing the rate at which historic material is lost, and maintaining historic character. Research on, planning for, and stewardship of historic structures focus on these concerns. Research defines historical associations, integrity, character, and the causes of material deterioration; planning develops and evaluates proposals for use and treatment in terms of their likely effects; and stewardship entails activities ranging from craft training to the identification and mitigation of threats.

Preservation of historic structures is an interdisciplinary effort requiring cooperation and communication among historical architects, architectural conservators, preservation specialists, archeologists, landscape architects, historians, ethnographers, and curators.

B. Research

Research about historic structures is a prerequisite for treatment and provides a basis for decision-making by managers. Situations benefiting from research-generated information range from review of weekly maintenance projects to long-term planning projects. Research also contributes to interpretation, compliance, and facility design.

To accomplish these purposes, research typically concentrates on three broad aspects of a historic structure: its historical, technical, aesthetic, or scientific associations; its developmental history or evolution; and the nature, performance, and capability of its materials and systems. This information is collected, analyzed, and organized through a variety of means, discussed below.

1. Identification, Evaluation, and Registration

Section 110 of the National Historic Preservation Act requires the NPS to identify and nominate to the National Register of Historic Places all structures and other properties under its jurisdiction that appear eligible. Historical areas of the national park system are automatically listed in the National Register in toto upon their establishment by law or executive order, but those structures and other features within them that contribute to their historical significance must still be documented for Register purposes.

a. Historic Resource Study

The historic resource study (HRS) is the primary document used to identify and manage the historic resources in a park. It is the basis for understanding their significance and interrelationships, a point of departure for development of interpretive plans, and the framework within which additional research should be initiated.

Although structures may be nominated to the National Register on an individual basis, they are most efficiently processed as part of an HRS. (For more guidance see "Baseline Research Reports" in Chapter 2.) With respect to historic structures, an HRS is adequate when three conditions–required for National Register nomination–are met. First, the thematic context must be sufficient to evaluate historical, aesthetic, technical, or scientific associations of structures within the study area. Second, the HRS must contain enough information about the developmental history or evolution of each structure to evaluate its integrity. Third, the study must contain enough information about the contributing environment of each structure to enable National Register boundaries to be defined and possible overlaps with cultural landscapes and archeological or ethnographic resources to be identified.

Research on structures or topics that were not included in an earlier HRS should be published as an addendum to that document.

b. National Register Nominations

National Register nominations may be prepared either for individual structures or for groups of structures. Collective nominations are appropriate for structures that are physically related, as in a historic district, or thematically related, as in a multiple property nomination. (For additional guidance see "Resource Identification, Evaluation, and Registration" in Chapter 2.)

As noted in the introduction to this guideline, the cultural resource types in the NPS Management Policies and this guideline are adaptations for management purposes of the property categories used by the National Register. Park resources classified as structures may be listed as buildings, structures, or objects in the National Register. Historic and prehistoric structures also may be included in the Register as contributing elements of historic districts, either as components of developed areas or as landscape features.

c. List of Classified Structures

The List of Classified Structures (LCS) is the primary computerized database containing information about historic and prehistoric structures in which the NPS has or plans to acquire any legal interest. Properties included in the LCS are either in or eligible for the National Register or are to be treated as cultural resources by law, policy, or decision reached through the planning process even though they do not meet all National Register requirements. Data fields in the LCS include identification, category of significance, condition, use, threats, treatments, cost estimates for treatments, and physical description.

The LCS has three major applications: (a) to describe historic structures on an individual or collective basis at park, regional, or Service-wide levels, (b) as a common information source for other automated management systems such as the Maintenance Management (MM) program and the Housing Inventory, and (c) as an analytical tool in budgeting, scheduling, and program development.

(For more information see "Service-wide Inventories" in Chapter 2 and the List of Classified Structures [LCS] User's Manual, 1993.)

d. Categories of Significance

All cultural resources are managed under a uniform standard of preservation responsibility. The following categories of significance are used to establish LCS management categories, determine appropriate levels of graphic documentation, and make other related management decisions for prehistoric and historic structures within the national park system.

Category Ia: Individual structures that qualify as national historic landmarks, are listed in the National Register as nationally significant, or that possess national significance by act of Congress or executive order.

Category Ib: Structures that do not possess national significance on an individual basis, but contribute to the national significance of a park or historic district.

Category II: Structures that individually or collectively qualify for the National Register and possess significance at the state level.

Category III: Structures that individually or collectively qualify for the National Register and possess significance at the local level.

2. Documentation and Investigation

As a rule, research about a historic structure should complement existing information and strive to produce a comprehensive understanding of the structure in order to adequately address management objectives. Research effort should be proportional to the significance of the structure and the range of effects associated with the objectives. Although individual features, areas, or systems may be emphasized, research should approach the structure as a whole.

