Improvements to odor control in Nut Island Headworks
Quincy, Mass.
BEST PROJECT
Sent by: Walsh Construction
Owner: Massachusetts Water Resources Authority
Main design company: Hazen and Sawyer
General contractor: Walsh Construction
This $61.6 million project improved facilities and systems that control hydrogen sulfide gases produced during waste decomposition processes. Aside from their unpleasant odor, these gases can be harmful in high concentrations, underscoring the critical need for optimized HVAC systems to provide fresh air to work areas to maintain plant-wide safety.
In addition to requiring a strict sequential construction process to maintain seamless treatment operations during demolition and construction, all equipment planned for replacement was located underground. Major items included four 55,000-cubic-foot-per-minute fans, installation of carbon-containing fiberglass tanks, custom air handling units, and three new oil boilers with two new 20,000-gallon diesel tanks. Most of the facility’s ductwork also required replacement due to long-term exposure to the highly corrosive gases. These challenges were compounded by pandemic-related supply chain delays that required frequent sequencing and schedule adjustments throughout the project.
Photo courtesy of Walsh Construction
To gain access to the work area, the project team temporarily replaced the existing prefabricated deck planks with waterproof panels that could be removed and reinstalled each day. Radio communication and hand signals helped crane operators overcome extreme job site visibility limitations, allowing them to accurately maneuver large sections of materials and equipment in underground spaces.
Comprehensive daily work plans, contingency strategies, and extensive task hazard analyzes helped protect workers from hazards such as high gas concentrations, treatment process chemicals, and silica dust from pedestal demolition, bases and slabs. Complex operations in confined spaces, such as the installation of equipment in effluent channels and work inside new tanks, demanded impeccable execution with no margin for error.
Photo courtesy of Walsh Construction
While most of the construction took place underground, the project team was aware of its effects on the surface. Because Nut Island is part of the Boston Harbor Islands State and National Park, visitors often take advantage of the well-maintained gardens and boardwalks that surround the treatment facility.
Photo courtesy of Walsh Construction
Privacy fences kept most of the work out of sight, while the crane’s strategic location in a parking lot allowed the footpath to remain open throughout the work. The project team paid strict attention to restoring the disturbed landscape, using only native plantings and adhering to the existing aesthetic.
