SLO's drinking water no longer violates standard for contaminant

San Luis Obispo’s water no longer violates state and federal standards for a chemical compound that at high levels is associated with cancer and other health problems.

In July, city officials sent a notice to San Luis Obispo residents warning that one sample site tested above the maximum contaminant level for trihalomethanes, a byproduct of the reaction between the chlorine used for disinfecting tap water and natural organic matter in the water.

The notice was sent to all water customers, but only households in the neighborhoods near the sample site at Johnson Avenue and Southwood Drive were affected, officials said at the time.

The violation did not pose an immediate health risk to water customers, according to the notice sent.

Some people who drink water with higher levels of trihalomethanes over many years may experience liver, kidney or central nervous system problems, and they may have an increased risk of developing cancer, according to the notice.

The water sample results for the second quarter of 2015 at that location showed total trihalomethanes at levels of 82.1 parts per billion — above the maximum contaminant level of 80 parts per billion.

But third-quarter water-quality testing results show that San Luis Obispo’s drinking water meets the state and federal regulatory compliance levels for trihalomethanes at all of the city’s sample sites, according to a news release issued Monday.

In order to reduce the potential for trihalomethanes, the city evaluated each surface water source — Nacimiento, Whale Rock and Salinas reservoirs — and made changes to the mixing ratio from each source.

Officials also made operational changes in the water distribution system to reduce the amount of time that water stays in the system and increased the monitoring of the amount of chlorine in the system. Future improvement projects are also planned to lower levels of trihalomethanes.

“Residents can feel confident that their water quality is high,” Water Treatment Plant Supervisor Dean Furukawa said in the news release.

For more information about the city’s water, go to www.slowater.org.

This story was originally published September 28, 2015 at 3:36 PM with the headline "SLO's drinking water no longer violates standard for contaminant."