SEMAFO Inc reports that there has been a pit wall failure at Mana in the Wona pit. No mining was underway in the area, and no-one was injured. A pit wall failure occurred on Friday August 2, and the team has been “working diligently on assessing the impact.” The incident took place in the northern part of the Wona pit where there is no active mining. No-one was injured, and no equipment was damaged.
“Currently, we are mining in the southern part of Wona pit. However, under the 2019 mine plan, some 45,000 oz were expected from the northern portion of the pit between late August and year-end. To mine securely and regain access to ore in Wona North, we will have to push back the pit wall and mine approximately 6 Mt of waste material. As a result, mining of ore in the northern part of the pit will be deferred until the first quarter of 2020. These 6 Mt were part of the life of mine plan in 2021 and therefore do not represent additional tonnes or cost.”
After evaluating multiple scenarios to compensate for the ore from Wona North in 2019, SEMAFO established that there would be insufficient ore to feed the mill for approximately ten weeks. It now expects to suspend the processing of ore at Mana between mid-August and end of October. The mining plan for the Siou pit remains unchanged. Development of Siou open pit is ongoing with ore expected in the fourth quarter; and development of Siou underground is proceeding on time and on budget.
In addition to ongoing geotechnical assessment, SEMAFO says it conducts yearly independent geotechnical reviews in conjunction with Golder Associates that include pit slope parameters. “Safety will remain our top priority as we conduct a full analysis to ensure continued stability of our mining operations.”
SEMAFO estimates the impact at Mana to be approximately 40,000-50,000 oz of lower production than originally contemplated. Therefore, annual guidance at Mana has been revised to 130,000-140,000 from the original 170,000-190,000 oz. “There is no change to our Mana all-in sustaining cost (AISC) guidance. During the shutdown, mining costs of approximately $22 million for Siou and Wona will be capitalised in development and there will be a non-recurring charge of approximately $7 million mostly representing fixed costs for the period.” Boungou guidance remains unchanged at between 220,000 and 240,000 ounces of gold at an AISC of between $470 and $510 per ounce.