Calmer Waters for Trinity Bridges

Dallas ’ Calatrava Bridge Overcomes Delays, Design Changes

Texas downpours further postponed work on the future highway bridge designed by Santiago Calatrava, but work is finally ramping up on the first of three new bridges in Dallas.

By Annie Koo

Stalled four months last year for an extended bidding-redesign process, the $69 million Margaret Hunt Hill Bridge, the first of three planned bridges in Dallas’s Trinity River Corridor Project, is seeing still more delays. This year, blame it on the rain. Crews were delayed a week for rain and on the site just one day in June  before more than a month of downpours postponed further work on the design by Santiago Calatrava. 

Value engineering reduced the original cost of the Margaret Hunt Hill Bridge. World-renowned architect Santiago Calatrava designed the first of the three Trinity River Bridges in Dallas, now under way.

“The unseasonably wet conditions have been a big issue,” says Rebecca Dugger, director of the Trinity River Corridor Project, the umbrella development that oversees the Margaret Hunt Hill Bridge. She says crews should start drilling piers once the site drains.

Even before the bridge broke ground in December 2005, problems beset the project. As designs were being finalized, says Dugger, one of the site’s outfalls had to be physically relocated since it was in the path for the center pier of the bridge.  Like the Trinity River’s levee embankment, these outfalls provide flood protection to the corridor.

But perhaps the most substantive delay was the extended bidding-redesign process that began in June 2006. Houston-based Williams Brothers Construction Co. Inc.’s winning bid came in at $113 million, nearly double Calatrava’s original $57-million estimate. The budget blow sent both architect and city consultants back to the drawing table until October, when Williams Brothers., the sole bidder in the second round, won again for $69 million.

Dugger says the price cut was based on value engineering. For instance, the center arch, originally cast to have a heptagonal cross-section, was redesigned as a cylinder. The bridge piers were also tapered into cylinders, down from their teardrop shape.

“Simplified shapes made for simplified fabrication, which brought costs down,” Dugger adds.

Other adjustments were made, such as replacing a steel drainpipe for a PVC one and using several smaller support beams rather than a few larger ones.

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Williams Brothers’ price drop could also be attributed to the use of foreign steel, says Enrique Guillen, Central Dallas Area Office project engineer of the Texas Department of Transportation. Buy America regulations typically oblige federally funded projects to use domestic materials. However, says Guillen, Williams Brothers vied for a duplicate bidding process, a means to waive the regulation if the bid using foreign steel comes in at least 25% less than the domestic steel version.

Criteria met, Williams Brothers’ foreign steel fabrication will begin in the fall by Cimolai Costruzioni Metalliche of Pordenone, Italy.

Barring other delays, the cable-stayed bridge should be completed by October 2009. Its design calls for a 395-ft-tall central parabolic steel arch, Guillen says. Fan-like cables reeling off this span support the deck that sits on a combination spread-footer and drill-shaft foundation. The foundation caps are stabilized by 32 54-in. drill shafts that reach 90 ft into the ground, he says. The bridge will have three lanes in each direction for vehicular traffic.

The Margaret Hunt Hill Bridge, a private donor name change from the original Woodall Rodgers Freeway Extension, will provide direct freeway access to downtown. The site’s only current but rarely trafficked roadway, the Continental Avenue Viaduct, which does not have access to freeways, will become a pedestrian and bicycle thoroughfare according to Dugger.

The bridge is one of three in the master plan of the Trinity River Corridor Project, a development to revitalize the desolate floodplain that divides West Dallas and Oakcliff from the downtown cityscape. Though the adjacent bridges are considered necessary for traffic relief, Dallas’s choice for expensive, Santiago Calatrava-designed bridges was more a matter of branding the city with the architect’s international acclaim.

“Construction was in the works regardless of whether they look pretty,” insists Dugger, who says an infrastructural study from 1997 predates the $69 million Margaret Hunt Hill Bridge.

The second bridge, also by Calatrava, is 65-90% designed, says Dugger, who expects to see initial plans by the end of the year. It will widen and replace the existing IH-30 bridge, which, unlike the Continental Avenue Viaduct, is heavily used and poses more difficult traffic issues.

An initial proposal to open a temporary reversible high-occupancy-vehicle lane on the existing IH-30 bridge to reroute traffic during the second bridge’s construction was criticized by TxDOT, which did not want a throwaway structure. Dugger says another option might be to build the Calatrava replacement in segments around the existing bridge, preserving normal traffic flow during the bulk of construction, until the pieces need to be set in place.

“We could potentially do it over a weekend,” Dugger says. She cites Calatrava’s Olympic Velodrome built for Athens in 2004, which was assembled in less than five days under this method.

Just southeast of the IH-30 span, a third bridge is intended to replace and increase capacity on the 50-year-old IH-35 bridge, though neither funding nor substantial planning is under way.  

Key Players:
Margaret Hunt Hill Bridge

Owner: Texas Department of Transportation, Dallas Area District
Architect: Santiago Calatrava LLC, New York
GC: Williams Brothers Construction Co., Houston
Structural Engineer: Huitt-Zollars Inc., Dallas
Civil Engineer: Chiang, Patel, & Yerby Inc., Dallas

Useful Sources:
For additional information on the entire Trinity River Corridor Project or to find the latest construction updates on the Margaret Hunt Hill Bridge, visit:

• City of Dallas Trinity River Corridor Project
http://www.trinityrivercorridor.org

• Woodall Rodgers Extension, Project Pegasus, Dallas
http://www.projectpegasus.org/wre.htm

• The Trinity Trust
http://www.thetrinitytrust.org/