Pleasanton's water utility shut down a drinking water well earlier this year after detecting unsafe levels of toxic chemicals linked to adverse health effects, including cancer and birth defects.

Zone 7 Water Agency, which supplies treated drinking water to Pleasanton, Livermore and Dublin, took similar measures after discovering elevated levels of the chemicals in some of its groundwater wells.

The contamination was discovered as part of a new push to assess the presence of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), two common types of man-made chemicals known as PFAS, in drinking water systems and groundwater sources across the state.

Last week, the City Council approved expanding a current water quality evaluation contract with Carollo Engineers to include a feasibility study on building PFAS treatment systems for the city's wells. The study is expected to cost about $200,000 and to be completed by February 2020.

PFOA and PFOS are chemicals once used in numerous industrial and consumer applications, such as flame retardant foams commonly used at airports, and in water-repellent coatings for carpets and outdoor apparel, many of which were likely to have been discarded in landfills. They are no longer manufactured or imported to the United States.

These chemicals are particularly concerning because they don’t readily break down in the environment and have been found to accumulate over time in the human body. Studies indicate the chemicals can cause tumors and problems with reproductive and developmental health, according to the EPA.

About a quarter of Pleasanton’s drinking water comes from three wells located in the city; the other 75 percent is purchased from Zone 7. Both the City of Pleasanton and Zone 7 found trace amounts of the chemicals in the tested wells.

All three of Pleasanton’s wells tested for PFOs at a level high enough to trigger public notification, and one well tested for combined PFOA and PFOS at so-called “response” levels, which triggers a requirement for public water agencies to either take the source out of use or provide broad public notification.

As of August 2019, Notifications Levels are 5.1 parts per trillion for PFOA and 6.5 parts per trillion for PFOS. The Response Level for PFOA and PFOS combined is 70 parts per trillion. A part per trillion is equivalent to a single drop of water in 20 Olympic size swimming pools, according to a city press release.

In May 2016, the United States Environmental Protection Agency established the first voluntary health advisories for drinking water suppliers. Utilities were advised to notify the public if combined levels of the chemicals reached 70 parts per trillion.

Since the EPA’s health advisory, California has gone about setting its own, more stringent, guidelines for water systems to follow. To date, there is no established safe level for PFAs in drinking water.

In March, the state Water Resource Control Board’s drinking water division ordered more than 600 water system sites throughout the state, including groundwater wells in Pleasanton and Zone 7, to test for PFAS, including PFOA and PFOS on a quarterly basis.