Manteca has sent the City of Lathrop a $6 million bill for wastewater treatment dating back to 2016.

It represents charges that Lathrop is contractually responsible for that were not billed and were not paid.

It marks the second time in 26 years that Manteca went for years without billing Lathrop and that Lathrop went without paying Manteca for a charge they agreed to pay

In July 2000, Manteca realized it had been undercharging Lathrop since 1991 for rate increases that had been imposed due to increased costs of operating and maintaining the sewer plant.

The amount was $2.3 million.

Lathrop officials refused to pay the amount, claiming Manteca never notified them of any discrepancies during that period.

Lathrop at the time said it only owed an additional $292,125 for sewer service it paid for Manteca to provide from 1998 to 2000.

That amount was an under charge that they argued was the most Manteca should be allowed to collect.

Manteca then sued Lathrop.

The two cities ultimately agreed that Lathrop would pay $400,000 plus in back charges.

The current failure to bill Lathrop and collect fees for services rendered apparently came to light when the current finance department went to adjust billing charges for all wastewater treatment plant customers based on rate increases approved by the City Council.

Manteca has gone for 14 years without increasing rates — including for “bulk customers” such as the City of Lathrop and Raymus Village, an urbanized style subdivision in San Joaquin County’s jurisdiction to the northeast of Manteca proper and the Lathrop Road/Highway 99 interchange.

The city dropped the bill this time around when there was a change in the finance department and a replacement department director was promoted from within.

That was immediately followed by Manteca going through six city managers in less than five years plus almost a 100 percent turnover in department heads with several being replaced multiple times.

The $6 million means the operations and maintenance fund for the wastewater treatment plant is not only not being fully funded, but Manteca ratepayers have been essentially subsidizing Lathrop when it comes to a number of residents flushing their toilets.

Lathrop charges their individual users just like Manteca. The cost of treatment of wastewater from Lathrop in Manteca is either reflected in those monthly rates or not passed on to Manteca due to lack of one city not billing another or was never reflected in the individual charges.

Either which way, paying Manteca going forward and/or addressing previous years when the money wasn’t paid Manteca apparently because Lathrop was never billed for its contractual obligations, could place upward pressure on existing Lathrop sewer rates.

They also have their own wastewater treatment facility in addition to capacity within the Manteca plant.

Lathrop has 14.7 percent of the original plant capacity of the Manteca treatment plant built in the 1980s on West Yosemite Avenue.

The original plant was paid for by a federal program that provides regional sewer plant funds to upgrade treatment facilities nationwide.

At the time, Lathrop was not incorporated. The sewer system serving the community through an independent district had significant issues.

The agreement made Manteca the plant operator.

A bulk rate was set for the Lathrop district. It was obligated to pay Manteca its fair share of operations and maintenance based on the gallons of wastewater processed.

The City of Lathrop, when it incorporated in 1989, absorbed the obligations.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com