The compression gauges required a special excavation procedure. As noted
previously in Chapter 3, these gauges were mounted vertically within Section N2. To do
this, a coring rig was used to cut a circular hole through the depth of the base material
(approximately 6 inches deep by 4 inch diameter). A hammer drill was then used to drill
a small diameter hole (approximately 0.5 inch diameter) extending from the bottom of the
cable trench to the bottom of the core hole. This was done so that the cabling would
disturb as little material as possible and extend from the bottom of the gauge.