Precious little oil ever washed up on the berms, according to the commission - a finding corroborated by a log of oil sightings and other government documents obtained by The Associated Press through a public records request.
Republican Gov. Bobby Jindal ordered the berms built over the objections of scientists and federal agencies - and secured money from BP to do it - out of frustration over what he saw as inaction by the Obama administration. During the crisis, Jindal boasted that the sand walls were stopping oil from coming ashore, and the idea proved popular in Louisiana.
In its stinging report, however, the commission, appointed by President Obama to investigate the spill, called the project "underwhelmingly effective, overwhelmingly expensive." Still, the panel did concede that the sand might ultimately prove helpful in Louisiana's long-term effort to restore its badly eroded coastline.
Jindal disputed the commission's findings on the berms.
"This report is partisan revisionist history at taxpayer expense," the governor said in a statement. "The report's assertion that the berms did not pass the commission's 'cost benefit analysis' is insulting to the thousands of people whose way of life depends on the health of our working coast."
A BP spokeswoman said the company had no comment.
Over the summer, the state received grudging government approval to build 36 miles of berms, and it has erected roughly 14 miles so far. An estimated 19 million cubic yards of sand has been moved to make the barriers, which rise six feet above sea level and are around 300 feet wide at their base.
BP originally committed $360 million to the project. Of that, $195 million has been spent so far.
Garret Graves, who has been helping coordinate the project for the governor, said the state will press on with the project, but will make the sand barriers deeper instead of extending them lengthwise. He said that will allow them to serve a dual purpose: protecting the shoreline from oil and restoring the coast.
Jindal, a first-term Republican governor and former congressman who has been mentioned as possible presidential hopeful in 2012, has pronounced the sand barriers a "great success."
"We disagree," the commission said in its report. "From a long-term coastal restoration perspective, the berms may indeed be a 'significant step forward,' as Gov. Jindal has claimed, but they were not successful for oil spill response."
The government has said that much of the crude that spewed from BP's well following the April 20 rig explosion was skimmed, burned, collected or dispersed. E-mails, internal reports and a log of oil sightings obtained by AP confirm that very little of the estimated 200 million gallons that gushed from the bottom of the sea has been seen on or recovered from the berms.
In its report, the commission said the National Incident Command - the task force headed for much of the crisis by retired Coast Guard Adm. Thad Allen - was initially skeptical of the plan, but allowed "political considerations" and influence from the White House to affect its posture toward the project.
Rob Young, a coastal scientist at Western Carolina University, said the $360 million could have been better spent on removing oil and restoring damaged lands than on a "back-of-the-napkin kind of project" that so far has amounted to nothing more than drawing a "pencil line of sand."
But Billy Nungesser, president of oil-soaked Plaquemines Parish, said the berm project was absolutely the right decision at the right time.
"It's easier to throw rocks now," he said. "If they let us armor those islands, it will be the start of the coastal restoration that will protect the marshlands that have been so badly damaged."
Pearson Cross, a political science professor at the University of Louisiana at Lafayette, said the episode will be a "bit of a blow" to Jindal politically, but shouldn't be too much of a problem if the governor continues to hammer home his argument that the state was taking action when Washington wasn't.
"Half the people will believe him," Cross said.