SAN FRANCISCO—A San Francisco Bay Area Rapid Transit (BART) janitor made over $276,000 last year—four times his base salary—with the help of 2,485 hours in overtime, according to public compensation data released Tuesday, November 1, by the Las Vegas-based non-profit Transparent California.

Liang Zhao Zhang’s official job description includes scrubbing floors, polishing elevators and sweeping station sidewalks. He managed to turn his $57,945 base salary into six-figures every year for the past three years thanks to overtime and other pay benefits.

“This employee signs up for every overtime slot that becomes available,” BART spokeswoman Alicia Trost said in a statement. “He is likely working almost every day of the year cleaning our stations. He is signing up for time that is also available to others—if he doesn’t take them, someone else will.”

Zhang worked an average of 114 hours a week in 2015, which equates to about 6.8 hours of overtime every single day – an additional $162,050.06 annually.

His overtime combined with other pay benefits received throughout the year accumulated a total of $271,243, according to data. Zhang has received a combined $682,000 in pay and benefits over the last 3 years.

Zhang worked upwards of 4,000 hours in 2015 – more than double what the typical employee clocking 40 hours a week might work, which is about 2,000 hours.

“His supervisor reports he is well respected and a diligent worker,” said Trost. “He has seniority and chooses to work these hours.”

“If we didn’t have janitors working overtime, our stations would be dirtier and the overall BART experience would be impacted,” she added.