22
Geotechnical News •September 2015
GEOTECHNICAL INSTRUMENTATION NEWS
Disposal of monitoring
equipment
The equipment to be disposed fell into
two categories, that with monetary
value and that with only scrap value.
Each batch for sale required offers
from a minimum of three indepen-
dent parties – this was a Municipal-
ity requirement to avoid fraudulent
practices.
Robotic total stations (RTS)
The modern RTS were popular sale-
able items. These were sold to third
parties in a number of batches. Some
of the older instruments, which were
no longer supported by the manufac-
turer, had no commercial value and
donating these instruments to non-
profit organisations such as schools
or charities was examined, but proved
not to be a viable option.
All sales were carefully documented
to verify the traceability of the instru-
ments. This was performed with the
manufacturer. One key component of
the successful sale was that the instru-
ments have been fully maintained, on
a regular basis, during their use in the
project and full service histories were
available.
Other monitoring equipment
Equipment with no monetary value
was sent to recycling plants. Consider-
able effort by both SG and DM was
expended on documenting each ele-
ment of the monitoring system, such
as location, how removed and eventual
disposal method.
Lessons learned - designing a
monitoring system with removal
in mind
A system is usually designed to moni-
tor specific entities or parts of struc-
tures. During installation consideration
of final removals is generally not
given any priority. Location of moni-
toring equipment is as important for
removal as for maintenance purposes.
• Consider maintenance options for
equipment. Does it need mainte-
nance, and if yes at what fre-
quency?
• Consider product life span, will
it need to be replaced during the
project lifetime?
• Consider equipment fixing to the
substrate, does it need to be per-
manent?
Over the duration of the contract
changes occurred in the urban envi-
ronment and also in applicable safety
legislation. Certain elements could not
be removed in a similar fashion to that
used for installation and additional
measures were required.
Some elements could not be removed.
For example, at locations such as back
facades of buildings, where access
could only be achieved with the help
of the residents, not all residents were
willing to assist. Prisms were installed
in difficult to reach locations within
very narrow streets (no cherry picker/
scissor lift access possible). These
were installed up to 13 years before
their removal under less rigorous
health and safety requirements. If
a prism could not be removed using
normal methods a risk assessment was
performed to determine whether or
not leaving the prisms in place could
lead to a future liability. In a number
of cases these consisted of prisms
located above pavements (sidewalks)
where a falling prism could potentially
hurt pedestrians below. A number of
special measures were undertaken to
remove these prisms. These included
use of certified abseilers who accessed
from the top of a building.
Projects with a lifespan such as North/
Southline (13 years) should consider
that circumstances change. This does
not mean every possible option should
be considered, but budgets may be
stretched in ways which could not
have been foreseen at the time of con-
tract award. At the time of installation
it was anticipated that the monitor-
ing would be in place for a period of
approximately 6 years. In practice it
was in place for over double that time.
It is customary to produce as-built
drawings and for large monitor-
ing projects these are important for
programmed removal. A complex
monitoring system with a large num-
ber of parts (in total the GIS accounted
for 21,998 individual measuring points
and the monitoring database consisted
of 208 million readings) cannot be
fully removed without proper docu-
mentation and this needs to be pro-
duced over the monitoring period.
David K Cook
Mott MacDonald
8-10 Sydenham Road
Croydon
CR0 2EE, England
Tel: +44-20 -8774-2554
E-mail:
Thijs Claus
Witteveen + Bos
Hoogoorddreef 15
1101 BA Amsterdam
The Netherlands
Tel: +31 570 69 79 11
E-mail:
