Dean Tistadt spent a ­quarter-century finding creative solutions to the Fairfax County public school system’s most vexing challenges.

Through tropical storms and blizzards, Tistadt, the chief operating officer and assistant superintendent for facilities and transportation, kept the lights on and ensured that a fleet of 1,500 buses ran on time. He oversaw a construction budget totaling $1.5 billion and supervised the construction of 11 schools and renovations to 36 other buildings, adding nearly 8 million square feet to the sprawling system.

Tistadt, 63, who retired on Dec. 31, had seen and fixed it all. But he left behind one problem he always wanted to solve: overcrowding at Bailey’s Elementary near Seven Corners.

“Of the challenges I’ve faced in my career, this is the most insolvable,” Tistadt said, acknowledging that this particular issue stymied him. “I’ve prided myself on being creative, being a problem-solver. . . . I leave with regret at not being able to change it.”

At Bailey’s Elementary, the total enrollment this year surged above 1,300, making it the largest elementary school in the region. Within five years, its enrollment is projected to reach 1,600. Tistadt said much of the recent growth is driven by a high birth rate in the Bailey’s Crossroads area, which has attracted many immigrant families. The school has become one of the most culturally diverse in the county.

Dean Tistadt retired December 31 from the Fairfax County Public Schools. He was the Chief Operating Officer for the system. (N/A/FAIRFAX COUNTY PUBLIC SCHOOLS)

It is also home to some of the school system’s poorest students, with about 65 percent of the children receiving free or ­reduced-price meals.

The school, built in 1952, was last renovated in 1995, and it was designed to accommodate 1,000 students. Tistadt’s team set up 19 mobile classroom trailers to compensate for the lack of space.

Bailey’s Parent Teacher Association member Christine Adams, the mother of a fifth-grader, said children are crammed into “every nook and cranny.”

“It’s been a problem plaguing us for years, and it gets progressively worse,” Adams said. “The truth is, it’s just a matter of time until we hit the breaking point because you just can’t keep filling up a school that’s already over capacity.”

Adams said that Tistadt was dedicated to helping the parents at Bailey’s find a solution to the school’s overcrowding problem. “I know he would have loved to wave his magic wand and fix it,” Adams said. “But he couldn’t.”

A George Mason graduate, Tistadt was a county budget analyst before joining the school system in 1988. He worked his way up through the administration, and he garnered broad authority in 2002, when he took over as chief operating officer and assistant superintendent.

“Any public official wants to be able to walk away believing they have made a positive difference in the lives of those for whom they served, and that is certainly Dean’s legacy,” Superintendent Jack Dale said. “He demonstrated a great passion for and belief in FCPS and worked tirelessly and unselfishly on behalf of Fairfax students and their families.”

But the situation at Bailey’s Elementary stumped Tistadt. In his last interview before retiring, Tistadt said he was unable to win over the Board of Supervisors, specifically Supervisor Penelope A. Gross, who represents the Mason district, home to Bailey’s Elementary.

Tistadt said he offered Gross multiple options to alleviate the crowding at Bailey’s, including a plan to renovate a nearby county library into a state-of-the-art education facility using schools money. Tistadt said none of the options were taken seriously.

“They give one excuse after the other,” Tistadt said.

Gross, who has represented the Mason district for more than 17 years, disputes Tistadt’s views of the Bailey’s predicament and said that she has put a lot of work into the issue. She said Tistadt’s plans to renovate the Woodrow Wilson library next to the school would have violated zoning ordinances.

The crowding at Bailey’s “is a very serious matter, and I don’t deny that,” Gross said. “The solution has to be the right one, not just the one of the moment, because it is a long-term investment, not a temporary solution.”

School board member Sandy Evans, who represents the Mason district, has been a vocal advocate for addressing Bailey’s crowding woes and said that it’s time for the county to step up and help the schools solve the problem.

“We must have the help from the county. These are their constituents, too,” Evans said. “They say, ‘Oh, that’s the school system’s problem.’ Yes, but simply there are times when the county needs to come in and step up.”

Tistadt will be replaced by ­Jeffrey Platenberg, who was the Loudoun County public schools’ assistant superintendent for support services. Platenberg is scheduled to begin work Tuesday.

In retirement, Tistadt will live near Charlottesville in Fluvanna County, where he plans to kayak and keep up with the latest thrillers by John Sandford and Lee Child.

Before his retirement, Tistadt gave a final presentation to the school board, outlining an $870 million budget to renovate facilities and build three elementary schools and a high school between 2014 and 2018. Part of the plan includes a new elementary in the Bailey’s area. The plan will not move forward, however, until the administration, school board and Board of Supervisors can agree on where it should be built.