San Francisco’s Water: No Longer Pristine?

May 2nd, 2017 No Comments »


Soon, San Francisco’s pristine water will be blended with groundwater.  The program is called the San Francisco Groundwater Supply Project and is part of the San Francisco Public Utility Commission’s (SFPUC) effort to develop numerous water supply alternatives to reduce dependence on the Tuolumne River.

Those who support this project believe having San Francisco dependent on one source for 85% of its water leaves us vulnerable to extremes in climate change.   Those against blending fear it will negatively affect the water responsible for the good taste of many of our local foods and beverages in San Francisco, including sourdough bread, beer, and coffee.

This is a plan to diversify our water needs to prepare for future extreme weather events, or a disaster such as an earthquake, when water sources are damaged. The plan will allow more water to remain in the streams and rivers we currently divert for our drinking water.  San Francisco is required to come into compliance with environmental laws that didn’t exist when the system was built.  Locally, increased releases are now required in San Mateo and Alameda Creeks that total 7-8 million gallons per day. The Tuolumne River is currently the subject of negotiations at the State Water Board.  Currently, about 80% of the river’s flow is diverted for agricultural use and 10% for urban uses but the Board wants to increase spring flows, which will require additional releases. To provide streams and rivers with more water is the motivation for the blending of groundwater now imminent.

In addition, reduced snowmelt and increased climate variability will reduce the amount of Tuolumne River water available in the future.  The PUC’s own studies have shown a 7% reduction in flows by 2050.  Sadly, even with these conservation measures, the City has still been using pristine water, the envy of the nation, to clean our City’s streets.
The amount of water added in the first year is planned to be 3%.  In four years, the amount of blended water will increase to over 15%.  Reports of the water’s taste vary.  In a side-by-side comparison, some recognize no difference in taste, some believe the flavor is improved, and others prefer the original taste of the unblended water.  However, no difference is noticed without a side-by-side comparison.

The groundwater will come from an aquifer 400 feet underground, in six different locations on the western part of the City between Golden Gate Park and Lake Merced. Contaminants that exceed state standards of safety have been found in all but two of these wells: nitrate, hexavalent chromium and/or manganese.  Rather than treating these at the wellhead, the SFPUC will pump the groundwater to the Sunset, Sutro and Summit Reservoirs, then blend the ground water with the Hetch Hetchy imported supply.  This blended water will be distributed to the whole City, however, most of it will be provided to the west end of San Francisco.

What are these contaminants?

Nitrate, which has been regulated since the 1960s, is considered an acute contaminant because it is harmful to infants and fetuses.  Nitrate is produced by the leaching of fertilizer or sewage into the groundwater.

Hexavalent chromium, colloquially known as the Erin Brockovich chemical, is only regulated in California, which adopted its standard in 2014 because it is a carcinogen.  While it has been associated with industrial pollution, hex chrome actually occurs naturally in groundwater throughout California.  Golden Gate Park’s contamination is also almost certainly naturally occurring.

Manganese is what’s known as a secondary contaminant: it is regulated not for health issues, but because at high levels, it gives water an unpleasant odor and taste.
Is blending a problem?  Blending water supplies is an approved method of meeting drinking water standards.  In this case, the blending will be at least 6:1 (actually more, since these chemicals aren’t found in every well).  So the concentration will be several times below the health standard.

Will these contaminants prevent groundwater from being tapped in an emergency?  In the case of the well containing nitrate, yes.  However, hexavalent chromium is regulated for its long-term effects.  Drinking water containing this chemical during a short-term emergency, while not ideal, should not be hazardous.  During an emergency, two wells found to have no contaminants, could be used as an emergency water source.

One of the reasons water is in short supply in California is because farmers are not mandated to conserve water as urban consumers are.  Flood irrigation, used by farmers since the dawn of civilization, is still primarily used to irrigate crops (50%).  Although this method  recharges aquifers and is less effected by evaporation than sprinklers, it is still considered wasteful.  Today, the use of drip irrigation has more than doubled since 1991.  Many crops, e.g. alfalfa, previously believed to not be suited for drip irrigation, are now successfully irrigating crops with a tremendous savings in water.  Tomatoes, now irrigated by drip, produce more fruit per acre and the quality of the tomato is more reliable.  By providing more incentives and programs encouraging the use of drip irrigation, which is expensive for farmers initially, the State of California would allow more water to remain in the Tuolumne River.

~ Glenn Rogers, Jennifer Clary

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