mesh" aliquot is one taken from the ball-milled soil that will not pass through the 100 mesh sieve. LFE Laboratories, which processes about 60% of the total NAEG soil samples, receives 10 gram BM fraction aliquots for analysis. Los Alamos Scientific Laboratories (LASL) received BM fraction aliquots from samples collected in Areas 13 and 5 (GMX) and sieved aliquots from the four sites on TTR (Double Track, Clean Slates 1, 2, and 3) and from A, B, C, and D Sites in Area 1l. Lab X has received only sieved samples. For TTR and Area 11, a number (about 7% of the total samples) of “eross-check" soil aliquots were sent out for analysis, wherein more than one laboratory received an aliquot from the same sample collected in the field. Aliquots from these samples that were sent to LFE were from the BM fraction, while those going to LASL and Lab X were aliquots from the sieved fraction. On a number (about 3%) of soil samples from TTR and Area 11, as much of the total BM soil sample as possible was sieved so that the entire sample as it came from the ball mill was divided into two fractions, <100 mesh and >100 mesh. The weights of these two fractions were recorded and aliquots from both fractions sent to LASL for analysis. (As a general rule, only enough sample is passed through the sieve so that a 50 gram aliquot of the "fines" of <100 mesh soil is obtained for shipment to LASL or Lab X.) In addition, inter-intralaboratory samples (about 2% of the total from TTR and Area 11) were sent to all three laboratories to look for differences between laboratories and to estimate the withinlab variability (between aliquots from the same sample). These provide us with additional information on differences between 239-240,,, concentrations in BM and sieved aliquots from the same soil sample. This paper analyzes the data from Area 13 and TTR that have been reported to date by LFE and LASL. Results are not yet available from Lab X for TTR. The conclusions reached from the analyses of these BM, <100 mesh, and >100 mesh data are relevant to the question of how to proceed in (1975) have reported preliminary estimates of 239-240 Pu inventory ai These are based on results i ae cae for the TTR and Area 11 safety-shot sites. 120 a» a7 et al. As noted above, Gilbert et Mediwe surface soils on the TTR and in Area 11. ee ae, obtaining final estimates of plutonium inventory and distribution in