Visual Impact Analysis, Fort Missoula Cellular Equiptment Installation

This project consisted of an analysis of the visual qualities of the Fort Missoula Historic District. The project centered on an analysis of the effects of the proposed cellular equipment installation on the historic water tower at Fort Missoula, a contributing element to the Fort Missoula Historic District. The report was prepared for the Northern Rockies Heritage Center.

The visual impact analysis was conducted in three phases. Phase one included recording the existing visual character of the tower and base area from various locations within the Fort Missoula Historic District and from various locations within a mile radius of the tower. The historic district boundary map from the NRHP form and the Northern Rockies Heritage map with the Fort historic buildings identified were both used to document locations within the district where the tower was visible. Using historic photographs which included the water tower, digital photographs were taken from historic view points for comparison. Phase two of the assessment included walking 30-meter transects across the entire district and recording the existing quality of visibility with a 0 to 3 rating scale on district maps. The arbitrary rating scale included: 0 for not visible, 1 for only the tank being visible, 2 for only the tank and tower legs being visible, and 3 for the entire tower and at least some of the base area being visible. Phase three of the assessment included analyzing the proposed alterations to the tower and base area, in conjunction with the data collected during phase one and two, to determine the proposed project's level of visual impact.

The assessment of the integrity of the water tower included determining the current physical features and condition of the resource. The tower was surveyed in the field and current features and conditions noted. The proposed undertaking was analyzed using the seven aspects of integrity defined by the National Register. The seven aspects include location, setting, workmanship, feeling, association, materials, and design. Retention or loss of these aspects was used to determine the proposed project's level of impact to the integrity of the tower and base area.

The proposed cellular equipment installation on the Fort Missoula water tower and at its base were analyzed for its effect to the visual character and quality of the Fort Missoula Historic District and larger Missoula community and for its impact to the integrity of the water tower, a contributing resource to the historic district. The project proposed conforming additions to the water tower legs and converting the existing pump houses into the project's required equipment storage areas. The additions to the legs will follow the existing vertical alignment and color of the current structure. Although the original spatial organization of the tower legs were altered by six inches at each addition location, the overall effect will be minimal. The project's equipment storage will be within the confines of the existing pump house structures and therefore, will have no impact on the existing visual environment of the base area.

The project conformed to the vertical alignment and coloration of the tower legs, with minimal alterations to the basic spatial organization of the tower. In addition, the equipment storage was contained within existing structures, eliminating possible visual impacts to the base area. The current visual quality of the tower is low and the effect of the proposed project on the visual character is barely present. Therefore, the proposed project will have no adverse effect on the historic district and larger community viewshed.

The retention of the seven aspects of integrity for the Fort water tower and base area was be good. Therefore, the results of the assessment indicated a finding of no adverse effect for the proposed cellular equipment installation project on the integrity of the water tower and base area.

Historic properties can be adapted for new uses without seriously damaging their historic character. But to do so, a treatment approach needs to be identified and the standards and guidelines outlined for that approach need to be followed. Information on treatment approaches, standards, and guidelines for historic properties comes from the Secretary of the Interior's Standards for the Treatment of Historic Properties. The identified treatment approach recommended for the Fort water tower, a contributing resource to the Fort Missoula Historic District, was rehabilitation. This approach emphasizes the retention and repair of historic materials, with latitude for replacement if appropriate. Using this treatment approach, the character-defining features of the resource were protected and maintained while the deteriorated historic components were repaired. The standards for using the treatment approach of rehabilitation for a historic property include:

1.) A property that will be used as it was historically or be given a new use that requires minimal change to its distinctive materials, features, spaces, and spatial relationships.
2.) The historic character of a property will be retained and preserved. The removal of distinctive materials or alteration of features, spaces, and spatial relationships that characterize a property will be avoided.
3.) Each property will be 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 or elements from other historic properties, will not be undertaken.
4.) Changes to a property that have acquired historic significance in their own right will be retained and preserved.
5.) Distinctive materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a property will be preserved.
6.) Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture, and, where possible, materials. Replacement of missing features will be substantiated by documentary and physical evidence.
7.) Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatments that cause damage to historic materials will not be used.
8.) Archaeological resources will be protected and preserved in place. If such resources must be disturbed, mitigation measures will be undertaken.
9.) New additions, exterior alterations, or related new construction will not destroy historic materials, features, and spatial relationships that characterize the property. The new work shall be differentiated from the old and will be compatible with the historic materials, features, size, scale and proportion, and massing to protect the integrity of the property and its environment.
10.) New additions and adjacent or related new construction will be undertaken in such a manner that, if removed in the future, the essential form and integrity of the historic property and its environment would be unimpaired.

With choosing rehabilitation as a treatment approach, the form and detailing of architectural materials and features that define the historic character need to be identified and methods of protecting and maintaining these elements should be addressed. Defining characteristics of the water tower include the metal frame and cylindrical tank, its roof, and the concrete footings. The tower's current condition includes extensive rusting along the metal features. To protect and maintain the Fort water tower, the corrosion now present needs to be removed and the structure repainted. The recommended procedure for removing corrosion and repainting historical metal structures included:

1.) Identifying the particular type of metal prior to any cleaning and then testing to assure that the gentlest cleaning method possible is selected.
2.) Cleaning soft metals such lead, tin, copper, terneplate, and zinc with appropriate chemical methods because their finishes can be easily abraded by blasting methods.
3.) Using the gentlest cleaning methods for cast iron, wrought iron, and steel "hear metals" in order to remove paint buildup and corrosion. If handscraping and wire brushing have proven ineffective, low pressure grit blasting may be used as long as it does not abrade or damage the surface.
4.) Applying appropriate paint or other coating systems after cleaning in order to decrease the corrosion rate of metals and alloys.
5.) Repainting with colors that are appropriate to the historic structure or district. Applying an appropriate protective coating such as lacquer to an architectural metal feature such as a bronze door which is subject to heavy pedestrian use.
6.) Evaluating the overall condition of the architectural metals to determine whether more than protection and maintenance are required, that is, if repairs to features will be necessary.

If repair is determined as necessary, this should be done by patching, splicing, or otherwise reinforcing the metal following recognized methods. Repairs may include limited replacement in kind, or with a compatible substitute material of those extensively deteriorated or missing parts of features when there are surviving prototypes.


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