The Namdini has many characteristics typical of mesothermal Birimian gold deposits.

The Namdini gold deposit is a large, structurally controlled, orogenic gold deposit within the Nangodi Greenstone Belt, with numerous features similar to deposits found elsewhere in late Proterozoic Birimian terranes of West Africa. To date the Namdini gold deposit has been delineated over a strike length of 1.15 km, up to 300 m wide and 700 m deep.

The rock types comprising the Namdini Gold Project included a steeply west dipping Birimian sequence of interbedded, foliated, metasedimentary and metavolcanic units which have been intruded by a medium-grained granitoid and diorite. The southern part of the Project is covered by flat-lying Voltaian Basin clastic sedimentary rocks that have been deposited unconformably on the Birimian sequence and postdate mineralization and the host sequence.

Underneath the weathering profile, the Birimian units include metasedimentary, metavolcanic, granitoid (tonalite) and diorite. The metasedimentary and volcaniclastic lithologies have been intensely altered with a resulting pyrite-carbonate-muscovite-chlorite-quartz assemblage. Alteration is most prevalent in the volcaniclastic units. Similarly, the tonalite is extensively altered and has been overprinted by silica-sericitecarbonate assemblages.

In all rock types, the mineralization is accompanied by visible disseminated sulfides of pyrite and very minor arsenopyrite ........

Mining will comprise a conventional hydraulic shovel operation typically using 400 t class excavators in backhoe configuration for mining ore and face-shovel configuration for mining waste. Rigid body Cat 785 (134 t) class dump trucks will be used for hauling ore and waste on designed access roads. An auxiliary mining fleet of dozers, graders, water carts and utility vehicles will support the mining operation.

Mining will be carried out using staged cut-backs with five identified Phases incorporated within the LOM Final Pit. The mining schedule defines movement of ore and waste on 10 m mining benches, by year, for each of the Phases. It is proposed to mine three flitches in the ore (allowing for blast heave), within 10 m benches.

Road width was based on 3.5 times the largest envisaged size truck width, plus an allowance for the high wall drain (culvert) and the low wall safety berm. The road was designed at 30 m overall width including an allowance of 4 m for the safety berm that should be a minimum of half the height of the wheel for the haul truck (0.5 times 3.1 m, so about 1.5 m high).

The Namdini Project will be mined on an outsourced contract.

The maximum peak fleet requirements for the Namdini Project are shown in Table 146 with an expected maximum 27 (134 t capacity) rigid haul trucks and four shovels, three in face shovel configuration and 1 in backhoe configuration.

The mine design for the Namdini Gold Project co ........

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Raw water supply and distribution
Raw water for the project will be extracted by pumps from the White Volta River and duty/standby transfer pumps used to deliver water to the raw water storage dam located east of the plant site. The impoundment will have a nominal capacity equivalent to ninety (90) days’ worth of site raw water demand.

Raw water will be pumped by a single duty pump with an uninstalled standby from the dam to the plant raw water tank.

Raw water will be used to feed the potable and stripping water treatment plants as well as reagent mixing, and gland water and cooling water make-up.

The raw water tank overflows to the raw water pond which has a capacity equivalent to a nominal 12 hours of plant raw water supply. The pond and tank are both connected to a suction manifold which supplies duty standby plant raw water pumps and low- and high-pressure gland water pumps. The high-pressure gland water systems are used for the multistage tailings pumps.

The tank overflow is also used for make-up to the process water pond.

Fire water
Fire water for the process plant will be drawn from the bottom of the raw water tank. The reserve is based on four hours of continuous firefighting using two hydrants at 36 m3/h.

The fire water system will comprise a pump with an electric motor to supply fire water at the required pressure and flowrate and backup diesel driven pump that will automatically start in the event that electric power supply fails. An electric jockey pump will maintain firefighting ring main pressure when the system is not in use.

Fire hydrants and hose reels will be placed throughout the process plant, fuel storage and plant offices at intervals that ensure complete coverage in areas where flammable materials are present.

Filtered and potable water
Raw water will supply the water treatment plant in the process plant. Water will be filtered and sent to the filtered water tank and a potable water treatment plant for sterilisation.

Additional ultra-violet sterilisation units will be installed on outgoing potable water distribution headers if required. Potable water will be reticulated from the potable water storage tank to the site ablutions, safety showers and other potable water outlets. Potable water will also be pumped to the mine services facilities.

Filtered water will be used in the plant for cooling system make up, cyanide wash and eluant solution make-up, high pressure cathode wash sprays, mill feed chute seal water, carbon transfer and elution heat exchanger de-scalant make up.

A sump pump is installed at the plant potable water plant areas.

Process water
Process water will be separated into two systems. The two circuits are designed to operate separately to avoid cyanide and high pH water being returned from the CIL TSF to the flotation circuit. The presence of cyanide and/or a high pH in the flotation circuit will have a detrimental effect on flotation.

The grinding and flotation circuits use water recovered in the tailings and concentrate thickeners and decant water from the flotation tailings TSF with make-up from raw water.

Water recovered from the CIL TSF decant with make-up from raw water will be used in the regrind and the CIL circuits only. CIL TSF Decant water and raw water make-up are delivered to the plant cyanide water tank. Duty and standby pumps will deliver water to the regrind feed pump suction for dilution and the CIL area for washdown and service water. Cyanide process water will also be used for cyanide make-up in the reagent area.

The Process Water pond is filled from the flotation TSF decant and any excess thickener overflow water plus raw water make-up that overflow from the raw water tank. Duty and standby high pressure pumps will deliver water to the SAG mill pebble dewatering screen, ball mill trommel and gravity screen and flotation concentrate launder sprays plus make up to the thickener overflow water tank that supplies the low pressure process water pumps delivering water to the SAG and ball mill feed chutes and cyclone feed hopper dilution.

A duty fluidising water pump is provided for each gravity concentrator.

Duty and standby pumps will be provided for raw water, grinding water and process water. The opportunity will exist for anti-scalant to be added to condition the grinding water and reduce fouling of pipelines, spray nozzles and screen decks.