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Passmore Slide Area
Passmore Slide Area As The Cleanup Begins
Glacial clay, silt, and sand deposits underlie much of the Slocan Valley. These deposits are subject to slumping where undercut by river bends, or road cuts. The slump hazard is sometimes unappreciated, as in most places the clay is concealed beneath a thick layer of sand. At this site, there is evidence of repeated ancient failures on the adjacent slopes.
A small seasonal stream, draining from the cliffs above, drained from the base of a waterfall to the river through underground passages. Shifting of the hillside blocked these passages above the failure.
In the days leading up to the slide, the bank had been creeping slowly onto Highway 6 in Passmore. On April 13, 2000 larger than normally observed movements in the slide area began.
There was a noticeable increase in surface water flow at the toe of the slide and significant bulging of the asphalt in the northbound lane at the north edge of the slide. Neither of which were observed before. Some cracking and falling of trees was also observed during the day.
Maintenance crews excavated material at the toe of the slope to maintain traffic flow through the area. The maintenance crew left the site at 3:30pm and the traffic was left at one lane alternating with flag persons approximately 30 metres on either side of the slide boundaries.
At approximately 5:15pm a 75,000 cubic metre slide catastrophically released. The debris flowed across the highway, and all the way across the Slocan river. River flow was completely blocked for approximately 5 minutes.
Personnel on site at the time had no warning of the release. They described the movement of the slide mass as fluid like and very fast.
The slide removed the power lines on the east side of the road and the fibre optic BC Tel lines on the west side of the road. The extreme force on lines caused them to detach from the poles for one kilometre to the north and 500 metres to the south. No injuries were reported and no vehicles or persons were in the path of the slide.
The highway was closed for several days, cutting off the Slocan Valley from Nelson and Castlegar except by a lengthy detour through Kaslo. Power and phone lines were also cut.
Passmore Slide Covering Highway
This is an edited combination of two descriptions from engineering reports
Src: http://www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr003/FieldTripGuide_A.pdf
Src: http://www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr003/FieldTripGuide_B.pdf
Slide area in Kootenays re-opened
Last Updated: Monday, April 17, 2000 | 3:31 PM ET CBC News
http://www.cbc.ca/news/canada/story/2000/04/17/bc_slideopen000417.html
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The engineered solution to this problem waterfall was to install a man-made catchment pool at it's base and pipe the water through a culvert all the way down to the highway. The culvert is exposed near the access road crossings but is buried for most of it's length.
From the parking coordinates cross the highway and walk left past the power pole. There's an elk trail that starts in the ditch past the bank and goes up into the forest.
Put your GPS in your pocket and follow the trail; it'll be easier. You'll still end up doing some strenuous climbing. The trail leads away from the cache, just trust that this is the easiest route. The trail will take you from the highway (watch for yellow flagging tape) up onto a low part of a ridge. When you reach level ground you'll see the ridge rises up to your right.
Follow the level ground into the forest straight ahead but keep the ridge fairly close on the right side (more yellow flagging tape). As you get closer to the mountain the forest floor will rise up but it will still be easy climbing. When it looks like you've run out of an easy route, you need to climb about 30 meters up the bank and you'll be on an old road.
Follow the road all the way up onto the main ridge. You'll be turning left as the road follows the ridge up but you first need to navigate all the trees that are across your path. It's possible to walk around them but it takes a bit of work.
From this point navigation is easy -- just follow the road -- but but the walking is difficult because the road has some very steep sections. You'll need to cross the culvert twice as you follow the road right up to the base of the waterfall. This is most likely a seasonal flow so it'll probably be dry before the end of June.
The ascent should take only about half an hour.
You're looking for a very black container, a bit smaller than the usual film canisters, with a stone on top.
Map
On the way down it's possible to pass the point where the old road meets the ridge and continue down the crest of the ridge to a point where you have to turn right. You'll be following a faint elk trail down to the point where the flagged trail meets the ridge. What would have been a steep climb is a fairly pleasant alternate route down.