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Fort Union Conclusions

FOUN Panorama
Understanding Damage Mechanisms
To date, there has been little coordinated attention to describe how changing weather conditions will affect built heritage at the material and systemic level. Only with a better understanding of damage mechanisms can we begin to implement remedial and preventive strategies, including the establishment of monitoring programs that can measure projected impacts to these resources.
Urgent levels of mitigation and support adaptation are required to reduce vulnerability from current and future climate extremes. Where adaptation is not undertaken in response to a perceived risk, vulnerability will remain unchallenged.

Damage mecahnisms
In raking light the texture of the original adobe block walls can be seen beneath the protective shelter coats.
Monitoring, or the systematic process of observing, tracking, and recording data for the purpose of measuring and assessing information deemed necessary for a stated objective is the key to cultural resource management. There are many monitoring systems now in place that capture how climate is changing. They do not, however, provide information about the impacts of changing climate on built cultural resources at the park or site level.

The challenge for cultural resource managers is to develop a suite of indicators at multiple scales that are essential for understanding climate impacts on built heritage (e.g., materials, construction systems, conditions, settings). These indicators should capture sufficient information to demonstrate change relative to climate stressors and, therefore, provide some insight into future weather-induced damage.  Because it is not realistic to measure every phenomenon on a site, it is important to identify aspects, including condition, that provide a generally accurate basis for anticipating future problems.  These indicators should be directly linked to the problem, measurable, and ideally display a time continuum (exist in the past and present). Such information could be useful for any site, focusing on measurable metrics that can be used as indicators of site vulnerability and site sustainability.

Snow on Site
Walls, impacted by prevailing winds, supported by additional bracing to prevent catastrophic failure.
As with natural ecosystems, cultural resources have the capacity to adapt to a changing environment but this adaptation is limited by time and space as well as the intensity of the change.  For example, annual summer ‘monsoons’ will continue to erode the adobe walls of Fort Union; however, changes in the occurrence of these monsoons, due to climate change, will stress the walls beyond their moisture threshold limits resulting in catastrophic failure due to adobe’s wet strength vulnerability. The aim is to provide a framework for defining site vulnerability and threshold limits based on site monitoring that integrates across a wide range of scales and over time.

snow on the ground
A view of the southeast end of the Mechanics Corral showing where snow can remain in shadowed areas.
The Integrated Vulnerability Assessment Methodology developed by the CAC team is intended to differentiate modes of deterioration based on their symptoms as well as their degree and frequency of treatability. Certain treatments, such as the application of shelter coats, are preventive, low impact, and cyclical. This treatment does not address other conditions such as deformation or leaning, which require more invasive interventions. A sustainable conservation and management plan for climate-sensitive cultural resources, such as those constructed of earthen materials and maintained as ruins, clearly identifies the type and rate of deterioration, where it occurs, and what interventions are necessary to reduce and/or remove the causes of damage.
The Integrated Vulnerability Assessment Methodology
The Integrated Vulnerability Assessment Methodology is the culmination of four phases of work conducted by the Center for Architectural Conservation. This methodology, developed and implemented at the Third Fort at FOUN, is comprised of three components:

  • The Rapid Assessment Survey (RAS)
  • Wall Profilometry for validating RAS findings
  • Passive RFID embedded monitoring

These three parallel data sets provide the foundation for an integrated approach that leverages the benefits of both qualitative and quantitative techniques. Each dataset complements and reinforces the other, compensating for weaknesses that would otherwise arise from the implementation of any method in isolation - as is often the failure with most contemporary vulnerability assessment protocols that emphasize either quantitative or qualitative tactics.
Rapid Assessment Survey (RAS)
National Park Service stabilization crew executing the new rapid assessment survey during the summer of 2019.
The Rapid Assessment Survey (RAS) is the framework of a seasonal site-wide assessment, intended to substantiate annual maintenance, stabilization, and monitoring decisions. The primary objective prioritizes wall sectors based on observed wall conditions that define vulnerability factors. It does not, however, replace expert judgment to actualize its findings.
The value of the RAS is derived from consistent annual implementation, providing a structured observational approach. It replaces past informal annual surveys, from the early park forms to the annual site ‘walk-around’ by the stabilization crew.
Wall Profilometry
CAC staff working on profiles for the Machanics Corral.
Wall profilometry characterizes both a wall’s geometrics, as well as its differential surface deterioration and loss. In addition to its height, the most valued piece of information for assessing vulnerability of a freestanding wall is a record of its cross-section. Profile information is critical to maintenance and preservation, while the resulting surface deterioration typologies can be beneficial to understand surface erosion of adobe ruins across the region.
Passive RFID embedded monitoring
RFID tags
Installation of the RFID tags behind the shelter coat of the walls of the Hospital building.
Radio identification (RFID) technology, a passive embedded moisture detection tool, leverages the understanding of the primary failure mode. As a result, only the data necessary to evaluate the integrity of the water shedding elements of the adobe wall are collected, and only when necessary by the preservation staff during the seasonal survey.
In Closing
The primary objective of the RAS is risk-prioritization based on inherent vulnerabilities and the results should be evaluated both intrinsically and extrinsically. Data gathered from the RAS of the Third Fort, particularly contextual ‘aspect’ factors such as orientation, exposure, and wall geometry, provide validating performance scenarios that suggest certain combinations of both intrinsic and extrinsic factors have an exacerbating effect on both active and inactive deterioration conditions and therefore overall performance. This is the essence of understanding risk and threat and their effect on site vulnerability. The Integrated Vulnerability Assessment Methodology can lay the foundation for NPS to develop a long-lived Site Preservation and Management Plan that can respond to the coming needs of climate change and diminishing fiscal reserves.