A stepped-up inspection of D.C. fire hydrants is finding that nearly 10 percent don't work, fire union officials said yesterday. Firefighters doing the testing said they think that more than 900 hydrants across the city are not in working order, posing a significant public safety risk. The D.C. Water and Sewer Authority has greatly underestimated the severity of the problem, union leaders and other D.C. officials said. "Clearly, WASA has a much larger problem than what they realized," said Dan Dugan, president of the D.C. Firefighters Association. The fire department's most recent round of tests began after a fire April...