My day tracking the stimulus on the Mississippi.

MEDORA CROSSING, La.—If Michael Bay is looking for his next Transformer, I have found it in the middle of the Mississippi River. It's a dredge boat named the Dodge Island, and it's eerily anthropomorphic. On its side are two dragarms, giant metallic appendages that are lowered down by winches that make the sound of a whale's cry. When the arms are dropped dozens of feet into the river, its hands—called dragheads—scoop up sediment that has settled at the bottom of the river. It pumps the sand through its arms like a heroin addict injecting through the wrist. The sediment is pushed against gravity and into the tubes, where it's deposited in the ship's hopper.

The hopper rests inside the ship's belly, a hollow cavity meant to store deposits until they can be flushed out. It's the ship's namesake—the Dodge Island is classified as a hopper dredge—and it's there that the sand collects, 1,200 tons of it. Sprays of water come up from the bottom of the river along with the sand, gushing through pipes, and is then sifted back down into the river through a skimmer, which looks like an overgrown drain-stopper that lost its way to the kitchen sink. While the sediment is being dredged, it's hard to tell how much is in there because there's so much water pouring across the top. But the sediment is there, piling inside the hopper just like it was stacked at the bottom of the river. This batch of sand made the river's floor a few inches deeper and the ship's hopper 2,300 cubic yards fuller.

Making the river deeper is the Dodge Island's raison d'être. The dredge is out here to keep the river open to commercial ships and stop the river from flooding over the banks. If the sediment accumulates at the bottom of the river, larger ships aren't able to travel down the channel. That stops shipments, which forces companies to find a different way to get goods between point A and point B, which raises production costs, which raises prices. For example, if crude oil can't get to processing plants in Baton Rouge by boat, it's got to get there some other, more expensive way. It's the maritime version of repaving a road so truckers can drive across it without spilling their cargo.

Which is how the stimulus has found its way to the Dodge Island. Most of the stimulus's infrastructure funding is coming through departments of transportation in the various states, but this money is coming from the Army Corps of Engineers. In a place like southern Louisiana, where you can't go 15 miles without driving over some type of water, all infrastructure ends up being about the way asphalt and water mix. The Corps is paying a private dredging company, Great Lakes Dredge and Dock, to do the dredging. (GLDD won the contract in a low-bid sweepstakes.) It's a $3 million project, a large chunk of the Corps' $26 million stimulus budget for the New Orleans area.

Capt. Steve Taylor is the man at the helm of this $3 million expedition. He watches the body of the dredge from above in the bridge, the brains that operate the rest of the ship. Taylor is a thoughtful man who's been stewarding the Dodge Lake since 2004. He's dressed in tan slacks and a tan collared shirt, both neatly pressed but stained with ship grease. He and a few colleagues are watching the dredge's vital stats on a screen, cross-checking them with their location on a GPS-tracked map of where they are in the river. With the hopper full, they're turning the ship around to leave the dredging zone and go unload all the sediment back into the river. They'll drop it off in one of the deepest parts of the river, where the sediment will rest for a while but eventually migrate back to some other shallow crossing, where it will once again be dredged up. It makes the water cycle look square by comparison.