 A report in 1999 revealed that fuel taxes cover only 10 percent of the annual $674 million that the U.S. Army Corps of Engineers spends building and operating the locks and dams of the Mississippi River.Barges figured there were a lot more corn and soybeans in Iowa than there was scrap iron!Until then, some had limited themselves to pushing scrap downstream and coal upriver, but those commodities were dwarfed by the potential downstream grain business.