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Some of the cleanest water on the planet
A panel with 25,000 spaghetti-like strands of thin, hollow membranes is checked by a worker at the South County Water Treatment Plant. - photo by HIME ROMERO

Some of that water flowing from your faucet in Manteca between April and October likely first reached earth as a snowflake in the rugged Sierra terrain north of Yosemite Park.

Spring’s warm sunshine melts the flake captured in the snowpack allowing drops of water to start a meandering 85-mile journey.

First it flows into Donnells Reservoir. The dam built at 4,911 feet in a steep canyon of the middle fork of the Stanislaus River is the first of a series of reservoirs operated by the Tri-Dam Project, a partnership of Oakdale Irrigation District and South San Joaquin Irrigation District. Its westward journey takes it into New Melones Reservoir and eventually down to Goodwin Dam where it is diverted into a canal in the foothills above Knights Ferry. 

The canal empties into Woodward Reservoir 22 miles northeast of Manteca.

From there, it is piped less than a mile away to the Nick DeGroot South County Surface Treatment Plant that produces some of the cleanest water on the planet.

The state-of-the-art treatment plant improves substantially on Mother Nature. It takes water from the Sierra snowmelt and removes even minute traces of bacteria and particles.

• • •

Microscopic fibers cleanse the water

The water coming into the plant ultimately passes through a submerged panel containing 25,000 spaghetti-like strands of thin, hollow membranes.

It is those fibers known as ZeeWeed that cleanse the water.

As the water passes through, the hollow fiber membrane serves as a physical barrier to contaminants. The porous plastic fibers are hollow in the center. The surface is covered with billions of microscopic pores that filter out all known bacteria and almost every known virus, with minimal or no chemical use.

The fibers are only part of the process at the treatment plant that has redundancy, constant sampling and computer as well as human oversight to assure the cleanest water possible flows to Manteca, Lathrop, and Tracy.

The designer of the plant — Zenon (now GE) —  has engineers who are constantly monitoring operations 24/7 via computer hookups in case a problem develops.

Water quality starts on the remote, upper Stanislaus River middle fork watershed. It has minimum human use providing a fairly clean run-off. 

When the water reaches Woodward Reservoir, there are barriers in place to prevent human contact — and that of gas-powered water recreational vehicles — on the upper part of Woodward Reservoir near the intake line for the treatment plant.

The technical processes used to treat the water would fascinate a room full of engineers for weeks. 

The most simplistic way to explain how it works is that water initially coming in the treatment plant goes through a series of baffles that causes solids — dirt particles and such — to float to the top of a series of open concrete tanks.

The water then passes through numerous panels that each have 25,000 membranes that snag bacteria and viruses. From there the water is further treated and then sent to a storage tank awaiting its journey westward to Manteca, Lathrop, and Tracy.

The treatment plant is in place due to the foresight of SSJID board members who saw it as a way to protect water rights secured and developed for over 105 years for farming in Manteca, Ripon, and Escalon to work for urban users as well.

• • •

SSJID took lead on water plant

The SSJID took the lead and stayed on task even in the early going when the cities seemed far apart on any type of agreement that would work.

The plant was dedicated on July 14, 2005. It was the same month treated surface water started flowing to the three cities.

The SSJID board pursued the project based on four key benefits:

• It increases regional water supplies.

• It improves water quality.

• It keeps water in San Joaquin County.

• It reduces demand on groundwater.

Manteca, like Lathrop and Tracy, pumps water from underground aquifers. Unlike Tracy and Lathrop, Manteca takes most of its surface water only during high use months – typically April to October – to supplement groundwater supplies. The strategy effectively keeps water bills lower in Manteca as surface treated water has a higher cost per gallon.

Manteca leaders embrace the treatment plant as an insurance policy. It is part of Manteca’s water strategy to provide water for future growth, it gives the city redundancy with two sources of water both surface and ground, and it helps reduce the draw on groundwater which is critical as salt water intrusion becomes more of an issue.

The end results are famers who irrigate by ground water won’t have to worry as much about growth accelerating the depletion of their water sources.

The city has the added benefit of blending surface water where possible with wells were tighter arsenic standards require expensive retrofits with arsenic treatment plants. The strategy has saved Manteca in excess of $12 million upfront and reoccurring investment in replacement filters for such plants of up to $2 million a year based on arsenic removal facilities that are no longer needed due to the bending of surface and ground water to dilute arsenic parts per billion.

Manteca’s current share of water treated at the plant when SSJID supplies are available and the Stanislaus River watershed isn’t under drought conditions is 11,500 acre feet a year. In 2013, the city used 7,404 acre feet. In the first six months of the current year they have used 3,602 acre feet.

A future second phase expansion would provide Manteca with an additional 18,500 acre feet of water or essentially enough to accommodate the city more than doubling to 150,000 residents. Ripon and Escalon ultimately will tap into the treatment plant as well.

As an added bonus the Robert O. Schulz Solar Farm is next door to the treatment plant. It allowed SSJID to establish the first solar powered water treatment plant in California while avoiding in excess of $500,000 a year in PG&E costs.