Digital tools speed complex Texas interstate motorway upgrade

When asked how the project team managed to fast track a $1.5bn (£1.2bn) road upgrade in the United States from design onto site, the team points to the digital design tools that allowed them to plan in 3D.

“I don’t know how we delivered projects like this before we used digital design,” says Ferrovial design director Francisco Palacios.

The scheme in question is the upgrade for the Texas Department of Transportation (TxDOT) of a section of the 2,523km I35 interstate route near San Antonio that currently carries 200,000 vehicles a day.

The I35 is a key trade route through the United States between Mexico and Canada. Heavy congestion already impacts the route and the traffic volume is predicted to grow by 50% over the next 10 years. The work is being delivered by Alamo NEX Construction, formed by Ferrovial and its local subsidiary Webber. It will create extra capacity with new elevated lanes.

Under the I35 NEX project, a total of 35km of new viaducts with three lanes in either direction above the existing eight lane dual carriageway will be built in Guadalupe and Bexar Counties. They will run along a 15km section of the I-35 from the I-35/I-410 North interchange at the western end to the FM 3009 road junction to the east. Flyovers for the I-410 North and Loop 1604 West will also be constructed.

The scheme is part of TxDOT’s statewide Texas Clear Lanes project to provide congestion relief through non-tolled roads in five major metro areas including Austin, Dallas, Fort Worth, Houston and San Antonio.

Palacios describes the viaduct approach to capacity expansion as a standard one for TxDOT. He says that viaducts were chosen here either because of a lack of land available to expand the route at ground level or because of the cost involved in acquiring available land. Palacios adds that building the flyovers above the existing road is the only option.

The I35 NEX solution sounds simple in theory but relating the planned infrastructure to what already existed on the ground and communicating the design presented some challenges. Plus once the work moved onto site, it had to be planned so that it did not impact on the existing carriageways and further add to the congestion issues.

These conflicting problems have been unlocked by using a digital approach and planning the work in 3D from day one.

Digital approach

The contract was awarded to Alamo NEX Construction in June 2021 as a design, build and operate arrangement. Construction started a year later in May 2022 and the road is due to open in 2027. The firm will then operate the new road for five years.

Palacios says that being able to fast track the work from contract award to the start on site is down to the digital approach. The main tool used by the team was Bentley Systems’ Projectwise, which Ferrovial digital design manager Marta Raya describes as giving the project team a central platform with “a single source of truth” and the ability to share data easily across the project team.

According to Palacios, the approach made it easier to coordinate the work across a multidisciplinary team drawn from Ferrovial and Webber, as well as external subcontractors for specialist elements of the work.

“The digitalisation expedited the design process and made it as efficient as possible,” he adds.

Digitalisation expedited the design process and made it as efficient as possible

Raya says: “It avoided mistakes that have happened on previous projects where designs were produced using old information.”

Raya adds that currently there are over 300,000 files in the common data environment for the I35 NEX project and these are shared with the 500-strong design team.

“We also used an automated design review tool to check for potential conflicts between the design and the existing infrastructure within the 3D model and this helped us to identify 3,000 design errors before the work moved onto site,” she explains. “This helped us to speed up the design review process.”

As an example of the type of clashes that the project team has used the digital tools to overcome, Palacios points to the positioning of columns for the new viaducts.

“We needed 3D tools to display that,” he says.

Presenting the design in 3D was essential with the new structures set to run above the existing road

Bluebeam software and Bentley’s iTwin application were both used to help those outside the direct project team, such as the client and community stakeholders, view the design in 3D, which Raya says helped them gain a clear understanding of the work and accelerated the review process with the stakeholders.

The resulting design from this work is a conventional precast concrete structure founded on monopiles. The foundation design was driven by the need to minimise the impact on users of the existing road with just one pile needed at each location and slot the piers for the new viaduct within the space available below. The team has also worked to standardise the design
and use offsite manufacturing wherever possible.

Beyond design

While the digital approach was critical for the design stage, it is also proving to be useful now the work has moved onto site.

Over the remaining four years of the build phase, Alamo NEX Construction will construct 1,500, 3m diameter piles amounting to 23 linear kilometres. It will also install 4,700 bridge beams, each measuring 40m to 45m and with a total length of 200km.

According to Raya, the project team is using the 3D models to help with coordination and she believes this approach is helping to deliver the work to a tighter schedule as a result.

With the final design being completed in the next 12 months, we will be entering peak construction this year

Coordination is key too as, although the contractor can close some lanes of traffic on the I35, the length of time those closures are in place must be kept to a minimum and most of the work has to be delivered from arterial routes next to the interstate.

Work is also undertaken during night time closures but, again, this has to be carefully planned so the road can reopen each morning.

Palacios says that so far work is going well and more than 200 piles had been installed when NCE spoke to the project team in May.

“We split the construction into four sections and started work on all four at the same time,” he explains. “With the final design being completed in the next 12 months, we will be entering peak construction this year and the main challenges facing us will be logistical ones.”

Raya says he is confident that the digital approach will stand the team in good stead and having more detailed design at an earlier stage than on many projects will ease the challenges ahead. 

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