Standards > Monitoring
[Parks Canada citation needed.]
This article outlines the criteria that must be considered
for the systematic planning and implementation of a monitoring
program. The extensive bibliography serves as a source of
detailed information on specific methods, experimental techniques
and equipment referenced within this article.
Monitoring is the task of collecting and recording data in
a systematic and repetitive manner for the purpose of correlating
and comparing the physical performance and condition of the
quantity being examined to related quantities. Unlike inspection,
monitoring has an identified objective and is clearly defined
in terms of what is to be measured, when and how this is to
be accomplished for how long and who is responsible for the
execution of the program and for interpreting and using the
Monitoring is one on-site method of assessing changing structural,
material, geotechnical and environmental conditions which
affect the conservation and maintenance of historic structures
and sites. The results obtained contribute to the evaluation
of restoration and maintenance techniques and the assessment
of problems and suspected changes of condition.
Regular and repetitive maintenance functions such as seasonal
inspections are not considered monitoring programs (see
Section .2.3 “Maintenance Procedures: Periodic Works”).
However, the need to establish a monitoring program could
be identified during regular cyclic inspections.
Monitoring may be an independent maintenance or project activity,
form part of a wider investigation and analysis pro-gram or
be incorporated into the regular maintenance activities of
the site. Correspondingly, it can be contracted out to a consultant
or carried out entirely by the area superintendent and staff;
the arrangement depends on the scope and complexity of the
work to be accomplished and the skills and availability of
the required resources.
2.0 Establishing a Monitoring Program
For those directly involved in projects related to site
development a monitoring program could be identified to:
- assess the possible presence and causes of deterioration
- understand situational behaviour of structural form
and material characteristics; and
- assess the effect of changes to the original loading,
member configuration or environment and the use of new
technology on the performance behaviour of the structure.
These post-development assessment requirements would generally
be identified by the design team in the maintenance manual
developed for the site.
For those concerned with the continuing on-site maintenance
and operation of the site, such a program could provide:
- assessment of deterioration and instability problems
identified during the routine maintenance work; and
- assessment of the effects of conservation and maintenance
procedures on the overall performance and appearance.
The routine for implementation varies with the scope of
work. In general, project managers and area superintendents
can best recognize the need to initiate these types of programs.
The reports, recommendations and requests they receive from
their staff will form the basis for judging the program’s
importance, scope and objectives.
3.0 Planning A Monitoring Program
3.1 General Considerations
A monitoring operation is a chain of potential weak links.
The need for reliable techniques is only one consideration.
Careful planning is essential and should encompass such
aspects as definition of objectives and quantities to be
measured and decisions on the type, number, location and
frequency of measurements and on the organization of personnel,
equipment, measurements and reporting procedures. Only if
each of these aspects is considered in detail before the
start of the project will there be any certainty of accomplishing
3.2 Terms of Reference
Regardless of the program complexity and whether or not
the work is to be done by site personnel, regional staff
or outside consultants, the following steps should be taken:
- Define clearly the monitoring objectives, including
relationships to other project work and the anticipated
use of results. This provides a guide for the appropriate
level of resource expenditure and requirements for precision.
- Define “normal” and “acceptable”
behaviour and assess anticipated behavior.
- If safety considerations exist, establish emergency
contingency plans (see Section 3 “Emergency
- Determine which behavioural or material properties
and characteristics are to be examined in order to achieve
objectives. This requires isolating prime phenomena and
identifying all factors which would influence results
and which might require simultaneous measurement and establishing
viable range and precision requirements.
- Identify locations to be examined and, if required,
establish a priority list of critical areas to be monitored.
Often it is sufficient to provide an extensive area of
low precision and low frequency of measurement, with a
provision for more accurate, concentrated and frequent
monitoring whenever the results indicate a change.
- Estimate the duration of the project and frequency
of measurements. Although a minimum number of readings
should be predetermined, it is important to be able to
match reading frequency to progress rather than to time
- Ensure that personnel with appropriate levels of experience
and familiarity with the method and equipment employed
are directly responsible for interpreting results and
3.3 Monitoring Program Considerations
Depending on the requirements of the program, maintenance
staff, professional and technical personnel or consultants
might form an on-site monitoring team. One individual
representing the team should co-ordinate the monitoring.
Establishing liaison channels in advance ensures continuity
and communication gathering, between those requiring the
information and those performing the work. Unless specifically
indicated in the terms of reference, the team is usually
responsible for the readings but not for interpretation
or action that may be required by the results. This aspect
of the work is not considered part of the monitoring,
which is essentially a data-gathering exercise.
3.3.2 Equipment and Methods of Measurement
- For each parameter to be measured, there are usually
several methods and types of equipment that might be suitable.
All have advantages and limitations. The following factors
will influence the final selection:
- Reliability The success of the program relies on the
repeatability of the measurements. In general, selection
of methods and equipment which are more sophisticated
than necessary should be avoided. For every instrument
selected there should be calibration methods and equipment
to ensure that the instrument continues to function correctly
through-out the duration of the project. Calibration helps
ensure that the interpretation of the data is appropriate
for the material and conditions being examined. This can
be obtained from a variety of sources, including available
calibration charts from equipment manufacturers, established
procedures and technical literature and experimenting
with the instrument to evaluate its performance relative
to a known set of conditions.
- Precision Requirements for precision usually reflect
the objectives of the program. The more stringent the
requirement, the more sophisticated, costly and time-consuming
the monitoring project becomes. If, for example, a comparative
visual observation will provide the information necessary
to arrive at a decision, then more sophisticated methods
of recording the data are redundant. A clear understanding
of the precision requirements is necessary to satisfy
- Ease of use
- Ease of repeatability of technique or method on-site
- Personnel requirements. This applies to the expertise
required to use the equipment and to record and interpret
3.3.3 Measurement Plans
General guidelines for personnel, time requirements and
frequency of each measurement should be established at
the initial stage. It is advisable to assess the data
on an ongoing basis in order to adjust the frequency of
readings and to evaluate the validity of the recorded
results. One should always establish routines for calibration
checks of the equipment.
3.3.4 Processing Results
It is here that errors, delays and ambiguities can often
occur. To avoid these;
- process data as it becomes available. This provides
a constant picture of the changing nature of the problem;
- allocate responsibilities for calculation and plotting
before the project starts: and
- prepare results carefully, thereby assisting in interpretation
of the behaviour under examination.
Monitoring results forms a basis for action or for informed
inaction. The report itself should establish a reference
for the interpretation of the results (if not included
as part of the terms of reference for the program) and
include details on the equipment used, numbering systems
employed, instrumentation performance, tests, calibration
methods, data processing techniques and pertinent comments
and observations which may have a bearing on the interpretation.
4.0 Monitoring Techniques
(See Vol. 111.10 “Special Investigation and
Analysis” and the bibliography attached to this publication.)
Unlike dimension and weight, many parameters cannot be measured
directly without altering or destroying the material or structural
form. Fortunately, methods have been developed which provide
an indirect means of assessment. These depend on the interrelationship
among certain physical and mechanical properties of the materials
of configuration being examined such as hardness, resistance
to penetration and ability to transmit ultrasonic pulses and
Once a specific program objective is determined, there is
often more than one method of gathering the required data.
The selection of the most appropriate technique should be
based on the criteria outlined in 3.3.2 above.
The Appendix groups some of the commonly used methods according
to the quantity to be measured. The lists are not meant to
be exclusive, but to illustrate potential solutions. Details
of each technique are not provided, although the general comments
are extended to provide guidance.