Paso Robles spending nearly $77 million to increase water supplies

As the Central Coast reels under four years of extreme drought, and residents of the Paso Robles groundwater basin decide whether they want to form a water management district, the city of Paso Robles is in the midst of building three major water infrastructure projects costing nearly $77 million and capable of producing as much as 7,300 acre-feet of water per year.

Two of the projects are complete, and the third is scheduled for completion in 2018. The finished projects are the Lake Nacimiento water treatment plant and an upgrade to the city’s wastewater treatment plant.

The Nacimiento water treatment plant cost $11.7 million and allows Paso Robles to use its allotment of 4,000 acre-feet per year from the Nacimiento pipeline. That means that during the winter months, the city of more than 30,000 can get most, if not all, of the water it needs from the pipeline and does not need to pump any groundwater, said Matt Thompson, the city’s wastewater resources manager.

One acre-foot of water is 325,851 gallons and is generally enough water to serve the needs of two five-person households for one year.

“Demand for water decreases a lot in the winter because people don’t irrigate much, if at all,” Thompson said. “It really means that we can give the groundwater basin a rest.”

The sprawling 790-square-mile Paso Robles groundwater basin needs a break because years of drought and pumping have caused aquifer levels to fall by more than 70 feet in some places, particularly in the Estrella area, which is immediately beneath and to the east of the city. All three of the city’s water infrastructure projects will minimize the city’s use of groundwater and help stabilize the basin.

Even though weather forecasters are predicting heavy El Niño rains this winter, it will not be enough to eliminate the drought, said county supervisor and former Paso Robles mayor Frank Mecham. Over the years, he has learned that no local government should ever turn down a supplemental water source like the Nacimiento pipeline, which runs 45 miles from Lake Nacimiento as far south as San Luis Obispo and provides water for five communities.

“All criticisms aside, I think Paso Robles has really stepped up to the plate to provide supplemental water sources and take some pressure off the groundwater basin,” Mecham said. “Whatever anyone can do to relieve the basin from being pumped more should do it.”

The city has also completed a $47 million modernization of its sewage treatment plant. Before the upgrade to the plant, the city struggled to meet state standards for nitrates, salts and disinfection byproducts in the water that it discharged into the Salinas River.

“The wastewater treatment plant is the biggest facility the city has ever built,” Thompson said.

Among other improvements, the modernization project includes a complete overhaul of the waste removal and filtering process, a new pump station and a new 190-kilowatt electrical generation facility powered by methane gas produced by the treatment plant.

The electrical plant will allow the city to cut its power bill at the plant by 40 percent, saving the city $160,000 a year. With its many pumps and fans, electricity is the biggest cost associated with running a wastewater treatment plant, Thompson said.

With the completion of the sewer plant, the city is now ready to begin its third and final supplemental water project — an $18 million tertiary treatment plant that will clean the 2.7 million gallons a day of water produced by the sewer plant to the point that it can be used for irrigation at city parks and golf courses, and for other non-potable uses, city planner Susan DeCarli said.

The city is currently in the planning phase for the recycled water project and expects to begin construction in late 2016 or early 2017 and be complete in 2018. The recycled water plant will use cloth filtration and ultraviolet disinfection to achieve tertiary levels of cleanliness.

Like the other water infrastructure projects, the tertiary treatment plant will be paid for with a combination of state and federal low-interest loans and grants, including a $6 million state Proposition 1 grant that the city has applied for. Proposition 1 was a ballot measure approved by voters in 2014 that allocated $7.12 billion for water infrastructure improvement projects.

Once complete, the facility will ramp up its production of recycled water over 20 years to meet increasing demand as the city grows, and it will produce as much as 3,300 acre-feet of recycled water per year, water that currently is discharged into the Salinas River.

“It’s kind of a waste,” Thompson said. “The water is pumped out of the groundwater basin and eventually is released into the Salinas River.”

However, the city will not entirely stop discharging water into the Salinas River. From January through May, when irrigation is at a minimum, the city will discharge into the river whatever surplus recycled water it produces.

This occurs when flows in the Salinas River are at their maximum and steelhead trout are migrating up the river to spawning habitat in the upper Salinas River watershed.

The recycled water project also calls for the construction of 5 to 10 miles of pipeline that will carry the recycled water east, where it is most needed.

“The pipeline may be completed shortly after the tertiary treatment facilities,” Thompson said. “Our goal is to begin delivery of recycled water in 2019.”

This story was originally published December 25, 2015 at 4:40 PM with the headline "Paso Robles spending nearly $77 million to increase water supplies."