Photo by Ron Simmons
Airport sinkholes cost taxpayers millions
ITA consultant was unable to fix drainage problems in Pennsylvania

The environmental engineering firm hired to oversee planning and construction of the proposed Kentucky TriModal Transpark was unable to adequately repair drainage problems at a Pennsylvania airport, contributing to the ongoing formation of sinkholes at that facility. Such was the conclusion of a study by researchers at Pennsylvania State University and the Pennsylvania Department of Transportation.

The Capital City Airport in New Cumberland, Pennsylvania has been plagued by sinkholes since it was built in the 1930s. Geotechnical investigations have confirmed the existence of many caverns beneath the airport property, resulting in the frequent and unpredictable formation of sinkholes.

"Every time we get a heavy rain, we have a new hole someplace," says Don Smith, director of maintenance for the Capital City Airport. "It's a never-ending problem."

The geology of the Capital City Airport is similar to that of the site chosen for development of the Kentucky TriModal Transpark.

Over the years, hundreds of sinkholes have opened up throughout the Capital City Airport, often resulting in the closing of runways until repairs could be made. Don Smith says that recently he poured 33 cubic yards of concrete into one sinkhole, and still was not able to fill it. He estimates the cost of fixing the average sinkhole at approximately one-thousand dollars, although one sinkhole repair cost as much as $30,000.

Smith says that no sinkhole repairs can be considered permanent. Last month, a contractor fixed a new sinkhole in a runway, but two weeks later heavy rains caused it to reopen. It is still undergoing repairs.

Such problems are common at the Capital City Airport, according to researchers Robert M. Belesky and H. Reginald Hardy, Jr. In a 1987 study, they determined that sinkhole occurrences have resulted in a "constant maintenance effort, a loss of revenue, and an increased risk to air traffic."

Don Smith is not aware of any sinkhole-related mishaps involving airplanes, but he says there have been numerous instances of the ground collapsing beneath maintenance trucks and lawn-mowing tractors.

ITA consultant could not solve the problem

The sinkhole problem at the Capital City Airport is blamed primarily on adverse geological and drainage conditions. In 1983, the engineering consulting firm Wilbur Smith and Associates (WSA) was hired to design a stormwater diversion system at the Capital City Airport. However, a 1987 report by Pennsylvania State University and the Pennsylvania Department of Transportation stated, "Although partially replaced and rehabilitated during the past two years, the storm-drain system continues to leak. Such concentrated leakage will accelerate subsurface erosion despite the implementation of other remedial measures."

That prediction came true, as drainage problems persist to this day and sinkholes continue to form at the Capital City Airport. Don Smith says that storm sewers are still sinking, cracking and leaking because of sinkholes.

Wilbur Smith and Associates is the same firm that is under contract to the Inter-Modal Transportation Authority to oversee construction of the Kentucky TriModal Transpark in a karst area that is even more fragile than the one in Pennsylvania. And while no one blames WSA for causing the problems at the Capital City Airport, their inability to design a workable drainage system at that location cannot be ignored.

"It's simple," says Roger Brucker, a cave expert and leading opponent of the transpark. "No one can fix a problem that's unfixable. You cannot permanently stop water or chemicals from draining into sinkholes. New sinkholes appear unpredictably, and existing ones get bigger."

Sinkhole problems at other airports

ITA officials have argued that drainage problems at the Kentucky TriModal Transpark can be avoided by diverting stormwater runoff into retention ponds. However, retention ponds do not always work, as evidenced by the experience of another airport in Pennsylvania.

A few years ago, University Park Airport near State College, Pennsylvania constructed a 600 x 150-foot, 30-foot-deep retention pond designed to capture 80% of all stormwater runoff at the airport. Shortly after completion of this pond, a heavy rain fell, filling the pond. The tremendous weight of the water caused the bottom of the pond to collapse, draining the stormwater into caverns beneath it. Airport officials spent $1 million to repair the damage and install a protective liner in the pond in an effort to prevent future collapse.

