Wastewater Treatment Facility Nutrient Upgrade Phase A Improvements

Upper Blackstone Water Pollution Abatement District awarded MWH this contract to provide construction management at-risk (CMAR) services for the Wastewater Treatment Facility (WWTF) Nutrient Upgrade Phase A Improvements project in Millbury, MA. Upgrades on this facility include upgrades to existing bioreactors, construction of a new magnesium hydroxide facility, installation of a new supplemental carbon system, upgrades to the electrical main service, and air pollution control improvements featuring regenerative thermal oxidizer (RTO) equipment.

All four bioreactors being upgraded needed to remain operational at all times between December and May, leaving a window of June through November for taking one bioreactor out of service at a time. MWH installed one of the new air pollution control units prior to demolition and sequenced the demolition work to maintain redundancy to the air pollution control system throughout the course of construction.

MWH worked with the Owner and Design Engineer through the pre-construction phase to provide input and fast track an improved construction schedule to complete one of the bioreactor upgrades prior to the first winter. This created schedule float and eased MOPO for the remaining three upgrades. This required early procurement of equipment with long lead times, so MWH worked with Owner and Engineer to complete equipment specifications and issue these contracts and deliver equipment on time. We also collaborated with the Owner and Engineer during the preconstruction phase to ensure the project would stay within budget by implementing constructability ideas. For example, the design included a geothermal heat recovery system for the new magnesium hydroxide facility. This system would have doubled the depth of excavation and required additional shoring. Therefore, MWH suggested considering alternative HVAC heat recovery means, reducing the excavation, reducing risk to surrounding structures, saving on cost of work and cost of extended overhead in the schedule.

The new chemical facility included several design elements to showcase and test sustainable design options for future projects at the plant. These items include a vegetated roof, passive lighting, heat exchanger system and solar wall heating. Permeable pavers around the building were also installed to increase stormwater infiltration. The automatic temperature controls system design will use warm air from the solar wall and recapture heat in the building to reduce heating costs in winter.