#14 Postby TexasStooge » Wed Feb 16, 2005 9:53 am
Report: Saturation led to Irving landslide
By RUSSELL RIAN / The Dallas Morning News
IRVING, Texas – An engineering report blames saturation from lake water over decades and heavy rainfalls during the last year for softening soil and causing a landslide near several homes at Vilbig Lake in south Irving this month.
Residents whose homes back up to the lake awoke about midnight Feb. 1 and found that their back yards had sunk 6 to 8 feet. No injuries were reported, but the landslide collapsed decks, toppled birdhouses and broke fencing across a 250-foot swath through five yards in the 1200 block of Lakeshore Drive.
"There is not an immediate danger to the homeowners," said Jim Cline, Irving's public works director, but, "We do know that steps will need to be taken to secure the homes for the future."
Mr. Cline said he did not know whether any other homes were in danger, but the city has no plans to do further investigations in other areas, and he said homeowners would be responsible for fixing their property.
Homeowners said they want to check out the original plans for the area to see whether it was properly filled but will have to meet to discuss what to do next. Residents said insurance is unlikely to help pay for any repairs.
"We're looking for some help if there's anything that can be done," said Jim Ferguson, whose deck collapsed in the landslide.
The city has fixed slope failures on public land, along highways for example, but does not fix erosion problems on private property, such as when landscaping timbers serving as retaining walls collapse, Mr. Cline said. All the land involved is private property along a private lake, he said.
"We've got to be very careful stewards of the city dollar, and to make improvements or repairs to private property is outside the scope of that," he said. "We certainly recommend the homeowners go ahead and start looking at what they need to be doing to preserve their property."
The city will be looking at fixing a city drainage pipe adjacent to the landslide area that will require further study. Mr. Cline pledged to share any engineering data, such as soil samples, with the affected residents, which could save them some expense. He also offered to help residents garner funding from other agencies if it's available, but he said he was not aware of any federal or other funds from other agencies that would help.
Homeowners have taken temporary measures to divert rainfall in the meantime.
"We've got all our back yards covered with tarps to keep rainwater out of the soil and to keep it from further eroding," Mr. Ferguson said.
Homeowners also have put in temporary piping to divert water.
"It seems to be working," he said. "It's keeping the soil from collapsing any further."
A seven-page report by Dallas-based HBC/Terracon released Tuesday concluded: "The landslide appears to be the result of the loss of soil strength and water."
Developers used a highly plastic clay as fill when the area, a former sand and gravel quarry pit, was developed about 1983, the report states. Water seeping from the lake and rainfall – which was at near-record levels in 2004 and into this year – gradually softened the clay, causing the ground underneath to slip.
"Slope failures are not unusual for 20-year-old slopes constructed with highly plastic clays," the report says. "The large rainfall may have been a large contributor to why the slope failed when it did."
Terracon officials, who also are working on possible further studies needed to repair the city's pipe, could not be reached for comment. The city has spent less than $1,500 on studies so far, Mr. Cline said.
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