Flood Mitigation Project – FAQ Page

We know that it is feasible to create a hydraulic solution that has a single point failure system or in other words, has redundancies that prevent the lifting system from failing.  The hydraulics solution requires more engineering studies to resolve these details, especially at the connection between the lower and upper decks as they will likely be uncoupled.  These studies are currently underway.

The current of the Fox River in this location does not move quickly, but moving debris is a significant concern. Debris containment on the outside of the pit walls is being studied. Additionally, the trusses will have to be braced in the other direction.

Hydraulic systems work in the cold without negative consequences. If we were to consider a water hydraulics system, it would require antifreeze.

Many different systems were evaluated. A barrier dam solution needs vertical elements (visual disturbance) or they could be hydraulically lifted, but it is difficult to create a water-tight seal. Also, the pressure of holding back water above three feet becomes difficult. Even if barriers are erected around the house, once the water rises above 4-5 feet, the pressure would push the water below the barrier system and the water would rise on inside the barrier. Cofferdam systems would work below grade but would need a an above grade curb along with a very complex system of hydraulically raised walls tied to the below-grade cofferdam that would rise up to form the above-grade dam that would somehow have to be sealed to the curb and to the adjoining elements. Rubberized plastic barriers that are inflated with water are not designed for these heights of water and they are not anchored. These systems are not designed for quick response. Limited staff capacity dictates that any new system can be activated by one person in less than two hours during poor conditions. The costs of these systems have not been estimated and the site aesthetics would be compromised.

The unified jacking system synchronizes equal pressure across the structure during the extend/retract process to prevent damage to the glass regardless of differential loads. This system would be employed for the house lifting and the hydraulic lift option.

The lift cycle for the hydraulic system is designed to elevate the building less than 1” per minute over a two hour period.

The current rigid utility connections will be replaced with flexible connections with waterproof seals. Details will be developed in a later stage.

A whole lot of fill is needed to elevate the house over seven feet.  That much fill would destroy the existing landscape.  It’s also an environmental and permitting concern to add fill to the floodplain.

The house should be lifted high enough to allow for at least one foot of freeboard between the top of the water and the bottom of the structure. Based on the highest recorded past flood (1996) when water rose two feet above the 100 year-year design elevation, the minimum the house should be lifted is 6.5 feet. We assume that the flood waters are capable of rising over the 1996 amount, so nine feet was determined to be a safe height. The schematic design stage should further validate this assumption.

This current visionary endeavor to protect (flood mitigation) and preserve (restoration and conservation) is the genesis of our preservation plan. The studies completed in the last few years to inform the flood mitigation study, the current research underway with the glass, steel and travertine, and the previous reports will be compiled and made accessible. More time and resources will be dedicated to continue research and to create a guiding preservation philosophy.

Raising the house is a permanent solution rather than a technological solution, but it alters the entirety of parcel one (the original property owned by Dr. Farnsworth) since a tremendous amount of dirt would be added to create a natural slope. While the distance between the house and the river would not change, the house would be higher and the viewer would look down towards the river rather than being at the same level as the water. Almost all of the trees would be lost in this scheme.

If fill is placed or building is constructed in the floodway, the permitting is more complicated and has to be approved by the Federal Emergency Management Agency (FEMA). Normally, encroachments into the floodway are not allowed; however, in the case of the Farnsworth house, the land across the river is state park land, and there is little development in the area. Fill in the floodway may be allowable if it can be demonstrated that the fill will not cause a rise on any insurable structure. Studies are needed to look further upstream to determine what other structures could be potentially affected.

If working in the floodway is determined to be the best approach, extra time will be scheduled for special permitting, conditional letters, surveying, and erosion management.

The lower terrace was designed by Mies to flood so it makes sense to not lift both but this will require careful study and design to make sure the changes are subtle and barely observable. Philosophically, a small change that could save the building in its original and powerful context is likely worth the compromise.

The slab would be buried around two feet below grade and has a thin 1/4” metal edge that will hold the soil. When the system is employed, the top two feet of topsoil will rise. When the system is at rest, the only visible sign of it will be the small metal edge that likely will be covered with soil. Currently, there is dirt under the house.

This and a scissor lift were the first concepts investigated. The actuators, when elevated, would need to act as cantilevers to resist lateral loads that would occur from wind, water and debris. Hydraulics designers and manufacturers advise against the use of their actuators in this cantilevered/bending application. Also the ‘legs’ of the eight actuators would need to be tied together so they cannot pull apart or fold inward. In the proposed design, the hydraulic system is only used in their standard axial capacity to push the trusses into place, not to hold the building up during the flood event.

The first priority was to preserve the original relationship between the house, river and land. For the house to stay in its current location, some type of flood protection is needed. As noted above, we evaluated flood walls, inflatables and other systems. These systems either added visible features to the landscape such as large foundation pockets or were not able to be erected by a small staff within a two hour window. Since the ground water is between six feet and seven feet below grade, there is also the likely complication of water seepage from below.

The proposed system is a new application of standard technology. The trusses carry the load, the hydraulic system is only needed during the lift cycle, the system is waterproof and the pit creates access for maintenance. Additionally, the system will not be seen except during a flood event.

The design life of the system is 750 cycles (2 hrs up and 2 hrs down) or 3000 hours. If we run the system four times a year, it theoretically runs for 187 years. If we run the system 10 times a year it would have a projected life of 75 years.

A single-point failure system ensures that even if the system sustains the total loss or catastrophic failure of any single component, it will not compromise or jeopardize the overall system integrity. There are built-in redundancies such that should one piece of the system be damaged or fail to work, the entire system will not fail and the house will not suffer.

The hydraulic system is designed to need very little maintenance. Normal annual maintenance includes fluid, filter and hose replacement as needed. The system, including the emergency backup generators, requires periodic testing to ensure reliability (2-3 times a year). When the hydraulics system is in use, a visual ‘walk-around’ is needed before the building is lowered to inspect the state of the system and identify any areas that may need repair.

The skill sets required to maintain this type of equipment are essentially the same as those required for the normal maintenance of Farnsworth House. We do not anticipate any difficulty in finding suitable personnel within the greater Chicago Metropolitan area. Additionally, a qualified technical personal can be trained to provide the bi-annual inspection. An Operations and Maintenance Manual will be provided by the design team.