An environmental group is alleging that menhaden fishing ships may be dumping vast amounts of decomposing fish wastes into the Chesapeake almost every day during the fishing season, removing oxygen from water in a Bay that already suffers chronic "dead zones."

Omega Protein, the Texas-based company that operates the menhaden fishing fleet based in Reedville, VA, disputes the accusations by the Southern Environmental Law Center, based in Charlottesville, VA, saying its discharges comply with permit limits.

Rick Parrish, senior attorney for the environmental organization, said the dumping of "bail water" appeared to be a "custom" that has gone on for decades and may have stemmed in part from confusion over the law-dumping fish waste is legal in the ocean more than 3 miles offshore. In the Bay, he said, it is illegal without a permit.

"What needs to happen is the company and the EPA need to sit down at a table and figure out what is going on," he said.

Parrish said that when the fishing boats load freshly caught fish in their holds, they also pump in chilled refrigeration water to keep the menhaden cold. Before reaching Reedville, most of the refrigeration water, which contains fish blood and other wastes, is discharged.

At the dock, fresh water is used to "bail" fish out of the hold and into the processing plant. The water is reused until it becomes thick with fish parts and waste. Then it is dumped from boats on their way back to the fishing grounds leaving a "brown, thick and extremely pungent" streak in the water, according to Parrish.

He said discharges of fish wastes in the Bay are covered under the Clean Water Act and require a permit.

Omega's permit from the Virginia Department of Environmental Quality covers refrigeration water, but indicates that bail water goes through the processing plant where it is treated before being discharged. It does not mention releasing bail water in the Chesapeake.

Omega spokesman Ben Landry said the distinction between refrigeration water and bail water is "kind of ticky tack. It is difficult to separate the two, because it is largely the same type of water. We are permitted for what we are discharging and never had any problems with it."

Landry noted that the company has been under intense scrutiny in the Bay, where many recreational fishermen want to ban menhaden fishing, contending it deprives striped bass and other predators of their prey.

"For us to just be dumping a bunch of nutrients into the Bay, I'm sure it would have caught someone's attention by now," he said. Omega has invested about $10 million in environmental upgrades at its Reedville plant, Landry said, adding that dumping in the Bay would be "contrary to where the company is trying to go."

Parrish said his information was provided by Omega officials and consultants during the course of unrelated litigation over an injury to a fishing boat crew member. He said the SELC reviewed documents on file at the courthouse, at DEQ, on the Internet and in the possession of an expert witness in the injured worker's case.

He contends the bail water is distinct from the refrigeration water as it is laden with far more fish blood, parts and waste than refrigeration water. "Bailing water is hugely richer in nutrients and fish waste than refrigeration water," he said.

Rotting fish parts draw oxygen out of the water just like the excess algae generated by nutrients; both are decomposed by bacteria, which consume large amounts of oxygen.

Parrish said company documents show that bailing water has 37,500 to 150,000 milligrams of biological oxygen demand, or BOD, per liter of water. BOD, is an approximate rate at which waste draws oxygen from the water. In comparison, raw sewage has a BOD of 200 mg/l and an advanced wastewater treatment plant has a BOD of about 6 mg/l. In the letter to the EPA, Parrish said boats dumped about 50 loads of bailing water a month during the fishing season, averaging about 25,000 gallons each, making the BOD of the discharge equivalent to that of a huge wastewater treatment plant. The practice may have been going on for 30 years, it said.

The EPA and Virginia officials said they were investigating the allegations.

"EPA takes these allegations very seriously, and we are looking into them and will take appropriate action as warranted," said David Sternberm, a spokesman for EPA Region III in Philadelphia.

Curt Linderman, a water permit manager for the DEQ, said the Omega permit "can be really confusing" but said the agency "will certainly be looking into the letter." He noted that the permit comes up for renewal in 2010.

Parrish said he was not seeking any action against the company but wanted to ensure the issue is addressed when Omega's permit is renewed.