The Environmental Protection Agency must develop pollution standards for storm water runoff from construction sites or risk violation of the Clean Water Act, the 9th Circuit ruled.

The EPA identified the construction industry as a "point-source category" of pollution in its 2000 environmental plan, but then exempted the industry from the plan in 2004, skipping a three-year deadline to develop standards after listing.

The Natural Resources Defense Council, along with the Waterkeeper Alliance, filed suit against the EPA and its administrator, Stephen Johnson, for violating their duty to "promulgate effluent limitation guidelines and new source performance standards" for toxic storm water runoff from construction sites.

The environmental groups have standing because the polluted storm water ran into waterways that the groups' members use for recreation, the appeals court ruled. The National Association of Home Builders and Associated General Contractors of America, intervening on behalf of the government, argued that even if the runoff contained pollutants, the water wasn't toxic. The 9th Circuit disagreed. "In fact, the EPA has explicitly stated that storm water runoff from construction sites includes toxic and non-conventional pollutants," Judge Smith wrote.

The Clean Water Act clearly outlines the EPA's responsibility to develop standards for polluters within three years of developing a plan, the ruling states. The Act does not give the EPA authority to remove a point-source category from its plan once it is identified, or the three-year deadline would be meaningless, the court ruled. Also, the intensive listing process, which allows for public review and comment, shows that the agency seriously considered adding the construction industry before its listing.

"The three-year delay ... is not to decide whether to list a point-source category," Smith wrote, "but to allow the EPA to consider what the substance of the (standards) should be."