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Bacteria Detected in Water; Retests Show it’s Clean, Safe to Drink

Post Date:08/04/2017

Media Contact: Sue Stephenson, (925) 875-2295 (office), (925) 570-5739 (cell), 

We are resending this news release on August 7 because it may not have reached the entire distribution list on August 4. We apologize for the inconvenience if you receive it twice.

DUBLIN, CA  (August 4, 2017) – On Wednesday morning, August 2, DSRSD lab chemists became aware that two drinking water samples, that had been drawn the previous day, tested positive for bacteria (total coliform and E. coli). It takes 24 hours to grow the culture that tests for bacteria. Water operators flushed the system at the two locations (Scarlett Court and Asterwood Drive). Then they resampled the original sites and took five samples upstream and five samples downstream at both locations. Thursday afternoon, all subsequent samples were clean.

On Wednesday afternoon, a sample in a third location (Central Parkway) tested positive for total coliform. Again, water operators resampled at the original site, taking five samples upstream and five samples downstream and flushed the system. Thursday evening, all subsequent samples were clean.

In all three locations, the chlorine residual was low, but after water operators flushed the areas, the chlorine residual returned to normal.

“This is not a consistent problem,” says Operations Manager Jeff Carson, “and the drinking water is clean and safe to drink.”

Normally, District water operators collect weekly water samples on Tuesdays (23 samples per week totaling 92 samples per month). However, because there are five Tuesdays in August, they will collect 115 samples.

Definitions of Terms
Total coliform includes bacteria found in soil, water influenced by surface water, and human or animal waste. Coliform bacteria are unlikely to cause illness. However, their presence in drinking water indicates that disease-causing organisms (pathogens) could be in the water system. Most pathogens that can contaminate water supplies come from the feces of humans or animals.

E. coli (Escherichia coli) is the major species in fecal coliform and the best indicator of fecal pollution and possible presence of pathogens.

Chlorine is added to the water supply to disinfect it, to inactivate bacteria and some viruses, and to protect the water from contamination during storage. Chlorine residual in drinking water indicates there is a sufficient amount of chlorine to keep the water clean and safe to drink. The desired amount of chlorine residual in the water is no more than 2.0 milligrams per liter and no less than 0.2 milligrams per liter. The chlorine residuals in the three sample sites were 0.06 milligrams per liter. 


Founded in 1953, DSRSD serves 178,000 people, providing potable and recycled water service to Dublin and the Dougherty Valley area of San Ramon, wastewater collection and treatment to Dublin and south San Ramon, and wastewater treatment to Pleasanton (by contract). DSRSD also operates the Jeffrey G. Hansen Water Recycling Plant and the backbone recycled water distribution system on behalf of the San Ramon Valley Recycled Water Program. The District office is located at 7051 Dublin Blvd., Dublin CA, 94568. For more information about the District, visit


Dublin San Ramon Services District logo, Water, wastewater, recycled water 

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