LATHROP — Six water wells currently serve the 18,000 residents of Lathrop.

Five of those have traces of arsenic that measure higher than the federally accepted levels that went into effect in 2006 – forcing the City of Lathrop to look into costly and labor intensive methods at removing it and getting them back into compliance.

But thanks to a low-interest state loan, City Manager Cary Keaten believes that the city could be doing that as early as this fall – brining a $13 million state-of-the-art facility online that will filter water from the city’s five wells and send it back out into the system.

“The standard used to be 70 parts-per-billion but when the new standards went into effect that went down to 10,” Keaten said. “Our wells are testing between 15 and 25 ppb now and we believe that when that facility comes online those wells will be in compliance again.”

While testing for other freshwater sites and drilling exploratory wells might actually be cheaper than the arsenic treatment facility, Lathrop has only a very small area from which they can draw groundwater – inhibited by saline penetration from the Delta in areas west of the Union Pacific railroad tracks.

And while the media used to filter the arsenic from the water tends to be expensive, having a centralized facility will end up saving the city money over time rather than having individual filtering mechanisms at each of the wells individually.

Running the piping through town to facility – located out on the outskirts – will take considerable work up front but little maintenance once it’s completed.

“Normally something like this would come from the water enterprise fund, but we got a loan from the State of California – a revolving fund loan for infrastructure like this – that has a really low interest rate,” Keaten said. “We’ll be able to pay this back over the next 20 years. It’s a really good deal for us right now.”

The city, however, isn’t completely dependent on the six wells to serve all of their water needs.

As part of the surface water treatment project with Tracy and Manteca, Lathrop gets a portion of their water allocated throughout the year depending on the annual average rainfall. The plus side to that, Keaten said, is that in wet years there is an abundance of water while relatively dry years – like the one that municipalities are facing this year – might not yield the same amount of water.

“It’s good, clean water but we don’t always know what we’re going to get,” Keaten said. “In drought years like this we might not get our full allotment. That’s when we really have to depend on the wells.”