San Juan River: Sand Island
E. coli Monitoring 2019

Update July 25, 2019

Additional sampling conducted on July 15, 2019, and July 17, 2019, showed E. coli levels well below the advisory threshold. Final sampling on July 25, 2019, confirmed continuing low E. coli levels. The health advisory was lifted on July 25, 2019.

A health advisory for E. coli can be lifted after four consecutive samples over two weeks fall below the advisory threshold.


Update July 9, 2019

Recent sampling by the Division of Water Quality (DWQ) showed E. coli levels decreasing at Sand Island. Samples collected on July 9, 2019, showed 121 Most Probable Number (MPN) per 100 milliliters (mL), which is below the health advisory threshold of >409 MPN per 100 mL.


Update June 27, 2019

DWQ detected elevated levels of E. coli at Sand Island on May 23, 2019, during routine sampling. These values were above the health advisory threshold of >409 MPN per 100 mL.

Sample Dates and MPN Values

  • May 23, 2019: MPN 461 per 100/mL
  • June 13, 2019: MPN 613 per 100/mL
  • June 17, 2019: MPN 435 per 100/mL
  • June 27, 2019: MPN 688 per 100/mL