Revit plays key role in helping HMM reduce $100K design issue to ¼ the cost
Model based workflows were the key reason for winning this project. Hatch Mott MacDonald (HMM) teamed with Bowen Engineering as the General Contractor to pursue the Design-Build project. The RFP included a design concept developed by New Jersey American Water.
In order to be responsive to the RFP, a construction cost estimate was required to be submitted as part of the RFP response. HMM utilized Revit software to create a 30% model of the planned facility. Schedules within the model were used to calculate pipe velocities and confirm pipe sizing during the initial concept development. HMM provided quantity take offs from the model to the estimators at Bowen Engineering for the development of their construction cost.
The area that model based workflows really paid off was when the team decided that they had an alternate approach to the design of the treatment plant. HMM produced a second 30% design model of the alternate design concept that was incorporated into the proposal response. They were able to provide the details necessary for Bowen to create a second construction cost estimate as well. Both 30% design models, and renderings were completed within the 5 week RFP process without the need for a time extension. This would not have been possible in a standard CAD deliverable workflow.
New Jersey American Water ultimately selected the HMM-Bowen design build team and their alternate design concept. Selection feedback included praise for providing detailed drawings of the alternate design concept that allowed the selection committee to reconsider their original approach.
Schedules within Revit were created to perform integrated hydraulic analysis of the process piping throughout the water treatment plant. By combining data within the Revit database with some designer specific data, the schedules are able to identify pipe velocity, and headloss through each pipe, fitting, and valve element. As the process piping layout is modified during the design process, the calculated values are automatically updated and provide real-time feedback to the designer.
After award of the project, visualization was an integral part of the project delivery workflow. Throughout the entire design process, design workshops were held with all members of the project team. A review meeting with a standard project workflow would include discussions on 2D plan and section drawings. With the aid of design review, all review workshops were based on the 3D model. At no time throughout the design process did the team discuss 2D plan and section drawings. With the enhanced visualization of the model, the project team engaged the operations and maintenance personnel from the initial kick-off meeting and receive their detailed feedback very early in the design stage of the project. This was key in reducing the amount of re-design after 65% project milestone.
Visualization was also important to help the design-build team identify and solve significant structural design issues. In a standard 2D project workflow, the structural issue would not have been identified until the construction phase of the project and would have resulted in a significant change-order and re-design efforts.
The project team used the model to redesign the water analyzer waste disposal system after construction had started to address a significant cost issue. The original design required a sanitary sewer connection fee of $100,000. With a quick re-design at no additional cost to the owner, the permit application fee was reduced to $25,000.
The overall project performance, from the preparation of the proposal, initial construction cost estimate and construction of the facility was improved through the use of the model-based workflows. By introducing the Contractor’s estimating team and construction team to the model environment starting in the proposal phase of the project, they were better prepared to execute the construction, because they had full knowledge of the design intent and could easily visualize and identify issues before they occurred in the field.
The project delivery model utilized on this project introduced New Jersey American Water to the benefits of combining model-based workflows with alternative project deliveries such as design-build. New Jersey American Water has indicated that future design-build projects will require the use of model-based workflows as a result of this project