CHARLESTON, W.Va. -- Nearly 15,000 miles of natural gas pipelines are spread across West Virginia, enough to stretch from Charleston to Morgantown and back 50 times.

Such pipelines are considered by many experts as the best way to transport fuel, much safer than railroads or tanker trucks.

But serious dangers remain, as West Virginians were reminded Tuesday with scenes of a wall of fire above Interstate 77 from the huge gas-line explosion in Sissonville.

And despite numerous efforts at reform, recent investigations and audit reports show that many gaps remain in the oversight of the nearly 2.5 million miles of pipelines that crisscross the United States.

Nationwide, concerns about pipeline safety have grown, amid a boom in natural gas drilling in several states and in the wake of a string of serious accidents, including explosions in San Bruno, Calif., and Allentown, Pa., that killed a combined 13 people in 2010 and 2011.

"While many stakeholders agree that federal pipeline safety programs have been on the right track, the spate of recent pipeline incidents suggests there continues to be significant room for improvement," the Congressional Research Service concluded earlier this year.

In a March report, for example, the U.S. Government Accountability Office warned that many so-called "gathering" pipelines, which transport gas to processing facilities, escape federal scrutiny altogether.

Preliminary reports indicate that Tuesday's Kanawha County explosion occurred on a 20-inch-diameter transmission line near Columbia Gas Transmission's Lanham Compressor Station at Rocky Fork. That would put the pipe involved on the smaller end of the spectrum for gas transmission lines, one of the myriad types of pipelines that send gas from where it is produced to where it is used.

Gas companies use "gathering" lines to transport natural gas from well sites to compressor and other processing facilities. From there, transmission lines -- usually ranging from 20 to 42 inches in diameter -- carry gas across long distances from producing regions to local distribution companies.

From those companies, natural gas is piped through distribution lines or "mains" -- which range from 2 inches to more than 24 inches in diameter -- to homes and businesses.

In an analysis earlier this year, the conservative Manhattan Institute compared accident, leak, injury and fatality rates among various modes of transportation for oil and natural gas. They found, for example, that natural gas pipelines recorded less than one accident per billion-ton-mile of material transported. That compares to 650 incidents for highway transport and 20 for railways.

"The evidence is clear," the group said, "transporting oil and natural gas by pipeline is safe and environmentally friendly. Furthermore, pipeline transportation is safer than transportation by road, rail, or barge, as measured by incidents, injuries and fatalities - even though more road and rail incidents go unreported."

Still, in the last five years, pipeline accidents across the country have claimed the lives of 21 workers and 47 members of the public, according to data from the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration, or PHMSA.

In West Virginia, the worst recent incident listed on agency records was in April 2006. Four men at a Canaan Valley home building site were killed in a natural gas explosion that was later blamed on a cracked pipe.

Over the last decade in West Virginia, federal regulators counted 20 of what they called "significant incidents," involving deaths, injuries or significant property damage.

As with many public safety issues, reforms of pipeline safety sometimes come only after major accidents.

Congress passed one measure in 2002, following the deaths of two 10-year-old boys in a June 1999 explosion in Bellingham, Wash., and the deaths of 12 campers in a pipeline blast in Carlsbad, N.M.

Questions about pipeline safety recently received national media scrutiny from the public interest journalism organization ProPublica, from The New York Times and from the Philadelphia Inquirer.

Just last month, ProPublica explained, "Pipelines break for many reasons - from the slow deterioration of corrosion to equipment or weld failures to construction workers hitting pipes with their excavation equipment.

"One of the biggest problems contributing to leaks and ruptures is pretty simple: pipelines are getting older. More than half of the nation's pipelines are at least fifty years old," ProPublica reported.

In early January, President Obama signed into law the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011. The bill, aimed at strengthening federal oversight of pipeline safety, was based in part on a separate bill co-sponsored by Sen. Jay Rockefeller, a West Virginia Democrat who chairs the Senate committee with jurisdiction over the issue.

Among other things, the bill increased penalties for safety violations, required automatic shut-off valves on new pipelines, and increased public availability of safety information.

"Paramount to the success of America's pipeline system is an unwavering commitment to safety," Rockefeller said in December 2011, when the measure passed the Senate. "This legislation makes good on that promise by implementing long overdue improvements."

The March Congressional Research Service report, though, noted a "long-term pattern of understaffing" for pipeline safety within the Transportation Department.

"For example, the president's budget request for pipeline safety reports 175 actual employees in 2009," the report said. "However, the FY2010 budget request stated an expectation of 191 employees ("estimated") for 2009. On this basis, between 2001 and 2009, the agency reported a staffing shortfall averaging approximately 24 employees every year."

And the GAO report, also issued in March, said the federal pipeline safety office does not regulate most gathering pipelines in the United States, based on their location in remote areas.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.