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4 million gallons of untreated or partially treated sewage being released into Wolf Creek

The Nevada County Department of Environmental Health has been notified that approximately four million gallons of untreated and or partially treated sewage will be released into Wolf Creek from the Wastewater Treatment Plant in Grass Valley over the next 24 hour period. The release of wastewater is due to the large amount of rain received over the last three (3) days and the anticipated storms this afternoon and tonight. The extremely high flow of rain water into Wolf Creek is expected to dilute the wastewater significantly, however all contact with the water downstream to the Bear River should be avoided until further notice.   Currently, the plant is receiving more than 20 million gallons per day (average dry weather flow is 2.0+/- MGD).  Some manholes may overflow onto the street and while the liquid is mostly rainwater contact should be avoided.  The Grass Valley Wastewater Treatment Plant is designed to treat/handle approximately 7.3 million gallons of wet weather flow per day.   This morning, water from the Newmont Mine which typically flows through the plant was diverted temporarily to Wolf Creek directly as a proactive step to prevent storm flows from exceeding plant capacity. Newmont Mine’s water is not considered contaminated and only has manganese and iron levels that are above discharge permit requirements and will not cause an immediate public health concern. The diversion of the Newmont Mine flows was not sufficient enough to avoid an overflow of the plant, with 2” to 4” of rain predicted in the next 24 hours.  Nevada County Environmental Health is working collaboratively with the City of Grass Valley to minimize any impacts, and monitor the situation until there are no longer any remaining public health concerns

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