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Geotechnical News • September 2013
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GEOTECHNICAL INSTRUMENTATION NEWS
occurred and where grout intrusion
into the crevices had taken place to
seal these openings were clearly vis-
ible. Minor seepage from joints which
could be tolerated was recorded.
Lessons learned
Information on the geology of the bed-
rock and any relevant case histories in
a location could be of much help in the
planning and design of a water retain-
ing structure.
Unless the bedrock surface at the
location of a proposed water retaining
structure can be thoroughly examined
and, if necessary, treated, the presence
of joints or fissures should be expected.
Grouting should be included in the
planning, scheduling and costing.
Scheduling of the project should try to
avoid winter conditions for grouting
to achieve savings in the cost. A list of
contacts for resources which may be
needed at short notice may be useful.
Unusual water levels
Many projects are concerned with the
water levels or pressures in specific
locations, and use observation wells
or piezometers for measurements.
Unusual water levels noted in three
locations are described.
In the dumped impervious fill
described in the above section ‘A
cofferdam on the foreshore of a lake’,
observation wells were installed in
drilled boreholes from the crest of
the fill with the bottom of the pipes
estimated to be close to the bedrock
surface. In all but one case, the water
levels observed were below the lake
level, which was about 1m below the
crest elevation. The tops of the pipes
were about 1 m above the crest. In one
pipe, the water level was higher than
the crest and more than 1 m above the
lake water level. The cofferdam was
removed after the dock was completed.
On another site, observation wells
were installed in boreholes for explo-
ration of the site on the bank of a lake
where an extensive excavation of the
approximately 30 m thick overburden
to the limestone bedrock was planned
for site preparation. The groundwater
profile was fairly consistent with a
gradient toward the lake but in a few
wells in which the bottom of the pipes
was close to the bedrock surface, the
water levels were some 2 m above
the groundwater profile. Almost all of
the observation wells were destroyed
when the extensive excavation of the
overburden to bedrock was completed.
The third example is a location on
high ground on the bank of a river on
which a generating station was built.
The reservoir associated with the
station necessitated the construction
of a relatively low earth dam over a
depression and a small stream which
flowed into the river. The embankment,
about 200 m long, was built on the
surface of a deep deposit of sensitive
clay. The structure had been moni-
tored for settlement of the crest and
water levels were determined in open
standpipe piezometers installed from
the crest of the dam. The depths of the
piezometer tips ranged between 15 m
and 25 m below the crest. There was
no problem with the rate and amount
of settlement because the freeboard
adopted about 3 m, was adequate.
The tops of standpipes were about 1
m above the crest and protected by a
larger diameter pipe with a cover for
each standpipe. Although the water
levels in most of the standpipes had
stabilized at around elevations which
could be related to the reservoir level,
water could be observed at a few
locations slowly flowing over the tops
of the standpipes. Monitoring of the
dam over a period of many years had
shown that the settlement, stability and
routine maintenance of the dam were
all satisfactory.
Lessons learned
These examples of unusual water lev-
els remain unexplained puzzles. Other
than notes for the records, no investi-
gation to seek an explanation had been
carried out.
[But perhaps the lesson
learned is to delve deeper at the time
so that explanations are found – JD]
.
Earle J. Klohn 1927-2013
Earle J. Klohn passed away on July
22, 2013 in his 86
th
year surrounded
by his family. In the mid-1950s, Earle
was one of the founders of Ripley,
Klohn and Leonoff in Vancouver. He
was a pioneer of geotechnical engi-
neering in Western Canada. Earle
obtained a Bachelor’s Degree in Civil
Engineering with Distinction in 1950
and a Master’s Degree in 1952 both
from the University of Alberta where
he was taught soil mechanics by the
late Dr. Robert Hardy. Earle’s skills
encompassed the full range of geo-
technical engineering from founda-
tions to embankments to tailings dam
engineering. He won many awards for
his contributions to our field including
the Leggett Award in 1990 which was
presented to him by Dr. Leggett per-
sonally. Earle took his experience in
designing dams in the steep, wet and
seismic terrain of British Columbia to
many projects around the world. He
served on boards of review in virtually
every province and territory in Canada
and in many countries. He authored
over 60 technical papers and delivered
many state-of-the-practice lectures
on the analysis, design, and construc-
tion of building foundations and large
dams. Earle inspired several genera-
tions of civil engineers and influenced
the design of thousands of projects in
Canada and abroad in his 46 years of
professional life.
IN MEMORIAM