Research needed to supply missing information should be defined in terms of subject, scope, and level of investigation. The subject may range from one feature on a single historic structure to a complex of structures. Scope includes but is not limited to thematic context, physical documentation, temporal associations, developmental history, scientific value, and material analysis. Level of investigation describes the nature and location of sources to be consulted and the degree to which extant material will be disturbed or destroyed during research. These considerations are described in the task directive and research design for every substantial research effort. (See "Research Methodology" in Chapter 2.)

Destructive techniques, such as archeological excavation and selective demolition, should be used only when alternatives are inadequate to provide information essential for evaluating, planning for, treating, or interpreting a historic structure. Any research that would directly impact a cultural resource must be reviewed in advance through the compliance process. Research involving prehistoric and some historic structures may also require consultation with Native Americans or other associated ethnic groups.

a. Historic Structure Report

The historic structure report (HSR) is the primary guide to treatment and use of a historic structure and may also be used in managing a prehistoric structure. A separate HSR should be prepared for every major structure managed as a cultural resource. Groups of similar structures or ensembles of small, simple structures may be addressed in a single report. In no case should restoration, reconstruction, or extensive rehabilitation of any structure be undertaken without an approved HSR, Parts 1 and 2.

An HSR includes the following:

Management Summary. This is a concise account of research done to produce the HSR, major research findings, major issues identified in the task directive, and recommendations for treatment and use. Administrative data on the structure and related studies are included.

Part 1, Developmental History, is a scholarly report documenting the evolution of a historic structure, its current condition, and the causes of its deterioration. It is based on documentary research and physical examination. The scope of documentary research may extend beyond the physical development of the structure if needed to clarify the significance of the resource or to refine contextual associations; however, major historical investigation of contextual themes or background information should be conducted as part of a historic resource study. If the Inventory and Condition Assessment Program (ICAP) is used to describe the nature and condition of features, resultant reports (e.g., the historic asset assessment report) should be included in the HSR's appendix.

Part 2, Treatment and Use, presents and evaluates alternative uses and treatments for a historic structure. Emphasis is on preserving extant historic material and resolving conflicts that might result from a structure's "ultimate treatment." Part 2 concludes by recommending a treatment and use responding to objectives identified by park management. In most cases, design work does not go beyond schematics.

Part 3, Record of Treatment, is a compilation of information documenting actual treatment. It includes accounting data, photographs, sketches, and narratives outlining the course of work, conditions encountered, and materials used.

All aspects of a historic structure and its immediate grounds should be addressed in an HSR. Potential overlaps with other cultural resource types and natural resource issues should be identified, and applicable studies and reports should be called for or referenced. An HSR and analogous reports (e.g., a cultural landscape report) may be combined to address multiple resource types at a single property or area.

Parts 1 and 2 of an HSR should be prepared jointly as part of a comprehensive effort soon after acquisition of a structure or recognition of its status as a cultural resource. Given funding and time constraints, however, an HSR may be prepared incrementally. Incremental research and design should also be considered when a complete HSR does not exist or an existing HSR does not adequately address aspects of a proposed treatment such as replication of missing features, removal of significant features or large amounts of historic material, or introduction of new systems or exterior additions. In no case should a Part 2 be prepared without a Part 1.

The scope, level of investigation, and extent of schematic development are outlined in a task directive that is based on the recommendations of a historical architect in consultation with other cultural resource specialists and the park manager. Major factors considered in developing the task directive include the structure's significance, condition, and intended use. The task directive should also address participation of other cultural resource specialists and publication of the document.

The following standards apply:

• A historic structure report (HSR) is prepared to minimize loss of character-defining features and materials whenever existing information about the developmental history and condition of the historic structure does not provide an adequate basis upon which to address anticipated management objectives, whenever alternative courses of action for impending treatment and use could have adverse effects, or to record treatment.

• Architectural, landscape, and archeological investigations supporting an HSR have the least possible impact on the property studied and employ nondestructive methods to the maximum extent possible; they are prescribed and justified in a task directive that includes a research design and impact analysis.

b. Graphic Documentation

Documentation of historic structures is undertaken to record preservation treatment, provide a baseline for monitoring, aid in interpretation, support scholarly research, and serve as an objective reference for repair or reconstruction in the event of damage or loss. The scope, method, and level of documentation of a structure should be proportional to its significance as a cultural resource, the character of its features, the degree to which it is endangered, and the ways in which the documentation is most likely to be used.

All documentation is done in conformance with the Secretary of the Interior's Standards for Architectural and Engineering Documentation (see Appendix C). Where recording is done to establish a baseline for planning or before demolition, the following documentation levels are recommended: Level I for Category Ia structures, Level II for Category Ib structures, Level III for Category II structures, and Level IV for Category III structures.

