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Lathrop water passes federal compliance in all the categories

Tap water may get a bad rap in the age of water delivery and home filtration systems – especially when reports of trace elements of toxic chemicals keep popping up.

But according to the City of Lathrop’s 2018 consumer confidence drinking report released on the city’s water system, Lathrop’s potable water is within federal compliance in every single category for which it was tested and does not contain some of the elements of concern that have surfaced in nearby communities in recent years. 

The water that flows from Lathrop’s taps come from both groundwater aquifers and the water that flows down the Stanislaus River – either pumped, filtered, and sent into the water system or delivered from the South San Joaquin Irrigation District’s surface water project to help augment existing municipal water supplies within the region that the district serves.

That surface water became a cause for concern last fall when people began complaining to the Lathrop City Council that their tap water “smelled funny” – with one man going so far as to claim that the water gave him a sore throat. The smell, as outlined at the time by Lathrop City Manager Steve Salvatore, was likely due to the fact that SSJID uses a higher concentration of chlorine when treating surface water to ensure that no harmful bacteria is present when it flows out of the taps into people’s homes. Even the level of chlorine that was tested was within the federal guidelines, and Salvatore said that the issue can be resolved by simply filling a container with the water and letting it sit for a period of time to allow the smell to dissipate.

Of all of the Lathrop groundwater that was tested, the only regulated standard that came back with any amount was arsenic, and at 6.9 parts per billion, Lathrop’s water was well below the maximum containment level of 9 parts per billion. Arsenic is naturally occurring in the ground in the Central Valley, and agricultural and industrial runoff can cause it to leach into groundwater supplies. 

Lathrop, in the past, had issues with arsenic levels exceeding the maximum containment level – as many Central Valley communities did when the acceptable MCL was lowered by the Environmental Protection Agency. To combat the issue, the city constructed a state-of-the-art treatment facility near the city’s corporation yard on Louise Avenue that uses special media that binds to the arsenic and is then removed from the drinking water supply. 

Even chlorine, which is introduced into the city’s water system when surface water is added, is concentrated at only a fraction of the maximum containment level. Measured at an average of 0.67 parts per billion with the highest concentration at 1.22 parts per billion, Lathrop’s water still sits far below the MCL of 4 ppb. 

Even nitrates – which have been a common problem for some Central Valley communities in recent years – were absent from Lathrop’s drinking water, as were trace elements of a harmful chemical that forced Manteca to file suit against the companies that they believe are responsible for introducing it into their groundwater supply. 

Trichloropropane, or TCP, was a byproduct from the manufacturing of fumigants by the Shell Oil Company and Dow Chemical Company that has since become a contaminant that the State Water Resources Control Board now says must be monitored in groundwater. Letters sent by the City of Manteca to residents sparked a furor last year – the first year that the letters had to be sent out based on the new standards – but Lathrop has so far not discovered any trace of the harmful chemical in its drinking water supplies. 

A copy of the city’s consumer confidence drinking report can be found by visiting and searching the announcements section of the main page. 

To contact reporter Jason Campbell email or call 209.249.3544.