By; Ray Rollings
Over fifty years ago, the distinguished Harvard professor and engineering consultant Karl Terzaghi published a classic paper entitled Consultants, Clients, and Contractors. This paper explored the dynamic and often destructive interactions between these parties in major engineering works. Today, we often see the same destructive conflicts between the parties of which Professor Terzaghi spoke long ago re-enacted in our modern airfield paving projects. With runways and other airfield pavements commonly costing tens of millions of dollars, these are high-stake conflicts.
There are many potential sources of trouble of which a runway paving expert may be called to investigate. Designers can make mistakes and write poor specifications. Contractors can cut corners or use poor materials and techniques. Owners may try to save money by curtailing budgets for design and inspection. And when something goes wrong, all parties blame each other in an often combative atmosphere. A fully qualified airfield pavement construction expert is often needed to determine the technical issues and causes of the pavement problems and to support follow-on litigation.
The Inept Designer. Airfield pavement design must be adequately funded and conducted by experienced personnel with sufficient time to execute the work properly. Agencies normally mandate specific airfield pavement design policy. With this designated policy and the plethora of simplified design manuals and computer programs that are available today, preparation of pavement designs seems deceptively easy. Too often this leads the unwary to give pavement design a try as if thinking it really can’t be that hard, and there won’t be a need to spend money for a specialist consultant.
Recently, a portion of an Air Force concrete runway failed dramatically as soon as it was opened to aircraft traffic. The designer-of-record was an experienced highway engineer who had never worked with airfields. The designer used keyed (tongue-in-groove) joints in the pavements which promptly sheared off when exposed to heavy cargo and tanker aircraft traffic. The resulting surface was littered with debris that posed a safety hazard for jet aircraft. Only heroic around-the-clock repair efforts kept this very busy runway operational as the keys continued to fail. Keyed joints have been banned from use in Air Force pavements for over thirty years because of their structural inadequacy under heavy airplanes. The designer was ignorant of this ban on keyed joints which is in the printed Department of Defense design manual text but did not appear in the design computer program printout upon which the designer relied. He had used such keyed joints successfully in more lightly loaded highway applications and had no idea of the time bomb he was building into the runway.
The Contractor – Skill. Quality paving requires a skilled construction crew and an experienced superintendent. On one large Air Force apron paving project, the contractor’s superintendent had extensive hospital construction experience but none with paving. The paving equipment was marginal, and the government quality assurance personnel failed to enforce specifications. Halfway through paving, the government stopped the work because of widespread defects. The superintendent was replaced with an experienced pavement superintendent, more experienced workers were brought in to operate the equipment, and project specifications were enforced. The remainder of the pavement was placed with no defects while the original work was the subject of litigation. Airfield paving contractor skill levels are critical if good work is to be achieved, and enforcement of project specifications is equally mandatory.
The Crooked Contractor – Materials. A simple truth is no pavement can be any better than the quality of the materials of which it is constructed. A West Coast Air National Guard taxiway had to be replaced 12 years after its original construction because of cracking and swelling caused by the poor quality aggregate used in the concrete. This replacement cost the taxpayers 12 million dollars and fell well short of the 30- to 50-year pavement life the military usually sees from its concrete airfield pavements. Nobody could ever explain how these defective aggregates from a cheaper, nearby source accidently got substituted in the concrete for the more distant and expensive aggregates that had been tested and approved for the project. The recent convictions of two New York City testing laboratories for a decade of fraudulent concrete testing reinforces this concern. Construction fraud remains the elephant in the living room that we often tacitly ignore.
The Frugal Owner. An owner may try to hold down costs by limiting funds for site exploration, design, testing, or quality assurance inspection during construction. Such budget restraint almost invariably proves to be penny wise but pound foolish. At an overseas airport, the ends of an existing commercial airport runway were to be repaved as part of an agreement to allow US Air Force operations from the facility. The U.S. government agency responsible for awarding and administering the construction contract did not provide on-site inspectors for the work because of a combination of the cost of such staffing and difficulty finding personnel with the required skills for such a remote location. The contractor, either through his own cost savings plan or through ignorance, failed to follow the very specific contract requirements for curing of this special concrete. A few months after construction of the first runway end, the concrete began scaling widely because of the poor curing. The debris from the scaling posed a foreign-object-damage safety hazard for commercial, host nation military, and US Air Force aircraft. The contractor was required to diamond grind the surface of the concrete to remove the scaling. Unfortunately, the grinding revealed the contractor had also failed to meet smoothness standards, and the concrete aggregate had been badly contaminated with wood and other debris. The contractor’s contract for the other end of the runway was canceled, the host nation was left with an unsatisfactory runway, and relations between the host nation and the Air Force were strained. This could have been avoided by timely quality assurance inspection by the contracting agency which would have revealed the noncomplying construction before it became a crisis.
Compounding Errors. Failures are often due to a combination of factors rather than a single smoking gun. On a recent runway project for a Midwestern Air Force base, the concrete began spalling during the first winter following construction. The contractor and government agency that oversaw the construction promptly blamed this spalling on snow clearing operations by the Air Force. Such a conclusion conveniently relieved them both of any responsibility for the damaged pavement. However, on reviewing the situation, one finds the local snow-clearing operations, equipment, and personnel training followed Air Force standards that did not cause similar spalling elsewhere on the base and on dozens of other bases. Examination of the contract specifications revealed the government agency had failed to specify the correct amount of air entrainment that provides durability of concrete to freezing and thawing. Further laboratory tests revealed that (1) the concrete had a nondurable surface crust from improper finishing of the concrete and (2) a thicker upper zone of nondurable concrete caused by improper vibration of the pavement was widespread. Both the contractor and government field personnel hotly denied any failure to abide by the specifications. Finally, a higher headquarters ordered the government field personnel to release construction photographs that clearly revealed poor, non-specification construction practices. Although the airfield paving contractor clearly made errors and produced a deficient concrete runway, the government inspectors acquiesced to the procedures used and the government also produced a defective initial design (the low air entrainment). Consequently, the Air Force (and American taxpayer) are stuck with a high maintenance runway with no recourse for relief.
Conclusion. The owner, the designer, and the contractor all play crucial roles in building a satisfactory airfield pavement. However, they each typically have different and competing goals: (1) the owner wants quality at minimum cost, (2) the designer wants comfortable design fees to produce a professionally competent product with minimal liability, and (3) the contractor wants bare compliance with the specification at minimum cost to maximize profits.
If the pavement construction goes awry, litigation often ensues. In such a case, a well-qualified and experienced airfield pavement construction expert can be an invaluable asset in evaluating potential causes of the problem and providing expert witness testimony.
Ray Rollings has over forty years of airfield pavement experience as an Air Force civil engineering officer, Army Corps of Engineers civilian research engineer, teacher, and consultant. His airfield work has covered all seven continents and ranged from conventional pavements at major Air Force bases around the world to a compacted snow runway for C-17s in Antarctica to austere airfields supporting military operations in remote locations. Much of his work involves investigating pavement failures for the military, and he has been retained as an airfield pavement expert witness by the Department of Justice, U.S. Army Corps of Engineers, and U.S. Air Force. Ray has a BS from the US Military Academy at West Point, a MS from the University of Illinois, and a PhD from the University of Maryland. He may be contacted at email@example.com or 843-694-1631.