XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 139
Tailings engineers are not afforded many if any of
these amenities. The favorable location for a tailings storage
facility is dependent upon local topography and is locally
influenced directly or sympathetically by the geologic his-
tory that has emplaced the economically favorable mineral
body, typically resulting in less than favorable foundation
and site conditions. Tailings material by its nature can be
highly variable and difficult to work with—even when
coming from the same ore body over the long term—mak-
ing each tailings storage facility unique due to the local and
regional geologic conditions, climate, topography, surface
water hydrology, ore type, mineral processing method, sup-
porting operational resources, available consumable mate-
rials, company culture, governance, leadership, and other
considerations. Add to this incremental construction and
associated stress changes, variations in the ore body, and
mechanical and chemical weathering, all leading to the
temporal variability of the tailings properties and impound-
ing structure with limited ability to achieve a “steady state”
until well after the facility ceases operation. The lack of true
comparison between tailings facilities and water dams leads
to the conclusion that the use of water dam engineering
practices for tailings facilities may not be appropriate, as
supported by a number of catastrophic failure case studies.
The design process consists of matching the benefits
of the most reasonable tailings facility while managing ini-
tial capital costs and applying a construction method that
produces a structure with suitable stability and within local
regulatory requirements. The various design methods (tail-
ings utilizing the upstream, centerline, or downstream con-
struction methods) are all capable of producing safe, stable
structures when appropriately evaluated for the individual
settings and conditions, assuming there is a proper com-
mitment to operation as designed and implementation of
surveillance and modification programs over the facility’s
operating life and into closure and reclamation. In summa-
tion, no construction method should be unilaterally ruled
out provided it has not been eliminated through the appli-
cation of local legislation.
Dam Construction
Mining pundits regularly query why mine waste and/or
tailings cannot always be placed back into the pit or under-
ground from whence it came. While an idea with merit,
inherent limitations do exist. Once the host rock is liber-
ated from the ground it nearly doubles in volume, resulting
in an induced void space. The extracted hard rock mineral,
in this case, represents a small volume in the reserve. This
makes it impossible for most mineral processing wastes to
be placed back in their originating open pit or underground
location. However, even if this bulking factor were not an
issue, the mining area (pit or underground) is being mined,
and placing tailings where there is active mining is not pos-
sible except under very specific conditions and, for a por-
tion of the tailings stream, equally if not more challenging.
The ongoing beneficiation process further reduces the
particulate size, exposing large surface areas of the host rock
to allow for mineral liberation. This progressive particle
size reduction dramatically impacts the material behavior,
including changing the index and engineering properties,
increasing the water retention characteristics, and reducing
the material strength and permeability (two of many exam-
ples) directly impacting successful tailings management.
Tailings storage facilities fall into two categories:1)
engineered earth or rock fill containment (e.g., water dam),
or 2) facilities constructed of tailings that use controlled
material placement to create a drained shell that impounds
the finer residuals and entrained water. The engineered
structure is simply a containment bucket. The latter referred
to as a sand dam, uses naturally occurring classification or
mechanical segregation to extract the coarse tailings frac-
tion (e.g., sands and coarse silts), creating a stable free-
draining shell. These fine sands and silt-size materials make
ideal containment, provided that they remain unsaturated
and are preferably placed at a suitable density (e.g., dila-
tive on shear). Both structures require robust engineering
designs, and the sand dam requires strict tailings manage-
ment throughout the structure’s life by qualified engineer-
ing professionals with relevant practical experience in order
to achieve a suitably constructed containment.
Tailings facilities are incrementally constructed (thin
lifts) with an operating lifetime that can span a decade to
a century depending on the size of the reserve. The engi-
neering behind these structures is complex requiring care-
ful tailings management and continuous quality assurance
and quality control (QA/QC). The QA/QC process should
be similar to traditional construction QA with the excep-
tion that it is performed incrementally over the life of the
structure. This creates a need for continuous evaluation of
the constructed dam for consistency with the design vision,
and planning for variance in the original design is a critical
tenet of tailings management and design.
