Geotechnical News • March 2016
53
GEO-INTEREST
Two detailed geotechnical investiga-
tions were carried out by the defending
Geo-Consultant, one in 1990 and a
second in 1994, as described in Matich
et Al, 2007. At the same time, precise
settlement surveys were initiated.
The defendant Geo-Consultant also
commissioned independent expert
hydrogeological studies of groundwa-
ter conditions in the Russell Township
area, together with a forensic study
and overview of the evidence relating
to the distress. The results indicated
that the cause of the settlement was a
significant lowering of the groundwa-
ter table in the area by pumping from
wells for town water supply purposes.
By this time, however, litigation was
already under way involving lawyers,
insurers, and a variety of independent
experts.
From a performance standpoint, the
evidence was clear that the rink slab
had settled uniformly. However, in the
administration area, (lobby, dressing
rooms, concessions, etc), masonry
partition walls supported on concrete
slabs on grade had suffered damage.
This raised a significant question as to
why this difference in performance. A
geotechnical study of the granular fill
in this area was carried out. The results
suggested that the settlement was
possibly caused by inadequate com-
paction of the fill. This implicated the
second geotechnical Firm which was
responsible for geo-monitoring during
construction. In 1985 the concrete slab
and internal non-bearing partitions in
the Administration area were removed
and replaced at a total cost of about
$50,000. Settlement of the replacement
floor slab area continued unabated.
In terms of overall remedial mea-
sures, structural engineering special-
ists were engaged by the Owner to
study potential long term options. Not
unexpectedly, they were influenced by
the conclusive evidence for continu-
ing settlements of the grade-supported
concrete slabs, including the extensive
documentation from the geotechni-
cal investigations which was zeroing
in on the usual “suspect”, namely,
consolidation of the Leda clay, albeit
without explaining conclusively as to
the “why”? The structural engineers’
assessment of potentially feasible
remedial methods was qualified by the
underlying principle that any sup-
port of the floor slab on the existing
subsoil, including the sensitive clay,
would involve a degree of uncertainty.
Three types of repairs were indenti-
fied, namely:
a. Structural slab with grade beams
and piles
b. Light weight fill with slab replace-
ment
c. Urethane foam injection under the
slab.
Estimated costs were approximately
$2,000,000; $1,500,000 and $250,000,
respectively, with structural rehabilita-
tion recommended by the geotechnical
“inspector” as the only viable option.
In this instance, only minor remedial
work was shown, by the original Geo-
Consultant, to be required.
Several factors are significant to this
discussion as follows:
i. The geotechnical studies by the
geotechnical “inspector” Firm
were unfortunately deficient in
a number of respects; (a) they
focussed only on the Arena site
without considering the geological
and subsurface conditions in the
site environs (the most important
deficiency in this case); (b) they
did not appreciate that piezometers
were indicating that the clay was
being consolidated from the bot-
tom up; (c) they did not notice that
settlement had also been expe-
rienced by houses in the Town-
ship of Russell; (d) they failed to
appreciate that site conditions had
changed since the original inves-
tigation, particularly with respect
to a regional drawdown of the
groundwater table due to pumping
(for water supply purposes) from
the granular till formation underly-
ing the clay. Large scale pumping
began in the mid-1970’s and was
discontinued in 1989 when a mu-
nicipal system was installed.
ii. The settlement of the Arena
stopped after pumping was discon-
tinued. It was agreed among the
parties that if no further settle-
ment occurred in the following
six months, the case would be
resolved through a minitrial.
iii. In practice settlements did cease
and appropriate resolution was
reached through a minitrial in
November, 1994 which lasted
only two days. The Judge report-
edly had first-hand experience in
construction, and had requested
a meeting on-site with technical
representatives of both parties, in
advance of the minitrial.
A number of important lessons derive
from this case:
• From the standpoint of the geo-
technical “inspector”. Undertake
such an assignment with care and
realistic assessment of professional
experience and capabilities to do
so. Make sure that facts that you
base your findings on are correct,
and that your work is carefully
checked and peer reviewed. These
are important principles in all geo-
technical studies, and even more
so where forensic dispute resolu-
tion is involved.
• It is of some importance to note
how a geotechnically straight
forward project such as this one
can “go wild” and have significant
unexpected adverse consequences,
including a heavy commitment
on the part of the original Geo-
Consultant in terms of time of
senior personnel spent against this
unwarranted claim and high non-
recoverable costs to defend itself
together with potentially perceived
loss of professional reputation.
• An important lesson learned is that
this dispute could have been re-
solved from the beginning without
resort to litigation.
