MWRA Nut Island Headworks Odor Control - How Lasers and Data Analytics Kept Bids in the Ballpark, and Treated Air Flowing at Nut Island

In 2016, Hazen and Sawyer (Hazen) was hired to design and provide construction services for the complete replacement of the HVAC and Odor Control systems at the Massachusetts Water Resources Authority's (MWRA) Nut Island Headworks facility in Quincy, Massachusetts. The existing facility includes more than 65,000 square feet of operating space over 4 above and below grade floors, including a completely buried odor control facility, and removes screenings and grit from the MWRA's western sewage collections system before sending the flow via a tunnel under Boston Harbor to the Deer Island Wastewater Treatment Facility for final treatment. To further add to construction challenges, the Nut Island facility sits in the middle of a heavily trafficked public park, with sweeping views of Boston's harbor and skyline. Upon initial review it was clear that trying to remove and replace all of the existing duct work, air handlers, fans, scrubbers and adsorbers based on as built drawings and field measurements could result in significant issues during construction, so our first step in the design process was to complete a detailed laser scan of the entire operating area of the facility, and use that data to build a 3 dimensional Revit model. The resulting model and point cloud located equipment and appurtenances within the existing facility with millimeter accuracy. Once detailed design commenced, maintenance of plant operation (MOPO) during construction was seen as critical to ensuring a safe working environment for those inside the facility. At the same time, it was critical that MWRA maintain treated air discharge to allow the public to continue to enjoy the surrounding park, while continuing to meet their discharge permit. The Hazen team used 4-dimensional design techniques to create a detailed, timeline based design with more than 75 staging drawings, showing how the contractor could construct the upgrades while maintaining ventilation and odorous air treatment, and meeting the contract constraints. The result is an ongoing, $58 million construction contract, with all submitted bids within less than 0.5% of the accepted bid price. In addition, while the contractor has proposed and executed different methods for MOPO than those shown in the design documents, the detailed staging and constraints, as well as the accurate laser scan and model, have resulted in a project that is tracking for less than 6% change orders at project completion. In addition, during startup testing of the wet scrubber system the Hazen team utilized historian data and BI dashboards to provide real time data analytics to evaluate wet scrubber operation, chemical use and control strategy integration to optimize scrubber controls. This presentation/conversation will detail how the Hazen team utilized 4D design to zero in on construction constraints that were reasonable and achievable, while limiting system downtime and allowing for continuous operation of the building's ventilation and odor control systems. It will also present design and construction success stories and lessons learned, and demonstrate how utilizing 4D design, with a focus on constructability and MOPO, led to consistent bids and helped to minimize project change orders, and show how PowerBI can be used to present tens of thousands of pieces of data in a way that is easy to share, evaluate and react to.