Geologists begin drilling in Beach Road landslide, as part of the investigation and monitoring of the stability of the area

In Haines, efforts are continuing to investigate the stability of the Beach Road area devastated by last winter’s deadly landslide. A team of geologists have been working throughout the summer to better understand how stable the ground is now, monitor and warn the public in case of further erosion or slides. KHNS’ Corinne Smith checked in with George Machan, an engineer with the Oregon-based geotechnical firm Landslide Technologies for an update on the landslide investigation and monitoring work. 

This interview was edited for length and clarity.

KHNS: So this week, Haines residents are seeing a helicopter overhead flying back and forth between the airport and the landslide. What’s the latest on the reconnaissance work over there at the beach road landslide?

George Machan: We are beginning a drilling phase of work that will go between now and well into October. And we do expect the helicopter to assist the drilling every day. Throughout the day, as needed, they need to help move different drilling pieces of equipment, but also to deliver water which is essential in their drilling process.

KHNS: What will this drilling work be able to tell us?

Machan: The geotechnical work up to this point has been on the ground surface. So we’ve done walking reconnaissance, and we’ve installed some instruments on the surface. The drilling now allows us to look below the surface, we’re going to drill and get samples of the soils and the rocks to some depth, you know, maybe approaching around 100 feet. And we’ll be able to discern the quality of those materials and how they may influence hillside stability. When we’re done looking at the materials, we’re going to install instruments into the ground. And those instruments will measure groundwater. For example, as rain storms influence groundwater as the storm comes in, we should be able to see an increase in the groundwater response to that. Another instrument that will be installed will be to measure any slippage of the hillside, if it were to occur, we’re not sure that it will, but the instrument will detect it if it does happen. So we will have both groundwater monitoring and potential slope surface or subsurface monitoring of movement.

KHNS: What is the picture of risk? Has that changed at all this summer? What’s the risk level of the landslide now?

Machan: Well, currently I would still consider it a hazardous condition. And so all of our people out there are taking their precautions. What we’re seeing is not much movement, but we have to be aware in case there’s a change in that movement suddenly, but this summer, our work, it’s been conducted safely and we have not experienced any adverse movement yet. You know, I would expect that to change as we go and fall into winter time. 

KHNS: How might that change? 

KHNS: Well, when the seasonal rains start to pick up and the rain infiltrates into the hillside and the groundwater levels start to increase, then the stability should be decreasing. But having said that, it doesn’t mean that the ground will move. We’re just saying that the risk is increasing. And the purpose of our instruments is to see whether movement does occur. We’ll be monitoring how much water gets into the ground, and whether that’s enough to make the ground move.

KHNS: What kind of monitoring tools are you installing, and what kind of measurements are you gathering?

Machan: The instruments that we’re installing on the surface, we call them extensometers. And basically, it’s a cable that stretches across a crack. If the ground moves and the crack opens up, then that instrument is going to stretch, and we’ll record it. So that’s a way of telling us if surface movement is occurring. The instruments that we’re putting inside of the boreholes, we’re putting a long, slender cable with a bunch of sensors in it, that can detect if the ground is deforming or shearing below the surface, whether it’s 10 feet or 50 feet below the surface, it’ll pick that up. And it will show us exactly where that movement is and the kind of shape of that movement. It’s fairly new technology, something has been developed over the last couple of decades. Then the other instrument that we’re putting in below the surface is like deep groundwater sensors and they’ll measure the pressure of the groundwater. So basically, if the water table increases or elevates, it increases the pressure on our instrument, and it measures that pressure. In a landslide, if the groundwater increases, that creates a buoyancy pressure that reduces the stability of the ground. So that’s how that data relates to us assessing the stability of a slope or a hillside.

KHNS: And is there any increased risk with drilling in terms of the stability of the landslide? Should people be concerned about that?

Machan: I would say not. I mean, we are drilling with water, but it’s a very localized water and the pressures involved with our water that we’re using are low pressure. So no, I would personally not be concerned being downslope of the drilling operation. Yeah, I can’t see a risk to the public from our drilling operation. Yes, it’s good that they’re aware of that. But it’s fairly self contained up there.

KHNS: And so what should the public know, in going out Beach Road, maybe to that neighborhood, or there’s a popular trail hiking trail out there called Battery Point – what should residents know in going out Beach Road and going out into that area?

Machan: I would still advise, when taken hikes in the national parks and there are hazards that we should be aware of…you know, you’ve got the wildlife to be concerned about, but also understanding the various geologic slope and landslide hazards here. As we go into the very rainy season, the hazards may increase. So use extra precautions. Be aware, be on the lookout and listening for that

KHNS: Thank you so much, George. Really appreciate your time.

Machan: You’re welcome. 

For more information on the Beach Road landslide investigation and monitoring work, see the Haines Borough’s landslide geosciences web page at hainsak.gov.