The purpose of a water treatment plant is to produce safe and pleasant drinking water, free of disease-causing organisms and toxic substances. The City of San Luis Obispo has a state-of-the-art treatment process which includes ozone and ensures a high level of protection to our customers.

City water comes from three sources: Salinas Reservoir (Santa Margarita Lake), Whale Rock Reservoir and ground water. Salinas Reservoir is our primary source of water. Whale Rock is our backup supply. Groundwater supplies a very small percentage (less than 5%) of the City’s demand for water.

The source of the City’s water is important because it sets the required level of treatment. Many communities rely solely on groundwater to meet their water needs. Groundwater typically requires only minimal treatment (such as the addition of chlorine) to meet state and federal standards, because water is filtered as it percolates through soil. This level of treatment results in very low operating and maintenance costs.

In contrast, water from lakes or rivers (surface water) such as the Salinas and Whale Rock Reservoirs, requires a significantly greater level of treatment to meet state and federal standards. The regulations require multiple treatment processes to provide multiple levels of protection from potential contamination sources. In addition, the City’s water supply reservoirs are patrolled on a daily basis to ensure that potential water quality problems at the source are minimized and eliminated. Increased treatment results in higher operating and maintenance costs.
 

WATER QUALITY

Water Quality/Consumer Confidence Reports
San Luis Obispo water continues to meet or exceed all State and Federal Safe Drinking Water standards.

Hardness
How hard is the City of San Luis Obispo's water?  In the City, the water hardness is 200 to 370 mg/l (11.7 to 21.6 grains per gallon).

The moderate hardness of the City's water does not pose a health problem.  Hardness in water does tie up detergents and soap so that they will not lather.  The harder the water, the more soap must be used to clean.  Soft water, on the other hand, can be more corrosive to plumbing. Groundwater from City wells is generally "harder" than the surface water from the lakes.

Fluoride
Does the City add fluoride to the water supplied to residents? Yes. 

The City has been fluoridating our water since August 3, 1954, following an advisory vote of the citizens in the City. Fluoride has been found to be an effective tool in preventing dental problems when used in optimal concentrations.

Contact:  Dean Furukawa, Water Treatment Plant Supervisor, 
              Phone - 781-7566.
              E-mail - dfurukaw@slocity.org.