1. Operations: 84 Wilkinson Road, Freetown, Sierra Leone
T: +232 (0)22 232 257 F: +232 (0)22 230 476 Reg. No. 1057/2003
Registered Office: Akara Building, 24 De Castro Street, Wickhams Cay 1, Road Town, Tortola, British Virgin Islands, Reg. No. 552189
Title
SECONDARY BLASTING STANDARD OPERATING PROCEDURE
Purpose
• To outline the standard parameters and procedure to be followed when conducting
secondary blasting
Scope
• This procedure is applicable to all personnel involved in secondary blasting starting from
preparation, marking, drilling, measuring, charging, stemming to firing of boulders and toes
APPROVAL SIGNATURE RECORD
Reviewer Role Title Approval
Document Compiler Blasting Engineer Collins Sikanyika
Reviewer 1 Drilling Manager Corne Muller
Reviewer 2 Chief Safety Officer Derick Van Der Merwe
Final Approval General Manager Christo Swanepoel
1. Introduction
Secondary blasting involves boulder blasting and toe blasting. There are two
methods of secondary blasting namely Popping and Plaster or Mud Blasting. Both of
these methods can generate significant nuisance from airblast (noise) and flyrock.
Popping uses fewer explosives than plaster but it involves considerable drilling
expense. Sometimes use of mechanical rock breakers to reduce oversize (boulders)
is preferred because is too noisy and more expensive.
This standard operating procedure highlights how secondary blasting is safely
conducted at Koidu Mine site it using the method of Popping.
2. Objective
To provide a standard safe work practice for drilling and blasting of boulders and toes
to minimize the risks of airblast and flyrocks

2. Operations: 84 Wilkinson Road, Freetown, Sierra Leone
T: +232 (0)22 232 257 F: +232 (0)22 230 476 Reg. No. 1057/2003
Registered Office: Akara Building, 24 De Castro Street, Wickhams Cay 1, Road Town, Tortola, British Virgin Islands, Reg. No. 552189
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3. Definitions
Secondary blasting - blasting of oversize rocks usually from previous blast
Popping – secondary blasting where an explosive charge is placed in a hole drilled
to center of rock then stemmed for blasting
Plaster or Mud blasting – secondary blasting where explosives are on top of the
boulder and packed in place with mud or clay for blasting
Boulder - any rock which due to its geometry cannot be safely loaded out of the face
by the available digging equipment
Primer – cap sensitive cartridge of high explosive which is used to initiate explosion
Misfire – charge or part of charge that has failed to fire as planned
Toe – an undesirable part of the blast which does not get blasted properly as
planned with the production blast and cannot be mine out
Flyrock – undesirable rock that is propelled through air from a blast
Airblast – shock wave travelling through the air resulting from the detonation of
explosive
Blasthole – a hole drilled into a rock for the placement of explosive to break the rock
Stemming – Inert material used in the collar part of the blasthole to confine the
energy (gases) generated during detonation
Blast Crew - personnel who are working under the direction of the Blasting Engineer
4. Procedure
4.1. Boulder Blasting
Preparation
Where possible, any boulder should be removed from the face and out of the
loading area prior to drilling. If room is available, boulders should be
arranged in a line on the bench in an area that is out of the way and which
provides adequate access for the drill.
Marking and Observation
Where possible, any boulder that is set aside for blasting should be marked
with spray paint by the Blasting Engineer. The marking should include the
blasthole position and the depth alongside to be drilled. Wherever practical,
all the boulders in one particular location should be marked for drilling from
the same side.
The position of the blasthole is determined by the size and shape (geometry)
of the boulder. In principle the blasthole should be positioned in the center of
the boulder and the depth should be determined in such a way that it just past
the center of the boulder about 50% to 60% of the boulder thickness as
illustrated in Table 4.1 below.
If more than one (1) blasthole is required due to the geometry of the rock,
care shall be taken to ensure that the blastholes do not intersect. Where
possible, only the minimum number of holes should be drilled in each
oversize rock so that the charges can work effectively. Where possible, all
blastholes marked shall be accessible from the bench floor.