New materials and replacement features introduced should be recorded in place with photographs or drawings that clearly indicate their extent. Physical evidence of the developmental history of a structure should be recorded before being removed or covered during treatment. Copies of task directives, daily reports, and change orders should also be retained in park files.

c. Archival Considerations

Although comprehensive, in-depth research is an ideal foundation for preservation work, most information about historic structures is collected on a piecemeal basis throughout the resource management process. Primary information sources include contextual studies, records of treatment, records of structural monitoring, photographic and graphic documentation, and reports of material analysis and archival research. To maximize the benefit of this work and minimize potential data loss, all field notes, primary documents, original maps, drawings, photographs, material samples, and oral histories generated during resource management are organized and preserved as archival material or museum objects in consultation with the park or support office curator.

C. Planning

Planning for historic structures encompasses such diverse activities as involvement in park planning, facility design, preparation of maintenance work procedures, and compliance. The central purpose of all such activities is to identify ways of protecting cultural resources while achieving other management objectives. This is usually best done by thoughtful evaluation of a diverse range of alternatives.

General direction for managing a park's historic structures is provided in its general management plan, development concept plan(s), interpretive prospectus, and resources management plan. Action plans that may affect historic structures include historic furnishing reports and cultural landscape reports. Historic structures may also figure prominently in planning for special populations and fire and energy management.

Treatment and use are the central issues in planning for historic structures. Closely related concerns include consideration of park administrative and interpretive needs, compatibility of new and old development, accommodation of building codes and contemporary regulations, and the overall condition of the structures.

1. Treatment Planning

Historic structure treatment involves one or more of the following actions: (a) preservation of existing materials, (b) replication of missing historic features, (c) addition of nonhistoric features, and (d) removal of existing features or materials.

Decisions about treatment occur at three planning levels. First, the ultimate treatment of a structure is established in the park's general management plan or development concept plan. Second, major conflicts inherent in the ultimate treatment or other related treatments are identified and resolved through an HSR, Part 2. Third, plans and specifications are prepared to direct construction or preservation maintenance. Standardized direction for preservation maintenance is provided by work procedures contained in the Historic Property Preservation Database (HPPD).

Decisions about treatment should reflect the value of a structure as a cultural resource, knowledge of craft techniques and building materials, consideration of current and intended uses, appreciation of threats to the structure, and projections of treatment costs relative to likely funding.

a. Ultimate Treatment

The ultimate treatment of a historic structure is a general definition of its development limits based on considerations of use and the historic character that should be presented to the public. It is accomplished through one or more construction projects, after which the structure is preserved by preservation maintenance. Subsequent rehabilitation or restoration may be needed to update the structure's functional aspects and to repair or replace damaged or deteriorated features. Pending ultimate treatment, a structure is stabilized and protected in its existing condition; it may also receive interim treatment compatible with its planned appearance and use.

The categories of ultimate treatment are preservation, rehabilitation, restoration, and reconstruction.

Preservation as an ultimate treatment maintains the existing integrity and character of a historic structure. This alternative precludes uses that would require major additions or demolition. It should always receive first consideration.

Rehabilitation maintains the existing integrity and character of a historic structure, but allows major additions or alterations to accommodate a compatible contemporary use. Rehabilitation does not apply to prehistoric structures, ruins, monuments, or outdoor sculpture, nor should it be the ultimate treatment for historically furnished historic structures even though they may require major modifications to perform as such.

Restoration reestablishes the form, features, and character of a historic structure at a specific past period. Restoration may be comprehensive or focus on the exterior. Complete restoration is done primarily to Category Ia structures and structures containing historic furnishings, although secondary aspects of their interiors may be adaptively used. Exterior restoration applies primarily to Category Ib structures and some Category Ia structures that are integral to the historic settings of parks. Treatment and use of their interiors must meet corresponding standards and must not affect the desired exterior appearance. Management Policies permits restoration only if (a) it is essential for public understanding of the cultural associations of a park and (2) it can be accomplished with minimal conjecture based on sufficient data. Restoration of prehistoric or historic ruins is prohibited.

Reconstruction produces a new structure identical in form, features, and details to a historic structure that no longer exists. Management Policies permits reconstruction only if (a) it is essential for public understanding of the cultural associations of a park established for that purpose, (b) the structure can be built at full scale on the original site with minimal conjecture, and (c) significant archeological resources will be preserved in situ or their research values will be realized through data recovery. Meeting the first criterion requires a demonstration that no other interpretive media or techniques can render the park's primary theme comprehensible to visitors. Reconstruction will be undertaken only upon specific written approval of the director after policy review in the Washington office.

b. Historic Property Preservation Database (HPPD)

The HPPD is a computerized database containing technical information on the treatment of historic and prehistoric structures and cultural landscapes. It contains work procedures for the Inventory and Condition Assessment Program (ICAP) and Maintenance Management (MM) program. Work procedures include skill requirements, work consideration, material and equipment selection, and work instructions. The HPPD also contains information for more intensive treatments such as rehabilitation and restoration.

c. Removal or Neglect

Demolishing a historic structure or deliberately allowing it to decay naturally is justifiable only when all alternatives have been determined infeasible in the planning process. Management Policies prohibits demolition unless necessary for public safety or to eliminate an unacceptable intrusion.

