WASHINGTON -- The House voted to approve the nation's costliest waterway navigation project Thursday, a $3.6 billion undertaking to ease shipping on the upper Mississippi and Illinois rivers. Environmental and taxpayer groups have opposed the project. Barge operators and farmers want to speed grain to Gulf of Mexico ports, and the Mississippi is the cheapest route for shipping to export markets commodities such as corn and soybeans, coal, chemicals and construction materials. Government scientists, however, had said that grain exports probably won't increase enough to economically justify the lock overhaul plan. House members overwhelmingly agreed to the plan anyway, as...