The National Trust has invested nearly half a million dollars to repair flood damage, study the impact of flooding in the area and develop solutions to this long-standing threat.
Each of the options were assessed on on effectiveness at mitigating the threat, cost, impact to the site, impact on the aesthetic integrity and on Mies’ original vision for Farnsworth House.
The National Trust convened a technical advisory review panel to examine nine different options to help preserve Farnsworth in the event of future flooding. The panel found the hydraulic lift to be the most promising choice as it preserves the building’s relationship to the site. However, other options were further explored, these include raising the building in situ or relocating it to a different location on the site.
From Silman Report
The past two decades have shown that flooding is a significant threat to the historic finishes and interior of the house, as well as to the exposed structural elements, which continue to deteriorate with each subsequent flood. Documentation shows that the average occurrence of a flood that breaches the house is every 15 years, but recent flooding has far surpassed this probability.
This potential increase in flood levels and occurrences led the National Trust to hire Wright Water Engineers (WWE) to assess the hydrology and flood risks of the house and surrounding lands. Their report (download here, PDF) confirmed that peak discharges and the frequency of flood events have increased over the years. It is expected that the site surrounding the house will flood annually, and there is a 20% probability that flood levels will rise above the terrace level in any given year.
The National Trust also hired Thornton Tomasetti (TT) to complete a preliminary feasibility study (download here, PDF) on ways to alleviate the threat to the house from flooding. TT’s report documents the existing design loads, analyzes the existing connections and initiates a cost/benefit analysis of several mitigation options.
The National Trust requested that Robert Silman Associates (RSA) prepare a more in-depth analysis (download here, PDF) of the three best scenarios based on the preliminary study provided by TT and the recommendations of the Technical Advisory Panel:
- Elevate the house and terrace in situ with additional fill placed under and around the house,
- Move the house to high ground on the site or move to a newly filled portion of the site close to the original location, and
- Employ a hydraulic or mechanical system to raise the house temporarily just prior to and during the flooding.