"The Corps announced today they would approve six segments totaling 45 miles," Allen said.
But Allen said experts are divided as to whether the plan is an "effective response" to the spill.
"There is not universal agreement on that. I said we take one small segment of it and start a prototype construction project and evaluate with the rest of the projects in relation to that. And that's where we are," he said.
He added that the massive construction project would not provide a quick fix to the threat of millions of gallons of crude slopping up on the Louisiana shoreline.
"Some of these projects are estimated to take six to nine months, some up to a year," he said.
"I thought the prudent thing to do was start a prototype project and keep asking questions," Allen said.
The government construction program comes after insistent demands by Louisiana Governor Bobby Jindal, a Republican, that the government approve a plan to use dredgers to build up a network of temporary barrier islands to keep oil from pushing into environmentally sensitive marshlands.