Plaquemine, La. — Beneath the churning waters of the Mississippi, divers from the international environmental organization Greenpeace are attempting an act of industrial sabotage. Their aim is to plug the discharge pipe here through which the chemical company Georgia Gulf Corporation drains toxic waste into the river. A few feet away on shore, the acrid smell of chemicals drifts by sheriff's deputies waiting patiently to make arrests.
It is another skirmish in the six-month war of words and deeds that Greenpeace is waging against polluters of the Mississippi. The old brown river is far cleaner today than at its nadir in the early 1970s. But daily dumping of metals and toxic chemicals - including known and probable carcinogens - continues almost the entire length of the river's 2,348 miles.
At its source in Minnesota, the river is a small stream of clean water. But from the manufacturing plants of Minneapolis-St. Paul to the petrochemical plants of Louisiana, the bank is lined with drainage pipes. About 590 industrial plants legally discharge waste directly into the river, according to Greenpeace reports. More than 600 city waste-water treatment plants discharge treated - and sometimes untreated - sewage.
One hundred hazardous waste management facilities, 55 active hazardous injection wells, and 27 federal Superfund sites are situated along the river, according to Greenpeace. The water carries runoff of fertilizers and pesticides from the farms of the Midwest.
By the time the river reaches Louisiana, it is a toxic sewer, says Greenpeace's Mississippi project coordinator, John Liebman, who has traveled the length of the river in the Beluga, a rainbow-striped research vessel. With its two chemists and laboratory, it has analyzed water samples from discharge pipes all along the river.
In addition to educational activities, Greenpeace has become known for protest acts like the Nov. 3 attempt to plug the Georgia Gulf pipe. That attempt was only partly successful, and no arrests were made.
[The Associated Press reported yesterday that four Greenpeace activists snarled Baton Rouge rush-hour traffic Tuesday night after they climbed a freeway bridge and unfurled a banner criticizing the Dow Chemical Company.]
Georgia Gulf was singled out for the Nov. 3 hit because of what Greenpeace called its unusually high rate of accidental spills. Last April, the company reportedly spilled 9,000 pounds of ethylene dichloride and 51,000 pounds of vinyl chloride into the Mississippi. Both chemicals are probable carcinogens. In 1981, the company (then Georgia Pacific) dumped 20 tons of phenols into the river, contaminating New Orleans drinking water without notifying authorities for days.
These discharges were accidental. But most of the toxic chemicals in the river are released legally. The United States Environmental Protection Agency (EPA) issues permits to industrial plants authorizing discharges up to a specified level, even for known cancer-causing agents such as vinyl chloride.
``The pollutants in waste water discharged to the river have been reduced by 90 percent since 1971,'' says Richard Kleiner, a spokesman for the Louisiana Chemical Association in Baton Rouge. ``The reductions will continue,'' as new innovations in technology and improved efficiencies make that possible, he says.
Meanwhile, some 1.5 million people in southern Louisiana get their drinking water from the Mississippi. ``The water companies are drawing water out of the river and treating it, and they wouldn't be allowed to do that if it were untreatable,'' Mr. Kleiner says.
EPA officials agree. ``Our latest information is that those facilities down there are in compliance with the Safe Drinking Water Act,'' says Kenton Kirkpatrick, deputy director of the water division of EPA's Region 6, which covers Louisiana, Texas, Oklahoma, Arkansas, and New Mexico. ``Human health is not endangered.''
Fish and wildlife have not fared so well. ``There have from time to time been certain levels of chemicals found in fish and wildlife that exceeded the federal Food and Drug Administration standards,'' Mr. Kirkpatrick says. And Mike Schurtz, a Louisiana Department of Environmental Quality official, says the water quality deteriorates detectably in the last 150 miles between Baton Rouge and New Orleans.
Eighty chemical plants are concentrated at the tip of the Mississippi, an area known as the ``chemical corridor.''
Thirty thousand people work in those plants, in a state that has had one of the highest unemployment rates in the nation since employment in the oil industry plummeted in the early 1980s.
But incidences of certain types of cancer are among the highest in the nation here, and there seems to be a consensus among industry, regulatory agencies, and citizens that the toxic dumping will eventually have to be further limited.
``Over the next three years we will be putting in additional regulations controlling toxic discharges. That's the highest priority of our water permit programs,'' says Jack Ferguson, chief of the permits branch of EPA's Region 6.
``We know we've got work to do,'' concedes Kleiner of the Louisiana Chemical Association. ``We're making the investment to be responsible citizens.''
But for now, the level of toxins legally allowable in the Mississippi is a source of controversy. The Jefferson Parish, La., Water Quality Laboratory samples the river each week as it flows down the last few miles of Louisiana. In 1987, the laboratory says, those toxics amounted to a total of 10,000 pounds of the suspected carcinogen cadmium, 42,800 pounds of chromium, 733,000 pounds of nickel, 11 million pounds of lead, more than 60,000 pounds of pesticides and herbicides, and more than 900,000 pounds of synthetic chemicals, all washing from the nation's longest river into the Gulf of Mexico.