President Obama believes America must build "21st century infrastructure—modern ports, stronger bridges, faster trains and the fastest Internet," and in his State of the Union this week he asked the Republican-controlled Congress to pass a bipartisan infrastructure plan, likely the trillion-dollar legislation Senator Bernie Sanders proposed earlier this month.

It's an ambitious plan that many agree is desperately needed.

The American Society of Civil Engineers says the US needs massive investments in all essential infrastructure, from bridges and airports to dams and railways. According to the society's most recent infrastructure report card, the US earns a D+ for its infrastructure. It is, in a word, a mess. This is about much more than potholes. This is about keeping the economy, literally and figuratively, moving. Much of the economic boom the United States has experienced over the last 50 years is because the network of highways makes it easy to ship goods. If it continues into a state of disrepair, the long-term hit to our economy could be catastrophic.

"The grades in 2013 ranged from a high of B- for solid waste to a low of D- for inland waterways and levees," the society wrote in the 2013 report, which is issued every four years. Things got a bit better, but not by much. "Solid waste, drinking water, wastewater, roads, and bridges all saw incremental improvements, and rail jumped from a C- to a C+. No categories saw a decline in grade this year." Bringing it all up to current standards will be a massive, and massively expensive, undertaking akin to the construction of the interstate highway system. At the bottom line, the US would have to invest $3.6 trillion to bring it all up to snuff by 2020.

"Let's set our sights higher than a single oil pipeline," President Obama in the State of the Union, referring to the controversial Keystone XL oil pipeline. "Let's pass a bipartisan infrastructure plan that could create more than thirty times as many jobs per year, and make this country stronger for decades to come."

There's a lot of work to be done. Here's an overview of the American infrastructure that needs to be fixed, and some good places to start the work.

Highway Funding

In 2007, taxpayers spent $146 billion on highways in the United States, with three-quarters of that coming from state and local governments and the rest from the feds. For major highway projects, federal funds are matched with state or local dollars, especially if the project benefits interstate travel. Much of highway investment comes from the Highway Trust Fund, funded by an 18.4 cent per gallon excise taxes on gasoline, and 24.4 cents per gallon on diesel. There are also revenues generated various taxes on trucks.

Unfortunately, highway fund revenues have been insufficient to fully fund existing highway spending, with Congress authorizing billions of dollars in transfers from the US Treasury's General Fund into the Highway Trust Fund to keep it solvent, including a $10.8 billion transfer last August. It has ongoing funding needs that will continue unless a more permanent solution can be found, either by raising the national gas tax (which hasn't been increased since 1993), or some other funding measure. The Congressional Budget Office expects the Highway Trust Fund to have an annual shortfall of $15 billion.

A number of solutions have been proposed including mileage-based fees on drivers, additional gas taxes, or simply pulling more money from the Treasury's General Fund. And that's just for highways.

Falling Down Bridges

One in 10 bridges are deemed structurally deficient, meaning the bridge has a significant defect that requires reduced weight or speed limits. (It does not necessarily mean the bridge is unsafe.) Another 14 percent of the nation's 607,380 bridges are considered "functionally obsolete," meaning they are no longer suited to their current task because of overuse or a lack of safety features, yet are still in use.

This is not an academic issue. Just last week, an overpass collapsed on I-75 in Cincinnati as it was being dismantled, killing a construction worker and gravely injuring a truck driver. It remains to be seen if the collapse was due to the age and condition of the span, or was an unfortunate demolition accident, but it underscores the risks we face. More well known was the collapse of the I-35 West Mississippi River Bridge in Minneapolis seven years ago. Thirteen people were killed and 145 injured. The bridge had been deemed structurally deficient in 1990, though the collapse was attributed to a design flaw that was exacerbated by an increase in bridge load over time.

"For many years we have underfunded the maintenance of our nation's physical infrastructure," Sen. Sanders wrote in an op-ed earlier this week. "I will soon be introducing legislation for a $1 trillion investment, over five years, to modernize our country's physical infrastructure."

Waterways

Inland waterways, including canals and rivers, move the equivalent of 51 million truckloads of goods every year—and half the locks are more than 50 years old. According to the ASCE, the problem is so bad that many barge operators have supported an increase in their fuel tax to increase funding to the Inland Waterways Trust Fund, the main user funding mechanism for construction and rehabilitation of inland waterways. So, what needs to be done?

The US Army Corps of Engineers, which maintains most of the system, says it will take $13 billion through 2020, with 27 percent of that going towards new lock and dam facilities and 73 percent toward improving existing facilities. Without an increase in funding, it could take the Army Corps until 2090 to finish everything on the to-do list.

The Olmstead Lock Project on the Ohio River, estimated at $3 billion, has been one of the biggest drains on the Inland Waterways Trust Fund. Originally authorized by Congress in 1988 for $775 million, the project isn't expected to be completed until 2020. It's the largest and most expensive inland water navigation installation in the country.

Before legislation introduced last year, the project absorbed almost all of the Trust Fund, though now Congress has separately appropriated funds to pay for the project, freeing up cash for other overdue projects.

Ports, Harbors, and Dams

Then there are the hundreds of commercial ports and harbors. But it's not the cargo terminals that need upgrading—those have seen significant investment as shipments in standardized containers have risen over the past couple of decades. Instead, it's the navigation channels that need upgrading, and taxpayers foot that bill. To handle the New Panamax ships—which, at 1,200 feet long and 161 feet wide, are the largest capable of navigating the new locks being built in the Panama Canal—navigation channels as deep as 45 feet will need to be dredged.

The ASCE cites the Port of Savannah, in Georgia—the fourth busiest in the country—as needing improvement, claiming that deepening its channels by just six feet will reduce the cost of shipping in and out of the port by 15 to 20 percent.

Our dams are equally in need of investment and upgrades. In 2012, nearly 14,000 dams were considered a high-hazard, where failure of the dam would likely cause the loss of life. They're not necessarily unsafe, but if they were to fail, very bad things would result. Complicating matters, just 4 percent of the nation's 84,000 dams are owned and operated by the federal government; the rest are managed by state governments, regional authorities or private entities like utility companies. These dams are overseen by state, rather than federal, safety programs, many of which lack sufficient funding. South Carolina, for example, has one full-time inspector and one half-time inspector to inspect the state's 2,380 dams.

They're also frightfully expensive to maintain. The US Army Corps of Engineers says it will take more than $25 billion to do all of the maintenance required at the 694 dams it manages, and without an infusion of cash it will take 50 years to complete the repairs. According to the Association of State Dam Safety officials, rehabilitation of all dams categorized as high-hazard would cost some $21 billion.

"For the U.S. economy to be the most competitive in the world, we need a first class infrastructure system" said the ASCE report. "We must commit today to make our vision of the future a reality—an American infrastructure system that is the source of our prosperity."

Whether a Republican Congress and the Democratic President can actually get together and agree to do it is another question entirely.