No structure listed in or potentially eligible for the National Register will be removed or deliberately neglected without review by cultural resource specialists and approval by the regional director. If a potentially eligible structure has not been evaluated for the National Register, the state historic preservation officer (SHPO) will be consulted regarding its eligibility. If the SHPO agrees that the structure does not meet National Register criteria, removal or deliberate neglect may occur without further consultation under Section 106 of the National Historic Preservation Act.

Before a structure eligible for the National Register is removed or allowed to deteriorate, documentation recording it must be prepared in accordance with Section 110(b) of the National Historic Preservation Act and must be submitted to and accepted by the Chief, HABS/HAER Program. (For additional information see "Graphic Documentation," above.)

2. Use of Historic Structures

Many historic (but not prehistoric) structures directly support park functions by serving as visitor centers, housing, or administrative offices. Some such uses follow historical precedents; others are new, adaptive uses. The primary preservation issue in either case is the compatibility of the use with the structure. Considerations include wear patterns, adequacy of space and spatial configurations, the need for new electrical or mechanical systems, increases in fire risk, and changes necessary to accommodate disabled employees or visitors. Whenever possible, historic structures should be used rather than new facilities constructed.

Historic (but not prehistoric) structures may be assigned to other entities through leases, permits, or concession agreements if there are no feasible NPS uses. (See "Partnerships," below.)

a. Park Housing

The Federal Employees Quarters and Facilities Act of 1964 (P.L. 88-459) authorizes agencies to provide employee housing at fair-market rental value when necessary service or protection cannot otherwise be rendered or when community housing is inadequate.

NPS policy allows historic structures to be used for housing when "a given historic structure can be rehabilitated to meet housing standards without adversely affecting its historic character and if the rehabilitated structure will meet a need identified in the Park Housing Management Plan." Housing in Category Ia and Ib structures or structures used in part as museums is generally inappropriate.

(For more information see the Housing Design and Rehabilitation Guideline [NPS-76] and the Government Furnished Housing Guideline [NPS-36].)

b. Museums

Historic structures are often expected to house museum objects including historic furnishings. The furnishings may be historically associated with the structures or replacement items of the same vintage. While such museum use may be appropriate and even mandated, the requirements of collection management and the effects of public access should first be thoroughly explored and evaluated through preparation and approval of an HSR. Specific issues to be studied include energy utilization, accessibility, security and fire protection, and environmental control.

Historic structures containing related historic furnishings are managed so that measures to meet curatorial standards and measures to meet structure preservation standards are balanced. Proposals to furnish a historic structure with replacement or reproduction furnishings should be carefully evaluated to ensure that physical work to meet curatorial standards will not entail unacceptable adverse effects on the structure.

3. Commemorative Works and Plaques

Commemorative works will be erected in parks only if authorized by Congress or approved by the director. Approved commemorative works will be sited to avoid disturbance of natural and cultural resources and values. Plaques or other memorial devices will not be affixed to historic structural material.

Construction of a commemorative work will not be approved until a determination is made that the work will meet NPS design and maintenance standards. Recommendations for approval will be made by persons qualified in the fields of preservation, park design, and maintenance. Once constructed, commemorative works will be listed in the LCS and managed as cultural resources. (See Management Policies 9:17.)

4. Codes, Regulations, and Contemporary Development

Although historic structures that functionally serve park staff or visitors are generally expected to meet modern safety, access, and energy efficiency standards, their character may impose limitations on functional modifications and adjacent development.

a. Design Compatibility

Contemporary additions or development adjacent to historic structures should be designed to complement the structures' visual and physical characteristics. Concern for the compatibility of additions extends to both the exteriors and interiors of historic structures. Special attention should be given to new construction within historic districts.

A new structure or addition will be compatible if it maintains the overall pattern of development in the area and is visually unobtrusive in terms of scale, texture, and continuity of architectural style or tradition. Scale is defined in terms of similar or harmonious proportions, especially height and width. Texture refers to the surface quality of materials, especially reflection of light. Continuity encompasses such characteristics as use of color, internal organization of space, massing, roof forms, architectural details, site relationships, palette of materials, and placement of windows and doors. Unless a new structure is a reconstruction, it should not duplicate or mimic a historic structure.

b. Accessibility

With the exception of prehistoric structures, every historic structure should be made accessible to all visitors and employees to the highest degree feasible. As a general rule, a historic structure is expected to meet all requirements for accessible buildings outlined in section 4.1.6 of the Uniform Federal Accessibility Standards (UFAS; 49 FR 31528). If the Advisory Council on Historic Preservation finds that compliance with the requirements would threaten or destroy the historical integrity of a historic building, alternative requirements outlined in section 4.1.7(3) of UFAS may be followed.

