The EPA began looking at Hawai'i's runoff-management systems in 1999 after a massive investigation of the California state transportation department uncovered problems under the federal Clean Water Act.

The agency said it found that Hawai'i was "significantly behind other state and local governments in meeting national and state storm water requirements." The investigation found that sediment-laden runoff was allowed to flow from state highways into storm drains and onto the nearshore reefs. At airports, construction projects generated muddy runoff, and airport tenants such as car rental firms washed oily water into drains that flow to the sea. At some of the DOT's own projects, stormwater control procedures were not followed, the EPA said.

Under the consent decree, the department agreed to conduct extensive training of its personnel and contractors and subcontractors it hires; establish strict inspection and maintenance schedules for its facilities; sweep streets of dirt and dust on a regular basis; and conduct a range of other activities aimed at reducing stormwater pollution.

Many of those programs were put into effect months and even years ago, said Scott Ishikawa, spokesman for the state Department of Transportation.

These and other changes should significantly improve the environment, said Granta Nakayama, EPA's assistant administrator for the office of enforcement and compliance assurance.

"Storm water runoff is a major threat to our water systems and wildlife. This settlement recognizes the importance of compliance with environmental obligations by the state Department of Transportation and their contractors," Nakayama said.

There is a 30-day public comment period on the consent decree, which takes effect when it is signed by a federal judge.