(c) 3. in a 100-foot systematic grid near ground zero, within an inner fence (count: 498) (see Figure 2). Two sampling lines where both Am concentrations in the soil and FIDLER readings were determined, at short intervals, for the purpose of estimating the distance--variability relationships (Figure 2). Along each line, 15 groups of 4 adjacent soil samples were collected. The spacing between groups is 20 feet in Line 1 and 150 feet in Line 2. The samples themselves are rings, 5 inches in diameter, 5 cm deep. FIDLER readings were taken both at the surface of each soil sample and at one foot above the ground. Readings were taken immediately before the soil samples were collected. Table 1 indicates the general levels of Am activity from FIDLER readings. Table 1. Levels of FIDLER Activity (log, of FIDLER counts in 10% cpm units) Data 400 Ft. Grid 100 Ft. Grid Line l Line 2 Number of Readings 352 498 60 51 Mean Standard Deviation Minimum Maximum 0.054 0.72 0.83 -0.58 0.398 0.495 0.293 0.369 -1.0 -0.70 0.35 ~1.72 1.76 2.17 1.48 ~0.07 Previous studies (Gilbert et aZ., 1975) have established that Pu and Am concentrations are in a nearly constant ratio: Pu(x) = Am(x) x R(x) (x: location of sample) (1) with R(x) = 9.4 + 0.14 ((mean Pu/mean Am) + 1 standard deviation). We note that FIDLER readings taken aboveground (1 foot) integrate gamma rays within a circle 1 meter in diameter about x, weighting most heavily the Am directly under the detector crystal. As a consequence, the relationship between Pu(x) and FIDLER(x) (FIDLER count above x) is expected to be more complex than in Equation 1. Intentions Putting Lines 1 and 2 aside, the FIDLER readings total 1,004 observations against 174 for Pu concentrations. In earlier efforts (Gilbert et al., 1975; Gilbert and Eberhardt, 1974), these FIDLER data were used mainly to 370