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Lathrop seeks state permit to discharge into SJ River

The City of Lathrop is now a quarter of a million dollars closer to earning a permit that will allow for the discharge of treated wastewater into the San Joaquin River. 

On Monday the Lathrop City Council approved setting aside $250,000 from the wastewater connection fee fund to continue to further the process towards what has been a longstanding goal of doing away with the ponds and spray fields that are currently used by the city.

The move, if approved, would add even more funding to the nearly $100,000 that was earmarked for the effort earlier this year as a way to get the ball rolling on the process that will require extensive environmental engineering before approval would even become a possibility. 

Currently Lathrop’s wastewater is treated at one of two facilities – the City of Manteca’s water quality control facility and the City of Lathrop’s consolidated treatment facility. While Manteca has the permit necessary to discharge treated effluent into the San Joaquin River, Lathrop has to use spray fields and holding ponds – even though the water that is being dispersed, which undergoes tertiary treatment, has the potential to be even cleaner than tap water in some respects. 

The tertiary process typically takes treated wastewater and removes whatever solids still remain before disinfecting it with chlorine and then removing the salt. The end result in a product that in some cases is cleaner than it was when it began and is therefore safe to discharge into the San Joaquin River which eventually flows into the Sacramento-San Joaquin River Delta and out to the San Francisco Bay and ultimately the Pacific Ocean. 

Because Lathrop does not currently have the permit that it is seeking, the tertiary treated wastewater is currently sprayed over rural agricultural fields to filter down into the groundwater supply or stored in ponds.

If Lathrop is able to eliminate the need for spray fields and holding ponds, that land could ultimately become available for future development. 

The discharge permit would also help stabilize the City of Lathrop’s water and sewer rates since the need to acquire land for dispersal – either through purchase or agreement – would go away as soon as the permit was issued. The City of Lathrop has been working on making progress in this arena for more than two years, and with the backing of some developers in the community that want to see the longtime goal realized, the council is continuing to make resources available.

For additional information about the item on the council agenda, or to see other matters that were before the council visit the City of Lathrop’s website at 

To contact reporter Jason Campbell email or call 209.249.3544.