In 2002, Golden Star Resources put the Prestea Mine (previously known as the New Century Mine) under care and maintenance and conducted exploration and feasibility studies to determine the economic viability of re-opening it for commercial purposes. The mine had operated for over 100 years and was mined to 34 levels with a strike length of over 6 km.
Whilst on care and maintenance the mine was partially flooded, requiring dewatering to put the water table between 25 and 26 Levels and rehabilitation of shafts and airways. During this time, exploration teams identified a high-grade orebody in the West Reef, about 200 m west of the main mining reef. This narrow vein orebody will be extracted by driving an Alimak raise upwards then drilling along the strike of the orebody. Pillars left between the Alimak stopes, along with a crown pillar, will improve ground stability between vertical stopes.
When the orebody was discovered, there was very limited airflow to 24 Level. Only a small booster fan pulled air from the southernmost intake shaft towards the main exhaust. This fan provided approximately 4-5 m3/s for initial exploration. Two small surface exhaust fans also operated at the top of the south waste shaft to provide the primary exhaust for the mine.
SRK was contracted to audit and troubleshoot the ventilation system at the Prestea Mine and provide a safer working environment at the West Reef. Our feasibility-level ventilation study identified ways of providing sufficient airflow to support mining of the West Reef in future mine projections. This included replacing the doors on 24 Level with airlock doors between the intake and exhaust shafts and sealing old stopes along the 3.5 km strike length connecting the West Reef development area.
Our ventilation analysis also indicated fan operating points needed at various stages in the mine cycle plus other ventilation modifications to enhance the system. We proposed initially installing an interim booster fan to push air up from 24 Level to the main exhaust shaft and later replacing the main surface fans with a single, larger exhaust fan. Based on our ventilation analysis, main and booster fans were procured by Golden Star. The new surface fans were installed in mid-2016 and we supported initial field-testing of the fan start-up.
SRK has since been involved with providing training to staff on proper field measurement techniques and ventilation modeling practices. We are also generating updated studies on the ventilation system as mine projections and conditions change.
