Opinion ID: 384591
Heading Depth: 2
Heading Rank: 1

Heading: Construction of the Dome

Text: 4 R. B. Butler, Inc., had contracted with the Public Service Board of the City of El Paso, Texas, to construct four 221-foot thin-shell concrete domes over trickling filter units, one at the Delta Street Sewage Treatment Plant. Butler was the general contractor for this project, and Dow Chemical was the subcontractor directly responsible for the design and construction of these domes. 5 The domes to be constructed by Dow consisted of two separate structures-a styrofoam form and a concrete shell. The form was made of ten-by-six-inch styrofoam logs which were fused together with ten-gauge reinforcing wire by means of a rotating fusion head (a machine into which the logs were fed). The styrofoam form was constructed in such a manner as to create a dome structure over which concrete would later be sprayed. The styrofoam structure served only as a form and, after the concrete dome had been sprayed over it, did not play any functional role in the support of the dome. 6 The following machinery was employed to construct the styrofoam dome: a control point (the center of the trickling filter over which the dome was being built), two beams, a rotating fusion head, and a rider bucket, from which an employee fed the styrofoam logs to the fusion head. (The functioning of the fusion head is later described with more detail.) The boom went in a circular direction and the styrofoam logs were fed into the fusion head and became welded to the other logs. As part of this welding process, there was a continuous feeding of ten-gauge wire reinforcement into each fusion interface (the point at which the two logs would meet). 7 Upon completion of the styrofoam dome, after a self-furring wire mesh was laid over the styrofoam, concrete was then sprayed over the form. The concrete was applied in sections; and, in order to monitor the depth of each layer of concrete, which was to be three-eighths to one-half inch thick, a device similar to an automobile's dip stick could be utilized. By placing the stick in the wet cement, exact thickness could be gauged. 8 During the construction of the styrofoam dome, a depressed area (a dimple) appeared on the outer surface. In order to fill the depression to achieve the desired contour, Dow Chemical used foam-in-place urethane with mesh reinforcement. In addition, a scaffold was constructed on the inside of the styrofoam dome in order to provide additional support under this dimple. 9 Royal also points out, as relevant to its arguments of defective design or testing, that the present domes were the largest constructed by Dow, and the first to use 6 X 10 inch styrofoam logs or 10-gauge welding wire during the welding process. The previous domes successfully built by Dow had used 6 X 8 inch logs and a smaller gauge welding wire, and the largest of the previous domes had been 160' in diameter as compared with the 221' diameter in this instance. (The present dome had an arc length of 130', and it collapsed when concrete had been laid around the styrofoam form around the lower 55 feet or so of its arc length. The arc length measures the circumference surface of the dome from its bottom to its apex; actually, measured vertically, the apex of the present dome was 52' from the ground.)