Water officials say the toxic algae blooms found in Lake Del Valle, which provides drinking water to parts of the Tri-Valley, won't threaten the area's drinking water.
The algae was found earlier this month when the East Bay Regional Parks District ran a routine screening test. Zone 7 Water Agency takes water from this lake and other sources to sell to water departments and municipalities in the Tri-Valley, including the city of Pleasanton.
Samples of the algae have been sent to a Florida lab for additional testing, and Lake Del Valle has been closed to swimmers. The algae could be lethal to dogs and harmful to people, East Bay Regional Park District spokeswoman Carolyn Jones said. There is no current estimate to when the lake will be reopened but will be closed until the lake is free of toxins.
Zone 7 general manager Jill Deurig said her agency pumps water from deep inside Lake Del Valle, and the algae is only on the surface and is five miles from the agency's water intake pipes. However, Zone 7 water treatment plants use methods that would get rid of algae, including the use of chlorine.
Jones said it's unusual for algae blooms to form in colder months, and the source of the toxic algae hasn't been determined. While algae blooms are common in park lakes, this is the first toxic bloom to have formed in Lake Del Valle.