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A plugged valve caused a sewage spill into Wolf Creek in the early hours Monday, and Grass Valley officials are investigating why an alarm system didn't sound when it happened.
An estimated 10,000 gallons spilled at the Grass Valley wastewater treatment plant at 355 Freeman Lane, at the southern end of town, according to a statement from the county Environmental Health Department.
Signs have been posted in the area warning of bacteria in the creek, and contact with the water should be avoided. Creek water will be tested in a few days for fecal bacteria, and spring water flows are expected to dilute the pollution in a few days, county Environmental Health Director Wesley Nicks said.
“The partially treated sewage that was discharged may contain bacteria and other pathogenic microorganisms that can cause illness in humans and animals,” according to a county's statement.
When the water is safe again, the signs will come down, Nicks added.
The effluent spilled over the top of a large cement tank and drained into the creek nearby, and what remained on the ground was neutralized, City Engineer and Public Works Director Tim Kiser said.
The plant was working properly when workers left at midnight Sunday, but others coming in at 7:30 a.m. Monday discovered the spill and unplugged the valve, Kiser said.
A pump moves partially treated sewage into the holding tank, and the valve allows some to drain into another area for the next step in treatment. The pump should have moved through eight or nine cycles overnight, and it was unclear when the valve became plugged, Kiser said.
A monitoring system should have sounded an alarm when the effluent neared a high level in the tank; workers are trying to figure out why that didn't happen, Kiser said. In the meantime, the trigger has been set for a lower level in the tank.
An estimated 10,000 gallons spilled at the Grass Valley wastewater treatment plant at 355 Freeman Lane, at the southern end of town, according to a statement from the county Environmental Health Department.
Signs have been posted in the area warning of bacteria in the creek, and contact with the water should be avoided. Creek water will be tested in a few days for fecal bacteria, and spring water flows are expected to dilute the pollution in a few days, county Environmental Health Director Wesley Nicks said.
“The partially treated sewage that was discharged may contain bacteria and other pathogenic microorganisms that can cause illness in humans and animals,” according to a county's statement.
When the water is safe again, the signs will come down, Nicks added.
The effluent spilled over the top of a large cement tank and drained into the creek nearby, and what remained on the ground was neutralized, City Engineer and Public Works Director Tim Kiser said.
The plant was working properly when workers left at midnight Sunday, but others coming in at 7:30 a.m. Monday discovered the spill and unplugged the valve, Kiser said.
A pump moves partially treated sewage into the holding tank, and the valve allows some to drain into another area for the next step in treatment. The pump should have moved through eight or nine cycles overnight, and it was unclear when the valve became plugged, Kiser said.
A monitoring system should have sounded an alarm when the effluent neared a high level in the tank; workers are trying to figure out why that didn't happen, Kiser said. In the meantime, the trigger has been set for a lower level in the tank.
