Engineers Give US Infrastructure a D+ America's infrastructure is still crumbling -- it's just crumbling a little less than it was. For that faint praise you can thank the American Society of Civil Engineers, which is out this week with its most recent report card on the state of the nation's highways, byways, waterways, railways, levees, landfills, ports, airports, parks, power stations, hazardous waste dumps and other fixed ornaments. The engineers give the U.S. a grade of D+ overall. But lest you think that's bad, it's better than what the ASCE gave the U.S. in 2009, when they last performed this same exercise. At that time the U.S. got a straight D. No category got a lower grade in this year's report than they did the last time around, and a few saw improved marks. The crumbliest categories, according to the report, are levees and inland waterways, both of which got grades of D-. Bridges, railways and solid waste facilities -- all in relatively good shape -- earned the engineers' highest marks (C+, C+ and B-, respectively). To bring all of America's infrastructure up to where it would be earning a respectable B would cost, the Engineers say, $3.6 trillion between now and 2020. Are we spending it? Current U.S. spending falls short by $1.6 trillion, they find. Society president Greg DiLoreto warns ABC News that unless government and industry make good the deficit, every household in the U.S. will see its income drop an average $3,100 over the next seven years. That decline will come in part from slower job growth and lower U.S. exports, as manufacturers find it harder to move goods and raw materials. Even now, LiLoreto says, the inland waterways of the U.S. are experiencing on average 52 service interruptions a day. "Barges are stopped for hours each day with unscheduled delays, preventing goods from getting to market and driving up costs," the report says. Projects to repair and replace aging locks and dredge channels take decades to approve. It calls inland waterways "the hidden backbone" of the U.S. freight network, carrying the equivalent of about 51 million truckloads of stuff each year. Yet most of the system hasn't been updated since the Eisenhower administration. As for levees, we've got 100,000 miles worth, in all 50 states plus the District of Columbia. Most originally were built, LiLoreto says, to protect farmland. Over many decades, farms have been replaced by homes and towns. So, today, when a levee breaks, he says, it's not broccoli that gets inundated. It's families. Although fully 40 percent of Americans live near levees, no program exists to monitor their structural safety. The nation's rail system is a rare bright star in the infrastructure firmament: Amtrak, notes the report, almost doubled its ridership between 2000 and 2012. "Both freight and passenger rail have been investing heavily in their tracks, bridges and tunnels," the report says. In 2010, freight lines upgraded more than 3,100 miles of track. Consequently, the grade given railroads by the ASCE saw the biggest gain, rising to C+ from a C- in 2009.