CHICAGO – When Tom Linblade began canoeing the Fox River in Chicago’s western suburbs decades ago, he knew what to expect come midsummer. When the weather was hot and the water slow, the river would turn pea-soup green and smell “pretty nasty.”

Today, Linblade, 64, of Rockford, still paddles the Fox River about two or three times a year and has seen a “tremendous change” for the better in the water quality. He’s even seen fishermen pull good-sized bass from below a dam near Aurora.

“They’re catching just about any kind of fish there,” said Lindblade, vice president of the Illinois Paddling Council. “Now, I’m not sure I’d really want to eat a lot of them, but the fish are there.”

As the landmark Clean Water Act celebrates its 35th anniversary on Thursday, Lindblade’s experience is representative – a story of huge gains with work yet to be done.

Industries no longer discharge untreated wastewater. Towns no longer use rivers and streams as conduits for sewage. And fish and other aquatic life are returning to waterways once too polluted for them to survive.

“Our idea of a messed up waterway now is different than our idea of a messed up waterway 35 years ago,” said Toby Frevert, who joined the Illinois Environmental Protection Agency a year or two before the Clean Water Act became law and now is manager of the agency’s water pollution control division.

But Illinois still hasn’t met two key goals of the Clean Water Act: to make all waters fishable and swimmable by 1983 and to eliminate pollution discharges by 1985. There have been daunting challenges in meeting those goals.

By the time the law took effect in 1972, industries, agriculture and urban development had taken a tremendous toll on waterways.

When Frevert traveled around the state in the early days of his career, he saw streams with little or no oxygen – and therefore no fish – and industrial plants such as paper mills and meatpacking facilities dumping wastewater with very limited treatment.

The Clean Water Act came about partly as a result of public outrage over a fire on Cleveland’s Cuyahoga River in 1969. Its objective was to “restore and maintain the chemical, physical, and biological integrity of the nation’s waters.”

It established a structure for regulating discharges of pollutants into American waters and gave the U.S. Environmental Protection Agency the authority to implement pollution control programs.

Yet some Illinois rivers, lakes and streams still are polluted with heavy metals, such as mercury, and PCBs – which can build up in fish and eventually affect people’s health – nutrients such as fertilizer, which can lower oxygen concentrations; and pathogens, such as fecal coliform bacteria.

In its 2006 report on the quality of the state’s waterways, the state environmental agency – which enforces the federal act – rated about 40 percent of the river and stream miles it had assessed as fair or poor for fish consumption, 38 percent poor or fair for supporting aquatic life, and almost 88 percent fair or poor for primary contact, such as swimming.

The agency also rated 27 percent of the Illinois lakes it assessed as fair for fish consumption, about 13 percent fair or poor for aquatic life and about 53 percent fair for primary contact.

“We’ve made great strides, but there’s a lot to be done,” said Jill Watson, a spokeswoman for the Illinois EPA, who said the state’s industrial history resulted in a lot of recovery work.

An environmental advocacy group, Environment Illinois, said the state hasn’t done enough.

Using EPA data, the group issued a report last week that found that 46 percent of the 276 major Illinois facilities with federal water discharge permits exceeded their permit limits at least once in 2005, ranking Illinois 37th in the nation.

The total number of times Clean Water Act permit limits were exceeded in 2005 was 693, placing Illinois 12th among states, according to Environment Illinois.

“The results are clear. Facilities in Illinois and across the country continue to dump more pollution than allowed by law,” said LuCinda Hohmann, the federal field organizer for Environment Illinois.

But Watson questioned how Environment Illinois did its analysis.

“We don’t allow people to go around having disregard for the environment,” she said. “If we find out they have violated a permit, they are subject for potential violation notices and potential enforcement if they can’t come into compliance.”

But there is no doubt there have been huge gains in Illinois water quality in the past 35 years.

Frevert said perhaps the biggest success story is the Illinois River, particularly the stretch from Ottawa to Peoria.

He’s heard unconfirmed stories that, during the Depression era, sludge was so thick on some stretches of the river that a young boy could cross on the matted mess.

“Now the Illinois River’s got sauger and walleye and species of fish that my father’s generation would have never dreamed could live in that river,” Frevert said.

He said the challenges for the future are more subtle and complicated than the obvious problems with sewage treatment and industrial waste first tackled under the Clean Water Act.