In just a few days, with the crack of the starting pistol and an eruption of cheers, the 121st Boston Marathon will commence in Hopkinton. For the past few years, this is where I've covered the annual event for WGBH News.

It’s quite a scene. Thousands of spectators gather near the start line on Hopkinton Common, where a plethora of temporary tents offer goods and services, from fried dough to souvenirs. Tens of thousand of runners get bussed into this small town of 15,000 and take up residency, for a few hours, in an area dubbed the Athlete's Village.

Amidst all this, there is one little, logistical quirk that has long caught my eye. Those tens of thousands of runners arrive in the chilly early morning hours, almost invariably geared up in sweatshirts, jackets, sweatpants and the like. But when they start the race hours later, most set off for Boston in little more than shorts and a shirt, if that.

By early afternoon, the road leading away from Hopkinton Common is lined on both sides with hundreds of plastic bags, all stuffed with clothes that were left behind. So, who is bagging up all this stuff? And what, exactly, do they do with it?

It turns out the answer to those questions hinge on one woman: Judy Pitasi.

"I've been involved with the Marathon for 26 years," Pitasi explained as we ambled across a quiet Hopkinton Common.

"My brother was a back-of-the-pack runner and I used to meet him at Heartbreak Hill with a dry shirt, bananas and water. I moved [to Hopkinton] in the late 1980s and contacted the BAA because I really wanted to get involved."

Over the years, Pitasi has housed runners, as well as worked water and security duties. But a decade ago, she found her true niche among the veritable village of volunteers and staff who get the race off and running here each year.

There had been previous attempts to collect discarded clothes for charity, but the effort was far from centralized, and the results were — let’s just say, spotty.

"One particular year, the charity didn’t come and I was finishing up what I was doing and they were throwing all the bagged clothing in the trash and I went crazy," Pitasi said. "I went up to the information tent and ... I was mad. I said, 'What the hell is going on? Why are they throwing this all away?'"

In her mind, it was a waste.

A few months later, Pitasi got a phone call from Dotty Ferriter-Wallace, the Hopkinton Marathon Chairperson and the woman who, as Pitasi put it, she had "passionately spoken up at." And just like that, Pitasi was designated the founding captain of the Boston Athletic Association's official clothing collection program.

"I started with 10 people, walking myself from downtown Hopkinton up to the Village, which is probably a quarter of a mile," said Pitasi. "I’d probably walk it 25 times through the day."

Along the way, she and her small team bagged up all the clothing they saw. All. Of. Them.

"Shirts, sweatshirts, sneakers, socks, anything they might be sitting on the ground with — blankets, towels, tarps, blow-up pool mattresses and yoga mats," she said. "Just a plethora of stuff."

She also forged a crucial partnership with Big Brothers Big Sisters of Massachusetts Bay, which provides ten moving trucks to cart all the clothes away and put them to good use.

"They take a percentage to their own thrift store, and the balance gets sold to thrift stores across the country," explained Pitasi. "And the proceeds from that go back to Big Brothers Big Sisters for their mentoring program."

In the early years, Pitasi and her small team would collect about 10,000 pounds of clothes each year — nothing to sneeze at. But after 2013, a service that allowed runners to have a bag bussed back to the finish line in Boston was eliminated due to security concerns, and the scale of Pitasi's operation expanded.

"It just exploded," she said. "Now I have 201 volunteers. We cover all the way to Ashland town line, and now we’ve gotten up to 52,000 pounds."

For the record, that’s a serendipitous 26 tons of clothing — one for each mile in the Marathon. And the proceeds now cover the cost of a full-year of mentorship for about 20 Massachusetts children.

"They’re lifelong commitments, usually," said Pitasi. "They get a big brother or a big sister, and not only do they do events but they follow them through school and they become lifelong friends, like family. It’s great."

These days, Pitasi is more of a program manager, but on race day, she still can’t help herself from getting hands-on. Case in point: Last year, when word came down that a runner had left his keys in a discarded warm-up jacket.

"And I had the dubious honor of going through the bags," Pitasi said, "And I found the keys. And, of course, it was the last bag."

Did she get a tip for her efforts?

"I got a very nice thank you note and a Starbucks gift card, which was very thoughtful," she said.

Of course, the thoughtful thank-yous are not why Pitasi combed diligently through countless bags; it’s not why she was so enraged a decade ago to see all those clothes going to waste, or why she has worked so tirelessly to build her program.

"It’s just inside me," she said. "I’ve gone without at a period in my life, so I know what it’s like not to have 'the best' or to have your shoes worn out or whatever. So I think I have a good understanding of what others might need."

So, runners, don’t hesitate to throw off those extra layers at the start of this years’ race. Lighten your load, because if you leave it, Pitasi is going to find it and make sure it lightens the load for someone else down the road.