Carpenters and ironworkers worked in a 19-foot-deep excavation site earlier this month, systematically laying long lines of rebar to form the foundation of a critical component in Paso Robles’ new sewer plant.
“This is what will really clean up the wastewater,” wastewater treatment manager Matt Thompson said of the all-new biological nutrient removal basin that will soon be erected.
That basin, along with other new treatment systems in the works, is part of the city’s $49.6 million upgrade of its 59-year-old plant.
The upgrade is the largest public works project in Paso Robles’ 125-year history.
One of the main goals is to stop chemical pollution of the Salinas River — and thousands of dollars each month in costly state fines — that the city’s wastewater discharge causes today.
The new plant will also generate 150 construction jobs at its peak, a larger daily treatment capacity of almost 5 million gallons and long-term sustainability.
“The new plant will replace obsolete technology, allowing us to meet the requirements of more stringent clean-water standards with the most advanced, cost-efficient methods and equipment in the area,” Councilman Steve Martin said.
At the north end of Paso Robles between Highway 101 and the Salinas River, the 13-acre sewer plant was built in 1920 and expanded in 1954. While it’s seen two small upgrades in 1972 and 1989, city leaders have said building a modern facility is long overdue. The new plant, which will bring 12 permanent jobs in place of the current seven positions, is being designed for a 40-year lifespan.
The project began in April and is expected to wrap up in September 2015.
So far, workers have cleared out several old structures, installed bypasses to continue treating 3 million gallons of sewage each day and excavated several sites for new equipment and buildings.
The project is about 20 percent complete.
After the elaborate clarifiers, basins and chemical systems are built, workers will connect the systems, install the instruments and controls and bring in fiber optics to link everything to a control room.
But first, much of the old plant had to go.
“It’s nearly 20 years beyond its useful life,” Thompson said of current operations.
Bar screens had deteriorated, filters were overloaded, and underground piping and electrical systems failed. A thick crust of corrosion caked pumps and pipes.
Even so, as much material as possible is being repurposed. Old pond rocks will line a new channel to deliver treated wastewater to the river. And redwood from an old barn on site will be added to the interior of the operations center.
Of the new technologies coming in, one highlight is the biological nutrient removal system that will snag all of the ammonia and most of the nitrates from the wastewater.
Namely, it will stop the waste pollution of salts, nitrates and disinfection byproducts discharged into the riverbed that has plagued the city. Essentially, the system will grow a special kind of bacteria that will remove ammonia and nitrates.
The state has fined the city $6,000 to $9,000 each month for the pollution since 2001, after the state changed its water quality rules in 1999.
“Those fines are going to continue until we can complete this upgrade,” Thompson said.
Removing the ammonia may also mean the return of steelhead trout to the seasonal waterway one day.
Sustainability is an overall theme of the project and will be seen in many facets.
First, the new plant will use one of many sulfur springs on the site — a natural phenomenon for which Paso Robles is historically known — to flow hot water into a new operations building so its offices, labs and control room will get free radiant floor heating.
Second, the project will reduce the sewer plant’s utility bills by about 40 percent by generating energy from the gas produced by wastewater sludge.
The current plant burns off that gas and wastes it, Thompson said, because it doesn’t have the technology to use it now.
Third, solar energy may be in the plant’s future. The city is eyeing its property on the east side of the river for solar panels to one day offset all of the upgraded plant’s costs. Plans for that are tentative, Thompson said.
Long term, the upgrade will allow the city to use recycled water to irrigate its parks, vineyards and golf courses by 2025. But first, a separate piping delivery system for that must be built.
Overall, the new plant is on track to come in under budget at $47 million, Thompson said.
The $36.4 million construction contract is with Fresno-based W.M. Lyles Co.