The EXO Adjustable Foundation System
installed in late 2007

Bartoszek Engineering designed an adjustable foundation for all of the clean rooms that were installed at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. WIPP is a DOE operated salt mine where low level radioactive waste is buried. Part of the mine is used for waste disposal, and part is dedicated to research. The reason EXO was installed here is that the salt at WIPP has a very low level of natural background radiation. The downside of the salt mine is that salt is a visco-elastic plastic, not a true "rock". Once a tunnel is excavated at WIPP over time the salt creeps back in to fill the space. The floor heaves up, mostly away from the walls where the deflection is least. The walls bulge in, as does the ceiling. The foundation had to be designed to absorb as much as 2 inches of floor motion the first year.

Clean rooms 2 through 6 were relatively easy in that they weighed around ten tons each and their steel box beam floor was strong enough to support their internal loads if it were supported on just a few points. Clean room 1 was a completely different story in that it contained the cryostat and tons of lead shielding. Clean room 1 weighed ~75 tons and analysis of its floor showed that the beams in its floor were not strong enough to support the cryostat if they were only supported from a few points to the salt floor.

The solution was to mount clean room 1 on its own new much stronger sub-floor that was hydraulically adjusted in height by three 50 ton cylinders. All the other clean rooms are supported by ACME screw jack feet called "peg-legs" bolted on to their steel floors.

The biggest problem with the design has proven to be the lack of good information about just how much pressure the salt can take without creeping. The first feet of clean room 1 proved to be too small and caused that room to sink into the salt. We solved that problem by making new larger round feet to reduce the pressure against the salt.

Some of the photos were taken by Larry Bartoszek on his trips to WIPP for the initial installation. Some were taken by EXO collaborators and come from the E-log.

Click on any of the thumbnails to get an enlarged view. You are welcome to download any of the images. If they are used for other than private viewing, credit to the EXO collaboration and Bartoszek Engineering would be appreciated.

The overall design

These renderings show what the clean rooms would look like on their new foundations. The second row show bringing module 2 next to module 1 and standing it on its peg-legs.

The design of the sub-floor for clean room 1

The tricky part about installing Clean Room 1 onto its sub-floor is that it had to be brought in on a fork-lift at WIPP sitting on the steel pallet shown below. We had to hold up the clean room from four corner pillars with jacks so that the fork-lift could back out from under the clean room. The jacking column is shown in the fourth picture. The beam shown in the fifth picture was installed into the corners of the clean room floor and used to reach the jacking columns. The cantilevered extension was necessary because the jacking columns would interfere with the sub-floor if they were too close. The fact that the cryostat is not centered in clean room 1 explains why the sub-floor has an extra 8 X 20 beam to spread the foot-print of the hydraulics further apart.

The design of the peg-legs

Peg-legs are columns with ACME screws that can change their length raising and lowering the clean room. To make it possible for a person to rotate the ACME screw in close quarters, the end of the screw is mounted on a spherical roller thrust bearing. There are four peg-legs on houses 2 through 6 because there is a floor beam in the center of the clean room floor. It was much easier to attach peg-legs in the corners as shown than to make a special peg-leg that could straddle the intersection of two beams for a three point support. The three threaded rods shown around the peg-leg were to allow it to stand on its own prior to assembly to a clean room.

The steel pallet

The steel pallet allowed the 41 ton fork lift at WIPP to carry the clean rooms even though its forks were not long enough to cross under the clean rooms.

Installing Clean Room 1's sub-floor

Larry Bartoszek went to WIPP for the installation of the sub-floor and the commissioning of the hydraulic system. Everything worked as designed, it just takes a lot of pumping to make those 50 ton jacks go through their whole stroke.

The modules' ride down the mine shaft elevator

The first picture shows the module entering the elevator up on the surface. The second shows the opening at the bottom of the elevator shaft.

Installing Clean Room 1 on its sub-floor

These pictures show some of the process of getting clean room 1 on its sub-floor.

Installing Clean Room 2 next to Clean Room 1

Everything pretty much worked as designed, which was a great relief to me. A lot of thought went into the process of the installation.

All six modules assembled at WIPP

All six modules installed in the WIPP tunnel. Just the beginning of re-creating the set-up at Stanford shown on other pages. The second picture shows the proximity of the salt wall on the back side of the clean rooms.

New feet for module 1

These pictures show the new larger round feet that keep clean room 1 from sinking into the salt.

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