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Detailed Engineering Assessments Confirm Integrity of Main Hoisting Shaft at Prieska Zinc-Copper Project
Orion Minerals NL
Incorporated in the Commonwealth of Australia
Australian Company Number 098 939 274
ASX share code: ORN
JSE share code: ORN
ISIN: AU000000ORN1
Detailed Engineering Assessments Confirm Integrity Of Main Hoisting Shaft At Prieska Zinc-Copper Project,
Northern Cape, South Africa
Detailed visual and mechanical inspection of the top 380m of Hutchings Shaft completed.
Condition of shaft concrete lining and steelwork exceeds expectation.
Shaft steelwork mechanical integrity unaffected by having been submerged.
Shaft amenable to refurbishment and re-use.
Further inspections planned to obtain video footage to 200m below shaft water level.
Orion Minerals NL (ASX/JSE: ORN) (Orion or the Company) is pleased to share the latest results on detailed
inspections completed on the main hoisting shaft (Hutchings Shaft) at the Prieska Zinc-Copper Project (Prieska
Project). The Prieska Project is in the Northern Cape province of South Africa approximately 290km south-west of
the city of Kimberley (Figure 1). Prieska Copper Mine operated as an underground zinc and copper mine,
exploiting the Copperton deposit, between 1971 and 1991. Orion intends to establish new mining operations to
continue the extraction of the remaining Copperton deposit, a volcanogenic massive sulphide – style (VMS)
deposit, with significant residual potential.
“Figures" referred to throughout this announcement can be viewed on the pdf version of the announcement,
available on the Company's website, www.orionminerals.com.au.
Figure 1: Location of Prieska Zinc-Copper Project.
Detailed visual and mechanical inspections of the Hutchings Shaft barrel and steelwork, from the surface down
to a depth of 380m, have confirmed that the shaft steelwork and wall integrity have been well preserved. This
makes the option of refurbishing the existing shaft for future use a realistic and viable option to be considered in
ongoing bankable feasibility studies.
A large volume of engineering data has now been collected for assessment and is being used to formulate and
cost the detailed shaft refurbishment plan. This is a significant step towards de-risking the mine re-establishment
project.
The shaft inspections are being conducted as part of the ongoing mine feasibility and environmental studies at
the Prieska Project. Mine feasibility and environmental studies were commenced in July 2017, with the
appointment of lead consultants, DRA Projects SA Pty Ltd for mining studies and ABS Africa Pty Ltd for
environmental studies.
The commercial viability of mining operations, planned to be established within the footprint of the historic Prieska
Copper Mine, is substantially enhanced by being able to leverage off the substantial suite of pre-existing
infrastructure which includes, amongst others:
- an operational water treatment plant and associated 60km long water pipeline, supplying water from
the Orange River to the project site;
- the Cuprum Electrical Substation, situated on the project site, already connected to the national grid
and owned by the national power utility company, ESKOM;
- a 60km tarred road, which forms part of the regional R357 highway, linking the project site to the nearby
town of Prieska;
- the Copperton village, located 4km away from the main hoisting shaft;
- a 1.7km airstrip near the project site;
- the Upington to De Aar railway line that runs past the Groveput siding, 45km away from the project site;
- over 37km of underground excavations including roadways, pump stations, workshops and a crusher
chamber;
- a decline roadway and three vertical vent shafts; and
- a concrete-lined, 1km deep, vertical hoisting shaft (Hutchings Shaft).
As such, a detailed assessment of the mechanical and structural condition of the existing Hutchings Shaft has
been commissioned to assist with planning and costing of the shaft refurbishment strategy. The Hutchings Shaft is
intended to be recommissioned as the main means of rock hoisting, people and materials transportation and as
the primary means of ventilation intake.
The Hutchings Shaft serviced historical mining operations until the mine closed in 1991. During that time, the mine
produced 430,000 tonnes of copper and 1.01 million tonnes of zinc from 45.6 million tonnes of ore processed, at
annual production rates that peaked at 3.0 million tonnes per annum. Almost all production was hoisted through
the Hutchings Shaft.1
Shaft Configuration
The Hutchings Shaft was established approximately 350m away from the upper part of the orebody. It was
originally sunk to a depth of 841m and later deepened to the present 1,024m (Figure 2).
Figure 2: Isometric views of Hutchings Shaft and existing excavations.
The shaft is concrete-lined with an inside diameter of 8.84m. The shaft steelwork consists of a lattice of buntons
and dividers that are configured to provide two compartments to house rock hoisting skips and a central
compartment to house a square cage to transport men and materials (Figure 3).
The shaft barrel is topped by a rectangular concrete headframe which is 68.6m high (Figures 4 and 5). The shaft
operated with a Koepe-type winder mounted on top of the headframe to hoist the rock skips and a separate,
ground-based, double-winder to lift the people and materials cage.
