Under the influence of 60-degree temperatures, Mt. Roberts sent an avalanche down to clog Gold Creek on Monday afternoon.
The toe of the slide, estimated at 30 feet deep, significantly slowed the flow of water in the creek. That forced Alaska Electric Light & Power to turn off creekwater-powered generators in its plant on Capitol Avenue downtown about 3:42 p.m, said Gayle Wood, office manager for AEL&P.
"Our Gold Creek facility is not producing any power right now because there is no water going into the flume - insufficient stream flow to run the turbines," Wood said.
The plant is "a small producer at best - producing only 2 to 3 percent of our capability" and the other three Juneau electric plants - the largest at Snettisham - have plenty of water at this time of year, Wood said.
Volunteer firefighter Greg Germain, who took photos about three hours after the avalanche, said the slide went all the way across Gold Creek gulch, about 200 yards above the Last Chance Mining Museum.
"It's right underneath the overlook on Perseverance Trail. It's hard to judge how deep it is because
everything is so immense there, but I would guess at least 30 feet," Germain said.
Juneau police sent an officer to survey the slide, said Capt. Tom Porter.
"He reported back that water was flowing through it, and it looked like it was opening up," Porter said. "Time and nature seemed to be taking care of it without any catastrophic release."
When Renee Hughes and Gary Gillette, who live at the Last Chance Mining Museum, arrived at the museum's parking lot about 9:30 p.m. Monday, they immediately knew something had happened.
"The air definitely has a heavy smell of mud because the slide did bring a lot of debris in it," Hughes said. "You could still see a lot of turbidity in the water and there were big chunks of snow in the creek. I have never seen it go that far to the left of the chute."
A tourist arrived at the mining museum in a cab last weekend, Hughes said, and stated, "Oh, I don't want to see the museum. I want to go crawl around on the snow."
"I said, 'You must be the most stupid individual I have known in this life,' " Hughes said.
A museum volunteer noticed someone climbing the snow in the gulch on Saturday, and Hughes was horrified at the possibilities. "We have seen so many search-and-rescues up here, it's not funny. People from out of town just don't know (about the avalanche danger)."
According to police and firefighters, no one was exploring the chute when the avalanche happened.