A study was conducted of the potential applicability of nuclear measuring techniques for determining soil density and moisture content at depth, and changes in these properties, for Navy civil engineering purposes. Measurements were obtained under two different types of engineering requirement to assess measurement capabilities: (1) in base material and subgrade soil beneath the pavements at five airfields, to detect long term variations; (2) in hydraulically placed foundation soils at two construction sites, both before and after densification of the soil was attempted by driving compaction piles, to detect changes due to the densification effort. The data were analyzed and statistical procedures were developed to determine the magnitudes of measurement error. Measurement errors were relatively low compared with the measured temporal variations in the soil properties at th soil densification sites, but were so large as to obscure a large portion of low-level, long-term changes occurring in the pavement subgrades. (Author).