LOUDOUN COUNTY'S expansion has been so swift -- detractors would say irresponsible -- that even prophesies of explosive growth have understated its actual dimensions. Back in 1985, for instance, a Post article proclaimed Loudoun "the next frontier" in the region's suburban development boom, based on forecasts that the county's population, then 70,000, would double in 25 years. In fact, the population more than tripled in 19 years; today it is about 235,000 and rising by about 300 people every week. Now, the county's elected Board of Supervisors faces a critical decision on whether to dampen growth somewhat, or maintain the dizzying expansion.

At issue at a meeting today are two distinct and huge swaths of land, which together encompass a large portion of western Loudoun. The issue is not really development, or even the pace of development -- although we wonder whether most Loudoun residents are really prepared for the impact on traffic, schools and taxes of further unfettered expansion. The problem is that Loudoun's pro-growth Board of Supervisors appears ready to make a fateful decision without bothering to consult the county's residents.

A little recent history: Five years ago, voters in Loudoun, dismayed by the staggering pace of development, elected a slow-growth Board of Supervisors. After three years of raucous public debate the board voted, in January 2003, to block the construction of more than 80,000 new homes, worth billions of dollars. Then came the backlash: a wave of lawsuits by landowners and developers that, taken together, represented what The Post's Michael Laris called "one of the broadest legal challenges to a local government in Virginia history." At the same time, developers and their allies helped organize a political counterattack, which bore fruit last November when a six-member Republican majority rolled to victory.

Since taking office in January, the new Board of Supervisors has been debating what to do about the lawsuits. In practice, settling the cases would mean a green light for tens of thousands more new homes, many in the rural western part of the county; a decision to fight the lawsuits would mean applying the brakes somewhat. But the board's debates have taken place in executive session, out of view of the public. Today a vote is expected; Loudoun residents may wake tomorrow to discover that the board has remade plans for half their county in a single, silent stroke. Rather than showing its contempt for the public by shutting it out of a major land-use decision, the Loudoun board should delay action, consult as broadly as possible -- and deliberate in public.