The lip of the Shot Cactus crater was irregular itn height and width ranging from little or no lip on the reef or north side of the crater to peaks of 14 feet on the inland side. Lip width likewise varied from 0 to 170 feet. Large masses of saturated soil were thrown out of the crater and deposited as earth mounds for distances up to 300 feet from the crater edge. Impact craters existed as far out as 700 feet. Figures 11, 12, 35, and 36 are photographs of the Cactus area after shot time, showing the lip and moundsof throwout material. In order to give a clearer picture of the lip, preshot and postshot profiles have been constructed using the crater radii as the zero reference or datum plane, Figure 37. Representative lip height is taken to be from 8 to 14 feet and width from 115 to 170 feet. The majority of the large masses of throwout material lie within two crater radii of the crater edge. Lack of adequate data has prevented refined methods for predicting lip dimensions. Scaling of lip height into high yield ranges, however, may not be justified. It would appear that as the yield of the device increases, the slope of the crater sides decreases and the lip height tends toward a maximum. A maximum lip height, however, should not affect lip volume. Percentage of lip volume to crater volume has been calculated from dry sand data and is probably representative of most soils, Reference 7. These percentages are 20 to 30 for near surface aboveground burst, 15 to 20 for surface burst, 10 to 20 for near surface underground burst, and 50 to 70 for deep underground burst. For a surface burst, therefore, such as the EPG shots, mostof the cratered media is throwout or fallout and almost all the large masses of material or ejected fragments (throwout) are within two crater radii of the crater edge. The EPG shots neither supported nor invalidated the prediction method for lips given in TM 23-200 since the limits of accuracy given in the TM were large enough to allow a wide variation in the ip dimensions. The Shot Cactus lip, for example, could range between 314 to 131% feet high and 127 to 213 feet wide. ° Depression Measurements. Permanent vertical depression of the ground surface was measured at NTS from an air burst and it was felt desirable that these measurements be repeated for a surface burst at the EPG. These measurements were made using concrete gage pads as stations for both Shots Cactus and Koa. Transient displacement measurements made by Project 1.8 could then be used as a check. The data was not expected to have a high degree of accuracy because of the probability of postshot ground motion produced by relief of internal stress and wave action caused by other shots! Postshot surveys were not completed until 1959 because of the hazard to survey personnel from the high residual radiation levels. When recovery of stations was attempted by Holmes and Narver, it was found that most of the stations had been destroyed throughthe use of bulldozers and draglines by project personnel effecting a fast recovery of their instruments with minimum radiation exposure. Depression measurements for both Shots Cactus and Koa are listed in Table 10. There are only two measurements of value for Shot Cactus, Stations 171.05 and 181.03. Station 181.03 was at a distance of 850 feet from ground zero and gave a downward displacement of 0.72 inch. The overpressure was approximately Transient displacement measurements made by Project 1.8 at approximately this distance, however, indicated a maximum downward movement from the rest position of 0.89 inch with a minimum movement above rest position of 0.82 inch and a residual displacement of 0.22 inch above the position of rest. Station 171.05 was 980 feet from ground zero and gave a permanent downward displacement of 1.08 inches. The overpressure at this station was approximately Since only one transient displacement measurement was obtained for Shot Cactus a comparisonat this station was not possible. The only records of value for Shot Koa were for Stations 180.02 and 180.03, which were at distances of 3,131 and 3,950 feet from ground zero. Station 180.02 showed a permanent displace- ment of 4.57 inches downward while Station 180.03 registered an upward displacement of 4.24 inches, giving an increased elevation. An overpressure of approximately _was registered close to Station 180.02 and an approximately 40 ‘Age 39 Delered