NYS DOT Delivers First Model-based Contracting 3D Project in Its History; Delivered the Project Under Budget and Restored a Critical Bridge to the Community

• NYS Route 28 connects Ulster County and Delaware County, New York to the regional highway network and is part of an emergency lifeline corridor during significant flooding events
• The NYS Route 28 Bridge over the Esopus Creek frequently floods during heavy rains due to an inadequate hydraulic opening in the structure
• New York State Department of Transportation (NYSDOT) needed to design a new bridge that will last at least 75 years and remain open during large storms, while minimizing maintenance and repair costs

Project Overview

NYS Route 28 connects Ulster County and Delaware County, New York to the regional highway network and is part of an emergency lifeline corridor during significant flooding events in Ulster County. The NYS Route 28 Bridge over the Esopus Creek frequently floods during significant rains due to an inadequate hydraulic opening in the structure. The topography of the area allowed for the water to escape the stream bank channel and wash out both the southern and northern approach. New York State Department of Transportation (NYSDOT) needed to design a new bridge that will last at least 75 years and remain open during large storms, including 100 year floods, while minimizing maintenance and repair costs.

Challenge

NYSDOT wanted to deliver this project primarily as a 3D deliverable as New York State’s first “Model-based Contract” but did not have previous experience delivering a 3D project. They sought input from other states but found that only a handful of states had attempted a 3D plan set in horizontal construction. They also needed to address the challenge of deciding the most cost-effective and least disruptive design alternative to replace the bridge, including on the same alignment, upstream, and downstream.

Breakthrough

Prior to this project, NYSDOT had only successfully designed one other project using Bentley’s OpenRoads. However, based on this previous project, they knew that the best way to successfully deliver this one was with the OpenRoads suite of software.

Using OpenRoads Designer and OpenBridge Modeler, they were able to model and compare the three alternatives. Using the application showed that based on costs and impact to the community, the downstream option would be the best.

The proposed bridge was 800 feet long and almost 10 feet higher in elevation than the existing 330-foot structure. There was a super elevation transition on the bridge and the girders were variable depths across the bridge. They were able to successfully model the complicated structure using OpenBridge Modeler, including to model the parabolic tapers on the bridge girders and the complicated diaphragms.

A major flood control berm limited flow during high flow events and needed to be removed as part of this project. NYSDOT quickly put together a model and 3D solid that showed the nearly 30,000 cubic yards of embankment that needed to be removed. The ability to create 3D solids of the cut-and-fill shapes aided in design intent and quantity calculation.

They also used iModels and delivered a 3D model that couldn’t be modified by users, which gave them much needed reassurance in their first effort stamping a 3D model. Utilizing iTwin Design Review allowed for digital review that, compared with traditional print and scan methodology, allowed contractors to access data from the 3D model on their tablet and easily get elevations.

“The NYS RT 28 over the Esopus Creek Model-based Contracting project is the perfect example of what is possible when engineers face an extraordinary problem but have a collaborative partner like Bentley by their side to help them to succeed,” said Zack Maybury, NYSDOT’s P.E. design squad leader.

Outcome

Using the 3D model in construction has reduced quantity discrepancies between the contractor and the engineer in charge (EIC) about calculation for materials, such as asphalt or cut-and-fill quantities. Now that they have 3D solids of the cut-and-fill volumes in the project, there have been no discrepancies. By providing these features in a solid format, it eliminates the possibility of misinterpretation of quantities.

NYSDOT delivered a 3D model that will be updated to reflect any design revisions, as well as the as-built environment. This living document and model will continue forward to function as a key feature for asset management and bridge inspection. The use of this model for asset management will enable the project to fully make use of a 3D model in design, construction, and inspection.

NYSDOT modeled and evaluated three distinct bridge alternatives to determine an economical design with minimal public impact during construction. NYSDOT was cautious that this method of project delivery might cost more to administer until contractors were more familiar with it. However, they were ecstatic when bids came in actually lower than the engineer’s estimate. They successfully created an iModel of the proposed bridge, advancing this solution for future use by the department. This project advanced the use of Model-based Contracting as a realistic project delivery method for not only NYSDOT, but other DOTs and agencies as well.