Homestake shaft surveyed, water level measured
LEAD ? Video surveillance of the Ross shaft at the Sanford Underground Laboratory at Homestake showed the exact water level in the mine.
Friday morning water was 4,688 feet below the surface, or about 138 feet lower than expected. ?Computer models predicted the water would be higher,? Sanford Lab operations director Greg King said.
The former Homestake gold mine is 8,000 feet deep, and the mine has been slowly filling with water since it was sealed shut in 2003. The South Dakota Science and Technology Authority is reopening the Homestake as an underground science lab.
Sensors in the mine have signaled rising water levels at intervals, but Friday?s surveillance in the Ross shaft was the first precise measurement of the water level.
A new video camera attached to the Ross ?cage? (an elevator car) also surveyed the shaft. The camera?s remote pan, tilt and zoom capabilities allowed technicians to more accurately survey the condition of the shaft. (A simpler video camera surveyed the shaft last year.)
King said the camera confirmed that the cage can still safely travel up and down the shaft.
No mining personnel were on the cage during Friday?s video surveillance. Technicians have descended as deep as the 3050 level.
Though Friday?s water level was lower than computers predicted, it was higher than Sanford Lab officials had hoped. ?We thought the 4850 Level was flooded, but we weren?t sure how high the water had risen? said Dr. Jose Alonso, director of the Sanford Lab.
Dr. Alonso said the water level would not disrupt plans to begin pumping water out of the lower levels of the mine later this month.
Pumps will remove water from the mine in 1,200-foot steps or columns.
Next week mining technicians will start a pump at the 2450 level. That pump will lift water to a ?sump? or reservoir on the 1250 level, where a pump already has been installed and tested.
A pump at the 3650 level will lift water to the 2450 level.
Below the 3650 level, water will be pumped in 300-foot steps by a series of submersible pumps.
The Ross and Yates shafts at Homestake are 5,000 feet deep. Tunnels, ?drifts?, lead to underground shafts that access lower levels of the mine. Deep labs protect sensitive experiments from cosmic rays.
The first physics experiment at the Sanford Lab will be at the 4850 Level, which Alonso said could be dry as soon as July.
In addition to starting the pump at the 2450 level, next week technicians will reopen the Yates Shaft. The Yates hoist and motor were successfully tested last week.