The six-year-old Torrance, Calif., company increased its Garden State workforce nearly fivefold with the acquisition of most of Birdsall’s assets in June, following the bankruptcy of the once-prominent Eatontown firm. And Partner now has the foundation for an East Coast hub that can feed its business across the country, largely because its bench of engineers is suddenly deeper and more diverse.

“Our clients are spread across the 50 states,” said Frank S. Romeo Jr., Partner’s director of East Coast operations. “And really, the idea is to grow the operation here in New Jersey and make this almost a brain center to provide expertise to our project managers, our relationship managers, our staff and our clients nationally.”

Partner’s reach comes from its roots as an environmental due diligence company, a practice that has drawn some of the country’s largest banks, Romeo said. But taking on more than 70 former Birdsall employees has effectively added new practices such as land development and mechanical, electrical and plumbing, he said, while boosting Partner’s capabilities in surveying, energy and health care.

And Partner hopes to add at least 30 new hires in the next six to eight months — all in New Jersey — to help service a national platform that already has 24 offices nationwide.

For many ex-Birdsall engineers, most with decades of experience, the state of affairs is far from where things stood less than a year ago. The 90-year-old firm and seven of its former executives were indicted in March, with authorities charging they bundled political contributions from employees to skirt the state’s pay-to-play laws.

“Anybody in the service business had to be affected by something like this,” said Anthony Sartor, chairman and CEO of the engineering firm Paulus, Sokolowski & Sartor, in Warren. “They had to think about what transpired there and how to examine what their policies have been.”

Sartor added that economic conditions or debt problems have forced other service firms to fold in the past, “but I’ve never seen anything like this, where a firm is just decimated because of the actions of a few at the top.”

Birdsall filed for Chapter 11 bankruptcy in March, giving way to the sale of most of its assets to Partner. So began a transition in which Partner managed to carry over a stable of business and clients from Birdsall, despite the cloud of the scandal.

“You don’t want to lose sight of the individuals and the work that was done,” said Chris Gaffney, the New Jersey group president for Toll Bros. Inc. Like other clients, the Horsham, Pa.-based homebuilder retained Partner for Regency Woods at East Windsor, a 200-unit residential project predating the recession.

Gaffney also said Partner’s national footprint allows it to “augment what some of the folks that were left at Birdsall had. And it really allowed them to take some of the stuff they’ve worked very hard on and just take it to the next step.”