An 800-foot ship carrying carbon black oil was stuck in the center of the Mississippi River last week — unable to move because of high sediment levels.

Fortunately, it was freed after two days. We are lucky that it did not block traffic or leak oil, but this incident highlighted the danger of failing to invest in dredging.

Soil naturally collects on the bottom of the river and reduces its depth. The Army Corps of Engineers maintains the Mississippi River’s depth through dredging.

Recent floods increased the speed of river water and, in effect, the rate at which this sediment collected.

Frankly, the corps does not have the budget to keep pace — even though the federal government has $6 billion in shippers’ tax money set aside for this very purpose in the Harbor Maintenance Trust Fund.

After joining Congress, I have told everyone that if we fail to dredge the Mississippi River, an economic, safety and environmental catastrophe could occur.

I delivered this message to Republican and Democratic House leadership, President Barack Obama, the Army Corps of Engineers and the Coast Guard.

Unfortunately, parts of the river are now too shallow for cargo ships to travel. As a result, the amount of cargo a ship can carry is restricted. It is like reducing an interstate to a single lane and imposing size restrictions on vehicles because the roads were not maintained.

If the river closes entirely, the United States will lose $295 million a day and valuable export power.

The Mississippi River is the single most important U.S. commercial waterway. It carries goods to and from 30 states and two Canadian provinces.

In 2009, $13.4 billion of agriculture products — including two-thirds of the Midwest’s grain — were exported along this route.

Unfortunately, the federal government is not keeping it open for business.

The solution is simple: The president must immediately request a supplemental appropriations bill to fund the corps’ dredging work. In the long term, Congress must appropriate the $6 billion set aside in the Harbor Maintenance Trust Fund.

Rep. Cedric Richmond (D-La.) serves on the Homeland Security and Small Business committees.