Another old Penn Pike bridge going down in explosion early hours Sunday

When demolition crews of Joseph Fay Company hit the switch at about 2 am or so Sunday morning in Hempfield Township Sunday morning another piece of turnpike history, the Wendell Road bridge, one of the original 1939 concrete arch bridges will shudder and shake, rumble and tumble, amid a cloud of dust, into a heap of rubble in the roadway. That's the plan at least.

They don't die easily

Other original concrete arch bridges from 1939 have defied their executioners by hours, hanging proudly aloft when all the logic of physics suggested they should have fallen. They were built tough of heavily reinforced concrete in a single pour, some of the first structures in America to be made of concrete mixed in large batching plants as opposed to small onsite mixers.

There were steel plate girder bridges too of an interesting through girder design with massive deep girders. All that remain from construction in 1939 and 1940 are single spans over both directions of roadway. But according to "The Pennsylvania Turnpike: a History" by Dan Copper the original 160 miles (257km) of turnpike between Carlisle outside Harrisburg and Irwin outside Pittsburgh built in 25 amazing months of construction had 307 bridge structures. 21 of these - bridges for cross streets going over - were built with central piers in the small median area. In the absence of any median barrier these piers were criticized as a hazard, and at some point early on they were replaced by single span structures.

Tight dimensions

The dimensions were tight by today's standards. The vertical abutments were only about 7ft (2m) off the edge line of the pavement, and there was no real breakdown shoulder. The grassed median was only about 10ft (3m) wide, even narrower in places. Along with four 12ft (3.65m) lanes the bridge spans across both directions of traffic were as little as 72ft (22m).

The overall design was so revolutionary few focussed on the bridges

Of course most attention was paid to the overall high design speed of the road with its long sight distances, its consistent minimum curvatures, 12 foot (3.65m) lanes, the eleven trumpet interchanges, ten service plazas, massive cuts and fills, and decent sized bridges - called viaducts then - over ravines, and the seven tunnels totaling some 6.7 miles (11km) through the mountain ranges that allowed a maximum 3% grade versus 8% on the old Lincoln Highway.

The 1950s improvements were extensions east to Philadelphia and the Delaware River border and west past Pittsburgh to the Ohio border.

First making it all 2x2 lanes required doubling of tunnels

The seven tunnels - six abandoned or partially built railway tubes, the other blasted and drilled for the pike - were all single tubes providing a lane each direction. So these soon became choke points as two lanes of traffic had to compress to one at the portal to each tunnel. Main work in the 1960s on the original stretch of the Turnpike was to double the tunnels or bypass them with deep cuts.

Total reconstruction of concrete pavement

1997 saw the announcement of the start 'total reconstruction' of the original mainline, a program that has gone in fits and starts. The over-bridges have to go because the median is being widened to allow inside shoulders and eventual third laning plus full outside shoulders - 56 feet (17.1m).

The opportunity is being taken to straighten or smooth the curves in the highway by doing minor but helpful realignments. The Turnpike doesn't like to get involved in property acquisition. Near the Wendell Road Bridge widening a service plaza has been taken out of service and will be demolished to make room for the wider turnpike.

Central piers back

With a continuous barrier in the median the new over-bridges can rest on central piers, and each direction of traffic now gets a span about as long as the original span that got cross traffic across both directions of the turnpike.

How about preservation of one original?

For historic preservation it would be nice if they could preserve at least one of the old bridges, perhaps using it over one direction of traffic while building a new span for the other - something that wouldn't work everywhere.

New bridges are built a couple of feet higher (600mm) than the original bridges reducing over-high truck hits. The Turnpike still posts a 13'6" (4.12m) height limit, the same as on the other major interstates in PA, but gradually it is being developed to physically accommodate higher trailers should the decision be made to post a higher limit in the future.

Bridge out of service for about 6 months for cross traffic, 6 hours for Turnpike

The Wendell Road Bridge scheduled for demolition int he early hours this Sunday was taken out of service for cross traffic Feb 19. The contractor has until the end of August to replace it and restore service for people crossing over the Turnpike.

It is the second of five bridges to be replaced in the stretch of the pike between Irwin (MP67) and New Stanton (MP75). The locals - some 9k veh/day - have to make long detours meanwhile. Conditions were too tight - buildings too close - to allow construction of a new bridge alongside the old as is sometimes done in bridge replacements.

Early hours Sunday is fun time

The Turnpike itself will be closed for six hours in the 8 mile (13km) Irwin to New Stanton segment between midnight Saturday night and 6am Sunday (actually 5 hours because of daylight savings end).

People living in 24 houses within 300ft (90m) of the bridge are being required to be elsewhere - with friends or at a motel - during the demolition. Also local roads nearby will be closed off by policed for 15 minutes around the time of the explosions.

The demolition crew will place the charges and wire them.

The Turnpike won't say what time that will be since they don't want to encourage a crowd of siightseers. But our guess is somewhere around 2am, given 2 hours for setup. They've drilled holes for the explosive charges ahead of time but can't start to place the explosives or wire them until midnight when traffic underneath is closed off.

Come the fun moment, the scores of charges are wired to go off simultaneously in order to break the bridge into as many pieces as possible to drop it into the roadway below in manageable chunks. A mixture of tangled steel rebar and concrete rubble it won't be easy to handle, but they've developed the techniques.

"Demolition by explosives is the quickest, most efficient way to do the job," says Joe Agnello of the Turnpike.

If all goes well amid the big flood lights, the guys operating the wheel loaders will move in maybe five minutes or so after the big boom, after the dust has cleared, and with the rumble of diesel engines, the annoying beep-beep-beep of backup horns, and the clang of steel buckets, they'll scoop up the rubble, and drop it into waiting dump trucks for removal to a landfill. And so they'll aim to finish the clean up of the pavement with brooms before dawn, so this stretch of the turnpike can be put back in business by breakfast-time on the sabbath.

TOLLROADSnews 2007-03-09

ADDITION AFTER THE EVENT:

"Everything went fine," says Turnpike spokesman Joe Agnello. The turnpike was closed at midnight and the explosives were set off at 00:57. Dust and smoke rose into the air and the old Wendell bridge fell into a heap of rubble as planned. There was no damage to surrounding buildings.

The mainline of the Turnpike was reopened to traffic at 05:47, 13 minutes ahead of target. The closure for the explosion was just under five hours (since an hour was lost to the change to summer time).

22 of the original concrete arch bridges remain on the first Irwin to Carlisle 160 mile (257km) section of the Turnpike. Ten of these are scheduled for demolition in the current five year program as part of total pavement reconstruction.

The next old over-bridge to be removed will be Babcock Blvd bridge in Allegheny County, further west of the original section of the Turnpike at MP34.8 this coming weekend - March 18. A 1950s bridge its demolition will require a similar early hours Sunday morning closure of the Turnpike, this time an 11 mile (17.4km) stretch between Beaver Valley (PA8) and Cranberry (I-79). A more conventional concrete girder bridge it will be taken apart and lifted out by crane.

These bridge replacements costs between $3m and $4m each.

Next stage is replacement of the old concrete pavement with two travel lanes and a full hard shoulder each direction, all of asphalt, the two roadways separated with a 50 foot (15.2m) median versus the 10 to 15ft (3m to 4.5m) of the original median. Third laning can then be done later in the center.

TOLLROADSnews 2007-03-12