Highway 97 update

Blast on the problem slope on Highway 97 (from CBCnews)

Attempts to deal with the slope problem on Highway 97 in Canada continue in a quietly controlled manner, and there are now some signs of success. The focus continues to be upon small blasts at the head of the slope to remove material, which is then transferred to the toe to support the mass and to protect the highway. The size of each blast is now reportedly 2000 cubic metres. The result of this work is that the rate of movement has slowed from over 10 mm per day to 8 mm per day now. However, care is needed in interpreting these movement data as the reduction could be caused natural variation or response to another stimulus (the slope could be draining for example).

Meanwhile the road is still closed indefinitely, and Houdini the goat appears to be in good health!

Did you hear the one about a goat in a landslide?

A bit of light relief over at the Highway 97 site in Canada, which continues to slip. Arthon have a pictorial report on their website of the rescue of a mountain goat that had fallen down the tension crack and become wedged 10 m below the surface (all images from the Arthon website):



Fortunately, the goat (now named Houdini) was spotted and a rescue was put in place. Enter the gallant abseilers (you wouldn't mess with these guys on a dark night):


They abseiled down and tranquilised the goat, who was then hauled back to safety:


Meanwhile the slope is still moving 10-15 mm per day and as a result the road is still closed. A water taxi has starts on Saturday morning to allow people to get around the blockage.

Hat tip - Andrew Giles again.

Highway 97 latest update

The latest update on the Highway 97 landslide in Canada (see here and here) is as follows:

1. The slope is still moving. Between 19:00 on Monday and 14:00 on Tuesday the mass moved about 15 millimetres (i.e. about 0.8 mm per hour). This is quite high for a large mass. The rate of movement is described as being constant;
   
2. The mobile volume is now estimated to be 200,000 cubic metres;
3. The road remains closed (unsurprisingly!);
4. There are provisional plans to remove material from the top of the unstable slope and to move it to the toe. The aim here is to reduce the mass that is driving the movement and to increase the mass that is supporting it.

I am sure in the background there is an enormous amount of work going on. Analysis of the pattern of movement in time and space, especially by looking at vectors of movement and accelerations and decelerations will give a pretty good idea of what is happening in the slope. This gives a potential for providing a short term warning of an impending collapse, but does not really tell us how likely this is in the medium term.

Interesting slide on Highway 97 in Canada

Thanks to Andrew Giles for bringing this one to my attention. Highway 97 in British Columbia is currently being upgraded through the Okanagan Valley (Fig. 1). This project is being undertaken by Arthon - their project website describes this as:

"Four lane roadworks and 1,000,000 m3 rock removal over a 7 km section of BC's main north-south highway corridor. The B.C. Ministry of Transportation awarded Arthon Contractors Inc. a $38.6 MM contract to complete roadway construction by summer 2009".

Fig. 1: Google Earth image of the location of the problematic slope on Highway 97.

The rock removal appears to be a widening exercise in which a substantial amount of rock has been removed to create a platform. Unfortunately, last Friday the contractors noticed that a crack had appeared in the slope above the works at the location shown on Fig. 2.

Fig. 2: Google Earth perspective view of the area of the unstable slope before the slope cutting had commenced.

The crack in question is not insubstantial. I must note here that I am very impressed with the openness of those involved - the contractor has placed images on their website of the nature of the problem (Fig 3.), even showing comparison views of the crack opening.

Fig. 3: Arthon Ltd image of the crack on the slope (from the Arthon Ltd web page)

The block of rock that is moving is large - about 300,000 cubic metres (Fig. 4), with the crack at the rear extending downwards for at least 10 m.

Fig. 4: Arthon Ltd image of the mobile block (from the Arthon Ltd web page)

Unsurprisingly, the authorities have stopped both the work on the slope and the traffic on the road, and now it is a game of wait and see. One possibility is that the slope will collapse completely, it may keep creeping or it may stop. Whatever happens the authorities have quite a challenge on their hands to know how to deal with this slope. The pattern of displacement against time is one tool that could be used in this case.

I'll post again as this develops. In the meantime, congratulations to all for their transparency in this case.