nents: the coconut palm (Figure 4.6), the Pisonia tree (Figure 4.5), and three species of large shrub. The Pisonia is a broad-leaf tree, numerous clumps of which averaged some 50 feet in height and 24 inches in diameter at the base. The Pigonia tree clumps bore a marked resemblance to the branching system and leaf size of an American Beech forest. Also, examination showed the root system to be similar. It became increasingly apparent that this similarity would make the Pisonia portions of the stands the most useful for verification of the breakage-prediction system developed. Palm, on the other hand, is unlike either the coniferous or broadleaf trees which comprise the bulk of the earth's temperate vegetational area and was thus of lesser value for this experiment. The following general conclusions were reached: i. Ground-level pressure measurements, made 2,000 feet into the tree stand, substantiated Upshot-Knothole conclusions of no attenuation in peak static overpressure; TABLE 4.3 SUMMARY OF EPFECTS ON MINES, SHOT 4 L denotes Laid; N denotes Neutralized. Mine Types Mx 6-0 Surface 30 ft case depth 125 ft case depth Mk iu-9 60 ft case depth Mk 18-9 Mk 25-0 Row 1 2,000 fmwGZ RKomber Number Row 5 11,100 toG2 Numb Row 6 12,800MwGZ - Row 7 13,400 fw GZ Nurshy L N L n L K L N L N L N - ~ ~ - - 3 4 3 4 2 2 4 ° 2 4 4 4 9 ° 3 3 6 e - ~- - - - 4 4 6 3 6 - - a 3 3 ‘4 4 4 sos 4 4 3 3 3 a 4 4 i I 1 L i 0 4 64 - USSR R-1A 1 1 alnes neutralized at each location Number Row 4 7,000RwWGZ N - Percentage of ali Number Rew 3 4M00NM AZ L Mk 36-2 Mk 36-2 Mk 39-0 Row 3 3440%tOGZ « 4 200 $2 93.6 4 3 3 - - ~ ~- - - 4 o 4 4 1 Q 4 4 o 0 - - - ~ - - =- - - - 2 - - - 65.6 - 62.6 ~ - - - ~- é - =- - = 8 ‘4 ° + 0 q therefore, for this purpose, further measurements of overpressure in tree stands should not be necessary. 2. It was not possible to .ssess the stand influence by observation of damage, because of non-uniformity of stand composition; nor was it possible to determine the peak-dynamic pressure attenuation, because the three gages in or near the stands showed large, unexplained variations. 3. Observed damage from two devices of different yields compared favorably with the TM 23-200 isodamage curves (Reference 7) prepared for broadleaf tree stands. 4. Damage in broadleaf stands will be principally limb breakage and defoliation, with occasional breakage or uprooting of the main stem. 5. Snubber-wire arrangement for measurement of maximum deflection of tree stem is not feasible in a forested area composed of broadleaf trees and brush species where limb breakage is the principal form of damage. 4.4 MINEFIELD CLEARANCE Project 3.4 had the objective of determining the effects of a megaton-range surface detonation on an underwater naval minefield. Inert versions of the following US and 67