HAMPDEN – The fixings for a flawless Fourth of July aren’t in the supermarket aisles or the weather forecast. They’re buried in a grassy hillside, safely stashed in a concrete bunker once used to store ammunition for the military.

The wooden bins there are filled with heart, butterfly, star and crackling shells. Boxes containing colorful multishot cakes, candles and rockets are stacked 6 feet high next to boxes packed with spinning wheels, fountains and waterfalls.

In just a few days, the bunker will be almost bare after workers at Blue Hill Pyrotechnics have put on 20 fireworks displays around the state on July Fourth. Principal owners Rick Briggs and Edward Murphy, however, will quickly restock the storage facility so they have enough on hand for the rest of the busy summer season.

Fireworks aren’t just for summer any more, according to Briggs. Eight years ago, between 70 percent and 75 percent of the firm’s business centered on Fourth of July activities. This year, only about 35 percent of the company’s fireworks displays will be linked to Independence Day celebrations.

The volume of shows is heaviest during the summer tourist season, with shows at fairs, festivals, concerts, auto races and other sporting events, said Briggs. But Blue Hill Pyrotechnics puts on fireworks displays year-round. Regular winter shows include New Year’s Eve events and snowmobile gatherings. More and more, the firm is creating displays for private events such as weddings, anniversaries and family reunions as well as school events such as graduations, dances and reunions.

“A couple of years ago, we built a ground display for a proposal,” said Briggs from his office on Ammo Drive. “The gentleman took his fiancee for a walk [on a golf course]. We hid in some trees, then lit it when we heard them approaching. It spelled out ‘Will you marry me?’ When she threw her arms around him and said, ‘Yes,’ we had two fireworks shoot up into the air. It was great fun.”

Using fireworks to propose marriage probably never occurred to founder Alton Herrick, who used to make the shells himself for the Blue Hill Fair on the front porch of his downtown home during the 1950s and’60s. Herrick and his sons sold the company to an Owls Head couple in the 1970s, who in turn sold it to Eric Hake of Veazie in 1987. Briggs and four others bought the company a decade later, adding a limousine service in 1999.

Briggs and Murphy, former Hampden firefighters, each own 40 percent of the firm. Three investors, who wish to remain anonymous, own the other 20 percent of the business, according to Briggs. While he refused to reveal specific figures, Briggs said that revenue has doubled in the past five years after 10 years of “stagnant revenue.”

“The millennium hoopla really helped,” he said, “and there was a ripple effect from that. But we’ve also done a lot of networking. Our wedding business is growing because we’ve networked with wedding consultants and have a booth at the bridal shows for the limo service, but people are intrigued that we also offer fireworks indoors and outdoors.”

The cost of an outdoor fireworks display runs from $1,000 for a five- to eight-minute private show to $15,000 for Bangor’s Fourth of July show, which lasts about 20 minutes, said Briggs. The smaller shows require two “shooters” to set up, set off and clean up after a show, while the larger displays could require 25 people.

The more shells used and the larger the shells, the more expensive the show, according to Briggs. Shells range in size from 2 inches in diameter to 16 inches. The smaller shells retail for about $2 each while the large shells can cost as much as $1,000 apiece.

Last year, the firm used 75,000 individual aerial shots, 40,000 multiple-burst aerial shots, 105,000 special aerial shells used in finales, and nearly 100 spinning wheels and other fireworks used on the ground. During that time there were no injuries or accidents, he added.

Blue Hill Pyrotechnics employs three full-time employees, including Briggs, 40, and Murphy, 55, in addition to 130 trained shooters, many of them firefighters, on an occasional basis. Some shooters do just one or two shows a year close to home, while others travel throughout the state and do 25 to 30 shows a year.

At least one person at every show must be licensed with the state fire marshal as a pyrotechnic technician and undergo a background check. They are paid a flat fee per show, based on how much setup and cleanup time is required. The average shooter earns about $50 per show, said Briggs.

“Our shooters don’t do it for the money,” he explained. “They truly love it and take a lot of pride in the work. This is like being on stage for them. The audience reaction is more important than getting paid.”

For safety reasons, the fireworks industry is very well regulated, explained Briggs. Permits must be obtained from local officials for every show and each site must be inspected by a fire marshal before the show. Often, the fire marshals oversee the actual display in their local communities.

State law requires that the safety perimeter around the place from which fireworks are shot be a minimum of 140 feet from the crowd, the closest building or any flammable material. An additional 70 feet must be added for each inch in diameter of the largest shell being fired. So, when 16-inch shells are used, the safety circle must be 1,300 feet or more in diameter.

Federal regulation of the transportation of fireworks is even tighter, said Briggs, who drives an 18-wheeler to factories in Wolverine, Mich., and Logan, Utah, to pick up fireworks a half-dozen times a year. Transporting explosives requires proof of $5 million in liability insurance, permits from every state the truck passes through, and a license from the Bureau of Alcohol, Tobacco and Firearms.

Insurance costs for Blue Hill Pyrotechnics have increased dramatically in the past few years, as they have for other businesses, said Briggs. Insurance costs account for about 15 percent of the fee for each show, while personnel costs are about 10 percent, he said.

Blue Hill Pyrotechnics has only one in-state competitor – Central Maine Pyrotechnics of Hallowell. That 15-year-old company put on 23 Fourth of July displays last year, according to information posted on its Web site.

While national events rarely affect the fireworks industry in Maine, Briggs said the Sept. 11 terrorist attacks made the public very unsure of whether fireworks were appropriate. The firm not only lost about a dozen jobs shortly after the event, but the company’s cash flow was off by 30 percent in early 2002, when most clients schedule summer events.

“We were concerned there for a while,” said Briggs. “Usually, people start booking for the summer and put down a deposit in January and February. It wasn’t until the second week of May when people felt comfortable about it and then the floodgates opened. We are fully booked now.”

Briggs will spend the Fourth doing one of the firm’s smaller shows in York Harbor so that he can oversee other displays in southern Maine. Murphy will be in Camden. They’ll arrive home between 3:30 and 4 a.m., and get a few hours sleep before heading out again.

“Starting Saturday, June 29, we start a nine-day run and we’ll be in a different town every night,” he said. “It’s like being carnival workers.”

Briggs said that he’s shot fireworks off of barges, islands, bridges, riverbanks, mountaintops, golf courses and parking lots. He’s battled rain, wind, snow, heat, fog, black flies and mosquitoes to mount displays in every county in the state. But in the end, it’s the “Oohs” and “Aahs” that make it all worthwhile.