After years of planning and construction, the $11.7 million Lake Nacimiento Water Treatment Plant is now officially open and sending water to Paso Robles residents, allowing ratepayers to finally drink the water they’ve been paying for since 2012.
“Completion of the plant marks a milestone for the community and will greatly enhance the city’s water portfolio and long-term sustainability,” city water resources manager Christopher Alakel said.
Under construction since May 2014, the Lake Nacimiento Water Treatment Plant is designed to treat 2.4 million gallons of lake water per day. Paso Robles has an 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 city’s share is supplemental to its Salinas river underflow and groundwater supplies.
The new water source also is expected to relieve some of the pressure on the struggling Paso Robles groundwater basin, where overpumping and drought have caused a drop in water levels and led to some wells going dry in unincorporated North County.
“This is a direct offset to groundwater pumping,” Alakel said of the plant.
The lake water has been available since 2011, but the treatment plant’s construction was delayed for several years, largely because of ratepayer protests over the city’s water rate increases needed to pay for the plant. The rate hikes have been appearing on water bills since 2012, and the city has been paying for its share in the Nacimiento pipeline without being able to use most of the water. In 2015, the city has used three quarters of its annual share to recharge the Salinas River.
Located in the city’s well field on the south end of town, the treatment plant has undergone rigorous testing this fall. After touring the facility and monitoring its operations, the state permitted the plant on Nov. 17.
The plant will be operated seasonally from May to October when Paso Robles is hot and dry and demand is highest. It will be seasonal because the cost of using Nacimiento water is 10 times the cost of using groundwater when accounting for its delivery and treatment costs. But for 2016, the system will run year-round because most of the plant’s equipment is under a one-year warranty,and city officials want to make sure everything continues to function properly.
This winter, as the city continues long-term testing at the plant, residents will notice substantially softer water since Nacimiento will be making up about 80 percent of the city’s total water supply to customers. Groundwater contains a significantly higher level of hardness than lake water does, Alakel said. Soft water, by comparison, generally creates the feeling of softer hair after showers and less residue on water fixtures. As such, the city is urging water customers to turn down their water softeners this winter to reduce salt-loading at the sewer plant, Alakel said.
Starting in 2017 and going forward, the plant will be operated seasonally to supplement summertime demands. During that time, the facility will treat 2.4 million gallons of lake water per day — making up about 32 percent of the city’s summertime water use, which averaged 7.4 million gallons per day in 2014. During the rainy season, the city’s water users consume as little as 2.5 million gallons per day, which can be provided by the city’s river underflow wells.
In February 2014, the Paso Robles City Council allotted $12 million in construction funding for the plant, so the final $11.7 million cost was slightly under budget. The plant is staffed with four operators; additional cross-trained staff from the city’s water operations department will pitch in when needed.
Lake Nacimiento Water Treatment Plant
The new plant uses a five-step mechanical and chemical treatment process to make the lake water drinkable. Byproducts generated from the treatment process are diverted to the city sewage treatment plant.
Step 1: Water is piped in from the Nacimiento turnout and into the plant, entering a chamber where it’s mixed with chemicals to oxidize certain metals to make them readily removable.
Step 2: The water is flowed into a series of chambers to mix with chemicals designed to consolidate organic matter, such as decomposing plant material. The process uses micro air bubbles to float particles and solids to the water surface, producing a foam-like substance that’s scraped off and discarded.
Step 3: The water is pushed through a mechanical filtration system to remove fine particles and bacteria.
Step 4: The clean water then flows into four pressure vessels to address the water’s taste and odor.
Step 5: Chemical disinfection makes up the final step, as the chlorinated water travels zigzagged paths through a contact basin.