KANSAS CITY, Mo. (AP) — The nation is falling behind on maintaining its aging levees, dams, ports and harbors and needs to get creative as it seeks ways to pay for the critical projects, the U.S. Army Corps of Engineers’ commander general said Wednesday.

Lt. Gen. Thomas Bostick told reporters that finishing all the projects that have been authorized would cost about $23.5 billion but that that corps’ annual budget for the work usually hovers around $1.5 billion. He said that figure doesn’t include addressing a maintenance backlog as projects — many of them decades old — exceed their design life.

“It is going to take you decades to finish the work and then you are going to have new projects here and there,” Bostick said, speaking during the Society of American Military Engineers conference. “The reality is Congress cannot do this alone. The federal government cannot do this. And the message to local towns and communities and business is we cannot rely on the federal government to solve this fiscal challenge.”

Bostick said the corps is looking at alternative means of financing projects, including through public-private partnerships. The question, he said, is how to “monetize the project in such a way that investors would come in and over a number of years get a return on their investment?”

The corps said that 16 percent of the dams it operates are categorized as extremely or very high risk. Since 2009, delays and interruptions have more than doubled on the nation’s inland waterways’ locks and dams.

There also has been a 50 percent increase in hydropower facility downtime since 2000, the corps said.

Bostick highlighted the findings of the American Society of Civil Engineers, which has given America’s overall infrastructure a D+ grade, its dams a D, its inland waterways a D-, its levees a D- and its ports a C. The group has called for Congress and the Obama administration to come up with a way to pay for infrastructure maintenance and updates to help manage floods.

The ASCE noted in its report that the Association of State Dam Safety Officials estimates that it will require an investment of $21 billion to repair aging high-hazard dams, while the National Committee on Levee Safety said the cost to repair or rehabilitate levees is estimated at $100 billion.

“I wouldn’t be concerned at this point from a safety perspective. But there are projects, individual projects that are at high risk,” Bostick said.

He noted that extensive flood control work was undertaken after Hurricane Katrina, lessening the effect that Hurricane Isaac had seven years later in 2012.

“The nation will invest in times of crisis but the question is: Can you set priorities when there is not a crisis but one is looming so we can make the right decisions?”