The severely corroded pipeline that forced the shutdown of the country's largest oil field had not been internally inspected or cleaned by BP Oil for at least 14 years, according to U.S. Department of Transportation records.
The lines at Alaska's Prudhoe Bay oil field carry eight percent of the domestic crude oil production but are exempt from federal regulation.
Pipelines regulated by the federal government are required to be tested every five years.
At least 73 percent of the pipeline will need to be replaced because of the extensive corrosion, according to company officials.
Members of Congress and environmental advocates are asking how the multi-billion dollar BP Oil, which heavily touts its commitment to corporate responsibility, could allow conditions to deteriorate to such a point.
"I would call it a catastrophic failure," said Lois Epstein, an engineer and consultant for the Pipeline Safety Trust, an advocacy group. "They had 80 percent or more wall thinning, which is an enormous percentage, and it really never should have gotten that bad."
The Department of Transportation increased its scrutiny of BP's Alaska operation only after the discovery of a 250,000 gallon crude oil spill there in March.
The spill went undetected for days until a worker who was passing by smelled the oil. The spill, which was caused by another corroded pipeline, has lead to a federal criminal investigation of BP.Shortly after the spill, The Department of Transportation ordered BP to conduct an internal inspection of key lines using "smart pig" technology, which measures the thickness and integrity of pipeline walls.
DOT officials disclosed the 14-year gap in testing or cleaning to Congressman John Dingell (D-MI) in June. Dingell, the ranking member of the House Energy and Commerce Committee, called on BP to take "all steps necessary to repair or replace problem pipelines quickly, so the American consumer does not pay for BP's laxity." He also urged Congress to hold hearings on what went wrong and whether federal regulation may be needed.
BP did not respond to requests for additional comment for this story, but has defended its maintenance and inspections practices in the past.