Crews are grading ground and trucking in supplies to build a second assembly plant at USSC Group Inc., the bus-train-airplane seating and fire-suppression company in Exton that counts SEPTA and Amtrak among its clients.

The factory is on the site of the former West Pharmaceutical center, which USSC opened last year after an extensive industrial redesign and conversion by Eli Kahn and Goodman Properties. From his 325,000-square-foot headquarters, CEO Joe Mirabile pointed across the parking lot to the site of the 182,000-square-foot plant that he says will employ an additional 100 workers after it opens next year.

His biggest headache is finding enough people to do the work. “I’ve got 72 openings right now,” in addition to his staff of 250 — even before the new building opens, Mirabile said. Workers are commuting from nearby counties and from Philadelphia, an hour from the Exton station on the Paoli-Thorndale train line (or 40 minutes by express), plus a four-mile ride up Pennsylvania Route 100.

He suspects increased hiring by Amazon at its facilities in Delaware and other markets adjoining Chester County is making it ever tougher to find workers. USSC is boosting its starting wage by $1, to $15 an hour next year, plus an “extremely competitive” health-care plan. The company pays a lot more for machinists, welders, engineers, and other skilled staff.

USSC moved to its current quarters last year from the smaller former National Foam building nearby, which was quickly rented to a vending-supply company. Kahn and Goodman also designed the new building.

Among the factors driving USSC’s expansion are contracts to supply new seating for SEPTA’s bus fleet and part of its train fleet. Mirabile says SEPTA accounts for 10% to 15% of the company’s business. Mirabile says some of his workers commute long distances on SEPTA, and it’s a point of pride to see the company’s products in use locally.

To train workers, USSC, like an increasing number of area manufacturers, offers its own apprenticeship program; state and federal programs, promoted by the Chester County Economic Development Council, county officials, and manufacturers’ groups, pay for part of the cost.

Mirabile has also hired students from Cristo Rey, the Catholic high school in North Philadelphia whose pupils work one day a week to gain job skills and pay their tuition.

Founded by Ulf Hammarskjold, USSC was purchased in 2015 by Mirabile and other managers in partnership with Boston buyout firm Dubin Clark (they also owned Party City and toilet manager Johnny on the Spot, among other businesses).

Since then, it has grown partly by acquisitions, most recently with the purchase of Firestorm, a 100-employee company that makes Fogmaker-brand fire-suppression systems for mines and other customers in Australia, New Zealand, the Philippines, and other Pacific countries, previously licensed by USSC in North America. The company won’t say what it paid. Mirabile hopes to expand smart-seat sales in those countries.

Mirabile said increased taxes (tariffs) on imported steel and other goods are driving up costs. His engineering team, headed by a luxuriantly bearded Princeton graduate and Drexel doctorate, John-Paul McGovern, is working on high-value products such as a proactive suspension system, with sensors and small motors, that would compensate for potholes and other road hazards on moving SEPTA buses.

The system, using technology developed by Amar Bose, famous for his sound-system work, is currently in testing, Mirabile said.

(Earlier versions of this article misidentified Fogmaker, Firestorm’s fire-suppression system.)