HISTORICAL NEWS SEARCH - Government of British Columbia

1992
Event type: Slope failure.
Precipitation: Not applicable.
Source: The Terrace Standard, March 2, 1994; March 3, 1995.
In 1992 in Terrace, a landslip undermined the sidewalk and a section of Lanfear Road, the feeder road to the
central Bench area. Erosion is gradually narrowing the road and rebuilding was estimated at more than $2 million. According
to city director engineer Stew Christensen, the existing road could last another 5 or ten years even. “But it could slide off the
hill next week.” The problem is caused by a series of clay lenses that make it almost impossible to predict stability. *1)
After the incident, the hill was closed to pedestrians and a 20-km/h speed limit put in place. Although the city of
Terrace had been talking about possible realignment of the road even before the slide, successive capital budgets had given
priority to other projects.
Before a final decision could be made on a new route for the road, a comprehensive geotechnical study of the hill
would have to be carried out. *2) City council would have to decide soon whether to allow a proposed subdivision at the top
of the hill. All options involved going lower down the hill, rather than going further west and cutting harder into the bank.
Cutting into the bank could threaten lots at the top of the hill causing land to slide.
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*1) A similar problem was encountered in Prince George during the construction of the road up Cranbrook Hill to the
University of Northern B.C. campus. The road there began sliding and construction cost eventually came in $16
million over budget (The Terrace Standard, March 3, 1995).
*2) In March 1994, Terrace city council approved spending up to $30,000 on a design study for Lanfear Hill (The
Terrace Standard, March 2, 1994).
January 3, 1992
Event type: Fatal snow avalanche.
Precipitation: Not applicable.
Source: The Terrace Standard, January 8, 1992; Jamieson and Geldsetzer 1996 (pp. 116-119).
On January 3 around 3 p.m., a massive snow avalanche on Thornhill Mountain in the Copper Mountain
range area just southeast of Terrace killed two snowmobilers, who with six others were riding on the north slopes of
the mountain. Though searchers were called in immediately, the victims were not found until 11 p.m. with the aid of
the Terrace RCMP police dog Echo. Due to strong winds and whiteout conditions, the bodies were not recovered until
the next day. (The Terrace Standard, January 8, 1992). The 400-m wide slab failed on a layer of graupel and partly
decomposed particles. The crown varied in thickness from 60-135 cm and averaged 115 cm. The size 3 avalanche
resulted in a 1.3 m deep deposit, 125 m wide and 200 m long.
The members of the group were each trying to ride as far up the slope, which reached 38 o , as possible (highmarking).
Two avalanche deposits, one to two days old, were visible on slopes adjacent to the high-marking slope. At
3:15 p.m., two riders were making their last climb of the day. One was 75 m ahead and started his descent when the
slope released as a large slab avalanche. The two snowmobilers were pushed off their machines and briefly visible on
the surface of the avalanche. When the avalanche stopped, they could not be seen anymore. The slope had been
repeatedly high-marked before it released. Presumably, the victims triggered the slope from an isolated weakness or an
area where the slab was thinner than average.
Using small trees for probes, the five surviving riders and additional snowmobilers started searching for the
two missing ones. They used the sticks to probe an area about 14 m wide one recovered machine that had been barely
visible in the deposit. The accident party initially probed in the right area for the second victim, near his snowmobile.
However, their improvised probes only penetrated only 35 cm, only half the depth where he was found. The chances of
recovering both victims alive would have been much better had the snowmobilers been equipped with transceivers,
shovels and probes.
A storm with 70 to 80-km/h winds made snowmobiling, part of which was along a ridge, slow and difficult.
The first searchers from Terrace did not arrived until 7:30 p.m. A search dog that arrived at 10 p.m. found the second
machine. Twenty-five minutes later, over seven hours after the avalanche, the first body was located under 70 cm of
snow within 2 m of the first machine. An hour later, the dog found the second body under 80 cm of snow 37 m uphill
from his machine at the side of the deposit. Both had asphyxiated.
The weather in the Skeena Mountains had been warmer and wetter than average. In December, almost three
times the normal precipitation fell. Between December 22-January 3, 125 mm of precipitation fell at the Terrace
airport, 1,100 m below the slopes of Thornhill Mountain. During the same period, moderate or strong winds from the
south had loaded north-facing slopes. On January 3, strong southwest winds had continued to load the slope.
It was the first ever fatal snowmobiling accident here. Both men were members of the Skeena Valley
Snowmobilers’ Club and were described as experienced snowmobilers. Ron Niesner, the club’s secretary, said the size
of the slide shocked even the avalanche technicians. “The thing was astronomical; it was just massive.” (The Terrace
Standard, January 8, 1992).
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