Richmond Review

‘Blended’ Water Coming in March

By Paul Kozakiewicz

Starting in March, groundwater held in a huge underground

aquifer under the west side will be pumped out and blended with

water from the Hetch Hetchy Reservoir in the Sierra Nevada

mountain range.

The $66 million plan, approved by the SF Public Utilities

Commission (PUC), calls for up to 1 million gallons of groundwater

to be blended in the Sunset Reservoir this year. That would

be three percent of the total water volume going to city customers.

The pumping would be ramped up over the next four

years to about five million gallons of water a day, or up to 15

percent of the water delivered to city customers. The PUC also

sells water to numerous California cities, which will continue

to receive unadulterated water.

Six wells have been dug to deliver water to the Sunset

Reservoir. There are two in the Outer Sunset District, two in

Golden Gate Park, one in the Outer Richmond and one at

Lake Merced.

The well at the West Sunset Playground has a design with

features that will allow it to serve as an emergency drinking

water supply. It can be connected to a generator for backup power, disinfect water and be

connected to a fire hydrant for filling trucks.

The well water will have to be treated with chemicals to balance

the water’s acidity and to negate excessive nitrates and the

minerals calcium, magnesium, sodium and bicarbonate.

Nitrates, which come from leaking sewage pipes and fertilizer

runoff, are at levels above state standards.

The blended water will be “harder,” containing more total

minerals, or total dissolved solids (TDS). The current water

being delivered contains 40 to 45 TDS, whereas the blended water

will contain 70 to 120 TDS. The water will have increased levels

of calcium, magnesium and bicarbonate.

According to experts, the harder blended water could taste

different and make a difference in the making of coffee, beer and

some baked goods, like bagels and bread. Some items would

fare better with the blended water, like hoppy beers, and some

would fare worse, like pilsner beers, which require soft water.

The change could give dough more backbone, but could also

make it tougher and limit fermentation.

The extracted groundwater will be treated with chlorine to

kill dangerous microbes and sodium hydroxide to lower its

acidity. Hetch Hetchy water also gets treated with doses of chlorine

and ammonia.

The PUC claims the underground water is needed for a

growing Bay Area, because the federal government might require

more water for the state’s rivers, and also in case of an

emergency that disrupts the water supply line from the Sierra,

like a major earthquake.

According to the PUC’s website, in a drought, the groundwater

blend will be distributed throughout the entire City.

According to the PUC, drinking the aquifer water without

blending it with Hetch Hetchy

water could create a health risk

because of the high levels of nitrates

in the aquifer water.

According to a recent story in the SF Chronicle, the chief hydrologist

for the PUC project, Jeff Gilman, said, “The nitrate

would only be a concern if you were serving that water directly,

but that’s not our plan.”

The underground aquifer is about 400 feet below ground level.

Wells have been dug to monitor it in case of saltwater intrusion

from the Pacific Ocean.


For more information, go to

the website at

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