Riverdale landslide activity expected to increase as spring runoff approaches

RIVERDALE — Geologically speaking, things are about to get interesting along the Spring Creek Road Landslide.

The landslide, which first occurred Nov. 19 and eventually forced the mandatory evacuation of three Riverdale homes atop the bluff, has been active ever since — losing a chunk here and there as portions of the cliff continue to slough off.

And now, a flurry of activity in the last two weeks seems to point to increasing activity along that slide face. At least five GPS points set along the top of the hill to monitor motion have dropped over the side of the expanding cliff.

“The slide is more dramatic now,” said Ben Erickson, a project geologist with the Utah Geological Survey who has been one of the experts keeping an eye on the landslide.

Erickson suspects there will be even more movement along the slide as more flowing water — which has been blamed for the disaster — is introduced into the area in the next few months.

“We haven’t even seen the high point of any spring runoff or storms yet,” he said. 

The slide area will probably see two peak groundwater flows this year, Erickson said. The first will hit in the spring, as the snow in the mountains melts and that water flows down into the valley. One bright spot, he said, is that Northern Utah is below 60 percent of normal snowpack this year, so the slide area won’t see as much spring runoff.

The second peak groundwater flow will occur this summer, Erickson said, when residents begin watering their lawns again.

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> Victims of fast-moving landslide vent frustrations to Riverdale City Council

Still, it’s not an exact science. Erickson says groundwater is a tricky thing, and it can shift and fluctuate, finding new flow paths beneath the surface.

“It’s just hard to say, because we’ve spoken with neighbors who’ve lived in the area since the 1950s, and they’re amazed at how much water is coming out of the spring at this point,” Erickson said.

FRUSTRATIONS WITH RIVERDALE CITY

Some residents are still critical of the city’s handling of the disaster.

Louis Donovan, who owns one of the three homes under mandatory evacuation, is currently living with family. He says he’s frustrated that the city would tell him he can’t live in his home, but then tell him it can’t do anything to help.

“How do you have it both ways?” he asked. “They’re telling me, ‘You can’t live here, but you can continue to pay your mortgage.’”

Donovan says he’s upset that it was the city, not him, that decided whether or not he could continue living in his home. He said he’s already filed for loan forgiveness with his mortgage company.

“I’m not looking for someone to bail me out here, but I’m also not looking for the city to tell me they’re smarter than me,” he said. “Where is my freedom? I probably would have evacuated anyway, but I didn’t get that option.”

Donovan said he believes that water leaking from city pipes has been contributing to the landslide. He pointed to a leaking valve box on 600 West, near the evacuated homes.

Meanwhile the edge of the landslide creeps ever closer to homes atop the bluff. As of last week, the slide was just 28 feet from Donovan’s house, the northernmost of the three evacuated homes, and Erickson projects it could be the first to go. The two other homes, he said, are now within 40 to 50 feet of the slide face.

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Riverdale Fire Chief Jared Sholly said some homeowners seem to think the city is hiding something, or that it’s dragging its feet, and he said that’s just not the case.

“In some fashion, they think we’re getting information on a daily basis, and that we’re not sharing it with residents,” Sholly said. “That’s just not true. We often just don’t have any new information.”

The city has had survey crews going in on a monthly basis to map the slide, but on the last outing, one of the surveyors had to be rescued when he got trapped up to his chest in mud that acts like “quicksand.”

“It’s become too dangerous to bring in surveyors, so now we’re doing drone flights to monitor the slide,” Sholly said.

Sholly concedes it’s a bad situation all the way around.

“The fact is, these people are losing their homes,” he said. “They’re losing everything, and we sympathize — I can’t imagine how horrible that would be.”

At the same time, Sholly insists the city is in a similar predicament.

“We don’t have control over certain things, and Mother Nature is one of them,” he said.

MORE COMPLICATIONS

At last week’s Riverdale City Council meeting, city administrator Rodger Worthen reported on the slide’s movement.

“It’s in the shape of an hourglass, if you will,” Worthen said. “It’s kind of moving both north and south, as well as eastward.”

Although the northern section of the slide has been active and is the closest to a home, the southernmost section has accelerated the most in recent weeks, according to Erickson. As a result, the city has issued a voluntary evacuation of a fourth home directly to the south of the others.

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Geologists and city officials have been seeing chunks of land falling since November, but now that it’s reached neighbors’ property lines it illustrates just how active and dangerous the slide is, according to Erickson.

“We knew things were falling off, but once it reaches the high point of the hill and gets into neighbors’ yards, you can visually tell how active it’s been,” he said. 

All along, geologists have said that the slide will continue until it finds its “angle of repose” — usually about a 45-degree slope. Although Erickson says the slide is beginning to develop a bit of an angle, it’s still extremely steep.

Usually, as material falls off a slide such as this and collects at the base, it buttresses the slide face, eventually making it more stable. But with all the water coming out of the side of the hill, Erickson says that material doesn’t have as much of a chance to collect at the base of the slide.

The landslide is also affecting a Union Pacific Railroad service road that lies between the hillside and the railroad tracks through that area. Justin Jacobs, a spokesman for Union Pacific, said his company is aware of the problem and is working to maintain access to that service road.

UP is also working with Weber County on a potential mitigation plan, Jacobs said. 

“My understanding is the water source is off our property,” he said. “But for us, the big thing is safety, and what comes next.”

Also at last week’s city council meeting, Worthen said that, thus far, the city has been unable to find any entities willing to help homeowners. He said the city was “flatly declined” by the Army Corps of Engineers, and requests for assistance from the Environmental Protection Agency regarding asbestos removal in one of the three evacuated homes were also declined.

However, using the city’s “dangerous buildings” code, Sholly said the city opted to pay for the removal of asbestos from the home.

The Smithfield-based Abate X Environmental Services Inc. was called in last Friday to deal with a “popcorn ceiling” and small floor tiles containing asbestos. The work was completed Monday, March 12.

As the precipice draws closer to these homes, Sholly says the question becomes: “Do you tear down the homes now, or wait to see if the slide stops but risk losing them over the side of the cliff?”

Right now, he said, the homes are structurally sound. And he isn’t certain the bluff would be stable enough to bring in heavy equipment to raze the homes.

If the slide continues on its path, city officials will be faced with the possibility of having to permanently close a section of 600 West, Sholly said. 

Contact Mark Saal at 801-625-4272, or msaal@standard.net. Follow him on Twitter at @Saalman. Friend him on Facebook at facebook.com/MarkSaal.