Alternatives to physical access for public programs may be considered if the Advisory Council determines that measures required for access would unacceptably compromise a building's historical integrity or character. (For additional information see Accommodation of Disabled Visitors at Historic Sites in the National Park System, 1983.)

c. Safety and Security

Structures, their contents, and the people in and near them can be protected by a combination of use management, facilities management, and protective systems. When existing or proposed uses of structures present safety or security problems, and when solutions to such problems would unacceptably compromise their historical integrity or character, the uses should be changed or limited to eliminate or minimize the conflicts.

Passive techniques and proactive management strategies are employed wherever possible to minimize damage or loss. Particularly for Category Ia and Ib structures, installation of security, fire detection, and passive fire suppression systems is encouraged if they will not significantly impair the resource value of the structures. Other modifications, including changes to facilitate emergency egress, should be considered only when they are the only viable options and will not significantly impair the historical integrity or character of structures.

Plans for treatment of historic and prehistoric structures should also address treatment of associated hazardous materials, including lead, asbestos, and underground fuel tanks. All work involving these hazards should be undertaken in ways that will minimize loss of historic material and character. (For additional information see the Loss Control Management Guideline [NPS-50] and other applicable directives.)

d. Energy Conservation

Historic structures should be managed to minimize energy use, but modifications to improve energy efficiency are acceptable only if they will not adversely affect the structures' historical integrity or character. Any proposed action that would alter the temperature, relative humidity, light, or air quality in a historic structure must be evaluated to determine its potential effect on the structure and any museum objects or archival materials therein. Such actions include installation of insulation, vapor barriers, and storm windows, and changes in energy sources.

5. Administrative Issues

Plans for treatment and use of historic and prehistoric structures should be reviewed during their preparation to ensure compliance with the Secretary of the Interior's Standards for the Treatment of Historic Properties and the additional standards in this guideline. Once approved, the plans should be used to program funds and staff time necessary for their implementation.

a. Compliance

All project plans for historic and prehistoric structures must be reviewed for compliance with Section 106 of the National Historic Preservation Act. Proposed treatment involving prehistoric and some historic structures may also require consultation with Native Americans or other associated ethnic groups. In planning undertakings involving historic structures, it is important to consider possible effects on archeological resources, cultural landscapes, museum objects, and ethnographic resources as well.

b. Funding and Staffing

Every treatment project, including preservation, is initiated by a programming document containing cost estimates and a scope of work. This information should be drawn from the Inventory and Condition Assessment Program (ICAP) or an approved HSR.

All research, planning, and treatment involving historic structures must be done by qualified persons. Staffing requirements for park cultural resource specialists should be included in the resources management plan for each park. Cooperative projects and temporary details of specialists from parks, support offices, and centers are encouraged to maximize use of existing skills and knowledge within the NPS.

c. Construction Documents

Working drawings and specifications for treatment of historic and prehistoric structures are prepared under the direction of a historical architect consistent with the Drafting for Design and Construction Guideline. In addition, construction documents will meet the following standards:

• Existing conditions are clearly documented if they are not included in an HSR or ICAP report. Provisions are made for a detailed photographic or graphic record of the treatment process.

• All aspects of the proposed treatment are consistent with the Secretary of the Interior's Standards for the Treatment of Historic Properties and the additional standards and other provisions in this guideline. Specific attention is given to use of materials, craftsmanship, design, installation of new systems, and structural reinforcement.

• Provisions are made for protection of all cultural and natural resources at the construction site. Significant material to be retained in situ is identified and methods of identification for new materials are prescribed.

• Specifications include procedures to be followed if structural problems are encountered or new features or resources are found.

• Specifications include special skills required of contractors and craftspersons.

D. Stewardship

For historic structures, stewardship focuses on five major activities: (a) control of treatment and use, (b) monitoring conditions of deterioration and structural failure, (c) protecting structures from human and environmental threats, (d) retaining or delegating responsibility for structures, and (e) developing the skills, knowledge, and attitudes needed to support the program. The last of these is addressed in Chapter 4 as part of training. Guidance for the others follows.

1. Treatment and Use

Treatment and use of historic structures follows the conditions outlined in approved planning documents such as the general management plan, historic structure report, and ICAP work procedures.

