Isabel Holmes Bridge
US 74 & NC 133 over the Northeast Cape Fear River in Wilmington, NC
This is a very modern bridge, modern in the sense that it has been designed to do a job and do it without complaint. It gets you over the river. Solid concrete Jersey barriers keep you from going into the river if you fall asleep at the wheel while driving over this bridge. The black glass and concrete operator's house will not make you strain your neck to look at its "beauty." The steel grate deck, the only part of the bridge that might wake you up, is as smooth as a steel grate deck can be. If you drive this bridge only once, you'll probably forget it. But at least you'll get across the river safely.
While this bridge was built in almost 30 years ago from the time of this writing, in all likelihood it would be built very similarly today. It would be a bascule bridge with a plate girder main span. This is the only portion of the bridge that is steel; the approaches are all supported by prestressed concrete beams. The main span is 316 feet, the second longest in the state. The bridge crosses a minor shipping channel, with the majority of marine traffic likely being that which serves the cement plants along the Northeast Cape Fear River.
The only design feature that I found somewhat interesting was the usage of simple Warren trusses for the floorbeams. I would have thought that such a simplified design would have used solid beams instead. I suppose the trusses were used in order to lighten the half-spans.
Many of the original Wilmington approach spans were replaced in the 2000s with a Y-interchange that connects the bridge to the Martin Luther King Parkway, a partial freeway carrying US 74; it also connects to Third Street, the main north-south thoroughfare in the downtown area. There is a stoplight for traffic for westward traffic entering onto the bridge, which puts an abrupt end to a rather nice freeway ride.
This bridge was the site of a 1920s bascule bridge, which prior to the building of the Cape Fear Memorial Bridge carried the main east-west routes in and out of the city. Traffic on US 17, 74, and 76 would head north through downtown along Third Street, cross over this bridge, head south along the current US 421 alignment, cross over the Cape Fear River, and then head west on the current alignment (got all that?) This bridge and its Cape Fear companion remained after the big bridge was built to the south. The Northeast Cape Fear River structure carried US 117 and NC 133. I'm pretty sure that at least one of these bridges had Warren deck truss approaches. The wrecking ball was taken to these two bridges in the late 70s, early 80s, making room for the two boring crossings we have today.
The National Bridge Inventory data claims that this bridge has a 28.8-foot wide deck. This number is incorrect, since the bridge has four lanes, but would make sense if the bridge had only two.
Facts
- Year built: 1980
- Route Carried: US 74 and NC 133 (formally US 117)
- Crosses: Northeast Cape Fear River
- Location: Wilmington, New Hanover County, NC
- Design: Bascule bridge with plate girder main span and prestressed concrete beam approaches.
- Length of main span: 316 ft.
- Average Daily Traffic: 16,000
- Sufficiency Rating: 66.3 out of 100
- National Bridge Inventory ID: 1290011
- Coordinates: 34°15'7.26"N, 77°57'2.57"W
Pictures
- Left: the bascule span, from the south. Center: the underside, showing the Warren truss floorbeams. Right: the ramps for US 74 and downtown Wilmington.