When an employee at Dewberry, a civil engineering firm based in Fairfax, was called up for active duty last month, his co-workers bought him a digital camera, and the company's technology department set up a link so he'd be able to send pictures back to his colleagues.

His co-workers and manager will fill in for him while he's away, not knowing how long that will be. And no matter what, by federal law, he will have a spot open for him when he returns, either the same position or a similar one.

This scenario is unfolding across the country at this moment, and perhaps more in this area -- home to many military reservists -- than in many others.

These call-ups are causing a bit of angst among employers, who worry about what to do when they lose a valuable worker for an extended, unknown period of time. Since the number of reservists required to report for duty was increased, companies have quickly reviewed pay and benefit rules related to military leave, and scheduled people to fill in.

Some companies will be calling on those who are "left behind" to pick up some extra work, said Michael Warech, practice leader of organizational effectiveness with Watson Wyatt, while others will examine how a department is run and perhaps change some of the workflow. Some employees, he said, will see a chance to try new skills until reservists return.

There is a sense of scrambling, for human resources officials and for other managers.

Kathy Albarado, president of HR Concepts in Herndon, a human resources consulting firm, said she is surprised by how many of her clients -- small and medium-size businesses -- don't have a plan in place for when a reservist is called up.

"It's just not common to actually get called up for any extensive length of time. But given our current climate, companies need that consideration," she said.

The Army, Air Force, Navy and Marine Corps each announced an increase in reservists on active duty this month. All told, there were 8,470 more reservists called up the week of March 5 than the previous week. As of March 5, the total reserve and National Guard members on active duty was 176,553, according to the Defense Department.

At any given time, the services may mobilize some units and individuals while demobilizing others, making these figures go up or down -- and making workplaces everywhere very aware of the major changes going on.

According to the Uniformed Services Employment and Reemployment Rights Act of 1994, employers must reinstate workers who are called for service. If their positions have been taken, similar ones, at the same level of seniority and pay, must be made available. In addition, employees coming back do not lose their seniority with respect to benefits.

There are exceptions, of course. If, for instance, a company's circumstances have changed drastically, so that reemployment is impossible, or if reemployment would cause undue hardship on the company (usually among very small firms), or if military service lasts for more than five years, those rules could be voided.

Some of the workers going on active duty are surprises to their colleagues, who didn't know they were reservists. Of course, there's a little trepidation at the worker-bee level about how everything is going to get done. At Dewberry, employees "were obviously concerned, but people just feel it's a patriotic duty," said Barbara H. Irwin, corporate director of human resources for Dewberry. "I think there's a huge sense of camaraderie."

That makes life a little easier when it's necessary for employees to change shifts or pick up a few extra hours for reservists, as is the case when a co-worker goes on maternity leave. Atlantic Coast Airlines in Sterling, for example, with 197 reservists out of 5,100 employees, will simply move shifts around to fill in for the ones on active duty. Not all 197 will be called up at the same time, of course, making it easier to fill in for those who are away.

Martin Schulz, an Army reservist and director of international equities with the National City Bank in Cleveland, was called up for duty back in December 2001. He was not looking forward to telling the president of his division that he would be sent off for an unknown period of time; after all, he was one of just two people who manage his equity fund.

"I asked some close friends how I should tell the company, and they told me to wait, because sometimes [the order] doesn't come through," he said. So he waited until the Army gave him a specific departure date.

When he told the president of his division, "he wasn't so excited," said Schulz. There was the concern for Schulz's well-being, of course, but also concern about how to fill his position.

But his partner, he said, who picked up a lot of Schulz's work, actually appreciated the experience in the end. "We had some issues, since there were only two of us managing the fund," he said. "One person was not enough to handle it."

In June, the bank hired someone from the outside who did a great job. And by "pure luck," Schulz said, that person decided to leave in October, meaning Schulz's exact job would be open for him when he returned. "I don't know what would have happened if he had stayed."

As for his partner, he thinks the leave cemented their relationship. "He saw a different part of the portfolio he'd never seen before," said Schulz. And now the two have an easier give and take when working on the fund.

That's why Warech of Watson Wyatt believes the experience will be good for the ones filling in. They will learn a little something along the way, thus "letting them have greater opportunity to use . . . skills they haven't used before," he said. "Companies are going to be calling on these individuals who are left behind to work longer, harder and smarter, so what's in it for them? Companies can give short-term incentive bonuses, like an extra week or two of vacation time."

Schulz returned to work in December after a year of active duty. It was a little strange at first, moving into a different office and getting back into much different hours. But it was a little like riding a bicycle, he said. "I tried to keep in touch with the markets and with people at work. It's not like you have to relearn everything."

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