Runway Concrete at the Denver International Airport

In the early 1990s, the city of Denver, Colorado, embarked on one of the largest public works projects in history: the construction of a new airport to replace the aging Stapleton International Airport. The new Denver International Airport (DIA) would be the fi rst new airport constructed in the United States since the Dallas–Fort Worth Airport was completed in the early 1970s. Of course, the size and complexity of this type of project lends itself to many problems, including cost overruns, worker safety and health issues, and controversies over the need for the project. The con- struction of DIA was no exception.

Perhaps the most widely known problem with the airport was the malfunction- ing of a new computer-controlled high-tech baggage handling system, which in pre- liminary tests consistently mangled and misrouted baggage and frequently jammed, leading to the shutdown of the entire system. Problems with the baggage handling system delayed the opening of the airport for over a year and cost the city millions of dollars in expenses for replacement of the system and lost revenues while the airport was unable to open. In addition, the baggage system made the airport the butt of many jokes, especially on late-night television.

More interesting from the perspective of engineering ethics are problems dur- ing the construction of DIA involving the concrete used for the runways, taxiways, and aprons at the airport. The story of concrete problems at DIA was fi rst reported by the Denver Post in early August of 1993 as the airport neared completion. Two subcontractors fi led lawsuits against the runway paving contractor, California-based construction company Ball, Ball, & Brosamer (known as 3Bs), claiming that 3Bs owed them money. Parts of these suits were allegations that 3Bs had altered the recipe for the concrete used in the runway and apron construction, deliberately diluting the concrete with more gravel, water, and sand (and thus less cement), thereby weakening it. 3Bs motivation for doing so would be to save money and thus to increase their profi ts. One of the subcontractors, CSI Trucking, whose job was to haul the sand and gravel used in the concrete, claimed that 3Bs hadn’t paid them for materials that had been delivered. They claimed that these materials had been used to dilute the mixture, but hadn’t been paid for, since the payment would leave a record of the improper recipe.

At fi rst, Denver offi cials downplayed the reports of defective concrete, relying on the results of independent tests of the concrete. In addition, the city of Denver ordered core samples to be taken from the runways. Tests on these cores showed that the runway concrete had the correct strength. The subcontractors claimed that the improperly mixed concrete could have the proper test strength, but would lead to a severely shortened runway lifetime. The FBI also became involved in investigat- ing this case, since federal transportation grants were used by Denver to help fi nance the construction of the runways.

The controversy seemed to settle down for a while, but a year later, in August of 1994, the Denver district attorney’s offi ce announced that it was investigating alle- gations that inspection reports on the runways were falsifi ed during the construc- tion. This announcement was followed on November 13, 1994, by a lengthy story in the Denver Post detailing a large number of allegations of illegal activities and uneth- ical practices with regard to the runway construction.

Chapter 2 Professionalism and Codes of Ethics 31

The November 13 story revolved around an admission by a Fort Collins, Colorado, company, Empire Laboratories, that test reports on the concrete had been falsifi ed to hide results which showed that some of the concrete did not meet the specifi cations. Attorneys for Empire said that this falsifi cation had hap- pened fi ve or six times in the course of this work, but four employees of Empire claimed that the altering of test data was standard operating procedure at Empire.

The nature of the test modifi cations and the rationale behind them illustrate many of the important problems in engineering ethics, including the need for objectivity and honesty in reporting results of tests and experiments. One Empire employee said that if a test result was inconsistent with other tests, then the results would be changed to mask the difference. This practice was justifi ed by Empire as being “based upon engineering judgment” [ Denver Post, Nov. 13, 1994]. The con- crete was tested by pouring test samples when the actual runways were poured. These samples were subjected to fl exural tests, which consist of subjecting the con- crete to an increasing force until it fails. The tests were performed at 7 days after pouring and also at 28 days. Many of the test results showed that the concrete was weaker at 28 days than at 7 days. However, the results should have been the oppo- site, since concrete normally increases in strength as it cures. Empire employees indicated that this apparent anomaly was because many of the 7-day tests had been altered to make the concrete seem stronger than it was.