IT WASN'T exactly music to the ears of frugal leaders in Northern Virginia's second largest locality, but what veteran Prince William County Executive Robert S. Noe Jr. told the newly elected board of supervisors about the future was at once candid, important and unnerving: the great promise of pleasant living in this extraordinarily dynamic county hinges on a hefty investment in taxes and bond sales. How each supervisor responds to this challenge could well determine whether the Prince William of tomorrow will be the envy of its neighbors and national counterparts or just another jampacked pocket of ill-serviced people with no place to go.

The numbers are eye-poppers: with about 200,000 residents today, the county is looking at an increase to 240,000 by two years from now -- and on to 300,000 by the approaching end of the century. Translation: more schools, roads, parks, police, fire and social services and sanitary landfill -- on the double. As Mr. Noe put it, "We can't provide the level of service that the people are accustomed to" without raising the county's real estate tax above its current rate of $1.30 of assessed valuation. In addition, he said, urgent road improvements and expansions of county facilities will have to be met through the issuance of bonds.

In the past, many supervisors have been content to whistle along the easy street to election, calling for lower taxes and arguing that bond issues are bad news. That may have a good ring to it, but it's a direct route to decay. The opposite doesn't have to be a spending binge. What administrators and supervisors with vision are urging is a solid investment -- a heavy down payment with mortgage for a place to live that will appreciate handsomely while serving its residents well. Right now, Prince William County is bursting with attractions for the future. But narrow-minded lawmakers can wreck it with penny-wise, backward policies.