In an unprecedented act, the U.S. Army Corps of Engineers announced yesterday that it would suspend work on about 150 congressionally approved water projects to review the economics used to justify them. The move follows last week’s decision by the Corps to suspend its deepening of the Delaware River to review the economic analysis, one of many that had come under increasingly vocal criticism from within and without the Bush administration. Now billions of dollars worth of other projects — as much as a fifth of the Corps workload — will come to a halt, in some cases indefinitely. The work suspension was met with delight by environmentalists and fiscal conservatives, both of whom have long accused the Corps of justifying many of its projects by overstating the economic benefits. Some critics, however, feared the suspension would take the place of more lasting action on the part of Congress to rein in the Corps.