But Wasson's recommendation for an immediate inspection was rejected by engineers at Martin/Martin three days later. Instead, the engineering firm stated in a May 19 letter to ballpark architect Ellerbe Becket that "based on our engineering design and assuming the nuts were installed properly, we do not believe there is reason for concern."
The letter, prepared by Martin/Martin's principal engineer Stanley Welton, stated that the nuts were "torqued tensioned based on a tested tightening procedure developed by Schuff Steel at the time of installation." (District records state that it was Martin/Martin that developed the tightening procedure at Schuff Steel's request.)
Welton stated that critical nuts on the upper concourse keep the grandstands from tipping forward. Since there is downward pressure on the nuts brought by the weight of the pre-cast concrete grandstands, "it [is] highly unlikely that the nuts would become loose under vibrations transmitted through the trusses," he stated.
The nuts on the upper concourse, however, were only tightened to about one-half of the tension called for in the original blueprints, stadium district records reveal.
Nevertheless, Welton sidestepped Wasson's recommendation to perform a physical inspection of every nut by noting that visual inspections were already supposed to have been done by ATL during construction.
"Perhaps the owner should hire ATL or a structural engineer to visually inspect the nuts to determine if they are tight," Welton concluded.
Despite the conflicting opinions on the type and timing of inspections that should be performed, the issue died down for about six weeks. It resurfaced once again, however, when it was brought up by Geiger Engineers, a New York firm that was hired during construction to provide "peer review" of Martin/Martin's engineering.
In a July 7 letter to Diamondbacks attorney Holm, Geiger principal Paul Gossen raised new concerns that the nuts might not be tightened correctly, especially in places where up to 16 Dywidag bars were used to secure a single truss.
"Even though the first installed bars in a connection may have had an initial tension as specified, the subsequent installation of the rest of the bars would relax the tension in these bars.
"Unless the tension in all the bars were checked and re-tensioned after the installation of all bars in a connection, there is a possibility that some of the bars are not pre-tensioned as desired," Gossen stated.
Gossen recommended that all the nuts on a minimum of three connections be examined to determine if any are loose.
Ten days later, on July 17, Geiger sent a second letter to Holm that suggested testing of the nuts could be done simply by applying a wrench with a "torque of 20 foot-pounds in the tightening rotation. If there is no movement on the nut, the nut is properly seated."
Geiger recommended expanding the test to a minimum of 10 connections, which could include up to 16 bolts each, to determine whether the nuts were securely fastened. The company also suggested that "it may be advantageous to take that opportunity to lock the nuts on the rods with a spot weld."
By late July, the team knew that two engineering companies and the former project manager for the construction of the ballpark had raised concerns over the safety of Dywidag nuts securing thousands of seats to the stadium walls.
Yet the team still had not formally notified the stadium district.
The district says it finally discovered there was a debate raging over the safety of the stadium on July 24, when Ellerbe Becket provided the district with a copy of a letter it had sent to Diamondbacks attorney Holm. The letter got the district's immediate attention.
"As we previously advised you concerning the alleged potential Dywidag problem at Bank One Ballpark, Ellerbe Becket, Inc.'s overriding concern is for the safety of all who could be put at risk. Once again, we urge your clients, and the District, to act without delay to ensure that any alleged potential problem does not pose any safety threat of any type at any time," the letter signed by Joseph C. Gross, Ellerbe Becket's principal, stated.
The Gross letter set off alarm bells at the stadium district, and special counsel Tom Irvine immediately contacted the team's attorneys to demand a complete report related to "any safety problem associated with any part of the Dywidag system."
Holm did not respond to Irvine's request for documentation for another month. The district did not receive a copy of Cook's alarm letter and supporting documentation outlining Martin/Martin's alternative tightening procedure and stipulation for field inspection during tightening of each Dywidag nut until August 21.