Station25-Engebi-NOBL, This structure was another blast hut for the same purpose as Stations 23a and b. The building was new, The original interior size, as per drawings received by H&N on January 30, 1950, was 20 feet by 15 feet by 7 feet high. On April 24, 1950, a letter from J-Division changed the size to 15 feet by 14 feet by 7 feet. The walls and ceiling were 16 inch reinforced concrete, with an earth fill placed against the front and two sides up to the elevation of the roof, Originally the structure was to have had a partition to divide the space into two rooms, with a separate exit door from each room, but this idea was discarded in favor of one room and one exit. ‘So as to standardize the blast doors, e clear opening of 2 feet, 2 inches by 5 feet, 6 inches was set, The doors were then made strong enough to resist the maximum anticipated side-on pressure, They were also so con- In nearly every case, the structed to be airtight and watertight. doors were installed in pairs, one on each side of the opening provided in the concrete wall. Stations 26a and b - Engebi — NOBL. These stations were the anchors for the barrage balloons, The anchors were concrete footings 5 feet by 5 feet by 2 feet deep. The drawings were completed February 8, 1950. On March 15, 1950, the bolt arrangement was changed, and on May 27, 1950, the final location of the stations was given by Los Alamos, Station 26c - Runit - NOBL. Same as Stations 26a and b, Engebi, Stations 27a through d — Engebi and Runit - NOBL. The stations were ball~-crusher gauge mounts utilizing a concrete foundation. The original sketches were given H&N on January 30, 1950, at a meeting in Washington, D.C. The concrete footing was approximately 2 feet, 6 inches square by 6 feet deep. A special problem that arose was that of a designing a hook and latch to hold the cover plate on during test tine when the pressure and temperatures were extremely high and still permit the removal of the cover plate rapidly a short time after the test. NOBL furnished the copper balls used in the gauges, H&N furnished all other parts, The top plate dimensions were revised by NOBL on September 27, 1950. Stations 27a and b on Engebi were relocated on October 27, 1950, in order to give clear access to the 300 foot tower base. Stations 28a + - Engebi and t - NOBL. These stations were velocity instrument posts for measuring the velocity of the shock wave and consisted primarily of an NOBL instrument mounted on a 10 foot high, 3 inch diameter pipe. These were used as part of the blast line measurements, The pipe was embedded in a concrete foundation, the pipe being curved 90° inside the foundations, An access pit was left at the point where the pipe emerged from the footing, The first design infor- mation was an oral description by the Blast Program Chief at the January 30, 1950, meeting in Washington, D.C, On June 21, 1950, the location tolerances were established, Final corrections by NOBL were made on June 28, 1950, On October 26, 1950, it was necessary to move Station 28j at Runit in order to move it out of the camp area. 5-160