The two hospitals in Prince William County are on pace for large and expensive expansions as they race to keep up with the county's growth spurt.

Potomac Hospital in Woodbridge recently received state permission to add 30 beds and replace much of the hospital in a new four-story, 180,000 square-foot building. And Prince William Hospital in Manassas kicked off a capital campaign last week to help fund an $85 million upgrade and expansion.

Prince William County grew by more than 65,000 residents from 1990 to 2000, according to census figures, and the fast growth rate is expected to continue.

Potomac's $75 million expansion will replace its medical surgical facility, including all 153 in-patient beds. The new building will contain 183 beds, all in private rooms. Construction will begin in early 2004, with the building scheduled to open two years later, said Leigh Dunlap, a hospital spokeswoman.

Potomac's expansion was approved this month by Robert B. Stroube, the state health commissioner. "There is a pressing need to add space and capacity to the hospital," said Dean Montgomery, executive director of the Health Systems Agency of Northern Virginia, a state advisory panel, which recommended that Potomac Hospital's expansion be approved. "They have a growing service area, demand is growing and they have high use."

Potomac's current building dates to the hospital's opening in 1972, and, despite upgrades over the years, needs a complete replacement, Dunlap said. The hospital's emergency room and birthing centers will remain unchanged, and the construction will not affect the hospital's current operations.

Hospital officials have said a lack of available inpatient beds results in long waits in the emergency room. In a separate project, the hospital will use its funds for an emergency room upgrade next year.

The project will be funded through the hospital's savings, borrowing and a capital campaign to be announced next year, Dunlap said. Potomac Hospital is a nonprofit affiliated with Inova Health System.

Up the road in Manassas, Prince William Hospital announced last week that it has reached $4.8 million in its campaign to raise $10 million. It also announced a $1.5 million donation by the Cecil and Irene Hylton Foundation.

A $13 million birthing center is already under construction at the hospital. Other projects include an expansion of its emergency room, renovation of its radiology department and creation of an outpatient surgery center. The hospital just received its second magnetic resonance imaging machine, which cost $3.5 million. Officials are also planning parking, road and other improvements.

The hospital, which decided three years ago to remain an independent nonprofit, needs to make the improvements to remain competitive and keep up with the area's increasing growth and sophistication, officials said.

In addition to the capital campaign, the hospital will be paying for the projects through borrowing and savings.

The western part of Prince William is the fastest-growing part of the county. According to the hospital, last year there were 2,000 births, an 18 percent increase. And in 2001, there were more than 50,000 emergency room visits, a 30 percent increase over the previous two years.