Update on Big Sky Discharge

UPDATE: DEQ Director Tom Livers will be onsite today with technical specialists to assess the situation. At this point, suspended sediment is the main concern from an aquatic standpoint. The wastewater stream is picking up a sediment load as it moves downstream. DEQ will be working with local and other state officials on a sampling and monitoring plan. The plan will include sampling for pathogens, hydrogen, phosphorus, suspended sediment, ammonia and total nitrogen.

DEQ and other agency officials will be on hand today at 5:30 pm at the Big Sky Fire Station in the Meadow, 650 Rainbow Trout Run, to give a brief update and answer questions.

 No human health risk for recent spill

Big Sky, Madison County (3/3/16)  – On Thursday afternoon a storage pond spill was reported to local and state agencies. The spill is of highly treated reclaimed water and it does not threaten human health. The discharge is below human health standards.

The reclaimed water is leaking from a storage pond.  Unrestricted flow is proceeding down the hillside into Second Yellow Mule Creek and then to the South Fork of the West Fork of the Gallatin River.

The source of the break is being investigated and it is currently still flowing. The outlet pipe flows to the Yellowstone Club golf course and irrigation of the turf grass is authorized in summer months.  In the winter this is an effluent storage pond.  Most of the effluent comes from the Big Sky Sewer District, with a small portion coming from the waste water treatment facility used at Yellowstone Club.

The combined water is highly treated wastewater, and the expected total nitrogen content of about 7-8 mg/L is below the human health standard of 10 mg/L as nitrate.  Biochemical oxygen demand (BOD) is below 10 mg/L.

There is an estimated discharge of 35 million gallons, based on the volume of the storage pond.  About 4 to 5 feet of water will remain in the lined pond once it fully discharges.

Kristi Ponozzo
Montana Department of Environmental Quality
Public Policy Director

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