With construction on Paso Robles’ new water treatment plant winding down, the plant is expected to make Nacimiento Lake water available this summer.
The new supply will come from the city's annual 4,000 acre-foot share in the Nacimiento Water Project, a 45-mile pipeline that carries millions of gallons of drinking water from the lake to residents and businesses within San Luis Obispo County.
The lake water has been obtainable since 2011, but construction of the treatment plant was delayed for five years largely because of public protests over proposed water rates needed to operate it. Meanwhile, the city has been paying for its share in the Nacimiento pipeline without being able to use the water because it couldn’t treat it.
Now, the $11.3 million project at the south end of the city is expected to be finished in early August.
Under construction since May 2014, the plant will treat 2.4 million gallons of lake water per day.
Since the lake water is supplemental to Paso Robles’ river underflow and groundwater supplies — and city officials say the cost to treat Nacimiento water is 10 times that of groundwater — the plant will run five months of the year when it’s hot and demand is highest.
“It’s a brand-new water source, and we’re the first to treat it this way. There’s no one treating solely Nacimiento water at a treatment plant,” said Christopher Alakel, the city’s water resources manager. “So we have a robust system with lots of options.”
It’s up to each agency partnering in the Nacimiento project to treat the lake water that goes out to their respective customers. Those methods are largely based on their respective geology and how their water systems are set up.
Paso Robles’ treatment plant has brought roughly 50 local jobs to the city, according to the main contractor, Cushman Co. of Goleta. Officials with that firm said they also brought in 11 subcontracting companies from a variety of trades in the county to help the plant take shape. Electricians, concrete workers, steel fabricators, pipe fitters, engineers and heavy equipment operators have been among them. Once the plant is operational, it’s expected to employ three plant operators with existing city staff.
On Friday, workers were busy erecting the operation building, applying chemical-resistant coating to a storage structure and installing underground piping.
Next up, start-up and testing the individual processes for function and regulatory compliance will take place, Alakel said.
Meanwhile, the Nacimiento pipeline has been shut down since the summer because of leaks. The system is expected to be fixed and running again by early April.
That should occur right in time for Paso Robles’ plant testing to begin, Alakel said.
The plant features a five-step process to make the lake water drinkable using mechanical and chemical treatment systems.
First, the water will be piped in from the Nacimiento turn-out and into the plant.
From there, it goes into a chamber where it’s mixed with chemicals to oxidize certain metals in the water to make them readily removable.
Then, the water is flowed into a tank that directs it into a series of chambers to mix with chemicals designed to consolidate organic matter, such as decomposing plant material.
That clarification process uses micro air bubbles to float particles and solids to the water surface, which produces a foam-like substance that’s later scraped off and discarded.
The third step in the treatment process takes the water into a mechanical filtration system that pushes the water through small porous fibers to filter out “anything of a particular size,” Alakel said. “It’s small enough to remove even the smallest bacteria.”
The clean water then moves onto the fourth step, which involves flowing it into four pressure vessels to address the water’s taste and odor, “not unlike a home filter,” Alakel said.
Chemical disinfection makes up the fifth and final step, as the chlorinated water travels zigzagged paths through a contact basin. The byproducts generated from each of these steps go into a separate area and diverted to the city’s sewage plant farther north.
The clean water then leaves the water treatment plant and blends with the city’s existing river wells along the Salinas River, and immediately goes into the city’s distribution system and out to the residents.
Also on the site is a bulk chemical storage area featuring six massive fiber-glass reinforced plastic tanks to hold the plant’s chemicals needed to treat the water.