It turns out the St. Paul parks and recreation department was warned about erosion problems at Lilydale Regional Park four years ago.
The warning came in a management plan for the park written by an environmental firm. Since then, there was another landslide that park advocates say should have served as a warning sign.
"This park really has been neglected for about 30 years or so," said Jon Kerr, head of the Friends of Lilydale Park.
Kerr knows nearly every inch of these trails. He's also familiar with every danger point, especially the one he led us to near the popular fossil beds.
"You're looking at remnants of a giant mud slide that happened about two years ago," he said.
The slide happened in May of 2011 after another series of rain storms. So much dirt and tree debris washed down the side of the bluff that Kerr said it temporarily created a new landscape.
"It literally came here and stopped up this waterfall for a while, so there was like a swimming hole for about three weeks that people were using and then it let loose and let all the mud come down the hill," Kerr said.
University of Minnesota soils researcher, Prof. Satish Gupta, said this type of river bluff erosion is very common after extended periods of rain.
"Water is trying to get out and the strength of the soil is very, very low so what you have is a failure plane over here and this mud is just going down over here," Gupta said.
Despite the 2011 slide, the park remained open. Tragically, it's the same kind of slide that happened again on May 22, killing two St. Louis Park students on a field trip.
Mohamed Fofana and Haysem Sani were fourth graders at Peter Hobart Elementary. Both were hunting for fossils in the east clay pit area along the bluffs when they were buried by the landslide.
Pictures of another class in the area the day before the accident show children climbing the bluff walls.
But this latest landslide happened in nearly the exact location as the 2011 landslide. In fact, along the same bluff line, about 50 yards away.
"It's always been an area that people are familiar with, the park would know might be a dangerous area," Kerr said. "But there are really no other warning signs for people who wouldn't know the area."
But a 2009 management plan for the park did see the warning signs. It reported that "erosion along the walls of the former clay pits should be evaluated and prioritized for stabilization."
The management plan recommended an erosion inventory to "identify potential approaches to controlling erosion at each point" and to "identify any site issues related to potential improvements."
The plan said such an inventory would cost the parks department between $11,000 to $15,000.
"That study was never done," said Brad Meyer, public services manager for the St. Paul parks and recreation department. "It's something that we didn't see an immediate cause for concern. So within the certain window of time we felt comfortable that we'd be able to take a closer look at it. And we just haven't gotten to that point yet."
But some members of the public have persisted. In a 2012 environmental assessment of the park one woman commented, "I'm seeing a hugely disturbing amount of erosion by Hidden Falls...where is the plan addressing that?"
The parks' department's written response read, "resources within the park including the bluffs, lake and wetlands will continue to be protected and enhanced as funding is secured."
"I think when you look at the entire bluff corridor, and Lilydale specifically, any time you're dealing with managing that type of activity funding will always be an issue," Meyer said.
At the very least, Prof. Gupta said some kind of erosion survey should have been done.
"If there's some problem that it's going to cause some failure and some lives are going to be lost, it's very, very important," Gupta said. "If it's a public area that they should be doing that kind of survey so if that slope is going to fail that they should kind of barricade the area to prevent the people from going in there right after the rain falls."
In fact, there are already barricades. At the popular Ventos View, an iron gate was placed years ago to prevent hikers from getting too close the bluff that is eroding just a few feet away.
Since the landslide deaths, the city has closed the park to hikers. It has also hired an engineering firm to investigate the accident. Crews are currently drilling test bores.
Shoring up the bluffs can be done with rocks. Gupta has advised several successful projects along Minnesota and Le Sueur rivers. Along the Mississippi River, St. Paul parks recently completed its own erosion control along north landing park.
"But depending upon how tall the slopes are or the banks are, it can get very expensive, but if any lives are going to be in danger I think it's worth doing it," Gupta said.
But all of this comes after a deadly landslide disaster --one that Jon Kerr believes should not have happened.
"I don't know that anything could have absolutely prevented this, but we do know that there were a lot of warning signs and each time there were warning signs, St. Paul parks had other priorities," Kerr said.
Meyer said although the department knew an erosion study was a high priority recommendation, they viewed erosion as a long-term threat to the park. Had they known this posed an immediate threat, they would have taken action.