Treatment of historic structures is divided into four categories: preservation, rehabilitation, restoration, and reconstruction. These categories parallel those used in planning for the ultimate treatment of historic structures. They are also the same as those outlined in Management Policies and the Secretary of the Interior's Standards for the Treatment of Historic Properties, commonly referred to as the Secretary's Standards.

One treatment category, preservation, encompasses four activities recognized in the 1995 Servicewide Programmatic Agreement (PA): stabilization, housekeeping, routine maintenance, and cyclic maintenance. Under stipulation IV of the PA these activities are referred to collectively as "preservation maintenance." (See Chapter 5 for additional information.)

The following standards apply to all treatments:

• Use is monitored and regulated to minimize both immediate and long-term damage.

• Use of destructive techniques, such as archeological excavation, is limited to providing sufficient information for research, interpretation, and management needs.

• All work that may affect resources is evaluated by an historical architect and other professionals, as appropriate.

• All modification, repair, or replacement of materials and features is preceded by sufficient study and recording to protect research and interpretive values.

• New work, materials, and replacement features are identified, documented, or permanently marked in an unobtrusive manner to distinguish them from original work, materials, and features. The manner and location of identification is recorded using the Inventory and Condition Assessment Program (ICAP).

• A proposed treatment project is initiated by the appropriate programming document, including a scope of work and cost estimate from an HSR or ICAP. Such projects include preservation maintenance as well as major treatment. No treatment is undertaken without an approved HSR or work procedure documenting the work, and Section 106 compliance.

• A treatment project is directed by a historical architect and performed by qualified technicians.

• Representative features salvaged from a historic structure are accessioned and cataloged, provided that they fall within the park's scope of collection statement.

• All changes made during treatment are graphically documented with drawings and photographs. Records of treatment are managed as archival materials by a curator or archivist within the park's museum collection.

a. Preservation

Preservation maintains the existing integrity and character of a historic structure by arresting or retarding deterioration caused by natural forces and normal use. It includes both maintenance and stabilization. Maintenance is a systematic activity mitigating wear and deterioration of a structure by protecting its condition. Stabilization involves reestablishing the stability of an unsafe, damaged, or deteriorating structure while maintaining its existing character. The following standards based on the Secretary of the Interior's Standards for the Treatment of Historic Properties apply:

• A historic structure is used as it was historically, or is given a new or adaptive use that maximizes the retention of historic materials, features, spaces, and spatial relationships. Where a treatment and use have not been identified, a structure is protected and, if necessary, stabilized until additional work may be undertaken. Adaptive use of prehistoric structures is prohibited.

• The historic character of a historic structure is retained and preserved. The replacement or removal of intact or repairable historic materials or alteration of features, spaces, and spatial relationships that characterize a structure is avoided.

• Each historic structure is recognized as a physical record of its time, place, and use. Work needed to stabilize, consolidate, and conserve historic materials and features is physically and visually compatible, identifiable upon close inspection, and properly documented for future research.

• Changes to a historic structure that have acquired historical significance in their own right are retained and preserved.

• Historic materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a historic structure are preserved.

• The existing condition of historic features is evaluated to determine the appropriate level of intervention needed. Where the severity of deterioration requires repair or limited replacement of a historic feature, the new work matches the old in design, color, texture, and where possible, materials. Repair or replacement of features is substantiated by archeological, documentary, or physical evidence.

• Chemical or physical treatments that cause damage to historic materials are not used.

• Archeological and landscape resources are protected and preserved in place. If such resources must be disturbed, mitigation measures are undertaken including recovery, curation, and documentation.

The following additional standards apply:

• Stabilization detracts as little as possible from a historic structure's appearance and significance. Reinforcement is concealed wherever possible so as not to intrude upon or detract from the aesthetic, historical, or archeological quality of the structure, except where concealment would result in the alteration or destruction of historically or archeologically significant features, materials, or physical or visual relationships. Accurate documentation of stabilization procedures is kept and made available for future needs.

• Maintenance is executed by qualified technicians in accordance with approved work procedures. Where such procedures are nonexistent or incomplete, a historical architect provides technical guidance.

• All features of a historic structure are inspected on a scheduled basis and information about their condition is entered into ICAP.

b. Rehabilitation

Rehabilitation improves the utility or function of a historic structure, through repair or alteration, to make possible a compatible contemporary use while preserving those portions or features that are important in defining its significance. Leased historic structures rehabilitated consistent with the Secretary of the Interior's Standards for Rehabilitation may be eligible for preservation tax credits. The following standards based on the Secretary's Standards apply:

• A historic structure is used as it was historically or is given a new or adaptive use that maximizes the retention of historic materials, features, spaces, and spatial relationships. Adaptive use of prehistoric structures is prohibited.

• The historic character of a historic structure is retained and preserved. The replacement or removal of intact or repairable historic materials or alteration of features, spaces, and spatial relationships that characterize a structure is avoided.

