Since adding 51,000 Montgomery County residents to her congressional constituency this year, Rep. Beverly Byron (D-Md.) has traded the concerns of suburban Baltimore for problems more peculiar to the Washington area--sewage disposal controversies, a fight over expansion of the post office in Potomac, National Airport noise pollution and gadfly Robin Ficker.

For Rep. R. Kenneth Robinson (R-Va.), his recently acquired 70,000 Manassas, Manassas Park and western Prince William County constituents have increasingly drawn the Shenandoah Valley-based congressman into the Washington area's special suburban problems, including the plight of Vietnamese refugees.

Rep. Barbara Mikulski (D-Md.), who hails from working class Baltimore city, has just opened a casework office in Columbia to better serve her 83,000 "New Town" constituents.

Byron, Robinson and Mikulski, thanks to that tricky political art known as redistricting, are all "newcomers" to the region's congressional delegation. And though each says the redrawn districts pose no out-of-the-ordinary adjustments, they, along with four senators, five other House members and one nonvoting delegate, represent all or portions of a Washington-identified populace that is among the most informed and demanding in the nation.

Byron, for instance, now represents civic-minded and largely affluent "up county" residents in Montgomery who care passionately about everything from Social Security to sewage treatment. When she held some recent get-acquainted town meetings in Potomac and Poolesville, the hot topics, respectively, were the proposed expansion of the post office and plans to build a sewage treatment plant.

Not on her agenda was Ficker, the self-styled watchdog for the taxpayer, defeated last fall when he tried to win a second term in the Maryland House of Delegates. He's contemplating a challenge to Byron, a conservative Democrat, and showed up at her Potomac town meeting, with his kids in tow, to distribute anti-Byron material.

Although her office now focuses on a new set of local projects and problems, Byron doesn't think the newly drawn 6th District, which extends from the northern half of Howard County to the western tip of the state, poses any special difficulties.

"I don't see that much difference--it's not like I picked up a military base or a port," says Byron, 50, who succeeded her late husband in the House seat and has been reelected twice since.

The old 6th District had Columbia and the part of Baltimore County where the Social Security Administration is located, so Byron is no stranger to the concerns of federal workers in Montgomery County. And she says her new district is "much easier" for her to cover and still commute daily from her home in Frederick to the Capitol.

Robinson's 7th District is as far flung as ever, stretching northward from suburban Richmond's Hanover County to rural Frederick County abutting West Virginia.

A staunchly conservative Republican in his seventh term, Robinson, 66, spent a lot of time in Manassas his last campaign, and an aide noted some reemphasis because of redistricting.

"There's been a shift in makeup, and we're just a little bit more oriented toward suburban concerns as opposed to more rural and agricultural issues," said Jim Hobgood, who is in charge of Robinson's Fredericksburg district office and has responsibility for western Prince William County casework.

Hobgood finds that "as you get closer to Washington, there's a tendency to get more of the government-related issues." There are additional federal workers in the new district, although Robinson has always had government employes among his constituents.

Recently, the office picked up two immigration cases involving Vietnamese refugees in Prince William County.

But Robinson, who lives in Winchester, says the number of federal workers in western Prince William is less than throughout the rest of his district and nowhere near what Rep. Stanford Parris (R-Va.) must deal with in the neighboring 8th District.

"There aren't really any new issues for me, and people out there in western Prince William are not heavily on the side of government employment," Robinson said.

"One nice thing," he added, "you don't hear a great deal about unemployment. People in western Prince William have the lowest unemployment rate in the district."

Mikulski's urban-suburban 3rd District, according to her press secretary, Liz Pettengill, is more spread out than ever, though still geographically compact in comparison to more rural congressional districts.

The 46-year-old former social worker is getting more involved in federal contracts and housing issues as a result of her increasingly suburban constituency, and has spent a great deal of time recently in Columbia.

"She made a foreign policy speech there, and we just opened a casework office in Columbia about two weeks ago," said Pettengill.

Mikulski is popular in Columbia, whose residents tend to identify with both Washington and Baltimore issues.

She carried more than 80 percent of the voters in her first election test there, which her aide says is understandable.

"The area is so congruent with our own old district ," she said. "They tend to be liberal Democrats."