The shaft was designed with the capacity to hoist 330,000 tonnes of rock per month.
Figure 3: (Top) Plan-view schematic showing the configuration of the Hutchings Shaft and (Bottom) photograph of the
Hutchings Shaft taken in January 2018 showing a similar plan-view perspective, with the accumulated water at the 350m
Level.
Shaft Decommissioning and Closure
The Hutchings Shaft was decommissioned when mining operations ceased in 1991 and has not been in use since
then. The shaft barrel was sealed by a concrete plug and the headframe bricked-in to prevent inadvertent and
unauthorised access and use of the facilities. It is suspected that a corrosion inhibitor may also have been applied
to the shaft steelwork prior to decommissioning.
Figure 4: Hutchings Shaft and winder room during historic mining operations (1971 to 1991).
Figure 5: The Hutchings Shaft headframe, standing 68.6m high (2017).
The winder room on top of the concrete tower was removed and most of the shaft equipment dismantled and
sold. The original winder is still in use at a mining operation in South Africa (Figure 6)
Figure 6: The original Hutchings Shaft rock winder in use currently at a South African mining operation.
Since mine closure, groundwater has slowly accumulated in the mine workings, submerging a portion of the shaft.
The water level has risen to within 350m of the surface, thus submerging 670m of the lower portion of the shaft.
Preliminary Shaft Condition Inspection
Determining the condition of the shaft for costing and planning purposes has required formulating inspection
programs that account for a large part of the shaft barrel being under water.
Orion obtained permission and re-established access into the underground mine and the shaft barrel from March
2017. During that time, Orion completed a preliminary assessment of the shaft integrity by commissioning an expert
team to undertake:
- visual inspections of the shaft barrel down to the water level;
- an engineering assessment of select steelwork in the headframe and shaft barrel;
- water quality testing at various depths down to 900m below surface; and
- probing of the shaft barrel to confirm the shaft is clear of large obstructions and excessive debris.
These preliminary inspections concluded that:
- no substantial obstructions were in the shaft barrel;
- the water quality was unlikely to accelerate corrosion;
- the main steel members, bolts and welding in the headframe and shaft barrel had been preserved; and
that
- shaft refurbishment and re-use was a realistic option to be considered for further assessment.
Detailed Shaft Inspection Method Statement
As a follow-on from the preliminary shaft inspections conducted in 2017, a detailed inspection program has been
under way since the start of 2018. The initial stage of this inspection program aimed to accurately determine the
mechanical and structural integrity of the shaft steel work down to a depth of 380m.
The second stage of inspection will involve obtaining video footage of the shaft steelwork and walls to a depth
of at least 200m below the accumulated water level.
Various characteristics of the shaft steelwork and infrastructure were assessed as part of the first stage. Table 1
summarises characteristics assessed, and methodologies employed.
Characteristic Assessment Methodology
Buntons, dividers and guides identification Aerosol paint markers
Buntons, dividers and guides condition Visual assessment / detailed photography
Buntons, dividers and guides connections condition Visual assessment / detailed photography
Shaft barrel connection condition Visual assessment / detailed photography
Shaft services and piping condition Thickness testing instrument
Bunton, divider and guide thickness testing Thickness testing instrument
Piping thickness testing Thickness testing instrument
Shaft wall / concrete lining condition Visual / mechanical assessment / detailed photography
Shaft dimensions assessment Laser distance measuring instrument
Bunton, dividers and guide positioning Laser distance measuring instrument
Steelwork weld integrity Magnetic particle inspection instrument (NDT)
Table 1: Shaft steelwork and infrastructure characteristics inspected during campaign.
The first stage of inspections has been undertaken in three phases: Phase one involved labelling steel members,
visual inspections and photography.
Phase two of inspections involved thickness testing of steelwork, followed by non-destructive testing of
connections and welds using magnetic particle inspection (MPI).
The final phase of inspection involved a diving expedition to obtain a sample of steelwork from 30m below the
water level, as well as retrieving comparison samples from above the waterline. These samples will assist with
determining the comparative condition of submerged shaft steel work.
Figure 7: (LHS) Diving platform at the 350m Level below surface. (RHS) The divers retrieved a section of steelwork from 30m
below the water surface to allow assessment of corrosion/preservation of submerged shaft steelwork.
Figure 8: (LHS) Divider from submerged Bunton Set number 81 tested steel thickness to 5.0mm; (Middle) section through
retrieved Bunton (RHS) location where bunton section was removed.
Assessment of Inspection data
Based on collected information the following preliminary conclusions have been made:
- The primary steelwork, connections and shaft walls presents well and better than was expected by the
shaft inspection team.
- Significant corrosion is limited to the top 45m of primary steelwork in the shaft. Structural integrity of the
steelwork below this level is amenable to re-use following selective replacement and repairs.
