A geologist at the Minnesota Department of Natural Resources said a city of St. Paul consultant didn't fully consider man-made factors that could have contributed to a landslide that killed two children in a city park last year.
Ryan Benson, a senior engineer with Northern Technologies Incorporated, discounted the possibility that man-made factors caused the bluff at Lilydale Regional Park to collapse.
But Carrie Jennings, a DNR geologist who was in the park the day of the incident, said that report was based on faulty assumptions.
• May 2014: District to pay victims' families $200K
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As evening fell on May 22, rescuers were on the scene of the landslide that had severely injured a fourth grader from Peter Hobart Elementary. Another student was dead, and a third was still missing. Conditions in the park were treacherous.
"First responders were having rocks starting to come down on their heads, and they wondered how safe it was," said Jennings, whom authorities called in to advise them on the geology of the area.
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The missing child was presumed dead, and the search was eventually called off that night.
Jennings, who has spent 22 years at the Minnesota Geological Survey and specializes in ravines like the one where the landslide occurred, returned to the site the next morning to help with the recovery effort. A tree part-way up the bluff posed a potential threat to the people searching for the body.
"They were just pulling and pulling on this tree, and it was like a tooth that just didn't want to give," she said. "It took probably a good half hour to get it out. And the sand that was unraveling as they were messing with this and was just raining out was dry."
For Jennings, that dry sand was an important clue, one that undermines the official conclusion reached by the geotechnical consulting firm the city hired to determine what caused the bluff to suddenly collapse. Northern Technologies Incorporated said recent rains had saturated the soil of the bluff, making it unstable.
At a news conference last year, Benson said his analysis pointed to natural causes.
"We can find no evidence that recent man-made activity was a trigger for this event," he said.
Jennings disagrees. Her theory is that storm water from a nearby culvert eroded the rock ledge that supported the bluff. The rock cracked and fell. The dry sand above it came pouring down, burying the children below.
After the official report came out, the geologist shared her analysis with St. Paul's Parks Department, but spokesman Brad Meyer says officials there weren't persuaded by it.
"What we have is an in-depth analysis that spans multiple weeks and findings and conclusions that we still stand behind, versus an observation that was maybe a matter of an hour or two either being on site or assessing the situation," Meyer said.
Jennings' report to the city was first brought to light earlier this week by Jon Kerr, a member of Friends of Lilydale Park who obtained the documents through an open records request. The group has long been critical of how the city has managed the park.
Kerr suspects St. Paul would rather not re-open the question of what caused the landslide.
"I can only guess that they're embarrassed. They've paid out a lot of money, and something horrible happened," he said. "We all agree, but they don't want there to be a lot more discussion about what happened before the incident, and what was known."
The city paid legal settlements to the families of children killed and injured in the landslide, totaling more than $1 million. It's also spent more than $250,000 on consultants.
An engineering firm is exploring whether there's a cost-effective way to make the bluffs safe enough to reopen the park.
But Jennings, the DNR geologist, said the city first needs to understand the root cause of the landslide. She argues that the key is better storm water management, especially important for sensitive areas prone to landslides like Lilydale Regional Park.
"We have a lot of rules about what you can do in the floodplain. And we have a lot of rules about how far back you are setting a structure from the edge of the bluff top," she said. "But that area in between — the Twin Cities is just loaded with those areas — we don't tell people how water can be managed going down those slopes."
That's especially important for sensitive areas prone to landslides like Lilydale Regional Park, Jennings said.