.iuded construction of concrete timing stations, in which lead brick Each c coffins housing certain of the scientific instruments were built. At these stations generators and air-conditioners were installed. Footings for the installation of blast-measuring instruments and structures for housing recording instruments were included at each site. A tank revetment was built on each test site to house the ground sample recovery tank during the blast. The test structures of the Corps of Engineers and the Bureau of Yards and Docks were located so as not to interfere with the AEC’S instrumentation structures. Laying of ground cable to the various instrumentation installations was performed in part by the scientific groups and partly by the Naval Task Unit 7.3.6, commanded by Lt. Commander Harry E. Rowand, USCG. Ditching for this cable was a part of the construction work. Cable laying by Task Unit 7.3.6 was commenced on 5 January 1948. The last submarine cable was laid on 9 March and underground connections were completed by 17 March. The Task Unit assisted personnel of the Scientific Task Group (TG 7.1) in laying and splicing type RG18U coaxial cable on the three test-firing islands.lg The cable system was extensive, tying in all test-firing stations and instruments of the proving ground with the control station on Parry island. Photographic towers were tied into the system. This permitted cameras in the towers to be actuated by an electrical impulse just before detonation time and record the blast phenomena. The nature of the soil at the test site was such that it was feared that the bomb blast would create such dust clouds as to blank out some of the test instruments and prevent the recording of necessary data. To obviate this possibility, sand blankets we~e laid along the vista from the firing tower to the gamma stations. Cement soil stabilization was also used as a means of dust control, as was surface oiling and paving. The over-all construction performed by troop labor included the clearing and grading of 221 acres; laying of 16,605 square yards of bituminous paving; 89,190 square yards of surface oiling; laying of 30,000 square yards of cement soil stabilization; fabrication of 27,566 square feet of forms; pouring of 2,534 cubic yards of concrete; placement of 222,655 pounds of reinforcing steel; quarrying of 1,069 cubic yards of coral aggregate; the placing of 156 three- to six-ton test cubes; the construction and stabilization of seven liaison-type plane landing strips; and backfilling 7,643 cubic yarsd of earth. On Engebi, which was the site of the first test, construction got under way in December 1947 and by 14 March was 98 per cent complete. Erection of the 200-foot firing tower by Morrison-Knudsen-Peter Kiewit Sons, Inc., required a total time of nine days. During the latter part of March and the first week of April, Engineer troops assisted scientific groups of TG 7.1 in the installation of technical equipment and completed cleanup of the island. On 6 April 1948, Engebi island was turned over to the scientists ready for use. Due to the presence of 142 natives on Aomon, construction there did not get under way until the latter part of December. In addition to the construction of instrument housing and other installations, the construction of the causeway linking Aomon and Biijiri was required. This job was done by the Hawaiian Dredging Company, Ltd., as was Construction of the foundation for the lagoon photographic tower. In addition to Aomon and Biijiri, the neighboring island of Rojoa was used for certain test installations. IDDetailscouttined in Sec. VII, kHlex 1. 99