Landslides are a natural phenomenon that can happen anywhere. But did you know that most Pennsylvania's landslides happen in the southwest region? The unique geography presents a challenge for local PennDOT teams as they perform critical work to restore infrastructure impacted by landslides.
Due to the large presence of claystone rock, the southwest region of the state is more susceptible to landslides than any other area of Pennsylvania. In fact, it is one of the more landslide prone areas of the United States. The claystone rock in the southwest region of Pennsylvania is often referred to as the Pittsburgh Red Beds, getting its name from the sedimentary rocks that are typically red in color.
The claystone rock that makes up the Pittsburgh Red Beds is very hard when confined underground. However, it can become weak when exposed to air or water. When the claystone rock turns weak, it can cause a downslide movement of rock, debris, or earth. These landslides can happen over a long period of time, or suddenly.
"Most of our rockfalls are also caused by red beds. The red beds in cut rock faces along highways can erode over time, which cause the stronger rocks above them to lose support and fall," said District 11 Civil Engineer Manager Daniel Bliss, P.E.
Smaller landslides may not cause a lot of damage, but larger landslides can cause damage to buildings, homes, utilities, and impede transportation routes. Allegheny County has a geotechnical crew that fixes these larger landslides. This year, the crew fixed a total of 29 landslides in six months.
"I'm just really proud of this crew. They worked hard all summer to get these landslides repaired," said Allegheny County Assistant Highway Manager Brad Stevens.
In 2016, Stevens worked as a foreman on the geotechnical crew that repairs landslides before moving into his current role. Now, he manages the crew and helps to plan the repairs. One step of the repair process is to identify if water was the cause of the landslide.
"We face a lot of uncertainty when going into a project. We start observing in the winter, but they could get worse or stay the same," Stevens said. "We don't know what is under the road until we start digging."
If the crew finds a spring or other source of water, they redirect the water out and away from the slide, so it does not cause another slide to happen somewhere else.
The crew started the construction season in April with a goal to repair 27 landslides, meeting and surpassing the goal with two more repairs completed before their end date of October 6. One major repair project this year was Route 1016 Log Cabin Road, which had several large landslides. The geotechnical crew was able to complete the repairs and get the road reopened for traffic after being closed for nearly 10 years.
"It's a team effort. I'm able to plan the repairs, but the foreman and the crew carry the weight. They were unstoppable this year," Stevens said.
Members of the geotechnical crew include Vincent Provenza, David Borowski, Jason Jones, Michael Jordan, Colin Eckroat, Nicholas Sterling, Lance Anthony, and Scott Brady.