3. Operations: 84 Wilkinson Road, Freetown, Sierra Leone
T: +232 (0)22 232 257 F: +232 (0)22 230 476 Reg. No. 1057/2003
Registered Office: Akara Building, 24 De Castro Street, Wickhams Cay 1, Road Town, Tortola, British Virgin Islands, Reg. No. 552189
3 of 4
Drilling
When drilling boulder, each blasthole should be drilled on the marked position
and to the correct depth as marked by the Blast Engineer. It is the
responsibiltity of the Drilling Manager to ensure that blastholes are drilled as
marked or planned.
Once a blasthole is drilled and the depth has been checked to ensure that the
hole does not daylight, it should be marked with a painted circle by the Drilling
Shift Boss. If a hole is too short, daylights or is otherwise in-effective, it should
be marked with a painted cross by the Drilling Shift Boss.
If a blasthole has already been drilled whether it be from a previous shift or an
old Butt from the shot it was pulled from, the Drilling Shift Boss will inspect the
rock to see if the hole has penetrated the boulder right through. If the
blasthole has not been drilled right through, the Drilling Shift Boss must
instruct the driller to drill another blasthole in the same direction ensuring that
the barrels do not intersect.
Care should be taken with large rocks to avoid aiming the blasthole in the
direction of something vulnerable to the rifle barrel effect.
Charging
Before charging boulders, all the blastholes should be rechecked for drilling
accuracy as explained above under drilling by the blasting crew. When
charging, each hole shall be loaded with just enough charge to fracture or
split the rock. The charge shall be pushed to end of the blastholes using a
charging stick made out of a non-sparking material. Charging will be done
using either of the two explained methods below;
Method 1: Using a primer (bomb) consisting of Cartridge(s) of splitex and
downline with 500ms or cortex 10g and the charges will be determines and
guided as depicted in Table 4.1 below. The advantage of charging boulders
with cartridges is that there is easy regulation of the amount of charge to put
in the blastholes.
Table 4.1: Guide lines for Boulder Blasting in Granite

4. Operations: 84 Wilkinson Road, Freetown, Sierra Leone
T: +232 (0)22 232 257 F: +232 (0)22 230 476 Reg. No. 1057/2003
Registered Office: Akara Building, 24 De Castro Street, Wickhams Cay 1, Road Town, Tortola, British Virgin Islands, Reg. No. 552189
4 of 4
Method 2: Using primer (bomb) consisting of 400g booster and downline with
500ms or cortex 10g then dipped in bulk emulsion e.g. HEF 100 before
charging to increase the energy. No pumping of bulk emulsion in the blasthole
will be done in boulder blasting apart from just dipping the prime in bulk
emulsion because it very trick to regulate pumping of smaller quantities of
bulk emulsion in the blastholes using the charging unit.
When fired, the blasting accessories and product used to break the boulder
should be recorded by the blasting crew.
Stemming
Once charged, blasthole shall be carefully stemmed to the collar with either
tailings or drill chipping or mud tamped into the hole to increase breakage and
minimize airblast and flyrocks.
Firing
Prior to firing boulders, the site should be physically walked by the blast crew
to ensure that each blasthole is tied in. After firing, the area must be re-
walked by the blast crew to ensure that each hole has been initiated and that
there are no signs of visible misfire.
Blasting of boulder shall be conducted as per Blasting Awareness Procedure
and on specific dates and time in line with the blasting schedules for the
week.
4.2. Floor and Toe Blasting
Preparation
Blasting Engineer should ensure that hard toe area is proper clean and
exposed. It should be ensured that no loose material should be on top of the
toe area before marking or staking of the drill pattern is done.
Marking and Observation
The blasting Engineer is responsible in marking the blasthole location (XY) on
the floor and toe blasting area then survey is responsible for determining the
hole depths (Z) and allocation of blasthole IDs or numbers. In determining the
pattern size, the blasting engineer will be guided by the average depths of
blastholes using the Table 4.2 below as a guideline.
Drilling
All blastholes should be drilled on the marked locations to the planned
depths. Poor drilling accuracy (XYZ) may cause smaller burdens and
spacings which increase the chance of flyrocks and airblast as the energy will
not be properly distributed in the rock.
Charging
All blastholes shall be checked for drilling accuracy (XYZ) against the planned
by the blasting crew. If the drilling accuracy is correct, they should be charged
using bulk explosive (HEF 100) and if not, they should be indicated as redrills
as per Drilling and Blasting Parameters Standard Operating Procedure but
the charges will be regulated as the guideline below in Table 4.2.

5. Operations: 84 Wilkinson Road, Freetown, Sierra Leone
T: +232 (0)22 232 257 F: +232 (0)22 230 476 Reg. No. 1057/2003
Registered Office: Akara Building, 24 De Castro Street, Wickhams Cay 1, Road Town, Tortola, British Virgin Islands, Reg. No. 552189
5 of 4
Table 4.2: Guideline for Toe Blasting
NB: Small Toes which are less 1.5m depth or thickness on the floor and side
wall will also be drilled, charged, stemmed and fired as boulders above.
Stemming
Stemming of all blastholes shall be done using aggregate or crushed stones
to the collar just like production blasholes to provide effective stemming to
minimize flyrocks and airblast.
Firing
The charged blastholes shall be tie up for firing just like production blastholes.
All the blasholes will be inspected to insure that they are tie in and after the
blast inspection shall be done for misfires by the blasting crew.
Blasting of toes shall be conducted as per Blasting Awareness Procedure and
on specific dates and time in line with the blasting schedules for the week.
5. Reference Documents
Drilling and Blasting Standard Operating Procedure
Blasting Safety Awareness Standard Operating Procedure
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