Herbert Edwards moved to the tiny town of Waterford in western Loudoun County 60 years ago, grew up there and bought a house in the 1930s.

Although the town of just over 200 persons retains much of its rural charm, for Edwards, one aspect of life has changed in a big way. "I pay more in taxes on my house now than I paid to buy the entire place in the 1930s," he fumed yesterday.

Edwards' feelings were widespread as residents received property assessments for next year that reflected the boom in the county's development. The assessment for the average residential property rose by an average of 12 percent since the last time a countywide assessment took place in 1984, said William C. Gardner, chief of Loudoun's assessment office.

For some Loudoun homeowners, however, the bite they received when they checked Friday's mail was much worse, with property assessments in some cases rising by more than 30 percent.

That news, combined with Loudoun County Administrator Philip A. Bohlen's proposed 3-cent increase in the real estate tax to $1.16 on every $100 assessed value of property, left some residents staggering. "I would hate to move," said Herbert Edwards. "The thing is, with taxes the way they are, a person has to do something."

Gardner said the flurry of complaints and questions coming into his office Monday was predictable, and no more severe than on previous occasions when the county has released assessments, some of which have reflected increases even greater than this year's.

Most Loudoun supervisors contacted yesterday said the increased assessments did not seem excessive, and merely reflected the rising value of land in Loudoun's realty market, as homeowners and corporations alike flock to the county that describes itself as Washington's "business frontier."

Still, the assessment figures, combined with a $108.7 million budget proposed by Bohlen last week, have been cause for sober talk among Loudoun officials about the costs of the county's enormous expansion. The budget proposal represents a 32 percent increase over this year.

"We're like the person that signed on to the Visa card. The bills are coming," said Loudoun Supervisor Frank Raflo (D-Leesburg), long an advocate of controlled growth.

Raflo believes that if this year's trends continue as he expects, Loudoun will soon have the highest rate of growth and the fastest rising tax rate in Virginia.

Loudoun Board Chairman James F. Brownell (R-Blue Ridge) agrees. "Things are happening so fast here, and the property assessments are just one reflection of it. Things are going to keep going up, up, up." Concern about this tends to be most severe in western Loudoun, where many families have lived for generations, and resentment of growth often runs high.

Suspicion countywide about the reasons for the increased assessments has been furthered by the timing of the letters announcing the increases, which came just one day after Bohlen announced his proposed budget increases. Some believe that the county may have exaggerated estimates of property value so that there would be more money to spend.

"You can't help the feeling that there might have been a little fooling with the books," said Supervisor Frank I. Lambert (R-Catoctin). "I don't know if that's true . . . . It's just the appearance."

Other officials yesterday vigorously denied there was any tampering. The budget and the assessment processes are "completely divorced" from one another, Gardner said.