Sibanye-Stillwater selected a test section in the Benbow Decline to demonstrate the effectiveness of Sovereign’s proprietary NOH2O® water-sealing grout and injection methods. The test grouting was performed to determine Sovereign’s ability to assist the mine development contractor in maintaining a net water inflow of <100 gallons per minute (gpm) into the decline while excavating the remaining 2,400 feet.
After mobilizing to the site on March 13, 2020 and as directed by Sibanye-Stillwater, the mine development contractor commenced drilling a number of holes in the decline ranging in depth from 60-80 feet in an effort to intersect the source of inflowing water. Observed water inflows ranged from 2–109 gpm at pressures of 200–350 pounds per square inch (psi). Hydraulic connections between grout holes and specific mine leaks were mapped by injecting dye into the grout holes and observing dye reporting through fractured strata in the walls of the decline. These observations were then used to make specific decisions in the field on where to inject grout.
The total water inflow of approximately 105 gpm into the 90-foot-long test section measured at the start of the grouting program was reduced to 40-45 gpm by March 23, 2020. As conveyed in a conference call at the end of the program, the mine development contractor and Sibanye-Stillwater concluded that the trial was successful, and the team was extremely satisfied with Sovereign’s overall performance.
