DANVILLE – An engineer believes that more heavy rain could cause a landslide on the bluffs overlooking Ellsworth Park on the west side of Logan Avenue, threatening houses and buildings there.
Some damage has already been done. The most obvious sign can be found in the parking lot of Dr. Bhirom Buranakul's offices at 102 N. Logan Ave. in Danville, where the edge of the asphalt parking lot cracked and dropped by about 4 feet.
On June 9, staff at the doctor's office first noticed about a 2-inch crack on the parking lot's west edge, nearest the steep, vegetation- and tree-covered bluff that overlooks Ellsworth Park.
Since June 9, the asphalt, curbs and hillside on the west side of the crack have continued to subside, to a measured 4 feet on Friday afternoon. The fissure runs generally north and south along the top of the bluff about 100 feet from just behind the large house that is Buranakul's offices across the west edge of his parking lot to the apartment building directly north.
But the cracks and fissures continue farther north and have affected five other buildings – two vacant apartment buildings, two owner-occupied homes and one apartment building.
Tammy Lopez, who has lived in one of the owner-occupied houses for about 12 years, brought the issue to the attention of city officials. Large gaps between the hillside and foundation have appeared at the back of Lopez's house, and one corner of the foundation has broken away from the rest of the structure.
Mayor Scott Eisenhauer said the city was contacted a few weeks ago by one of the homeowners, asking if someone could take a look, and City Engineer David Schnelle did and observed some movement and shifting. Eisenhauer said more heavy rains came and more slipping began to occur, and then the doctor's office notified the city of cracking in the parking lot.
Eisenhauer said the decision was made that more information was needed about the nature of the erosion, so the city contracted with Midwest Engineering Services Inc. in Champaign for an assessment. Earlier this week, the firm assessed the situation, and Engineer Daniel Tappendorf provided a written report, stating that water is seeping out of the hillside about halfway down and many of the trees on the slope are leaning.
"The sloped area contained debris on the surface, which is an indication that much of the sloped area could be comprised of miscellaneous fill material," he wrote.
Tappendorf said, based on his observations, a landslide is occurring on the slope starting near the west, or back, walls of the buildings and continuing about halfway down the hill where water was seeping out. Heavy rains in past weeks have caused the slippage, he continued, because of a significant increase in soil moisture and ground water levels. The saturated soil conditions not only increase the weight of the soil, increasing its tendency to slip down the slope, but also decrease resistance to slippage by reducing the internal friction of the soil.
"It should be understood that some slope 'creep' likely has been occurring for many years based upon the leaning trees observed," he wrote. "The soils appear to be moving relatively slow and incremental at this time, but it is possible that a sudden large landslide could occur especially during a rain event if water is allowed to flow into the cracks that have developed in the ground surface."
Tappendorf added that it would be prudent to limit occupancy in the residences until the foundations for the structures have been underpinned to stable ground or the slope stability issue has been rectified.
Once the city received Tappendorf's report, city officials met with each property owner and relayed the information.
Eisenhauer said the residents were not told to evacuate their homes or that their homes were in imminent danger, but were told that the engineer had some concerns regarding movement of the land.
"We are not forcing or mandating an evacuation; that brings with it some different legal issues," Eisenhauer said. "What we are doing is simply informing the residents of the information we have in our possession, and sharing the opinion of the engineer..."
Buranakul is definitely concerned about his offices, but not worried about it structurally, because the fissure is far enough behind his building, at this point, that he believes it won't be affected structurally.
But cracks and separation are affecting Lopez's house and others further north, and she is concerned about it sliding. She and her three children continue to live there, and she doesn't believe the whole house would go if the hillside gives way, only the backside of the house.
"If it's going to go, it's going to go," said Lopez, who had her children move some of their things from the back of the house to the front.
Lopez said the same thing happened about 10 years ago, and the gap between the ground and the corner of her garage, which sits furthest west, was big enough a person could walk underneath the garage foundation. She said dirt in dump trucks was brought in to fill it, and Lopez claims ground on city property gave way at the bottom of the hill 10 years ago, causing movement up toward her house.
But Eisenhauer said it's private property along the hillside, and the lots go a significant way down the hill to the toe of the slope. At this point, he said, the situation is the responsibility of the property owners.
But, he said, the city is going to pay for a second study that will include soil borings, which Tappendorf recommended, to determine the true scope of the situation and determine what options could resolve the issue and the cost of those options.
"We will share that information with the property owners, too," he said.