People in Your Neighborhood: After nearly 40 years, Point Loma native Peter MacLaggan leaves a liquid legacy

Peter MacLaggan, recently retired senior vice president of Poseidon Water, stands at the Carlsbad desalination plant.
Peter MacLaggan, recently retired senior vice president of Poseidon Water, stands at the Carlsbad desalination plant in March.
(Bill Wechter)

Senior vice president at Poseidon Water retires after leading the way for the Carlsbad ocean desalination plant, North America’s largest.


Every time someone turns on the tap in San Diego County, out flows the work of Peter MacLaggan.

MacLaggan, who has lived his whole life within about two miles of the house where he grew up in Point Loma, was the point man in the construction of the Carlsbad ocean desalination plant, a nearly $1 billion public-private partnership that since 2015 has supplied nearly 10 percent of the drinkable water consumed in the county.

MacLaggan, 65, retired March 31 after 20 years at the private company Poseidon Water and nearly 40 years in the water industry. As senior vice president of Poseidon, he led the legal, political and bureaucratic battles required to build the Carlsbad plant, the largest desalination facility in North America.

His father, James MacLaggan, was a prominent local pediatrician who practiced medicine until his death in 1988. The senior MacLaggan helped to see that all San Diego children got the polio vaccine in the late 1950s and was a past president of the California Medical Association.

For a time, the younger MacLaggan thought he, too, might become a physician.

“There was a seminal moment when I ran across a photo of my dad standing next to a dissected cadaver in medical school,” he said. “That was the end of it for me.”

MacLaggan decided to study civil engineering at San Diego State University, where he first became interested in the water industry. He secured an internship at a company making reverse osmosis water filtration systems, which led to a full-time job after graduation. His early experience included jobs on a seawater desalination project in Saudi Arabia and later a similar project on a U.S. Navy submarine.

“They were interesting applications that at the time were cutting-edge,” he said, and the process eventually led to the reverse osmosis filtration system used at the Carlsbad plant.

MacLaggan went from private industry to a job at the San Diego County Water Authority when the agency was still small. He was the 49th full-time employee in the agency’s history, he said.

“My charge was largely water reuse and recycling projects,” he said. “That technology was practiced in a few locations but was not well-thought-out in terms of statutes and regulations. Our focus turned to amending the California water code to make recycling more attractive and feasible.”

That experience piqued his interest in law, and as a result he earned a degree from the University of San Diego Law School to help him navigate the legal aspects of the water industry.

He left the Water Authority in 1997 to work independently as a consultant for a few large clients such as the California Water Trade Association. That led to his connection with Poseidon, which hired him full time in 2000 to lead the Carlsbad project.

“To me, it seemed like a great idea and very viable in terms of success,” MacLaggan said. “That’s why I took the position.”

If anything, he was overly optimistic about the time it would take to build the Carlsbad plant, which eventually took 12 years and cost close to $1 billion.

“My advice to folks was [that it would take] five or six years,” he said. “The biggest hurdle was the regulatory process. That’s what took all the time.”

One critical point where everything came together was Nov. 9, 2012, when the Water Authority approved an agreement to buy virtually all the water produced by the desalination plant.

Almost immediately after that, an appeals court dismissed challenges that the nonprofits Surfrider Foundation and San Diego Coastkeeper had filed alleging that the plant’s seawater intakes would kill or harm marine life. And on Dec. 24, 2012, the state approved $768 million in tax-exempt bonds to finance the biggest part of the project.

Two days later, construction began, and it was finished three years later.

“When the plant went online, it immediately doubled the local capacity in San Diego County,” said MacLaggan, who still surfs a few days a week and keeps in touch with friends from kindergarten.

Production also began at an opportune time for the region. Southern California was in the grip of a lingering drought and Gov. Jerry Brown had just ordered water deliveries cut by 25 percent.

At full capacity, the plant produces 50 million to 54 million gallons of potable water per day, enough to meet the needs of 400,000 people.

Poseidon is in the final stages of getting permits to build another plant about the same size in Huntington Beach.


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