In a restrictive housing market, only resourceful builders survive When Portland, Ore., put limits on urban growth in 1979, the measure enjoyed broad public support. The Urban Service Growth Boundary, or UGB, was designed to preserve farmland and prevent urban sprawl by imposing a strict outer limit on residential development. But this year, as the UGB approaches its 21st birthday, area builders are severely pinched by a shortage of land within the boundary, and many are calling the policy deeply flawed. At the heart of the controversy is Metro, the regional agency responsible for land-use planning in the area enclosed by the UGB, which encompasses parts of three counties, the city of Portland, and 23 of its suburbs. As the region's population