A v a l a n c h e

C o n t r o l ,

R e s c u e

a n d

E d u c a t i o n

pack overa large flat paved parking area was chosen as a
test site and found to contain consistent one finger resist-
ancesnowover auniform 2.1 m depththroughouttheentire
area. Footpenetration wasabout 2-3 cm. Theforcerequired
topenetratethesnowwithaprobewasconsistentand
typical of an avalanche deposit.
The areawas divided into a series of identical corridors
the width ofa 9memberprobeline and 50m in length.
Theproberswereinstructedtoprobeatarealisticrate
which they felt theycould maintain foran extended pe-
riod("atleastan hournon-stop").Thenumberofsteps
was controlled and recorded andthus the exact number of
probe holes could be determined. The time for the team to
complete each 50 metre stretch was recorded.
Fourdifferent setsoftestswere conducted,each em-
ployingavariationofprobingtechnique. Each 50metre
plot was repeated fourtimes and the probing times were
averaged.
Two basictechniqueswerecompared.Two testsem-
ployed 9 probers in the traditional coarse probe spacing.
Thealternativetechniqueemployed3probersspaced
openly to cover thesame areaas above howevereachprober
placed 3holesperstep.Thisisavariation oftheopen-
spaced techniquedescribed in Perla andMartinelli (1976,^{Figure 2Probe spacing in vertical plane for 3-hole-per-}
step probing. Optimal spacing occurs approximately 1 m
p.192) and McClung and Schaerer (1993,p.191).^{below surface. All dimensions in cm.}
Bilgiri probes were used. Fulldepth probes employed 4
sections (3.25m). The probes were shortenedto 3 sections^{THREE-HOLE-PER-STEP PROBING}
(2.45 m) forthree of the tests.One test was full depth (to_{Theopen-spacedtechnique illustratedinMcClungand}
ground) 2.1 m.The remainderwere to a depth of1.5m._{Schaerer (1993,p.191) shows each rescuer probing twice}
The probes were marked with tape to indicate 1.5 m._{perstep.In the technique employedinthese tests,each}
Theusualprobemasterwasemployedtodirectthe9_{person probed three times each step, to the left, in center,}
memberprobeline.Inone oftheopenspaced teststhe_{and then right.}
teamwasinstructedtoproceedat theirownindividual_{Inrealityiftheproberreaches totheside,theprobe}
paces._{will usually enter the snow at an angle. If he tries to main-}
tain the 75 cm spacingthe anglemay be 10-15 degreesfrom
FIELD TEST RESULTS^{vertical.Howeverif the probers space themselves finger-}
Times were averaged foreach technique and the rates of^{tip to finger-tip apart (~175 cm) the resulting lateral spac-}
probing were calculated(table 1).^{ing of probe holes is reducedto about 60 cm at a depth of}
1 m andthe anglesof the probe holeson eachside are slight.

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-3-section probes