While I was clicking around the 9/11 Memorial website looking to see why the fences were still up, I came across this interesting — but more than that, moving — video of the cleaning process for the memorial pools. (Scroll to the bottom of the page to see it here.)

It’s narrated by the chief engineer, Anthony Locasto, who explains that the pools are cleaned five nights a week by three men equipped with a vacuum system and brushes — and it takes them eight hours to complete the job. They start 30 feet down at the bottom of the pools; the lower void is another 10 feet below that. They finish on the ground level, where the waterfall is brushed and the names are cleaned and polished. The video was shot and edited by Jin S. Lee.

“I think it’s so important that the family members have a beautiful place to reflect, a place to be comfortable that they can call their own,” Locasto says in the video. “And knowing that I am one of the people who maintains this beautiful place … it’s just the greatest feeling in the world. It’s a great honor to be here.