BERLIN — Beginning today, the City that Trees Built and Jericho Mountain State Park are hosting one of the largest gatherings of all-terrain vehicles in New England.

The ninth annual Jericho ATV Festival, which runs through Saturday at Jericho Mountain, a park the state built with motorized recreation in mind, will feature demos, displays and the latest ATV models from several manufacturers.

But all attention will focus on the mud pit, which on both Friday and Saturday will see grudge matches and races.

Like metal moths, an ever-increasing number of ATV’s are drawn each year to the inner glow of the mud pit, said Kenny Chaput, who since 2010, has been the “mud-pit supervisor.”

Working with an all-volunteer crew that includes Michael Couch, he of the deft touch with a front-end loader and excavator, Chaput on Thursday watched the mud pit come to life.

About 175 feet long and approximately a third as wide, the mud pit is a “trial and error” exercise involving dirt and water, said Chaput, who works for the Department of Safety and whose family has a seasonal home in Milan, just north of Berlin.

Couch will be back at the mud pit around 5 a.m. today to check the consistency of the mud, Chaput said, and if it’s not quite right, he’ll stir the mixture and/or add more water or earth to it.

Chaput expects the tweaking will go on right up until the start of competition.

Since it began, the mud pit has gotten “bigger and bigger” said Chaput, while the machines that try to traverse it have gotten “better and better.”

Most ATVs, straight from the factory, can get through the mud pit eventually, said Chaput, while others that are modified and have nitrous-oxide boost systems will fly through it.

As evidenced at Jericho Mountain, mud-pit racing is becoming more popular among riders who are just looking for bragging rights and also those who are looking for money.

In the Open class of racers, the top three prizes are cash, said Chaput.

He traced interest in the event, saying that from some three dozen or so racers in 2010, the mud pit races in 2017 had more than 100.

The mud pit is designed to challenge racers, but not to injure them or their often expensive rides, said Chaput.

Spotters will stop a rider from proceeding if the rider is at risk of injury — something that has never happened before and hopefully never will, said Chaput — or if an ATV is at risk of mechanical failure.

ATV’s do occasionally get stuck in the mud, however, and a robust farm tractor drags them out.

“But it doesn’t stop them,” said Chaput, noting that “they come back,” partly because it doesn’t cost much to do so. You get three grudge runs for $10, said Chaput, while it costs $10 per race.

The gates at the Jericho ATV Festival open today and Saturday at 8 a.m. More information about the festival is available online at androscogginvalleychamber.com/jericho-atv-festival.