The CABRA event was detonated in hole U20aj of the Nevada Test Site as indicated in figure 1.1. The CABRA device had a depth-of-burial (DOB) of 542 m in the Tuffs and rhyolites of area 20, about 20 m above the standing water level, as shown in figure 1.2(l). Figure 1.3 is a plan map of the immediate Vicinity of hole U20aj showing the drill holes used in the construction of the cross section plot of figure 1.2. Stemming of the 2.44 m diameter emplacement hole followed the plan shown in figure 1.4. A log of the stemming operations was maintained by Holmes & Narver. Detonation time was 12:20 PST on March 26,1983, and a sub-surface collapse to a depth of 380 m was observed. No radiation arrivals were detected above ground and the CABRA containment was considered successful.