• Each historic structure is recognized as a physical record of its time, place, and use. Changes that create a false sense of historical development, such as adding conjectural features from other structures, are not undertaken. Work needed to stabilize, consolidate, and conserve historic materials and features is physically and visually compatible, identifiable upon close inspection, and properly documented for future research.

• Changes to a historic structure that have acquired historical significance in their own right are retained and preserved.

• Historic materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a historic structure are preserved.

• Deteriorated historic features are repaired rather than replaced. Where the severity of deterioration requires repair or replacement of a historic feature, the new feature matches the old in design, color, texture, and, where possible, materials. Repair or replacement of missing features is substantiated by archeological, documentary, or physical evidence.

• Chemical or physical treatments that cause damage to historic materials are not used.

• Archeological and landscape resources are protected and preserved in place. If such resources must be disturbed, mitigation measures are undertaken including recovery, curation, and documentation.

• Additions, alterations, or related new construction do not destroy historic materials, features, and spatial relationships that characterize the historic structure. New work is differentiated from the old and is compatible with the historic materials, features, size, scale and proportion, and massing of the structure.

• Additions and adjacent or related new construction are undertaken in such a manner that if removed in the future, the essential form and integrity of the historic structure would be unimpaired.

c. Restoration

Restoration accurately presents the form, features, and character of a historic structure as it appeared at a specific period. It may involve the replication of missing historic features and removal of later features, some having cultural value in themselves. The following standards based on the Secretary of the Interior's Standards for the Treatment of Historic Properties apply:

• A historic structure is used as it was historically or given a new or adaptive use that interprets the structure and its restoration period. Adaptive use of prehistoric structures is prohibited.

• Materials and features from the restoration period are retained and preserved. The removal of materials or alteration of features, spaces, and spatial relationships that characterize the period is not undertaken.

• Each historic structure is recognized as a physical record of its time, place, and use. Changes that create a false sense of historical development, such as adding conjectural features from other structures, are not undertaken. Work needed to stabilize, consolidate, and conserve materials and features from the restoration period is physically and visually compatible, identifiable upon close inspection, and properly documented for future research.

• Materials, features, finishes, spaces, and spatial relationships that characterize other historic periods are documented prior to their alteration or removal.

• Historic materials, features, finishes, and construction techniques or examples of craftsmanship that characterize the restoration period are preserved.

• Deteriorated features from the restoration period are repaired rather than replaced. Where the severity of deterioration requires replacement of a historic feature, the new feature matches the old in design, color, texture and, where possible, materials.

• Replacement of missing features from the restoration period is substantiated by archeological, documentary, or physical evidence. A false sense of history is not created by adding conjectural features or features from other structures, or by combining features that never existed together historically.

• Chemical or physical treatments that cause damage to historic materials are not used.

• Archeological and landscape resources are protected and preserved in place. If such resources must be disturbed, mitigation measures are undertaken including recovery, curation, and documentation.

• Designs that were never executed historically are not constructed.

The following additional standards apply:

• Archeological, documentary, or physical evidence is sufficient to permit accurate restoration with minimal conjecture.

• Restoration is essential to public understanding of the cultural associations of a park.

• Reinforcements required for stability of existing support systems and protective or code-required features (HVAC, electrical, security, fire protection, handicapped accessibility, etc.) are concealed whenever possible so as not to intrude upon or detract from a historic structure's aesthetic and historical qualities, except where concealment would result in the alteration or destruction of historically significant features, materials, or physical or visual relationships.

d. Reconstruction

Reconstruction entails reproducing the form, features, and character of a non-surviving historic structure, or any part thereof, as it appeared at a specific time and place. Reconstruction of an entire structure is always a last-resort measure for addressing a management objective and will be undertaken only upon specific written approval of the director after policy review in the Washington office. The following standards based on the Secretary of the Interior's Standards for the Treatment of Historic Properties apply:

• Archeological, documentary, or physical evidence is available to permit accurate reconstruction with minimal conjecture, and such reconstruction is essential to public understanding of the cultural associations of a park established for that purpose.

• Reconstruction of a historic structure in its historic location is preceded by a thorough archeological investigation to identify and evaluate those features and artifacts which are essential to an accurate reconstruction. Mitigation measures are undertaken including recovery, curation, and documentation.

• Reconstruction includes measures to preserve any remaining historic material, features, and spatial relationships.

• Reconstruction is based on the accurate duplication of historic features substantiated by archeological, documentary, or physical evidence, rather than on conjectural designs or the availability of different features from other structures. A reconstructed historic structure re-creates the appearance of the non-surviving structure in design, color, texture, and, where possible, materials.

• A reconstruction is clearly identified as a contemporary re-creation.

• Designs that were never executed historically are not constructed.

The following additional standards apply:

• The reconstructed historic structure is full-scale and on the original site.

