ee== The next slide gives an indication of increasing hole depth with time, and of course is not too different from the trend in the slide on yield escalation. However, it may be of interest that the depth of burial of the boxcar device iT«25 2,000 “ wes This was somewhat less than that of the Greeley device, which a --. buried at 3,990 feet. The current esti- mates of aotual yields, as noted previously, are 870 kilotons for Greeley and something like 1300 kilotons for Boxcar. At the Greeley location in the igneous formations of the Pahute Mesa area of the Nevada Test Site, it took about nine months for the resulting chimney of broken rock to fall in all the way to the surface, and that is not a desirable phenomenon at such a late date because of on-site safety considerations. This slide illustrates why-- the hole was about 300 feet wide and 150 feet deep with essentially vertical side walls. Boxcar was placed at a shallower depth in the same type of formation so chimneying could continue to the surface soon because of the cracking radius, and surface collapse did occur in about an hour and 45 minutes. This slide shows the result-- much like subsidences in the alluvium of Yucca Flat. The subsidence is about 900 feet wide and 275 feet deep. DOE ARCHIVES (ND 7