The just upgraded Harry Tracy Water Treatment Plant features a new and seismically resistant 11-million-gallon treated water reservoir, along with three new ozone generators and five new filters.
The improved San
Bruno facility now has the capacity to provide 140 million gallons of water per
day for 60 days within 24 hours of a major earthquake—enough to supply nearly
one million people during that time.
On an average day, Harry Tracy treats about 35 million
gallons of water that have been pumped up from storage in the Peninsula
Watershed reservoirs below. Within only an hour or so, the raw water undergoes
disinfection by ozone, isolation of the solids, filtration and finally
post-treatment at the new treated water reservoir.
The first stop is the ozone station, where this oxidant quickly eats away bacteria and other
microbes along with inactivating
viruses. Ozone also aids in taste and odor control.
Chemicals are now added to induce particles in the water to
coagulate. As the water circulates through a series of rectangular open-air
basins, the solids keep merging into increasingly larger clumps called “floc.”
These are removed in filtration, when the
flocculated water passes through two layers-- anthracite (a hard natural goal)
and then sand. (The five newly installed
filters raise the plant’s total number to 15.)
Finally, the filtrated water goes to our new treated water
reservoir for fluoridation, disinfection, and corrosion control. Now it is
ready for distribution to customers in northern San Mateo and San Francisco
counties.
The new treated water reservoir rests on 50- to 70-foot-deep
pilings, and the entire plant is now capable of withstanding a 7.9 magnitude
earthquake.
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