Saddled with a heavy load of mortgage defaults, Synergy One Federal Credit Union chief executive William White realized last year that the 41-year-old institution in Manassas, with $180 million in assets, could not survive much longer on its own.

He and the board of directors decided to invite local credit unions to submit merger proposals. After four rounds of judging, the field of 60 applicants was narrowed to five. Each gave a presentation on why they would be the best fit, but one stood out: Fairfax-based Apple Federal Credit Union.

“Apple is very community-minded and wants to help members from all walks of life, the same philosophy that we have,” White explained. Selecting the credit union, the fifth largest in the Washington area, he continued, would give Synergy One FCU stability and more product lines for its 25,000 members in Prince William County.

Last week, the two institutions received regulatory approval to merge, a move that will give Apple FCU, which serves schools in Northern Virginia, $1.53 billion in assets, some 143,000 members and 22 branches.

Terms of the agreement calls for all 50 Synergy One FCU employees at its two branches to stay on, creating a staff of roughly 350 people in total, said Apple FCU chief executive Larry Kelly. That number, he said, may grow before the merger is completed in November, as there are 30 job openings at the company.

White’s position at the combined entity has yet to be determined, but he expects to be “the face” of the company in Prince William County.

Kelly expects the merger, given the greater economies of scale, will result in better loan and savings rates for members. He does not expect Synergy One FCU’s mortgage portfolio to be a “hurdle” for Apple FCU, which has “enough scale and diversification” to weather any impact.

“It appears that the economy is slowly heading out of the recession around here, so we’re optimistic that we will be able to manage that portfolio in a reasonable manner,” Kelly said.

Synergy One FCU posted a $2.8 million loss in 2010, but by the end of June, narrowed it to $533,000.

Most of those losses, White said, stem from home equity lines that members could not repay once they fell on hard times. He pointed to statistics from that showed one in every 436 households in Prince William County was in foreclosure in 2010.

Mortgage defaults, in part, led regulators to require more credit unions to merge or liquidate assets in the wake of the downturn, said Bill Hampel, chief economist at the Credit Union National Association. The trade group counted 37 credit unions that were forced to liquidate or merge in 2010, compared with13 in 2007.

Voluntary liquidations or mergers, like that of Apple FCU and Synergy One FCU, often fluctuate. For instance, they declined last year as institutions worked to shore up their own balance sheets. Hampel said he expects consolidations could pick up again as credit unions grapple with higher compliance costs linked to the Dodd-Frank Wall Street Reform Act.

“The compliance burden is a fixed cost regardless of size,” so small credit unions may feel compelled to join a larger institution to manage the added paperwork, he explained. What’s more, credit unions may consolidate further as net interest margins — the difference between what it earns on loans and pays on deposits— continues to decline amid tepid loan demand.