These two pipelines are typical of the 325,000 miles of oil and natural gas pipelines that sprawl across the United States in that they are more than 50 years old.

And, without proper maintenance, they pose an increasing risk to the environment and public safety.

While the majority of pipeline accidents happen during excavations, tragic incidents caused by corroded and cracked metal due to age are a growing concern.

Part of the problem, experts say, is that many of the nation's pipelines are underground and difficult to inspect, moving dangerous material silently and unnoticed for decades until a leak or sudden explosion occurs.

Last year, 18 people were killed and 53 injured in pipeline accidents, making it the worst year since 2000, according to the US Department of Transportation's Office of Pipeline Safety (OPS).

A decade ago the situation was worse, with 22 deaths and 120 injuries in 1994. The worst year in the past decade was 1996, when 53 were killed and 127 injured. Still, worries linger that the age of the nation's pipelines -- some dating back to the 1920s -- could spell tough years ahead.

INSPECTIONS FAULTY?

Pipeline industry advocates say that pipelines can last indefinitely as long as they are maintained, but critics disagree, claiming old pipe should be replaced.

"Most are closing in on 50 years old. It defies physics and logic to make such an argument. Everybody knows that metal pipes wear out," said attorney David Beninger.

There is currently no law requiring pipeline operators to replace aging sections -- a prospect that would present a huge and perhaps unbearable cost to the oil industry.

Beninger represented the families of two 10-year-old boys killed by one of the most horrific pipeline accidents in recent memory -- a 1999 explosion caused when a pipeline leaked a quarter million gallons of gasoline into a creek that flowed through downtown Bellingham, Washington.

The explosion on the Olympic Pipe Line in Bellingham, which killed three, triggered an overhaul of US pipeline safety measures, including the Pipeline Safety Improvement Act of 2002 which called for increased inspections.

Stacy Gerard, the chief administrator at the Office of Pipeline Safety, said officials have increased visits to pipeline operators to ensure they are up-to-date on inspections.

But she said the OPS has been hard-pressed to ensure that all the new measures handed down are enacted.

Gerard admitted that the OPS wasn't doing a good job until the past several years.

"We did have a period of time where the mandates were more than the office could keep up with. We've caught up with the backlog. Of 77 (mandates) coming into the year 2000, we've addressed 90 percent, and we're current with 45 more mandates (in the Pipeline Safety Improvement Act of 2002.)"

The main defense against pipeline accidents, particularly for underground lines, are inspections using diagnostic devices known as "smart pigs," according to Raymond Paul of the Association of Oil Pipe Lines.

By September 2004, about half of the nation's mileage of liquid petroleum pipelines had been inspected by pigs, which derive their name from the squealing sounds they make as they detect wear and tear from within, said Paul.

But the devices may not be enough to prevent accidents.

"There are numerous types of smart pigs, and most of them are pretty dumb," said Bob Rackleff, founder of the National Pipeline Reform Coalition. "They don't pick up on things like longitudinal cracks (and) they can give off false signals."