The case stank from the very beginning. A pair of law students had stood watch at the Foster Farms plant in Kelso, Wash., then followed a truckload of chicken carcasses to a fish processing plant near the mouth of the Columbia River.

There they observed the phantom pipeline, which spewed chicken parts into the air and belched chemically rendered goo into the water.

That would be highly illegal. That was almost five years ago.

This week, the students’ gumshoe work helped lead to the criminal sentencing of California Shellfish Company Inc., which was ordered to pay a $75,000 fine for a felony violation of the Clean Water Act.

U.S. District Judge Anna J. Brown on Monday found that the company, doing business as Point Adams Packing Co., knowingly discharged poultry parts from its plant near the mouth of the Columbia without the appropriate permit.

The case began in June 2004, when Mark Riskedahl, executive director of the Northwest Environmental Defense Center, fielded an anonymous phone tip about strange doings at Point Adams Packing.

According to the tipster, Point Adams was allowing Modesto Tallow Co., doing business as California Spray Dry, to process chicken carcasses at its plant in Hammond and discharge goopy remains into the river.

Law student volunteers at the nonprofit environmental group, based at Lewis & Clark Law School, quickly learned that Point Adams held a permit to send fish parts into a stretch of the Columbia near Hammond, just across Youngs Bay from Astoria. But the company had no permit to send chicken remains into the water.

The tip came in on Chris Mixson’s first day as a law clerk for the environmental group.

Riskedahl dispatched Mixson and fellow law student Geoff Evans to track the chicken carcasses from their source. The two young men woke before dawn one morning and drove to the Foster Farms plant in Kelso, Wash., where they found trucks marked with the logo of Modesto Tallow Co.

Mixson and Evans followed the trucks back to Point Adams Packing and waited by a discharge pipe that snaked from the plant into the river. The calf-high pipe extended so far into the water that they suspected they might need divers to document the outflow.

Chicken parts suddenly spewed from a hole in the pipe. Chemically rendered poultry goo geysered two to three feet in the air from an opening no bigger than a silver dollar. The student investigators documented this discharge with a video camera and headed back to the law school.

Riskedahl drove out to the plant to see for himself and later described the outflow as “a nasty, putrid sort of rotten chicken-soup smelling effluent . . . the stench of death . . . one of the worst things I’ve ever smelled.”

The Northwest Environmental Defense Center reported to Environmental Protection Agency agents what they had found. The agents opened an investigation and took their case to the U.S. Department of Justice.

On June 15, 2004, federal agents carrying search warrants swept into Point Adams Packing and the home of its manager, Thomas E. Libby, seizing files that documented illegal wastewater discharges dating to December 2003. That same day, the gang at Lewis & Clark and Columbia Riverkeeper sent notice to California Shellfish and Modesto Tallow that they intended to sue them for their illegal discharges.

The two companies quickly resolved the threatened civil action. In September 2004, they each agreed to pay $100,000 to the Sierra Club and the Columbia River Estuary Study Task Force.

“The liability was so clear,” Riskedahl said, “that we were able to very efficiently resolve the matter.”

Criminal charges took years to resolve. Libby pleaded guilty to a misdemeanor violation of the Clean Water Act. He was ordered to pay a $3,250 fine and serve a year of probation. Modesto Tallow was found guilty of a felony violation of the law and ordered to pay $75,000 in fines.

The fine levied Monday on California Shellfish closed out the case.

The case fell during a four-year stretch in which Oregon’s U.S. attorney, Karin Immergut, put a major emphasis on prosecutions of environmental lawbreakers, said Assistant U.S. Attorney Dwight C. Holton.

“The importance of this case is that we’re not going to tolerate unpermitted dumping in the Columbia,” Holton said. “It’s not fair to other businesses that comply with the law, and it hurts our natural resources.”

Monday’s fine will go into a fund aimed at reducing pollution and cleaning up Oregon’s rivers, streams and coastal areas and preserving plants, fish and other wildlife.

“It’s nice to see that justice is done,” Riskedahl said. In the meantime, the student sleuths who helped make the government’s case have moved on to promising legal careers. Evans is working as an attorney in California, and Mixson is practicing environmental law in Nevada.