August 14, 2015:
The EPA sediment samples collected in the Animas River from Bakers Bridge to north of Durango have been validated. EPA has done a review of the data which included a comparison to background to determine if the metal concentrations are consistent with pre-incident levels.
Metal results that exceeded pre-incident levels were subsequently compared to risk-based screening levels. These results indicate that minor exceedances of background concentrations were observed for antimony, lead, silver, thallium.
However, comparison to risk-based screening values found these exceedances to below risk screening levels. The review and interpretation of these data was a collaborative effort that included state and local members of the unified command.
Sample date Aug. 11, 2015.