The City of Muscatine will continue to monitor the area known as Miller’s Hill (Fletcher Avenue) with no plans at the present to reopen Fletcher Avenue to traffic.
The section of Fletcher Avenue running up the area known as Miller’s Hill from Hershey Avenue has been closed since July 3, when a mass earth slide was discovered encroaching onto the roadway.
The threat of additional slides that could present a danger to the public prompted city officials to close the street from the top of Miller’s Hill to Hershey Avenue indefinitely.
“We know how important this road is to the people who live in the neighborhood,” Brian Stineman, Director of the Department of Public Works, said. “But the safety of the public is our primary concern and until those concerns are alleviated, we will keep the street closed.”
Stineman, a geology major in college, presented an update to the City Council at its Jan. 9, in-depth meeting, detailing the cause and effects of the erosion-mass movement where a large mass of sediment breaks away and drops down a hillside.
“What we are dealing with is the movement of soil from the scarp, or the bare face that is created by the ground moving, to the toe, or, in this case, the road,” Stineman said.
A study of the movement was completed in 1973 but the area has been prone to movement even before that study. In the last 20 years, the Roadway Maintenance Division has removed soil and trees (usually 1-10 dump truck loads of material per event) and has been able to reopen the street.
“In the past we have been able to handle these small slides and keep the street open,” Stineman said. “The difference this time is that the scarp, crown cracks, and transverse cracks indicate that this is a very large area with a much larger potential to move.”
The area of the slide could potential mean that it would take 450 to 500 dump truck loads to remove the slide when it has been taking only one to 10 dump truck loads in years past.
“That is enough to make me pause,” Stineman said.
If that area would move at the same time, Stineman said we would be talking about a very serious incident. One of his concerns is the potential for someone to be in that area, not aware of the danger and drive into a massive earth slide.
“The concern for public safety is why we chose to close the road in the first place,” Stineman said.
Something else that would have to be considered is the cost of the cleanup of the massive amount of material that could flow onto and over the roadway. The cleanup and roadway repair expense might be too high and would take away from other needed infrastructure improvements. The City would then have to determine if it would be best to just leave the material in place and keep the roadway closed.
“This is the only connection between Lucas and Hershey from Houser to Main Street, and has great value to the residents who live in that area,” Stineman said. “We are looking at a variety of options but this is not the right time to attempt any work on the hillside in hopes of opening the street.”
The city attempted to remove some of the soil at the toe (on the roadway) but the hillside began to move and the work was abandoned.
“Right now the only thing holding up the rest of the hillside is that toe,” Stineman said.
Soil Testing Services of Iowa, Inc., performed a study in 1973 on the ground movement and the successor to that company, Terracon, submitted a quote of $10,500-$50,000 for a geotechnical evaluation and slope stability analysis. The 1973 report also indicated that it might be possible to regrade the hillside to a 2:1 slope, remove the trees, and install sub-drain tiles and a retaining wall. However, what would have cost approximately $30,000 in 1973 is now estimated to cost $500,000. And that is without any repairs to the roadway itself.
“It may not even be feasible now to grade the hillside back,” Stineman said. “And there is no guarantee that further mass movements would not occur in that area.”
The Department of Public Works also reached out to companies that could use a long reach hoe to scrape back the toe of the slide and cut the tops off the trees in the slide area while leaving the root system in place with Braun’s Excavating submitting a quote of $17,500.
The City Council agreed with Stineman’s assessment of the need to continue monitoring the hill while also agreeing to discuss the Braun Excavating proposal during the upcoming budget hearings.
The last time the city closed the road was on April 18, 2013, due to the potential of landslides.
— City of Muscatine