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| Approach to seepage remediation assessment |
| Remediation decision-making process |
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This website is designed to enable users to undertake a sound and
systematic approach to identify and assess appropriate seepage
remediation methods. This section provides information about the
process, magnitude and impact of channel seepage; lists available
techniques and explains the remediation decision-making process
required to identify and implement appropriate seepage remediation
techniques.
A number of factors should be considered in the process
of determining the appropriate method of seepage
remediation for a particular
site. Each seepage remediation technique has its own technical
and economic characteristics that might make it suitable in one
location for a particular application, but not in another. Appropriate
techniques are determined by site-specific factors.
Factors to consider include:
- Scope and cause of seepage
- Site-specific conditions and channel operation details
- Objectives of remediation
- Criteria for assessment of various techniques
- Consideration of numerous options
- Financial and cost-benefit analysis
- Multi-criteria assessment to compare potential techniques.
These factors and the key issues that determine the appropriate remediation techniques
for a particular site are summarised in the flowchart below. The flowchart
consists of a number of steps that will guide users through the process of seepage
remediation. It has been developed to accommodate all levels of knowledge of
channel seepage and remediation. While the process is essentially linear, it
may be necessary at times to perform some iterations between tasks to refine
the options under consideration. Each stage of the decision-making process and
the relevant issues for consideration are described,
including maintenance requirements and monitoring to assess effectiveness.
The objective is to enable RWA’s to define objectives of seepage remediation,
determine site conditions and requirements, and strategically shortlist potential
techniques in order to reduce the number of options subject to detailed investigation
and assessment.
The decision-making process and guidelines are based on RWA survey information,
a literature review and the IAL trials. Site conditions, seepage rates and
channel remediation objectives vary, and the guidelines have been framed to provide
information to support the decision-making process, rather than to prescribe
a particular solution or approach.
Figure 1 Seepage remediation decision flowchart
| Summary |
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The guidelines on which this website is based are the result
of a cooperative venture involving IAL, the Murray-Darling
Basin Commission (MDBC), rural water authorities, suppliers,
contractors and consultant Sinclair Knight Merz. The project
has brought together the best available expertise and applied
it to address an issue of national importance.
The Seepage Task Force Study aimed to provide best practice
procedures and processes for channel seepage remediation.
The resulting guidelines were based on a literature review,
a survey of water authorities and three years of trials.
Given the diversity of site conditions, site requirements,
water authority objectives and assessment criteria, it is
not possible to make specific recommendations. This website
provides a process and information to enable water authorities
to make informed decisions regarding seepage management.
Options for channel seepage remediation need to be evaluated
on a specific basis.
Conclusions
- A large selection
of remedial techniques were reviewed and, in some cases
trialed in channels operated by Murray
Irrigation Limited (MIL), Murrumbidgee Irrigation (MIA),
Wimmera Mallee Water (WMW) and Goulburn Murray Water
(GMW). A wide range of parameters such as site conditions,
channel
operating conditions, channel capacity and size, impacts
and cost implications govern the applicability or suitability
of these techniques.
- A structured decision-support framework
was proposed, documented in the guidelines to explain
the importance
of the various
components to seepage remediation, and used as the basis
of this website.
- This structured decision-support framework
is designed to guide water authority staff in the activities,
data
requirements and decisions that they need to make regarding
the selection
of the most appropriate method to remedy channel seepage
in their area of interest.
- Trials of particular seepage
techniques were based on assessment of previous studies
and survey results
and consultation with
experts in the field, including the United Stages Bureau
of Reclamation (USBR). Special emphasis was placed on
the trialing of exposed flexible membrane liners, as
there was
little information available on these techniques, and
it was considered that these materials offered some promise
as a cost-effective solution. The following techniques
were
trialed as part of the project:
- At the commencement
of the IAL Channel Seepage Remediation Project,
it was apparent that a three-year
trial to assess
the potential of seepage remediation techniques with
expected durabilities of 20 years or more was limited.
While the
trials have documented important information on the
techniques, their installation issues and costs,
long-term durability
is one aspect that could not be assessed. The expected
lifetime
of the techniques has been based on previous experience
within Australia and overseas, where available, in
addition to the
manufacturers’ specifications in the case of
flexible membranes.
- From the perspective of durability
and channel maintenance, it is essential that further
monitoring of the trial
sites be undertaken and reported back to IAL to
build a history
of performance of the various techniques, and assess
their durability in Australian conditions. Annual
reviews of the
trials by water authority staff, documenting operational
performance, maintenance issues and requirements,
should be collated and disseminated to other water
authorities
and IAL members.
- Many conclusions can be drawn from
the literature review and the trials, relating to
the performance
of particular
techniques in certain locations. This information
is available on this website.
Key Points
- A regular review of available techniques, materials
and suppliers, particularly new developments
in the flexible membrane market, should be conducted
by IAL and RWA's to
keep water authorities
abreast of seepage remediation options.
- Updated
information, either from the regular review or from
trials and installations undertaken
by different
authorities,
should be logged on this website.
- Cost unit
rates and available materials should be reviewed
on a regular basis. Prices
and availability
changes and
new materials become available. This was
apparent during
the
three-year trials, where prices changed
due to increased product availability or local
manufacture,
and local
contractors becoming more familiar with
the materials and installation
techniques..
- This website should be used to
assist in evaluation of remediation options.
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the seepage problem |
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