QUALITY OF DRINKING WATER

What Was Measured?
The San Francisco Water Department (SFWD) supplies nearly all the municipal water districts in San Mateo County with potable water and monitors 71 different parameters for water quality.  These parameters are grouped by: clarity, microbiology, organic chemicals, inorganic chemicals, radionuclides, and additional constituents.  Every one of the monitored constituents is assigned a maximum contaminant level by California and the federal government.  Because of the health risks associated with lead and copper ingestion the U.S. Environmental Protection Agency puts a special emphasis on the monitoring of lead and copper in drinking water.  Annual Water Quality reports from 1989 to 1995 were reviewed.

The county does not monitor the quality of individual water-well users except for those wells on sites identified as having toxic or pollutant releases.

Why Is This Important?
Drinking water quality is a major indicator of environmental health.  Water-borne diseases become epidemic in communities with contaminated water supplies.  Contaminated water may lead to birth defects, infant mortality, along with other systemic ailments.

What Was Found?
Over 85 percent of the water that the SFWD delivers to San Mateo County originates from high altitude Sierra Nevada snowmelt in 459 square miles of protected Yosemite National Park watershed land.  The water is stored in Hetch-Hetchy Reservoir and delivered to the SFWD through pipelines and tunnels.  The remaining 15 percent of the water supply is derived from the watershed lands located in San Mateo County at the Crystal Springs, San Andreas and Pilarcitos reservoirs.

The entire range of monitored parameters prove that the drinking water delivered to San Mateo County residents and businesses is virtually pollutant free.  Of the 27 organic chemicals monitored only Total Trihalomethane (TTHM) was detected at a concentration ranging from 46 percent to 82 percent of its maximum contaminant level.  TTHM is a result of the chlorination process which is mandated by California.  Chlorination is used to eliminate bacteria and other micro-organisms from drinking water.  Copper was found at 0.076 percent and lead at 6.66 percent of their respective maximum contaminant levels.  It is believed that lead and copper are leaching from plumbing materials.

Cryptosporidium is not included in SFWD reports as a mandatory health related standard, but it has been monitored regularly by the SFWD since 1982.  Cryptosporidium is a pathogenic organism found in natural waters, and while it has only recently been detected in the environment, it is believed to have been around a very long time.  It can cause a diarrheal disease called cryptosporidiosis and is spread by direct and indirect contact with the feces of infected persons or animals, and through contaminated food and drinking water and swimming pools.  Healthy persons are not generally at risk from infection, but it can be life-threatening to immuno-compromised individuals such as those infected with AIDS, chemotherapy patients, or organ and bone marrow transplant recipients.

SFWD conducts a regular monitoring program to provide data on the occurrence of cryptosporidium.  To date, it has been detected in less than one-third of all the tests conducted and of those, the average level found is one organism per 50 liters of water.  This is well below typical cryptosporidium levels that have been reported in surface waters across the United States.  This very low occurrence is due to highly protected watersheds both in the High Sierra and locally.

What Is The Trend?
Water quality over the last seven years has Virtually not changed and remains excellent.

Source: San Francisco Water Department Annual Water Quality Report

Researcher: W. Goertz (Green Environment, Inc.)