The foundation slab of the six-cell box girder provides a basement area for locating blowdowns and other accumulators for the shake tables and servo-hydraulic actuators and access to the underside of the tie-down floor for anchoring test fixtures, and general storage. Headroom in the basement is 8 ft, and the space is used to run electric power and hydraulic lines to and from experimental equipment on the floor above. Access to the basement is provided by 2 stairwells on the North and a large in-ground vault on the South that accesses the fabrication yard. The vault contains a 6000 lb capacity scissor lift for moving equipment in and out of the basement.
Hydraulic hardlines feed the laboratory from an external pump house just outside the southwest corner of the building. The hardlines run along the basement floor and distribute oil into the four shake tables. There are multiple tapping locations to provide hydraulics for additional actuators. An array of oversized floor holes allow easy access from the lab floor to the basement hydraulics.