"The water in Sunnyvale is just fine," says Mike Di Marco, spokesperson for the water district. "People have no reason to worry about their drinking water."

According to Di Marco, unlike Morgan Hill and other areas in the south end of the county where property owners pump their own drinking water from private wells, Sunnyvale residents receive their drinking water from a municipal water system.

According to Jeff Valkanoff, water systems operator for the city of Sunnyvale, the city receives the main part of its water from the Hetch Hetchy water system and the Santa Clara Valley Water District. Valkanoff says a small percentage of residents receive water from California Water, and during high-demand times the city uses some groundwater. He says the city and other agencies perform regular testing on Sunnyvale's water supply to make sure the water is safe for residents.

Di Marco says, "In this water system, the water district and other agencies conduct testing on a regular basis on the more than 300 contaminants. There're a lot of checks and balances in place to make sure the water is safe."

He says, "It's a very different situation down in the south county, where people get water from individual private wells."

Although perchlorate is not yet a regulated contaminant, the water district has been testing for it unofficially since it was discovered in south county wells.

"We've found some up in the east and south sections of San Jose as well as on a small site that borders Sunnyvale and Mountain View, but they are not affecting the drinking water since residents here are served by a retail water system," Di Marco says.

The scare about polluted water in the south county began in 2000, when an environmental assessment found perchlorate at a former safety flare manufacturing plant—Olin Corporation, a 13-acre site in Morgan Hill.

Perchlorate, which can create various health problems, is both a naturally occurring and manmade salt, primarily used as an oxidizer for rocket and missile fuel, as well as for producing highway safety flares, fireworks, matches, dyes and other products.

"At this time, we don't know the effects of perchlorate," Di Marco says. "There are not many conclusive studies. But it has been suggested that it can cause thyroid problems and even tumors."

So far the Santa Clara Valley Water District has been assisting the Central Coast Regional Water Quality Control Board, which has jurisdiction over the contaminated area in testing more than 1,200 private wells in the south county.

Once testing results become available, they will be used to direct Olin Corporation in cleaning up the area—a process Di Marco says could take decades to complete.