1
25-042
Improved Drill and Blast Designs Free $3.6m of Ore for Surface
Copper Mine
Tacio Ferreira
Dyno Nobel, Phoenix, AZ
Liz Diaz
Capstone Copper, Globe, AZ
ABSTRACT
Capstone Copper’s Pinto Valley Mine faced challenges in
recovering rock and ore on final walls because of geotech-
nical constraints that require restrictions on methods for
loading blastholes adjacent to the pit boundaries to preserve
wall stability. The operation had been using the same drill
and blast designs for years. With changing geology, such
as harder rock, as mining progressed, material was being
left unmined in final walls because of poor breakage. The
amount of unrecovered, unprocessed ore was estimated at
approximately 380,000 tons a year generated from an aver-
age of 60 final wall blasts performed annually. The engi-
neering team from Capstone and Dyno Nobel engaged to
minimize the amount of material left on the final pit walls.
This paper presents how we collected data, reviewed
design standards, and found opportunities to improve ore
recovery from pit final walls without increasing drilling and
blasting costs. The results collected from implementing the
new design on two benches showed the potential for extra
revenue of approximately $3.6 million generated annu-
ally from reducing final wall unrecoverable underbreak by
nearly 71% on the mine’s highwalls.
INTRODUCTION
The Pinto Valley mine is located approximately 80 miles
East of Phoenix, more precisely in Globe, Arizona, and has
been in operation since 1972. Pinto Valley is a copper por-
phyry deposit. The primary host rock is the Precambrian-
age Lost Gulch Quartz Monzonite (equivalent to the
Oracle Granite or Ruin Granite). The deposit’s economic
mineralization is a hypogene ore body with chalcopyrite,
pyrite, and minor molybdenite as the only significant pri-
mary sulfide minerals. The open-pit mine extracts and
processes copper ore locally with the capacity to process
60,000 metric tons (approximately 66,000 tons) per day.
The operation produces a primary copper sulphide concen-
trate and a by-product molybdenum concentrate (1).
The mine uses traditional hard-rock mining methods
(i.e., drilling, blasting, loading, and hauling) to extract the
ore and transport it to the processing facilities. A series of
drilling-and-blasting standards and rules were developed
along the years of operation to meet fragmentation (i.e.,
dig-ability and processing), and slope stability (i.e., vibra-
tion limits) requirements. The drilling-and-blasting bench
heights at the mine are 45ft (13.7m). Where slope stabil-
ity allows, single 90ft (27.4m) benches are mined with two
passes of 45ft (13.7m) benches. Single-pass pre-split lines
help prevent damage and keep a cleaner highwall.
With the primary objective of maintaining highwall
stability near final pit walls, the mine faced challenges
associated with material unrecovered on the walls over the
years. This generated loss of revenue from unrecovered,
unprocessed ore. Other issues such as extra time spent to
trying to recover the hard material on the walls using sec-
ondary breakage techniques (e.g., hydraulic hammers and
excavators) often unsuccessful, coarse fragmentation near
the wall, reduced catch bench functionality, and wall stabil-
ity problems (e.g., overhangs) were also common and vis-
ible on the walls mined years prior (see Figure 1).
25-042
Improved Drill and Blast Designs Free $3.6m of Ore for Surface
Copper Mine
Tacio Ferreira
Dyno Nobel, Phoenix, AZ
Liz Diaz
Capstone Copper, Globe, AZ
ABSTRACT
Capstone Copper’s Pinto Valley Mine faced challenges in
recovering rock and ore on final walls because of geotech-
nical constraints that require restrictions on methods for
loading blastholes adjacent to the pit boundaries to preserve
wall stability. The operation had been using the same drill
and blast designs for years. With changing geology, such
as harder rock, as mining progressed, material was being
left unmined in final walls because of poor breakage. The
amount of unrecovered, unprocessed ore was estimated at
approximately 380,000 tons a year generated from an aver-
age of 60 final wall blasts performed annually. The engi-
neering team from Capstone and Dyno Nobel engaged to
minimize the amount of material left on the final pit walls.
This paper presents how we collected data, reviewed
design standards, and found opportunities to improve ore
recovery from pit final walls without increasing drilling and
blasting costs. The results collected from implementing the
new design on two benches showed the potential for extra
revenue of approximately $3.6 million generated annu-
ally from reducing final wall unrecoverable underbreak by
nearly 71% on the mine’s highwalls.
INTRODUCTION
The Pinto Valley mine is located approximately 80 miles
East of Phoenix, more precisely in Globe, Arizona, and has
been in operation since 1972. Pinto Valley is a copper por-
phyry deposit. The primary host rock is the Precambrian-
age Lost Gulch Quartz Monzonite (equivalent to the
Oracle Granite or Ruin Granite). The deposit’s economic
mineralization is a hypogene ore body with chalcopyrite,
pyrite, and minor molybdenite as the only significant pri-
mary sulfide minerals. The open-pit mine extracts and
processes copper ore locally with the capacity to process
60,000 metric tons (approximately 66,000 tons) per day.
The operation produces a primary copper sulphide concen-
trate and a by-product molybdenum concentrate (1).
The mine uses traditional hard-rock mining methods
(i.e., drilling, blasting, loading, and hauling) to extract the
ore and transport it to the processing facilities. A series of
drilling-and-blasting standards and rules were developed
along the years of operation to meet fragmentation (i.e.,
dig-ability and processing), and slope stability (i.e., vibra-
tion limits) requirements. The drilling-and-blasting bench
heights at the mine are 45ft (13.7m). Where slope stabil-
ity allows, single 90ft (27.4m) benches are mined with two
passes of 45ft (13.7m) benches. Single-pass pre-split lines
help prevent damage and keep a cleaner highwall.
With the primary objective of maintaining highwall
stability near final pit walls, the mine faced challenges
associated with material unrecovered on the walls over the
years. This generated loss of revenue from unrecovered,
unprocessed ore. Other issues such as extra time spent to
trying to recover the hard material on the walls using sec-
ondary breakage techniques (e.g., hydraulic hammers and
excavators) often unsuccessful, coarse fragmentation near
the wall, reduced catch bench functionality, and wall stabil-
ity problems (e.g., overhangs) were also common and vis-
ible on the walls mined years prior (see Figure 1).