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Salt triggers water concerns
Farmers leery of Manteca plans to recycle wastewater
Corn for feed being grown by Machado Dairy Farms at the Manteca treatment plant using recycled wastewater. - photo by HIME ROMERO

Marty Harris and at least 202 other rural residents are worried a plan by Manteca to use recycled wastewater to irrigate landscaping and farm crops could ultimately damage almond production.

The concern centers on the relatively high salt content found in treated wastewater up and down the Central Valley.

Harris is the spokesperson for Neighbors United, a new group forming to keep watch on growth and environmental issues that impact rural Manteca. They have presented petitions with 203 signatures so far to the council asking that workshops be conducted prior to any decision being made to use recycled wastewater for land applications.

That is exactly what Manteca has been doing since the early 1960s with land around the wastewater treatment plant. The council Tuesday night extended the current lease with Machado Dairy Farms for 182 acres at the treatment plant to grow feed and fodder crops using recycled wastewater. The city receives $56,710 annually under terms of the lease.

The concerns underscore a growing dilemma for San Joaquin Valley cities as growth demands and drought tighten water supplies and accelerate the dropping of groundwater tables. Cities like Manteca are looking for ways to stretch their water supplies. In Manteca’s case, reusing the 7.7 million gallons that is returned daily to the San Joaquin River for uses such as landscape irrigation would reduce the use of potable water for such purposes.

Harris believes that the city would protect current surface water supplies better if treated wastewater continued to be used to flush saltwater from the San Francisco Bay out of the Delta instead of water stored behind New Melones and other Sierra reservoirs.

There are also downriver users — or those relying on water that flows into the California Aqueduct — who have concerns that diverting large amounts of treated wastewater for use in the cities of origin will reduce their water supplies and what’s needed to maintain the Delta and river ecological systems.

Manteca does intend to conduct public meetings during the fiscal year starting July 1 as it puts together a recycled wastewater use master plan. City leaders have noted the Central Valley Regional Water Quality Control Board has strict quality standards they must adhere to with treated wastewater whether it is returned to the river, injected into underground water tables, or used for any type of irrigation.

This isn’t the first time that salt concerns have been presented to the City Council.

Years ago Mayor Willie Weatherford started pushing for land disposal as a proactive response to what he expects to be an eventual state demand to reduce salt levels in treated wastewater sent into the San Joaquin River. The mayor advocated creating wetlands and such in southwest Manteca as a way for the city to avoid what could be additional expensive treated processes for wastewater.

Ironically, the debate about recycled wastewater has shifted from reducing treatment costs to stretching the water supply while at the same time avoiding drilling expensive municipal wells.

Farmers fear if enough cities switch to land disposal they could eventually see salinity levels in wells increase. Permanent crops such as almonds are susceptible to being stunted and ultimately killed if roots leech too much salt.