Darigold plead guilty to federal charges of dumping in the Issaquah Creek, and agreed to pay $60,000 fee to help restore the creek.

The nation’s fourth largest dairy group already paid a $10,000 fine to the Department of Ecology, the maximum penalty the agency can give.

In addition to the money, the group issued a public apology.

The ammonia spill was discovered in October 2009, after a maintenance worker dumped ammonia from the dairy’s refrigeration system onto the roof, where it then went into the nearby creek.

Shortly after the spill, survey crews from the Washington State Department of Fish and Wildlife smelled the spilled ammonia, and discovered about 40 dead fish, including Coho salmon heading to spawn.

“You won’t see perfection in any large industrial setting, but we expect major upsets like this to be prevented,” said Larry Altose, spokesperson for the DOE.

In the past 10 years, there have been several instances of spills into the creek, including two dairy spills. The nutrient rich milk hurts the ecosystem, after excessive growth depletes all of the oxygen out of the water.

“Each of these cases, Darigold has responded quickly and seriously,” Altose said.

However, the instance with the Ammonia was different because there was clearly a better way to dispose of the chemicals, he said. “One of the purposes of the investigation is the penalty, but a more important part is to learn lessons.”