• The reconstruction does not simulate a damaged or ruined historic structure or constitute a general representation of a "typical" structure.

2. Monitoring and Inspections

Planning for maintenance of historic structures requires information about the nature and condition of their features. These data are collected on a systematic basis using the procedures outlined in the Inventory and Condition Assessment Program (ICAP). Major components of ICAP include the scheduled and major assessments modules that upload information into the Maintenance Management (MM) program to generate work requests. ICAP work procedures are contained in the Historic Property Preservation Database (HPPD) and are compatible with the MM program. ICAP interfaces electronically with the List of Classified Structures (LCS) and the Cultural Resources Management Bibliography (CRBIB).

As an integrated database with a growing capacity to coordinate information between maintenance and resource management, ICAP should be promptly implemented in all parks. All major assessments of historic structures should be based on ICAP, and reports of work done to historic structures should be recorded in ICAP.

(For additional information see the ICAP Reference Manual and Computer User Manual.)

3. Protection

Special attention must be paid to protection of historic structures from threats caused by use and environmental forces. Such threats include vandalism, smoking, storage of flammable materials and explosives, and vehicular and airplane traffic. Solutions include road patrols, restrictions on smoking and storage of flammables (as required in certain cases by Management Policies), proper collection and disposal of trash, housekeeping, routine and cyclic maintenance, installation of fire detection and suppression systems, limitations on or removal of traffic, and periodic inspections.

4. Partnerships

Not all historic structures in parks are or can be managed directly by the NPS. Several alternatives are available and deserve consideration, particularly when treatment or use cannot be supported by the NPS.

a. Leasing

Leasing historic property under Section 111 of the National Historic Preservation Act (P.L. 96-515) provides both resource protection and revenue that may be used to defray costs associated with either a specific leased property or any other National Register property under NPS jurisdiction. As prescribed in Management Policies, a lease must ensure preservation of the property and must not unduly limit its appreciation by the public, interfere with visitor use and enjoyment of the park, or preclude use of the property for other management purposes judged more appropriate or cost-effective. The regulations governing leasing of historic properties under this authority are contained in 36 CFR 18. (For further information see Director's Order 27, "Historic Property Leases and Exchanges.")

Except within national parks, national monuments of scientific significance, and properties that were always federally owned, leasing of real property including historic property can also be undertaken under P.L. 90-401 and 36 CFR 17 in situations where resource protection would be enhanced. However, the rental income cannot be retained.

b. Special Use Permits

Special use permits allow use of historic structures for short periods. They can be canceled at any time. They should not be used as substitutes for leases under P.L. 96-515 or P.L. 90-401.

c. Cooperative Agreements

Under P.L. 104-208, the NPS may "enter into cooperative agreements that involve the transfer of National Park Service appropriated funds to State, local, and tribal governments, other public entities, educational institutions, and private nonprofit organizations for the public purpose of carrying out National Park Service programs." On the premise that resource preservation is a park program in support of a public purpose, this authority has been interpreted to mean that the NPS can allow the mentioned entities to rehabilitate and use park historic structures.

d. Concession Agreements

The Concession Management Act (P.L. 89-249) authorizes the secretary of the interior to contract for accommodations, facilities, and services necessary for public use and park enjoyment. Such agreements can permit concessioner use of historic structures.

Concessioner-occupied historic structures in which the NPS has a legally enforceable property interest will be managed in accordance with Chapter 5 of Management Policies and with all applicable standards in this guideline. Specific standards for concessioner-managed historic structures follow:

• All historic structures are inventoried, evaluated, and nominated to the National Register.

• Additions or alterations to historic structures and new facilities adjacent to them are contextually compatible.

• A structure's interior finishes, features, and fixtures are evaluated and managed in accordance with their contribution to its significance.

• NPS-owned furnishings are evaluated for both integrity and associations and if consistent with the park's scope of collection statement are managed as museum objects.

• Concession agreements include provisions outlining responsibility for preservation maintenance and rehabilitation as well as research, planning, and other appropriate treatments.

• Fire suppression and security systems required for public and structural safety are designed to be as unobtrusive as possible and are located to minimize adverse effects on the historic structure while meeting applicable codes.

• Additions and alterations for accessibility are designed and located to be as unobtrusive as possible and to minimize adverse effects on the historic structure while meeting applicable regulations.

All proposals for concession projects that might affect historic structures, whether initiated by concessioners or the NPS, will be submitted to cultural resource specialists and concessions management specialists for review.

e. Conveyance

Except within national parks, national monuments of scientific significance, and properties that were always federally owned, Public Law 90-401 of July 15, 1968, allows the conveyance of a freehold interest in park real property, including historic property, with appropriate easements in situations where resource protection would be enhanced. (See 36 CFR 17.)