n May 31, 1889, after several days of rain, water poured over an earthen dam owned by the South Fork Fishing and Hunting Club, eroding it and then breaking it, flooding the city of Johnstown 14 miles downstream, killing 2,209 people.
In the years prior to the catastrophe, the owners didn't maintain the dam properly, falling into sins of commission and omission, setting up for failure. When the dam let go, warnings were not believed at first and unsystematic. Evacuations consisted of getting to high ground if you realized what was happening soon enough and you could make it.
It's still the deadliest dam break in U.S. history.
It's emblematic of what carelessness, inattention and lack of planning can mean when there's a dam upstream from you.
As the Association of State Dam Safety Officials says in its online package, "Living with Dams," failures are "low probability but high consequence."
A few months ago, notices posted on a wall in the Blair County Courthouse, just outside the prothonotary's office, caught a Mirror reporter's attention.
They were nondescript - but the reporter thought them interesting enough to mention to an editor.
They attested to the availability in local municipal offices of emergency action plans for high-hazard dams in Blair County, including 11 for which the Altoona Water Authority is responsible.
"Every three years, we have to submit updated plans to the state and federal governments," said Dan Boyles, the county's emergency management director.
The plans are hardly stirring.
Chapter headings include "purpose and scope," "situation," "concept of operations," "administration and logistics," and "exercise and training."
The 11 authority plans comprise 291 pages collectively, not counting the big inundation maps that are electronic attachments.
The key components of each plan are descriptions of procedures for "surveillance, warning and evacuation," as stated on the cover pages.
Monitor the dams, alert the people when something bad may happen, and get them out of the way, if it comes to that.
The detail is extensive, even excruciating:
"Of those 2,850 structures, roughly 400 are businesses and 2,450 are residences. According to the U.S. Census Bureau's 2010 tabulations, the average household size in Blair County is 2.39 persons; therefore, the population living within the inundation area is estimated to be approximately 5,850 people," it states on page 1 of the Lake Altoona plan.
That plan tells the chief operator of the dam when he needs to begin emergency surveillance - such as when there's a flash flood warning.
It tells him when to issue an early warning - such as when the water in the lake reaches 9.5 feet from the top of the dam.
It tells him when to issue a warning and evacuation notice - such as when the water level reaches 8.18 feet below the top of the dam.
Authority officials keep an eye on the dams any time there's a major rainfall, said authority engineer Kathy Pike.
The plan also tells Blair County 911 whom to contact when there's a dam emergency - including the Blair County Emergency Management Agency, the Pennsylvania Emergency Management Agency and 29 other agencies - mostly police, fire and ambulance departments.
It tells the Blair County Emergency Management Agency to notify local municipal emergency management agencies, relief organizations, the media, PennDOT, elected officials, hospitals, school districts and even Logan Valley Mall.
The plan attachments designate a total of 58 traffic control points, provide a phone roster and list mass care centers.
The inundation map tells where the water could go, although it doesn't indicate the depth of flow, according to Pike.
Clearly, the plans require lots of work.
But it's work that can pay off.
In September, a "super" rainstorm hit the Boulder, Colo., area, causing flooding so severe that half a dozen dams failed, according to Lori Spragens, executive director of the Association of State Dam Safety Officials, headquartered in Lexington, Ky.
But they were all low-hazard dams.
None of the area's high-hazard dams were among the failures.
It wasn't an accident: they'd all been inspected and upgraded as part of the same basic dam safety program reflected in the courthouse postings in Blair County.
Was that an accident? Or an example of how the program can work?
"It's a perfect example," Spragens said.
Dams are not something many people seem to worry about - even when they live downstream and nearby.
Ethel Jones of Valley Avenue, not far from the three dams up the valley near the Horseshoe Curve said, "I never think about it."
Valley Avenue is within the dam's failure inundation area.
It's never flooded at her house, she said.
Is it a good idea to have emergency action plans, just in case?
"Yeah," she said. "You never know what's going to happen."
Is she worried the dam might break, triggering the need for the action detailed in the plan?
"Noooo," she said.
"I don't think about them being up there," said Jones' Valley Avenue neighbor Bonnie Novack of the dams. "They've been up there as long as I can remember."
She's lived there 36 years, and her property hasn't flooded, even in 1972 with Hurricane Agnes, she said.
Farther downstream, near the Miracle League ballfield, Kathy Holmberg said she had been unaware her house was in the inundation zone.
There's no dam looming in the vicinity.
She wasn't worried after finding out it was, she said.
So unworried she joked with her daughter Christine Dively - who lives next door - about not getting a place on the Divelys' fishing boat for lack of room, if there would be a flood.
"I'll throw you a life preserver," Dively said.
It was no joking matter when, in July 1977, Holmberg's brother-in-law took his boat to help with rescues in the Tanneryville area of Johnstown, after the Laurel Run Dam broke there, she said.
Safety planning is a good idea, Holmberg said.
It improves the odds, like getting your brakes checked, she said.
The association doesn't necessarily recommend worry, but it urges people buying a home to learn whether it's in a dam failure inundation zone.
It's sometimes hard to tell.
Few people would realize that the area around Newry and Wall streets in Hollidaysburg - for example - are in the Lake Altoona inundation zone.
The association suggests contacting the state dam safety agency, the local emergency management office or the local soil and water district office for the necessary information.
"Ask questions about the dam's condition and hazard potential," the association website urges.
Agencies should be able to rate the dam's hazard potential, say when it was last inspected, tell it's condition, reveal whether the owner is financially capable of maintaining the dam and provide an emergency action plan, if tehre is one, the association website states.
Owners of homes in inundation areas should learn evacuation routes and the method of warning in an emergency, the association states.
"And always heed warnings to leave," the website said.