The Pennsylvania Department of Environmental Protection plans to test the Allegheny and Ohio rivers for toxins because of a dispute over sand and gravel dredging.

For decades, dredging companies have been scooping sand and gravel from the bottom of the rivers. Now, environmental groups say they have their first batch of evidence that the dredging may be stirring up toxic pollution.

Team 4 investigative reporter Jim Parsons has the details in a story you'll see only on Channel 4 Action News. The report, which first aired Aug. 3, 2004, appears below.

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New water quality test results do not show any unsafe levels of toxic material in either the Ohio or the Allegheny, but environmental groups say the results do show the need for more testing around dredging operations, so the DEP will do just that.

You see it being used every time you pass a highway construction zone -- sand and gravel from the bottom of the Ohio and Allegheny rivers. It's used to make concrete for Pennsylvania's highways. Even the state's DEP secretary -- the top environmental watchdog -- is a fan.

Kathleen McGinty, Pennsylvania DEP secretary: "The dredging industry is very important to Pennsylvania. We all need to start there and remember that. Whether it's concrete we need around our house or gravel that we all use, the dredging industry is important."

Dan Giovannitti, river dredging spokesman: "The availability of high-grade sand and gravel is phenomenal. There's just a lot of that stuff down there."

But just what's in that stuff worries environmental groups that are concerned about drinking water and aquatic life in the rivers.

Myron Arnowitt, Clean Water Action: "There are toxins in sediment at the river bottom that get churned up, and most of us drink that water out of the Allegheny and Ohio."

The dispute between the industry and green groups over the river bottoms is not new. What is new is a study of potential toxins in the river associated with dredging. The sand and gravel industry agreed last year to fund the study as part of a consent agreement with Clean Water Action.

Technicians took water samples upstream and downstream from six dredging operations in the Ohio and Allegheny rivers. Then, they tested for heavy metals. One of the test results caught the attention of Clean Water Action.

Arnowitt: "The biggest thing that jumps out at you from the results is the detection of lead."

Four of the six samples detected no lead at all upstream from the dredging operation. Lead did show up downstream, although at low levels: two parts per billion.

Arnowitt: "So we believe that demonstrates that the dredging can pull up toxic materials into the waterstream."

Robert Silber, Allegheny riverkeeper: "Pretty obvious when you have a 7-ton clam shell dredge scooping up all this muck at the bottom of the river, you're also going to be stirring up those chemicals."

But the dredging industry and the state DEP say the test results don't prove anything.

Tom Proch, DEP biologist: "These things are right at the detection level. They're an order of magnitude below drinking water standards without treatment. They're not something that starts clanging the environmental disaster bell."

Giovannitti: "The fact is we do not cause harm to the river, the river environment, to aquatic life, and we certainly don't impact water quality."

The DEP calls the test results inconclusive, so more testing is on the way.

Helen Humphreys Short: "We have been asked by Clean Water Action to perform the testing, and it is inconclusive. Again, we just want to get more information."

The state DEP permits for dredging companies expire next year. Environmental groups are working to build a case for the DEP not to renew those permits. Earlier this year, the Pennsylvania Fish and Boat Commission launched a campaign to have the dredging permits rescinded, claiming the dredging is harmful to aquatic life.

Team 4 will continue to follow this story.