The Northern Virginia Regional Park Authority will celebrate two major extensions of its Washington and Old Dominion trail with a ceremony Saturday in Leesburg.

More than 30 miles of the 44-mile trail are open because of the completion of a $200,000 bike-trail underpass at the Rte. 15 bypass east of Leesburg and the purchase of the last link of the trail in Arlington.

The trail begins near the Potomac River and runs to the foothills of the Blue Ridge Mountains. The section west of Leesburg is passable only on foot, and there is no trail crossing at the Rte. 15 bypass west of Leesburg.

The park authority last week paid the Virginia Electric Power Co. for the Arlington section of the trail. It was the final installment in a five-year, $3.5 million purchase of the bike trail park.

Work already has begun on the Arlington section, spokeswoman Dorothy Werner said. From Shirlington Shopping Center to Columbia Pike, a dirt trail along Four Mile Run is being paved, and "we're studying the one-mile section between Columbia Pike and Route 50, which seems like 100 miles, it will need so much work," Werner said. The park authority has built 11 bridges along the trail and may build several more in Arlington.

From Rte. 50 to Falls Church, the bike trail merges with the new I-66 bike trail along part of the route. It also may use some city streets, Werner said.

From Falls Church to the Loudoun County line, the trail is paved but is packed gravel to Leesburg. Loudoun and Leesburg officials and area bicycle groups are pressing to have more of the trail paved.

Saturday's celebration, with a drawing for a bicycle and prizes for the best decorated bikes, will be at 10:30 a.m. in downtown Leesburg where the bike trail crosses Rte. 15.