April 13, 2004 > Water, Our Precious Resource
Water, Our Precious Resource
First in a series exploring the Tri-City water supply
The catchphrase, "familiarity breeds contempt" is not quite true, but certainly a relatively fair characterization of our use of the well-known combination of hydrogen and oxygen atoms, forming H2O, commonly known as "water." For most Tri-City residents it simply exists in streams, lakes and oceans; it occasionally falls from the skies and is available on demand from faucets.
An average single family residence uses about 315 gallons a day and in the Tri-Cities, the total annual consumption is 50,732 acre-feet (an acre-foot - 325,900 gallons - is the amount of water it takes to cover one acre of land at a depth of one foot) which is equivalent to 45.3 million gallons of water each day! The story of how safe and clean water gets to the faucet is actually the result of a series of well integrated and complex operations by the personnel of the Alameda County Water District (ACWD).
In this first article of a series, TCV sat down with ACWD personnel to discuss the source of the Tri-City water supply and how it is managed. Assuring the Tri-Cities of an adequate water supply is a complex task involving advance planning, cooperation with other water suppliers, collection, maintenance of facilities and quality control. A roundtable discussion of these areas included Paul Piraino, General Manager; Karl Stinson, Operations Manager; Bob Shaver, Engineering Manager; Doug Chun, Water Quality Manager; Steven Inn, Groundwater Resources Manager; Jim Reynolds, Water Supply Engineer; Mike Halliwell, Groundwater Resources Engineer and Eric Cartwright, Senior Water Resources Planner.
Karl started things off by explaining that the ACWD has three basic sources of supply, Alameda Creek Watershed, Hetch-Hetchy water from the Sierra Nevada and State Water Project water from the Delta.
A little over half of our water supply is purchased from the State Water Project, collected in Lake Oroville then released in the Feather River to the Sacramento/San Joaquin Delta. It is then pumped to the South Bay Aqueduct that brings water to our service area. ACWD also buys water from San Francisco, owner of the Hetch-Hetchy reservoir in Yosemite. The aqueduct carrying this water passes through our area. The third source for ACWD is Alameda Creek Water that is allowed to percolate into subterranean "aquifers" at various depths. It is from here that water is pumped into the ACWD system. A recent addition to the groundwater supply is the use of a desalination plant in Newark that converts "brackish" groundwater through a series of filters (reverse osmosis) to become usable in the system.
Water from the State Water Project reaches ACWD at two treatment plants, one in Mission San Jose and the other (Treatment Plant #2) at the intersection of Mission Boulevard and 680. At Plant #2, water is treated by adding coagulants that help suspended particles to clump together and settle out. The water is filtered through anthracite coal or activated carbon and then "ozonated" to give it a clean taste. The Mission San Jose facility is in the process of upgrading to "ultrafiltration membranes" that will replace sand and coal currently used for filtering. Water from these facilities enters the consolidated distribution system, but they separately serve some areas too. The plant in the hills of Mission San Jose serves the hill area and Plant #2, some of the lower areas.
ACWD purchases about 30% of its supply from San Francisco (Hetch-Hetchy water), a "soft" water supply, which is brought to well fields in the northern sector of the ACWD and blended with "hard" groundwater. The high mineral content of groundwater is moderated by this blending process.
Water from Alameda Creek is also captured for Tri-City use (about 15% of the supply coming into the system) by pumping it into a "recharge" area at Quarry Lakes. Here the water is allowed to "percolate" through layers of earth to "aquifers" or areas that can be saturated with water. Pumps then bring some of this water into the distribution system. Sometimes, especially in dry months of the year, State Water Project resources are pumped into Alameda Creek to keep it flowing.
Past overuse of groundwater has allowed intrusion of saltwater from the Bay and currently, ACWD is creating a positive pressure of fresh water to push the saltwater back towards the Bay. In the past, pockets of "brackish water" were simply pumped out and discharged into the Bay, replaced by fresh water. Now, instead of simply sending the water to the Bay, brackish water, through a desalination process, is purified and joins the ACWD distribution system.
ACWD customers receive approximately 40 - 45% of their water from the State Water Project, 55 - 60% from blended groundwater and Hetch-Hetchy water. The introduction of desalination will create approximately 10% of the water supply over the next ten years.
The next installment of "Water, Our Precious Resource" will continue to look at water management by ACWD. We will examine some of the following questions. How is water managed to protect us from droughts and shortages? How is water diverted for our use without endangering the environment? What is done to protect our health? What protection is there for us in the event of a major earthquake or disaster? What is being done by ACWD to assure adequate supplies in the future?