Perhaps a defining moment for the Berkeley Pit came 20 years ago on Nov. 14, 1995, when 342 snow geese were found dead floating on the surface of its toxic water.
Although the pit, which opened in 1955, had been slowly filling with contaminated, acidic water since the mine closed in 1983, the story of those dead birds came to symbolize the environmental degradation that had been wrought due to mining.
Those 342 dead geese caught the attention of the nation.
It most certainly caught the attention of Butte.
Ted Duaime, hydrologist for the Montana Bureau of Mines and Geology, remembers that fateful day. He was one of the first people to discover the dead birds.
Duaime said he and a few of his staff were collecting pit water in large quantities for MSE Technology Applications, an engineering services company in Butte, in the days leading up to the snow geese's fateful visit. The men pulled up each day in an old Army truck to pump the water into the back of the truck. Duaime said the water was for treatability studies.
Duaime said that in the days before, the weather turned cloudy and overcast. A winter storm had blown in. That storm led the birds to land on the pit's water, presumably to wait out the falling snow.
"It was not uncommon to see waterfowl land in the pit with no apparent problems. These were caught overnight. It wasn't the best decision they made," Duaime recalled.
A Bureau of Mines staff member, using an early, over-sized cell phone, was among the first to spy the dead birds. He called Duaime from the pit. Duaime drove over to take a look. He then began making phone calls to alert the appropriate authorities.
Initially, officials believed about 150 birds had died.
Montana State University professor Timothy LeCain, who has written a book on the subject, said the birds were likely in the pit for a few days. The ones that had died first had been in the water long enough that they had turned a brownish-orange, making it harder to see them in the murky water.
Duaime said personnel from Atlantic Richfield, which owned the Berkeley Pit, took two boats into the toxic water. ARCO employees rode in one boat and scooped the geese carcasses into the second boat. Duaime said the state's Department of Justice asked him to collect a couple of birds. He did so, and the carcasses were sent to a lab in Wyoming.
Sandy Stash, who was then ARCO's project manager for reclaiming the Butte Hill, recalled that day during her commencement speech at Montana Tech last May.
Stash, who now works for Tullow Oil, touched on the topic of failure to the graduates and referred to the dead snow geese as "one of my doozies."
"If you Google my name, it's one of the first things that'll come up," she told the audience.
While the birds were being tested at a lab, she said she prayed, "please don't let it be the water in the Berkeley Pit."
ARCO sent dead bird samples to a lab in Colorado for necropsies to determine the cause of death, Stash said.
Pressure was mounting for an explanation.
"The press was calling every hour," Stash said.
She said that against advice and her better judgment, she went forward with a story she said she believed at the time — that the geese died from eating infected grain. But it was not the bad grain. Tests showed the pit water killed the geese — its acidity burned their throats.
"I wasn't only the lady who'd killed all the geese, I was the lady who'd killed all the geese and then lied about it," she said.
As a result of the geese deaths, Montana Resources and ARCO established new monitoring policies to make sure it wouldn't happen again. Those policies continue to this day.
The companies installed wailers to scare birds off the water. The sounds feature gunshots, a helicopter, alarmed bird calls, or sometimes rock 'n' roll music.
During the migratory season, Montana Resources sends personnel to the pit to check for birds. An employee observes the pit once an hour during the day and once every four hours at night. Mark Thompson, manager of environmental affairs, said MR saw close to 5,000 birds flying over in 2014 but had zero bird mortalities last year.
The dead birds inspired more than just policy changes at the Berkeley Pit.
MSU's LeCain, who gave a talk Thursday at Montana Tech on the snow geese, said he's trying to raise money to create an art project that would memorialize the dead snow geese.
"I don't want a memorial of the snow geese to say the geese were good and humans are bad," LeCain said. "That's not the story I want to tell.
"The copper that came from Butte was so essential to the modernization of the U.S. Not one of us would want to give up electricity. There's that side of the story," he said.
But pulling the copper out of the earth also caused environmental degradation. The geese and Superfund are the other side of the story.
"In some way I'd like to bring those two threads together in a more forward-looking way. We've all benefited from the copper. I'd like it to say how do we live on this planet with other animals. Welcome them here, but still make it good for humans."