News Article

04/08/2016

StormTech® chambers & Nyloplast catch basins flank the Sanford Fargo Medical Center in North Dakota

Virtual design and construction overcomes engineering challenges

3D model improves schedule, efficiency, costs, and safety on a large, complex medical center project.

By Sera Maloney, P.E., and Taylor Cupp, Associate AIA, LEED AP BD+C

Mortenson Construction was selected to build the Sanford Fargo Medical Center in Fargo, N.D., including the building and surrounding site. It is the seventh largest health care construction project in the United States and the largest commercial construction project ever in North Dakota. The project consists of a 1 millionsquare-foot building complex set on a 109-acre site. The building includes a steel structure with concrete foundations and shear core, clad with a precast concrete panel enclosure system with brick and limestone accents. The trauma 1 medical center capacity is 384 beds and 32 operating rooms. The surrounding site work includes the paved parking and road system, utilities, and 50,000 cubic feet of subgrade stormwater retention chambers.

From the infancy of the project, all stakeholders have focused on the owner’s guiding principles in setting business goals on the project:

  • be dedicated to health and healing;
  • put patients first;
  • ensure safety and support quality;
  • support the Sanford integrated delivery model;
  • optimize the flow of people, materials, and information;
  • be innovative, flexible, and adaptable;
  • be environmentally healthy and efficient;
  • support clinical research and education;
  • standardize where feasible; and
  • create architectural significance.

Engineering challenges

The Sanford Fargo Medical Center is sited within the glacial-period Agassiz Lake bed, which contains soils that are not conducive to supporting heavy loads. Consequently, developing a 109-acre site and designing and constructing a nearly 1 million-square-foot medical center has been a challenge. Water levels in the expansive clay soils have posed additional engineering challenges. A short, 30-month project schedule combined with a climate that is not favorable to winter construction required innovation and creativity in logistical planning and attention to the finest details in cross-discipline verticalto-horizontal collaboration.

The capability to reduce project cost and provide maximum value to the owner was recognized as being critical as early in the project as possible. A prime example is a test caisson program investigated early on in the project. The findings of the study resulted in an indepth study and pricing exercise to investigate the optimal footprintto-height scenario for the project. As a result of the poor soils on the project, reducing the footprint drastically and building vertical maximized efficiency, a rare approach for a site where plenty of land is available. The exercise shaved tens of millions of dollars from the final project cost and helped to better inform the geotechnical exploration on the project.

Project soils combined with water runoff have been one of the primary environmental concerns on the project. Rather than allowing site runoff to nearby city storm systems, more than 50,000 cubic feet of subgrade stormwater retention chambers flank the site, allowing infiltration directly onsite. The environmental impact has been a large reduction in necessary storm sewer systems running offsite and in sediment runoff.

Another key challenge was that the building structural design could not allow any backfill to be completed on the foundation until three levels of elevated deck were poured. The limitation would have extended the schedule by as long as three months. The Mortenson Civil construction team proposed and built a mechanically stabilized earth (MSE) wall around the perimeter of the building that resulted in one of the larger time-savings decisions made on the project. By incorporating the MSE wall, Mortenson was able to backfill within feet of the building in lieu of more than a 100-foot layback, allowing much closer building access for schedule-critical activities such as erecting steel and hanging precast concrete panels.

Additionally, logistical cross collaboration and innovation between civil work and building construction has led to time savings in tower crane operation by making use of a large culvert turned vertically to surround the tower crane base. This allowed time-sensitive backfill operations to proceed around the building while maintaining operation of one of three tower cranes onsite.

Virtual design and construction

The project team’s approach to virtual design and construction (VDC) has been to utilize its potential whenever possible on the project to enhance communication and decision making. A dedicated onsite, integrated construction team leveraged VDC processes such as existing conditions modeling, phase planning, site analysis, 3D coordination, site utilization planning, and construction system design that have led to an improved deliverable. The resulting outcome was a better understanding of some of the atypical approaches to construction methods targeting the delivery of a world-class facility in the most efficient manner possible.

Cloud and mobile solutions have permeated all trades on the project site, from the trailer to the field. VDC deliverables such as geographically located site drawings have leveraged the positional capability of many mobile devices in ensuring that the complex grid of subsurface systems is understood, installed correctly, and not impacted once in place. The portability of information to the field, whether on mobile devices or in job boxes, has saved the project countless hours in trips between the job site and field office.

An “all in” VDC approach on the project has led to the necessity of all players to communicate effectively among disciplines and software platforms. Interoperability of software has played a critical role in enabling cross-platform collaboration. For example, while architectural constructability reviews were taking place early in the design phases of the project through an Autodesk Revit design model from the design team (HKS architects), upfront investment in the MSE wall was investigated, communicated, and dissected though the use of Bentley MicroStation and Bentley InRoads. The capability to integrate various design and construction decisions in a unified platform in Autodesk Navisworks with dozens of other trades and coordinate the proposed design among the entire project team proved invaluable to achieving buy in between all parties. In the end, by having the ability to integrate virtually something unique like the MSE wall system or to test out the scenario, the project was able to achieve a significant cost and schedule savings.

By integrating new VDC processes, Mortenson was able to make critical decisions with the owner and project team using the computer model before implementation in the field. Each stage of the construction process was modeled and fully coordinated between key stakeholders, allowing any conflicts and decisions to be resolved early in the construction phase and therefore reducing time of construction. Georeferenced models allowed the civil construction team to use machine-controlled grading techniques that significantly reduced the time to complete the large earthmoving operation that has consisted of more than 300,000 yards of dirt to date.

A federated model-based turnover is projected for the owner at project completion in late 2016. The model is anticipated to assist in operations as the backbone of the complex database of information that a large medical center entails. Precise as-built conditions derived from the working models will assist the owner in all ongoing maintenance needs from an efficient above-ceiling network of systems to below-grade utilities that may require access in the future.