A distressed slope in the area of Dickson Road, Miller and Farren streets will require $7 million to $15 million to fix the landslide-prone area, according engineering and borough officials.
A preliminary geotechnical engineering evaluation from Pittsburgh-based Garvin Boward Beitko Engineering, Inc. indicates that the distressed area of Dickson Road at the sharp elbow intersection with Miller Street is constantly moving as a result of landsliding. The landslide area also affects Farren.
Sewickley Manager Kevin Flannery said a letter was being sent to residents notifying them of plans to monitor the situation and provide as much continued road maintenance as possible.
“There are no plans to do any kind of reconstruction of the roads,” Flannery said.
Borough officials plan to meet with the engineers and residents of the Dickson Road area to discuss the engineering findings and potential solutions.
Flannery said Sewickley's road program is updated annually and $7 million is a substantial amount to spend on fixing any one road. In contrast, the borough receives about $1,100 in annual state liquid fuels funds for the area.
“I think we’ve done our due diligence by going and doing the core boring analysis. We always study every road before we try to repair it.”
Based on test borings, mapping and geological studies of the site, engineers said the location shows telltale signs of ancient landslides that have continued to creep down-slope over the years, due to the unstable hillside condition.
Flannery said problem started 600 years ago. Early settlers built homes in the landslide-susceptible area when they shouldn't have.
"Nothing should have been built up there," he said. "You can't change what's already been done."
A multi-tiered retaining wall system, coupled with extensive site grading would be required, according to the report, which determined this. This would likely affect the geometry and location of some of the residential properties and dwellings, as well as utility locations, the report says.
The engineers estimate the retaining wall system and grading would cost between $7 million and $15 million to complete. This estimated cost range does not include "utility relocation, paving, acquisitions of property, construction-phase engineering evaluation/inspections, etc., required to construct such an extensive wall system.”
“Attempting to stabilize such a geologic feature," the report says, “would be challenging, as well as costly.”