: order of SM - 3 ~ During the 1957 PLUMBOB and 1958 NARDTACK II series at the Nevada lest Site a number of small yield nuclear devices were detonnted at the bottom of drilled holes. In contrast to the stemming practices of today these holes only contained one or more cement plugs between the device and the ground surface. Four of these events, PASCAL A, OTERO, BERNALILLO, and VALENCIA had senled depths of burial ranging from 3800 pes to 1360 wl3. (Use of scaled depth may not be strictly appropriate here). The maximum fraction of the total activity produced by these detonations which was deposited in the local fallout pattern was about 5.5%. Fallout fractions resulting from accidental ventings of detonations designed for complete containment, including line of sight and tunnel events, have not exceeded this number. (Final determination of the fallout fraction for BANEBERRY has not as yet been completed). The occurrence of a massive venting of an underground detonation designed for complete containment is accidental and unpredictable. For safety reasons, therefore, it has been the practice for many years, and currently is common practice, to assume that for essentially all underground detonations of this type, a prompt massive venting is credible. Current fallout prediction procedures are based upon this assumption. Current Fallout Prediction Procedures The currently employed fallout prediction technique was derived by modification of a method originally developed by the Special Projects Section , The original method was based primarily on fallout tee ee Weather Bureau, in 1955. U. 5S. data from tower shots in Nevada and has been described by Nagler, Machta, and Pooler (1), The modification of this method has been reported in detail by Cluff and Polmer (2) and ite application has been discussed by Mueller (3, and Morrell (5). te neo errant eeumpmae _ 4