What storm/flood level was used in the design of the caverns?
The roadway in front of the cavern is approximately 17 feet higher than the 500-year flood level. The portal entry is two feet above this level. Therefore the caverns will not flood from overland flow during a 500-year flood. To prevent flooding from a groundwater flow, the caverns have a groundwater drain and pump system installed around the perimeter that is similar to typical building basements. Groundwater modeling shows that the pumps can handle flow corresponding to 500-year flood plus five feet.
