Geotechnical News • March 2016
51
GEO-INTEREST
the timing of the incident was deter-
mined by destruction of arching in the
rock fill by the effects of spring thaw.
On the basis of this finding the (then)
Department of Highways Ontario pre-
pared guidelines covering embankment
design for unusual field conditions
such as prevailed in this case.
Lessons learned included (i) become
conversant with construction proce-
dures for earthworks which are based
to an important extent on successful
practical experience, and (ii) be on the
alert for local situations which may be
outside of such experience and analyse
them individually.
Project heavily reliant on practical
experience
This case history deals with a dredging
project in a Harbour in Ontario.
In the 1980’s, Public Works Canada
(PWC) was frequently encountering
claims from dredging contractors for
additional compensation for a variety
of recognized reasons including (i)
“changed soil conditions”, namely,
discrepancies between the anticipated
and actual subsurface conditions, and
(ii) variations in the interpretation of
geotechnical information between
contractors and design engineers.
At the time, site investigations for
PWC dredging contracts were usually
contracted out to geotechnical Firms
and there was not a consistency in
scope and quality of information pro-
vided by the Firms. This had impor-
tant implications to end-users, in this
case both the dredging contractors and
PWC’s design engineers.
PWC approached the general problem
in commendable fashion:
a. It appreciated the value of a Con-
tracts Dispute Advisory Board
b. It established Guidelines for Geo-
technical Investigations, for use
by geotechnical consultants and
design engineers,
c. In the case of this particular claim,
PWC and the dredging contractor
agreed to resolution by an inde-
pendent geotechnical engineer
acceptable to both parties, and
to give the reviewer access to prec-
edent on dredging contracts in ar-
chives at PWC and the contractor’s
offices. The soil type at issue was
“till”, a highly variable material
in composition, strength, boulder
content, etc; almost rock-like at
times; difficult to describe in terms
of “diggability”.
The first Author assisted in develop-
ing the Guidelines and was assigned
the task as reviewer on this claim.
Research showed that there was much
practical data on previous dredging
projects in till overburden in both
PWC and the contractor’s archives.
The reviewer was able to develop an
approximate relationship between “N”
values and undrained shear strength
for the class of till involved, and on
the basis of this and other factors, rec-
ommended that the contractor should
be compensated favourably in respect
to its claim. PWC accepted this find-
ing. It was supported by technical
evidence which would also be useful
on future dredging contracts in similar
soil conditions.
Lessons learned included (i) dredg-
ing is a construction methodology the
success of which is dependent to a sig-
nificant extent on practical experience,
(ii) the Owner appreciated this and
established guidelines on geotechnical
matters which would be of benefit to
all of the parties, (iii) the importance
to the Contractor of interrogating its
own experience from a geotechni-
cal standpoint was clear, and (iv) the
merits of the alternate dispute method
were demonstrated.
Selected mini-examples
Some “mini-examples” are provided
below which are among the more
straight-forward cases encountered by
the Authors. Although they were each
associated with contentious situations,
in most cases they were resolved by
methods other than resort to litigation.
Inappropriate use of terminology
Avoid embellishment and gratuitous
comments in reports such as “it is
our opinion that there are no environ-
mental concerns at this site.” Such a
statement was made in a report where
only a few test pits were put down at
wide spacing across a site. This obser-
vational statement (which led to a
lawsuit) should have been qualified by
stating that based on the limited scope
of the investigation, there appears to
be no significant contamination (at
the time of the investigation) at the
specific test pit locations. However,
there is no assurance that there are (for
example) no possible contaminants
between the test pit locations.
The important matter of terminology
and its potential implications is dis-
cussed later, in more detail, in Section
5.0.
Provision of a Certification/
Assurance Letter
This was required in a Request for
Proposal from a City Engineering
Department to the effect that their
10 acre site was “environmentally
clean” based on 10 boreholes at speci-
fied locations and depths across the
site. That’s one borehole per acre!
A clarification telephonic discussion
between the City Chief Engineer
and the prospective Geo-Consultant
indicated that the City Lawyer
required this Certification. A meet-
ing was therefore arranged where the
Geo-Consultant explained that their
proposed investigation program would
only examine one in one millionth of
the ground – and you are asking for an
environmentally “clean bill of health”
on this basis? After further discussion,
the lawyer responded – “now that you
have explained the situation, I under-
stand your concern and your need for
qualification.
So the “bottom line” here is, it pays
for the Geo-Consultant to communi-
cate with the client in a timely fashion,
especially in a “face to face” meeting.
