Trail Feature:
Pedestrian Box Underpass at South Van Dorn Street/I-495 Slip Ramp
Tax Map 81-2

Article Prepared By Robert Michie
NMTC, Lee District
Last Reviewed: 17 February 2004

Update/Resolution:

VDOT rendered the pedestrian underpass safe in December 2004 by removing the concrete shards shown in Photos 1 and 2.

Summary:

In the early 1990's, Fairfax County built a pedestrian tunnel underneath the northbound I-495 slip ramp at South Van Dorn Street (see Tax Map 81-2). Ten years later, parts of the concrete framing of the tunnel are showing signs of wear and tear. This tunnel is identified as Structure #5018.

Exhibit 1: Map of Subject Area

Discussion:

Exposure to weather over ten years as well as vibration from traffic has cracked the concrete framing around the tunnel entrance. Although it is doubtful if the stability of the tunnel structure itself is in question, a concrete shard on the right side of the South entrance is going to fall soon. A better view of this crack is in Photo 2. In a worst-case scenario, it could hit a pedestrian.

The North entrance has another problem. Although on side of the tunnel frame shows the same stress cracks as on the south side, the retaining walls flanking the entrance show signs of leaning outward. The differences between the top and the bottom of the wall on the right side of the North entrance, for example, shows a lean of about 4 cm (1.5 inches).

Field Check 26 October 2004

These photographs show the wear and tear on the structure:

[ South Tunnel Entrance showing broken framing ]

Photo 1: South Tunnel Entrance showing cracked and missing concrete frame

[ Photo 2: Eight-foot crack in South Side Facing ] Photo 2:
South side of Tunnel , right side as shown in Photo 1. This crack is sixteen feet long, and it is mostly separated from the frame and the retaining wall to its right.
It represents a hazard to pedestrians as that it can fall at any time, as the missing piece on the left side of Photo 1 illustrates. This, however, will be a concrete shard twice as long as the missing piece in Photo 1.

[ Photo 3: Warped Retaining Wall on North Tunnel Entrance ] Photo 3:
North side of the Pedestrian Tunnel, retaining wall on the right as you face the entrance. Note the apparent outward tilt of the wall, using the tunnel framing as a guide. The wall is leaning out about 4 cm ( about 1.5 inches) at the top of the frame when compared to the bottom of the frame.
The retaining wall on the left side of the North entrance shows the same outward tilt. Note the Structure number (5018) that appears near the centerline of the photograph.

Recommendation:

Have Fairfax County structural engineers check Structure # 5018 before freezing weather arrives.

Note: The structure was checked and the hazardous concrete shards were removed in December 2004.