of water. However, as Table 2 shows, there is insufficient evidence from the test program to support a conclusion concerning how K-factors vary with depth of water. A similar effect should result from detonations over very hard substrates such as rock because of the tendency toward the production of smaller particles, with, perhaps, higher specific activities. The crater volume from a near-surface detonation is not considered a good indicator of the value of Ky >» although both crater volume and Ky decrease (and the average specific activity increases) with increased height of burst. Under these circumstances, the Subcommittee recommends that DCPA assume for all practical purposes that no soil or substrate effect exists. If there is such an effect, the common soils in the country, being wetter than dry desert alluvium, should yield slightly lower Kj's and thus this recommendation will produce conservative results. 13