The Bisha Mine is located in a semi-arid ecosystem, and accordingly, careful water stewardship is one of our most pressing economic, environmental and social issues. Water is not only critical to mining operations but access to water is also an essential human right as well as being indispensable to maintaining healthy ecosystems. We continually look for ways to minimize fresh water use and maximize water recycling to protect surrounding habitats and community water sources. We periodically review our mine water plan, monitor our daily water balance and consumption, and conduct regular water monitoring. Additional flow meters were installed in 2015 to improve the accuracy of water balance management.
In 2015, we extracted a total of 1.74 million cubic metres (m³) of water for Bisha Mine operations compared to 1.93 million m³ in 2013 (a 9% decrease). All water used at the mine is drawn from groundwater resources (primarily the Mogoraib aquifer as well as a lesser amount from dewatering the mine pit located in the Freketetet aquifer and an aquifer near the Harena pit). Rainfall also contributes limited water resources, primarily supporting rehabilitation activities. Both the Company and two local communities (Mogoraib and Aderat) rely on the aquifer located along the Mogoraib River. The remaining two aquifers supplying BMSC are not shared with any community due to distance.
Based on the results of the groundwater monitoring program (which are provided to the Eritrean Impact Review Committee), there is no evidence to date that the mine operations impact water quality. To evaluate the potential impact on the aquifer dynamics, monitoring wells are located near the Mogoraib production wells. A declining trend in the static water level at the Mogoraib production field has been observed close to the production wells, where maximum drawdowns ranging from 2 to 3.5 m below background were measured during 2015, an increase of 0.5-1.0 m from 2014. It is important to note that these measurements reflect the conditions near the monitoring wells and don’t necessarily signify a decline for the aquifer in general. Monitoring data has shown local community access to water is not affected to date and BMSC has also not received any grievances related to water. This aquifer is relatively large, with rapid recharge observed during the annual wet season. To understand the potential medium and long term impacts of water extraction on the Mogoraib and other aquifers, further hydrological investigations were initiated in 2015. The results will be available during 2016 and incorporated into the overall water management program.
The primary water demand at the mine is in the process plant. BMSC has implemented a water policy to maximise the efficiency of water use which employs two main methods of reuse: recovery via a thickener that returns water to the process plant before discharging the tailings and a return water system that recovers water from the Tailings Management Facility (TMF) and returns it to the process plant for reuse. Treated sewage from the site also reports to the TMF and forms part of the total process water balance.
In 2015, approximately 119,000 m³ (7% of water use) was recycled from the TMF and returned to the plant as process water, a decrease of 61% over the amount recycled in 2014. The decrease is related to the increased acidity of the tailings pond due to the practice of sending naturally acidic pit water to the TMF. The acidic nature of the pit water, combined with the metal species (i.e., free Cu), impedes recovery in the plant. No water is discharged from TMF to the surrounding area as it does not meet the IFC effluent discharge standard. An upgraded return water treatment plant is being installed at site and expected to be commissioned in early 2016. This will significantly increase the quantity of TMF return water treated and used by the process plant, decreasing reliance on raw water from local aquifers.
Water quantity and quality monitoring is an ongoing and continuous activity on-site. The sample preparation laboratory was advanced in 2015, with equipment purchased and installation initiated. The lab will be fully operational in 2016. Water samples are sent to a certified outside laboratory for analysis.