Visalia to Put $68m into Sewage Treatment Plant

By Tim Sheehan, The Fresno Bee, Calif.

Jul. 20–VISALIA — It’s easy to take modern plumbing for granted — just flush the toilet and there goes the waste.

But things get downright expensive at the other end of the sewer pipe when it comes to dealing with millions of gallons of — well, you know.

Visalia officials expect to spend tens of millions of dollars over the next three years to upgrade the city’s wastewater plant and stop putting treated water into Mill Creek.

The project, with an estimated price tag upward of $68 million, won’t provide any additional capacity at the city’s Water Conservation Plant — a sanitized name for the sewage treatment facility.

Instead, much of the cost is to meet tougher state standards for nitrogen levels in treated wastewater. Ultimately, it’ll be repaid through higher sewer rates charged to homeowners, businesses and industries served by the plant.

“Nitrogen in somebody’s field is a wonderful thing,” said Jim Ross, Visalia’s public works manager. “Nitrogen in the ground water is a bad thing.”

Nitrogen is in the air we breathe and is a valued nutrient in plant fertilizer. But it shows up in wastewater as ammonia and nitrates — undesirable pollutants in drinking water.

Visalia’s plant, located just west of Highway 99, can handle about 22 million gallons of raw sewage each day. Ross said the current flow averages about 13 million gallons per day.

After working its way through screens, settling pools, bacterial filters and chlorination, the treated water is piped into ponds on the plant property itself, used to irrigate nonfood crops on city-owned farmland nearby or emptied into Mill Creek downstream from Visalia, Ross said.

By that time, much — but not all — of the icky stuff that started out in the water is gone.

“We currently don’t have any violations at all,” Ross said. “But the requirement is to protect ground water, and the concentration where nitrogen causes problems in domestic wells is 10 milligrams per liter, or 10 parts per million.”

After all the upgrades are in place, by 2011, “we’ll be discharging effluent less than 10 ppm,” Ross said. “It’s going to be a lot cheaper, even at $68 million, to avoid a problem than to try to clean it up afterwards.”

Visalia’s not alone dealing with the nitrogen problem.

“In general, over the last 30 to 40 years, the state has continued to tighten up its water quality standards,” said David Stringfield, a partner with Carollo Engineers, a Fresno company hired by Visalia. “In all of the cities I work with up and down the Valley, in the last 10 years the effort to protect ground water from excess nitrogen has been prevalent.”

Reedley and Delano are two examples. In Reedley, work is under way on a $35 million wastewater plant upgrade, Stringfield said, while Delano is getting ready to spend $40 million.

In both cities, however, the work will not only reduce nitrogen, but also increase capacity for growth in the community.

Lonnie Wass, a supervising engineer with the Central Valley Regional Water Quality Control Board, said nitrogen requirements for treatment plants are evaluated case by case.

“Cities have to show they’re treating with the best practicable treatment or control,” he said. “The bottom line is it cannot result in pollution of the ground water.”

Whatever a plant does to control nitrates, Wass said, “the work is to make sure it stays below 10 milligrams per liter in the ground water.”

Key parts of Visalia’s $48 million nitrate effort are:

Adding four more aeration basins, where air is bubbled through the water to help bacteria “eat” the dissolved nitrates and other chemicals. The plant already has four such basins.

Adding a secondary clarifier — a pool where solids settle to the bottom and lighter crud floats to the top and are removed. There are five clarifiers at the plant now.

Adding two digesters — enclosed tanks where bacteria decompose organic solids and create methane gas that fuels blowers for other parts of the process. The plant now has seven digesters.

A new “dewatering” facility to pre-dry the remaining solids left over from the treatment process.

About $6.8 million will be spent on needed repairs to the existing plant.

Another big expense involves no longer putting treated water into Mill Creek.

Treated wastewater is regulated by the state. But discharge into Mill Creek falls under U.S. Environmental Protection Agency regulations.

“It brings a much more rigorous standard,” Stringfield said.

Visalia City Council members last week approved the notion of building a 3.7-mile pipeline to carry treated water from the plant to 160 acres of city-owned basins west of Visalia instead of discharging into Mill Creek.

The pipeline, which could cost up to $14.6 million, will also make the water available to more farmers along the route who could use it to irrigate up to 2,600 acres of nonfood crops.

Last fall, City Council members approved a schedule of sewer-rate increases to help pay for the upgrades. The residential fees, just under $32 a month in August, will gradually rise to more than $42 per month by 2011. The residential rates include a fee for street sweeping.

Increases were also slated for commercial, retail and industrial customers, too.

City Manager Steve Salomon said last week that Visalia will likely have to draw reserves in the sewer fund and issue bonds or borrow other money, which would be repaid through more rate increases.

The reporter can be reached at tsheehan@fresnobee.com or (559) 622-2410.

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