area around the Roller Coaster events had been mechanically disturbed for one reason or another shortly after the events. this profile reflects such mechanical disturbance. other TTR profiles show similar results. It appears that A number of the Until it can be resolved whether mechanical disturbance has occurred and, if whether unique soil properties are responsible for the observed development, this type of profile cannot properly be interpreted. Selected soil profile sampling stations will be inspected later this spring to determine more precisely the soil characteristics with depth. For instance, gravel layers or clay layers within the sampling depth could significantly alter the interpretation of many of the profiles. Fig. Field notes are lacking in this respect. 6 shows a profile of 235 U and 238 U from Area 11, Site A. 238 U appears to be near natural background. The 235 The U, presumably from the exploded devices, rapidly decreases with depth to more or less a continuum. Since natura l 235 U levels are at least 10-20 times lower than those found in the 5-25 cm region, one must presume that device-29> U has migrated downward. A closer examination of the physical nature of the sampling site may allow confirmation of this presumption. This interpretation is based on the assumption that U contained in the device used at Area 11 Site A was predominately mass-235. RECOMMENDATIONS The following recommendations regarding profile sample collection and processing are made: l. When taking profiles, make field notes on any kind of soil stratification observed. Also note any evidence of mechanical disturbance in the immediate location of the profile. care should be taken to note microdrainage features. 28 Particular