Paso needs urgent upgrade to sewer treatment plant

A modern automated screen at right filters chunks into a plastic bag. The rusting screen at left drops overflow into a wheelbarrow. The rusting overflow system is an antiquated relic.
A modern automated screen at right filters chunks into a plastic bag. The rusting screen at left drops overflow into a wheelbarrow. The rusting overflow system is an antiquated relic. dmiddlecamp@thetribunenews.com

Paso Robles could face steeper fines and even a state order halting growth if the city does not complete a multimillion upgrade of its sewage treatment plant built in 1954.

“The plant is already 15 years beyond its useful life and is essentially polluting the Salinas River,” said Matt Thompson, the city’s wastewater manager.

The discharge of salts, nitrates, disinfection byproducts and other chemicals doesn’t meet state and federal water quality standards — and the city pays monthly fines for it.

There’s no way to stop them without the upgrade. It’s slated to cost $49.6 million in 2014 dollars, the year contractors will use to estimate the cost of materials by accounting for expected inflation.

Bar screens have deteriorated, filters are overloaded, and underground piping and electrical systems are failing, according to city officials. The thick crust of corrosion cakes pumps and pipes.

An aerial photo shows a green and frothy discharge from algae in the plant’s exit pipe on the city’s north end, while the water south of there is clear.

A recent tour of the plant showed that the first step in filtering solids from liquid still uses a screen from 1972 with a collection wheelbarrow beneath, something that officials say is almost unheard of for a city of Paso Robles’ size.

One of the city’s goals in upgrading the plant is economic stability. But to do so, customers’ sewer bills have to go up, officials say.

The increases would pay for upgrades, nix the violation fines and set aside money for future equipment replacements.

“We’re proposing steep increases, but it will prevent severe increases for future generations,” Thompson said.

But from what history has shown in Paso Robles’ drawn-out battle to increase water rates, the city could see residential backlash at Tuesday’s City Council meeting when increased sewer rates are proposed.

Pressure to upgrade

The plant is a financial risk for the city. Threats from the state’s Regional Water Quality Control Board only add to the pressure.

Because of excessive waste pollutants in the river, the city’s residents have collectively paid an average of $9,000 every month in fines over the past three years.

It’s so severe that the water board threatened in August to increase the fines to $10,000 per day if the construction and startup of a new plant doesn’t come by Sept. 1, 2015.

Water board engineer Matt Keeling said much of the money that Paso Robles’ population of 30,000 people pays now goes to fines rather than plant operation.

“The community needs to take that into serious consideration when they’re grappling with the increase” in rates, Keeling said. “Wouldn’t they rather their money be going to improvements and operation of their plant?”

Most sewer plants are useful for about 20 to 30 years, Thompson said, or up to 40 years “if you take really good care of them.”

Paso Robles’ plant has lasted 57 years, with small expansions in 1972 and 1989.

A combination of factors led the city to wait this long for such a major upgrade.

Among them are that today’s water board regulations weren’t so strict until 2004. The city’s residents have also paid a relatively low fixed sewer rate that hasn’t provided the kind of money needed for ample upgrades.

New plant proposed

The upgrade is essentially the construction of a new sewage-treatment plant, which is expected to take 2½ years. Building it could involve more than 300 workers such as engineers, ironworkers and carpenters, planners say.

The design, already complete, would eliminate the state compliance issues and fines, Thompson said.

It includes a new biological treatment process, energy generation system and an improved disinfection system.

One of the largest features is replacing the plant’s current trickling pond, where sewage is showered over rocks to allow for the physical and biological process of breaking down the carbon in the water — but not the nitrates.

Nitrates are among the culprits that have led the water board to penalize the city.

The upgraded version would include systems to break down both carbon and nitrates.

Until then, the city has “a classic case of nutrient pollution,” Thompson said as he slapped on a latex glove, picked up a rock and pointed to the dense mossy layer of algae created by nitrates and ammonia.

Because algae eat dissolved oxygen in the Salinas River, their concentration is one reason fish aren’t abundant, officials say.

Also, because the Salinas is a dry riverbed most of the year, the discharge doesn’t mix with existing water.

That means nitrates sink and accumulate in the groundwater, affecting drinking water quality, officials said.

If that continues, Thompson said the city’s drinking water could become unsafe within 50 years.

Officials say that the proposed upgrade would also help make Paso Robles’ water supply more sustainable.

One day, the city could use recycled discharge water from the plant to irrigate its parks, vineyards and golf courses. Adding those systems now, however, is too costly, according to city officials.


The city’s proposed new sewer plant is estimated to cost $49.6 million in estimated 2014 dollars (accounting for expected inflation), the year contractors will use to estimate the cost of materials.

There are two options to pay for it.

One is based on using a low-cost state loan and the other from conventional bond financing. The city is pre-approved for the state loan, but can’t get it until a new rate structure is set.

Both proposals call for increases to monthly sewer bills over a five-year span, raising the monthly fixed rate of $25.86 that is currently charged to a consumption-based rate that would charge users by how much sewage they discharge.

A two-person household would be charged less than a six-person household, for example.

That means a sewer bill of a typical household, which generates seven units of sewage per month, would increase to $54 or $73 per month by 2016, depending on which rate option the City Council chooses Tuesday. A unit is 748 gallons.