New York, NY —

New York City's watershed protection plan for the next ten years has won approval from the federal Environmental Protection Agency. That means the city can still avoid building a costly filtration plant because it's taking enough steps to keep the Catskill-Delaware water supply clean in other ways.

REPORTER: EPA Approval was widely expected after the city proposed spending $300 million to buy more land upstate, says Eric Goldstein of the Natural Resources Defense Council.

GOLDSTEIN: What it does is ensure the city has the ability to safeguard the most sensitive lands from being polluted before we need to clean it up at the end of the line.

REPORTER: The city will also build an ultraviolet light disinfection plant to supplement the use of chlorine. New York City gets 90 percent of its water from the Catskill-Delaware system which is the nation's largest source of unfiltered drinking water. The city was ordered to build a filtration plant for its smaller Croton system.