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Upgrades designed to increase sewer capacity by up to 4,000 homes

Efforts to squeeze out more capacity from Manteca’s wastewater treatment plant continues.

The City Council tonight is expected to approve an additional $100,000 expenditure with Pacific Advanced Civil Engineering for a study that is a precursor to a federally required arc flash study

The arc flash study needs to be done when there are major changes occurring to a treatment plant’s power distribution system. It will cost an additional $300,000 to complete that study.

Altogether, there are 10 interim improvements aimed at stretching the existing plant’s capacity. Those upgrades are currently being designed.

The $790,200 spent so far for the design work is being covered by federal pass through COVID relief funds that weren’t required to cover pandemic-related costs the city incurred.

The additional $100,000 will come from existing sewer related accounts.

Manteca — after completing the tweaks to the city’s wastewater treatment plant — is expected to have enough remaining capacity to accommodate between 3,000 to 4,000 more housing units.

That would be enough to sustain roughly six years of the current housing growth rate of 600 to 700 units being built yearly.

It is considered an interim project while the city gears up for expansion of the treatment plant.

The plant was designed to handle a flow of 9.23 million gallons of wastewater daily.

That capacity has been lessened over the years by state-mandated changes in the wastewater treatment process.

Solid waste loading issues, however, have effectively lowered the adjusted capacity even more.

The projects are designed to improve the process so the plant can end up functioning near its adjusted design capacity of processing 8.5 million gallons of water per day.

The plant was originally designed for 9.23 million gallons a day.

Staff in October 2023 when the expenditures were authorized, said the daily flow was between 7.3 million and 7.5 million gallons a day. The increased percentage of solids being processed due to water conservation measures is pushing the plant’s operational abilities  closer to where it would be capped at 8.5 million gallons a day.

Meanwhile, the city is working on a fourth phase expansion project that is being timed to hopefully go online before capacity runs out.

The existing plant was designed to allow a seamless increase in capacity.


To contact Dennis Wyatt, email