Tailings practitioners apply a process of evaluating
the deposited tailings incrementally for adherence to the
intended design while planning for conditions that may
deviate from the original plan. Planned and managed
deviance and having a well-thought-out optional plan(s)
is known as the observational method. The observational
method is a powerful tool that lends itself well to tail-
ings dam construction. The process does have limitations
Tailings engineers are not afforded many if any of
these amenities. The favorable location for a tailings storage
facility is dependent upon local topography and is locally
influenced directly or sympathetically by the geologic his-
tory that has emplaced the economically favorable mineral
body, typically resulting in less than favorable foundation
and site conditions. Tailings material by its nature can be
highly variable and difficult to work with—even when
coming from the same ore body over the long term—mak-
ing each tailings storage facility unique due to the local and
regional geologic conditions, climate, topography, surface
water hydrology, ore type, mineral processing method, sup-
porting operational resources, available consumable mate-
rials, company culture, governance, leadership, and other
considerations. Add to this incremental construction and
associated stress changes, variations in the ore body, and
mechanical and chemical weathering, all leading to the
temporal variability of the tailings properties and impound-
ing structure with limited ability to achieve a “steady state”
until well after the facility ceases operation. The lack of true
comparison between tailings facilities and water dams leads
to the conclusion that the use of water dam engineering
practices for tailings facilities may not be appropriate, as
supported by a number of catastrophic failure case studies.
The design process consists of matching the benefits
of the most reasonable tailings facility while managing ini-
tial capital costs and applying a construction method that
produces a structure with suitable stability and within local
regulatory requirements. The various design methods (tail-
ings utilizing the upstream, centerline, or downstream con-
struction methods) are all capable of producing safe, stable
structures when appropriately evaluated for the individual
settings and conditions, assuming there is a proper com-
mitment to operation as designed and implementation of
surveillance and modification programs over the facility’s
operating life and into closure and reclamation. In summa-
tion, no construction method should be unilaterally ruled
out provided it has not been eliminated through the appli-
cation of local legislation.
Dam Construction
Mining pundits regularly query why mine waste and/or
tailings cannot always be placed back into the pit or under-
ground from whence it came. While an idea with merit,
inherent limitations do exist. Once the host rock is liber-
ated from the ground it nearly doubles in volume, resulting
in an induced void space. The extracted hard rock mineral,
in this case, represents a small volume in the reserve. This
makes it impossible for most mineral processing wastes to
be placed back in their originating open pit or underground
location. However, even if this bulking factor were not an
issue, the mining area (pit or underground) is being mined,
and placing tailings where there is active mining is not pos-
sible except under very specific conditions and, for a por-
tion of the tailings stream, equally if not more challenging.
The ongoing beneficiation process further reduces the
particulate size, exposing large surface areas of the host rock
to allow for mineral liberation. This progressive particle
size reduction dramatically impacts the material behavior,
including changing the index and engineering properties,
increasing the water retention characteristics, and reducing
the material strength and permeability (two of many exam-
ples) directly impacting successful tailings management.
Tailings storage facilities fall into two categories:1)
engineered earth or rock fill containment (e.g., water dam),
or 2) facilities constructed of tailings that use controlled
material placement to create a drained shell that impounds
the finer residuals and entrained water. The engineered
structure is simply a containment bucket. The latter referred
to as a sand dam, uses naturally occurring classification or
mechanical segregation to extract the coarse tailings frac-
tion (e.g., sands and coarse silts), creating a stable free-
draining shell. These fine sands and silt-size materials make
ideal containment, provided that they remain unsaturated
and are preferably placed at a suitable density (e.g., dila-
tive on shear). Both structures require robust engineering
designs, and the sand dam requires strict tailings manage-
ment throughout the structure’s life by qualified engineer-
ing professionals with relevant practical experience in order
to achieve a suitably constructed containment.
Tailings facilities are incrementally constructed (thin
lifts) with an operating lifetime that can span a decade to
a century depending on the size of the reserve. The engi-
neering behind these structures is complex requiring care-
ful tailings management and continuous quality assurance
and quality control (QA/QC). The QA/QC process should
be similar to traditional construction QA with the excep-
tion that it is performed incrementally over the life of the
structure. This creates a need for continuous evaluation of
the constructed dam for consistency with the design vision,
and planning for variance in the original design is a critical
tenet of tailings management and design.
Tailings practitioners apply a process of evaluating
the deposited tailings incrementally for adherence to the
intended design while planning for conditions that may
deviate from the original plan. Planned and managed
deviance and having a well-thought-out optional plan(s)
is known as the observational method. The observational
method is a powerful tool that lends itself well to tail-
ings dam construction. The process does have limitations