BANGOR, Maine — Ahead of Wednesday’s concert, a video posted to YouTube shows a snippet of Phish’s rehearsal ahead of the groups show on the Bangor waterfront.

The venerable rock group is launching its summer tour in the Queen City and is expected to fill the 16,000-capacity Darling’s Waterfront Pavilion, with many others gathered outside the venue.

Phish fans, known as Phish-heads, often record and trade recordings of live shows. Some follow the group from town to town. The band arrived in town on Monday to begin rehearsing at the brand new Cross Insurance Center.

Phish’s crew arrived over the weekend and set up sound and lights, as a test run for both the band and for the venue.

“It was a great opportunity for the Cross Insurance Center to welcome the production crew into our building and see how a concert of this size would set-up in our venue,” said assistant general manager Todd Stoudenmire. “It has been a pleasure working with them and we are happy to have them.”

The Police Department is planning for an influx of people and has established a number of contingency plans to deal with the crowds, including redirecting Main Street traffic, Sgt. Paul Edwards said Tuesday.

“What we’ve been told is that whatever you have on the inside, you get two to three times that many on the outside,” the sergeant said.

Because the waterfront stage is on Main Street, the crowd potentially could spread out onto the busy roadway.

“That is what I’m worried about,” Edwards said.

Police also are concerned about people being too close to the roadway with dangers of falling into traffic or distracted drivers, who may be crowd-watching and not paying attention to the road, the sergeant said.

“We may have to change the traffic on Main Street,” Edwards said.

There also is a contingency plan if fans decide to jump the chain-link fence that surrounds the concert area, the sergeant said, declining to give details about what that plan entails.

When Mainers think of Phish, they often remember the performances at the former Loring Air Force Base in Limestone a decade ago that attracted more than 60,000 fans, Alex Gray, promoter for Bangor’s Waterfront Concerts, said Tuesday.

Bangor is going to see a huge crowd, but nothing like in The County, Gray said.

“If there was going to be a real Phish invasion, they would already be here,” he said.

Gates to the all-ages, general admission show open at 5 p.m. Blankets are allowed, but umbrellas, backpacks, coolers, outside food and beverages, weapons, contraband and cameras with detachable lenses and video cameras are banned, just like for any other waterfront concert.

“It doesn’t matter if it’s Phish or Jason Aldean,” Gray said.

“We’re doing the same thing we do with every other concert. It’s just a larger plan because of the larger amount of people expected,” Edwards said.

Local police also heard from other communities that have hosted shows that Phish fans like water, so they have issued a warning to stay out of the Penobscot River.

“Everyone local knows the river is dangerous and demands respect,” Edwards said. “It’s fast and the current can take you downriver and can kill you. Please, don’t go on the river.”

There is always a number of boaters on the river for concerts and that is OK, but police do not want to see people out in inner tubes or other nonmotorized flotation devices, the sergeant said. He asked that a safety warning about the river be posted on the band’s website.

Eastern Maine Medical Center is also preparing for the concert and holiday crowds with extra people on duty for both Wednesday and Thursday. EMMC’s Walk-In Care Center on Union Street will be open 8 a.m.-7 p.m. throughout the week to provide care for minor illnesses and injuries, and local ambulance crews will have additional staff on hand.

EMMC is encouraging concertgoers and holiday revelers who will be outside to drink lots of water, wear proper footwear, use sunscreen and take a break from the heat if needed.

“The saying ‘an ounce of prevention is worth a pound of cure’ definitely applies here,” Joel Farley, EMMC facilities and emergency preparedness administrator, said in a press release. “We want everyone to take care of themselves this week so they can have a great concert experience and Fourth of July holiday.”

With Phish shows also typically comes the “Phish Village,” or areas where goods are traded or sold that pop up in parking lots or grassy areas around the stage area. Edwards said officers who will be patrolling the area have been informed to be on the lookout for these gathering and commerce areas. Tents will not be allowed.

“Technically, they are not suppose to be vending,” Edwards said. “Basically, we’re going to leave vendors alone but we’re going to stop the ones doing illegal activities, such as selling beer or drugs.

“They cannot sell beer. Grilled cheese, I don’t really care about,” the sergeant said.

Concertgoers should just use common sense, Gray said.

“Be smart,” he said. “Don’t drink and drive and don’t make stupid decisions that could haunt you for the rest of your life.”