- Shaft steelwork recovered from underwater has been unaffected by being submerged and shows no
signs of added deterioration compared to similar steelwork from above the waterline.
- As expected, secondary light steelwork and pipework is compromised by corrosion and will be replaced.
Preliminary indications are that shaft refurbishment is the optimal route of re-establishing hoisting capabilities of
the Hutchings Shaft. The steelwork is repairable, though a portion of the steelwork will require replacement,
generally in line with assumptions that were made as part of formulating conceptual planning.
Dewatering Assessment
Investigations into the most practical manner to dewater the mine are well advanced. The favoured dewatering
approach is the use of a large submersible pump, lowered to the bottom of the shaft on its pipe column and
capable of pumping the water from the bottom of the shaft in a single lift. Available models of such pumps can
operate at pumping rates of up to 1,300 m3/hour, which could completely dewater the mine within nine months,
(see Figure 9 for example). The pump and rising main could be placed in the shaft such that the assembly does
not interfere with concurrent shaft refurbishment works.
Figure 9: A Ritz pump recently used for mine dewatering at an operation in the Democratic Republic of Congo.
Further Work
A large volume of useful data has been collected on the condition of the shaft and headframe above the water
level and 30m below the water level.
This information will be used to formulate and cost a shaft refurbishment plan for the mine feasibility study.
A remote-operated vehicle will be used to obtain additional video footage of the shaft steelwork and walls to a
depth of at least 200m below the water level.
Detailed civil and structural assessment of the concrete headframe will be conducted once winder selection and
proposed placement is completed.
Work on optimising the management of the water pumped from the mine during dewatering is in progress.
Orion’s Managing Director and CEO, Errol Smart, commented:
"it is encouraging that the Hutchings Shaft steel work is in such good condition after 26 years of being inoperable
and submerged. The shaft refurbishment plan forms a significant part of our strategy to take advantage of existing
infrastructure which will reduce the Capex burden on the Prieska Project build. The existing shaft infrastructure is
sufficiently-sized so that we are free to optimise mine production rates to the JORC compliant Mineral Resource
estimates we end up delineating. This gives us great design latitude to make the most of what remains at Prieska”.
Errol Smart
Managing Director and CEO
2 February 2018
ENQUIRIES
Investors Media JSE Sponsor
Errol Smart – Managing Michael Vaughan Barnaby Hayward Rick Irving
Director & CEO
Denis Waddell – Chairman Fivemark Partners, Australia Tavistock, UK Merchantec Capital
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Competent Persons Statement
The information in this report that relates to Orion’s Exploration Results at the Maisqhame Project and Namaqua-Disawell
Project, complies with the 2012 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and
Ore Reserves (JORC Code) and has been compiled and assessed under the supervision of Mr Errol Smart, Orion Minerals
Managing Director. Mr Smart (PrSciNat) is registered with the South African Council for Natural Scientific Professionals, a
Recognised Overseas Professional Organisation (ROPO) for JORC purposes and has sufficient experience that is relevant to
the style of mineralisation and type of deposit under consideration and to the activity being undertaken to qualify as a
Competent Person as defined in the 2012 Edition of the JORC Code. Mr Smart consents to the inclusion in this announcement
of the matters based on his information in the form and context in which it appears. The Exploration Results are based on
standard industry practises for drilling, logging, sampling, assay methods.
Disclaimer
This release may include forward-looking statements. Such forward-looking statements may include, among other things,
statements regarding targets, estimates and assumptions in respect of metal production and prices, operating costs and
results, capital expenditures, mineral reserves and mineral resources and anticipated grades and recovery rates, and are or
may be based on assumptions and estimates related to future technical, economic, market, political, social and other
conditions. These forward-looking statements are based on management’s expectations and beliefs concerning future
events. Forward-looking statements inherently involve subjective judgement and analysis and are necessarily subject to risks,
uncertainties and other factors, many of which are outside the control of Orion. Actual results and developments may vary
materially from those expressed in this release. Given these uncertainties, readers are cautioned not to place undue reliance
on such forward-looking statements. Orion makes no undertaking to subsequently update or revise the forward-looking
statements made in this release to reflect events or circumstances after the date of this release. All information in respect of
Exploration Results and other technical information should be read in conjunction with Competent Person Statements in this
release. To the maximum extent permitted by law, Orion and any of its related bodies corporate and affiliates and their
officers, employees, agents, associates and advisers:
- disclaim any obligations or undertaking to release any updates or revisions to the information to reflect any change in
expectations or assumptions;
- do not make any representation or warranty, express or implied, as to the accuracy, reliability or completeness of the
information in this release, or likelihood of fulfilment of any forward-looking statement or any event or results expressed
or implied in any forward-looking statement; and
- disclaim all responsibility and liability for these forward-looking statements (including, without limitation, liability for
negligence).
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