Rices Nachmans, a Tidewater department store chain, frequently makes pitches for national "co-op" advertising. But when it does, it never bills itself as simply a Norfolk-area company.

Besides outlets in this area, the chain has stores in nearby Newport News-Hampton, and it makes sure retail manufacturers know that it sells in two metropolitan areas. President Ed Nagourney says his strategy is a matter of dollars and cents. The bigger the perception these manufacturers have of Rices Nachmans' market, he says, the more advertising money he gets.

Nagourney sometimes has a problem, however. The Department of Commerce, which keeps tabs on the designation of the nation's metropolitan areas, officially recognizes the two markets as one-separated by only 2.5 miles of water-advertisers don't always believe him.

"When we tell advertisers that both sides of Hampton Roads are really one big market, I always have to prove my point," Nagourney said. "They have visions of us being 100 miles apart. It would be easier for advertisers to accept us as one market if official government figures listed us that way."

Nagourney's credibility may be on the rise because this is precisely what the Commerce Department may wind up doing. Many Tidewater business leaders close to the situation are betting that Commerce will consolidate both sides of Hampton Roads into one large Metropolitan area in 1982.

That could translate into a substantial economic boon here because national advertisers base the amount of money they pump into the nation's metropolitan markets on their size-and businessmen say that the biggest chunk of money goes to the 50 biggest markets. If both sides of Hampton Roads were consolidated, experts say that its population of 1.13 million would easily put it in the Top 50.

Latest figures show that south-side Hampton Roads has 771,700 people and is ranked by the Commerce Department as the nation's 51st largest SMSA, or Standard Metropolitan Statistical Area. It is officially known as the Norfolk-Virginia Beach-Portsmouth SMSA.

The Newport News - Hampton SMSA, the so-called Peninsula, has 355,500 people and is ranked 103rd. Both SMSAs include smaller surrounding cities.

At it does before every decennial census, the Commerce Department has been reviewing the criteria it uses to designate SMSAs. Among the changes likely to be made, it appears that Commerce will ease guidelines governing the consolidation of two or more SMSAs-or the recognition of adjacent metropolitan areas as one big urban area, as well as separate metropolitan entities.

At present, two neighbouring SMSAs can consolidate only if one alone has a population of 1 million. Under proposed revisions, two SMSAs can consolidate if together they have 1 million people. Whether they actually consolidate depends on the level of commuting between the two areas, which can be as little as 10 percent of the workforce of the smaller area if the two areas are fundamentally contiguous.

This is where the guesswork on the part of Tidewater business leaders comes in.

According to the 1970 census, the number of Tidewater workers commuting across Hampton Roads, including the military, equaled 8.7 percent of the Peninsula workforce. The removal of tolls on the Hampton Roads Bridge-Tunnel and the James River Bridge in 1976 presumably has encouraged commuting across Hampton Roads, and businessmen think that the 1980 census will prove that the 10 percent commuting requirement has been met.

If so, consolidation would occur after the publication of the commuting figures, which government officials say will be early in 1982.

The criteria for designating SMSAs-which in the new format would be dubbed simply MSAs (Metropolitan Statistical Areas)-already have been revised twice in anticipation of the 1980 cencus. The Commerce Department's Office of Federal Statistical Policy and Standards (OFSPS), which plans and coordinates federal statistical gathering, will present the new criteria to a high-level government committee early next year, on Jan. 31.

Joseph Duncan, the director of OFSPS, said he doesn't know if the committee will approve the changes. But he added that public comment concerning the criteria has been favorable. This factor-plus Duncan's support - suggests that chances for committee approval are good.

Duncan said that relaxing the standards for consolidated metropolitan areas would provide a richer mix of information on the integrated nature of neighboring, but separate, metropolitan communities. Because of the stipulation that one metropolitan area within a consolidated grouping have 1 million people, there are only 13 consolidated metropolitan areas in the country.

If the rules are relaxed, government officals say there would be six more based on 1970 population and commuting figures, and perhaps more after the publication of the 1980 census. Among the latter, officals say that Hampton Roads is as likely a candidate as any metropolitan area to join the list.

Technically, the two sides of Hampton Roads are not contiguous because they are separated by water. But Duncan said that his office has been leaning toward the assumption that Hampton Roads is fundamentally contiguous, which represents a softening of past OFSPS policy.

If the metropolitan areas weren't viewed as contiguous, the commuting level would have to be 15 percent of the Peninsula workforce before consolidation could take place.

Even the 10 percent commuting guideline probably will not be easy to meet. Duncan is aware of the removal of tolls on bridges spanning Hampton Roads, but says that the population of Hampton Roads - as well as the commuting level - has undoubtedly increased since the 1970 census.

"For consolidation in Hampton Roads," he said, "the growth in commuting since 1970 will have to equal the growth of the area workforce, plus make up more than a one percent gap" - the difference between the 8.7 percent commuting level ascertained in the 1970 census and the required 10 percent.* CAPTION: Picture, no caption