20 COLLAPSE OF TEXAS TOWER NO. 4 
supported by the concrete stiffening, to resist the force. It was agreed 
that the contractor’s operations were carried out in accordance “with 
the erection procedure contemplated by the plans and specifications. 
It appears that adequate provision was not made to stiffen the steel 
shells of the tower legs in the critical region. On July 12, 1957, the 
Bureau of Yards and Docks agreed to finance the direct costs of 
strengthening the legs at their indentations which ultimately would 
end up about 10 feet underwater after embedment of the footings. 
The heavy permanent platform was jacked up on the three “legs 
prior to any concrete stiffening being placed in the legs, being jacked 
up clear of the water on July 8, 1957. 
The water depth, as noted previously, turned out to be 185 feet in- 
stead of 180 feet as originally contemplated in the design. Also, the 
total range of tide was measured at 314 feet instead of the original 
estimate of 1 foot. Thus, in order to achieve a safe clearance of the 
platform above mean sea level, it was necessary to modify the design 
byv— 
; (az) Reducing the embedment of the footings from 20 feet to 
18 feet: and 
(6) Raising the platform to the maximum extent permitted by 
the design. 
These resulted in achieving a platform elevation of 66.5 feet in- 
stead of the 67 feet called for in the design. 
5. Repairs to Texas tower No. 4 
Agreement apparently having been reached to attempt repairs of 
the tower at sea, the design engineers, under contract with the builder, 
designed a collar connection encircling legs A and B as a means by 
which to secure the replacement diagonals t to the legs. Dardelet bolts 
having a serrated shank were inserted through the collars into the legs 
to keep the collars from moving vertically on the legs. The installa- 
tion of these bolts required underwater cutting and fitting to close 
tolerances and the repair was only as good as the. capability and integ- 
rity of the divers working under adverse conditions at an underwater 
depth of 65 feet. Moreover, the repair was made even more diffi- 
cult by the reactions of the legs to the forces of the sea in that, 
even at this time, the tower’s foundation was in motion. These re- 
pairs were completed by November 1957 and the tower was accepted 
by the Navy from the contractor. The Navy did not conduct an un- 
derwater inspection prior to turning the tower over to the Air Force. 
In the motion picture film of the construction of tower No. 4, which 
was shown during the hearings, a ball, suspended so as to move freely, 
was in rather violent motion at the time of Air Force acceptance. 
By the summer of 1958, the Air Force personnel operating the tower 
had complained of sensations of considerable movement of the plat- 
form with frequencies of 15 to 18 cycles per minute. Although those 
who observed the motion had no means of properly measuring its ex- 
tent, such motions did not occur during severe weather conditions as 
the maximum wind velocity and wave height during that period were 
about 30 knots and 15 feet, respectively. However, the frequency 
of the horizontal oscillations gave some clue as to the stiffness of the 
tower (design frequency was 37 to 46 c.p.m.) and the design engineers 