Such problems are common at airports built on karst. The Southwest Florida International Airport in Ft. Myers has spent approximately $4.2 million dollars to repair sinkhole-related damage since the 1980s. In one case, a runway under construction collapsed, partially swallowing a dumptruck into the underlying 30-foot-deep sinkhole. In another case, a sinkhole developed on the runway in front of a terminal. The Federal Aviation Administration ordered Lee County to reconstruct a 700-foot stretch of the runway. (See

Karst problems are costly in Warren County

Despite ongoing drainage problems at airports in other karst regions of the country, the Inter-Modal Transportation Authority continues to insist that the Kentucky TriModal Transpark can be built safely and within budget in the Sinkhole Plain of Warren County.

It should be noted that the Sinkhole Plain has a higher concentration of sinkholes and caves than any other region of the world, and is much more sensitive, environmentally, than other karst areas where airports are located.

However, ITA officials seem to be forgetting some costly and preventable problems that have resulted from similarly ill-conceived projects. Transpark opponents point to Warren County's history of expensive karst-related disasters as a reminder of what is likely to happen if the transpark is built in the chosen location.

"Who can forget the Glen Lily Road Landfill?" asks Dr. Michael May, a geology professor at Western Kentucky University. "Politicians built the landfill without the advice of competent geologists, and look what happened. Local taxpayers ended up spending at least four-million dollars to clean up groundwater contamination and build a monitoring system. History will repeat itself with the transpark."

Even ITA consultant Dr. Nick Crawford has previously recognized the danger that certain types of developments pose in karst areas. In the 1989 Warren County Comprehensive Plan, Dr. Crawford recommended that NO BULK FUELS STORAGE FACILITIES BE BUILT ON KARST. This recommendation followed a disastrous fuel spill into Lost River Cave just three years earlier, putting that cave at #1 on the EPA's Superfund cleanup list and costing taxpayers $1 million. Although some progress has been made in cleaning up Lost River, it remains polluted to this day and can never be restored to its original state.

What about other airports on karst?

In trying to defend its decision to build an airport on the Sinkhole Plain, the ITA has pointed to other airports in karst regions of Kentucky that have not experienced an extraordinary number of sinkhole problems. Specifically, airports in Somerset, Lexington and Glasgow have been mentioned. But what must be considered is the fact that those airports are built on karst that is not nearly as fragile and prone to collapse as the "Yellow" site near Oakland.

The Bowling Green Airport is located just 90 feet above the nearest river-less than half the vertical distance from surface to water table in Oakland. Jim Dinning, a member of the ITA Environmental Committee, said that the Bowling Green airport "collapses all the time." (See Bowling Green Daily News, March 15, 2001). Sediment cover masks many sinkholes in the bedrock, although subsidence does take place.

The Glasgow Airport is a small airstrip located on entirely different strata, the Salem-Warsaw formations. These are noted for their lack of prominent karst features because of their high content of insoluble materials. The "Glasgow Upland" has no sinkholes or sinking springs. The Glasgow Airport is 80 feet above the nearest river.

The Lexington Airport is located on older Ordovician limestones that have poor karst development. Caves and sinkholes are small, and collapse problems are minor. Vertical distance to the nearest stream is 120 feet.

The Somerset Airport occupies a karst-rich location that is susceptible to collapse, with large caves nearby. It lies 160 feet above the nearest river. However, the airport is a small strip sited at the edge of an escarpment. This is a setting in which collapse is least common, compared to Oakland or anyplace else on the Sinkhole Plain. The Somerset karst is subdued by a thick cover of residual sand and gravel naturally eroded from uplands nearby.

Although some airports have been built successfully on other karst areas in Kentucky, the Oakland site where the Kentucky TriModal Transpark is to be built is far less stable than any other karst airport site.

"With 190 feet from the surface down to the water table, it is far more dangerous," says Roger Brucker. "It has more cavities, and when the ground collapses, structures have much farther to fall."

The Sinkhole Plain is widely recognized for sinkhole development, and is used to illustrate the process in even the most basic of high school and college earth science or geology textbooks. The vast majority of credible scientists remain convinced that building the Kentucky TriModal Transpark in the Sinkhole Plain will result in cost overruns due to construction and maintenance problems caused by sinkholes. Regardless of steps taken to avoid drainage problems that have plagued other airports, accidental chemical and fuel spills are inevitable, and will cause irreparable harm to the environment by polluting underground streams that flow into Mammoth Cave National Park to the north, and the Barren River to the south.

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