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Gold King Mine Data, November 16, 2015

Data from Gold King Mine Response

Surface water and sediment concentrations are now below recreational screening levels. The river system as a whole is being maintained at pre-event conditions.

It is important to keep in mind that metal concentrations in water and sediment may fluctuate. Fluctuations occur because of weather and other events that change water flow rates or volume. They can also occur if sediments are accumulating at a higher than normal rate at a particular site, before being washed away by the next high water event. 

As the response to the mine release transitions to long-term evaluations, EPA will continue to monitor for any abnormal occurrences of metal concentration exceedances of risk-based screening levels.

This data submission presents data for sediment samples collected on 10/5, 10/8, and 10/12 from the San Juan River.

EPA has reviewed the data which includes comparison to screening levels for exposure during recreational use. The metal concentrations of the samples are below sediment/soil recreational screening levels, and are being maintained at pre-event conditions. Based on previous monitoring events it has been shown that metal concentrations may fluctuate from time to time because of water surges due to heavy rains or other events that may change the water flow rates or volume.

This data submission presents data for surface water samples collected on 10/5, 10/8, and 10/12 from the San Juan River.

EPA has reviewed the data which includes comparison to screening levels for exposure during recreational use. The metal concentrations of the samples are below surface water recreational screening levels.  Surface water sample results from a September 24 sampling event along the San Juan river exhibited an increase in metal concentrations relative to pre-event conditions, with some metal concentrations above the recreational screening values, presumably due to a rain event.  The September 28 surface water results indicate the metal concentrations to be below the recreational screening values, but still somewhat elevated relative to pre-event conditions.  The September 30 surface water results indicate the metal concentrations have returned to pre-event conditions.

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