Controlling Dust for a Hospital Demolition Protects Patients and Students
To make way for a billion-dollar facility upgrade at Methodist University Hospital (MUH) in Memphis, Tenn., DT Specialized Services (DTSS) demolished and recycled an 8-story, 100,000 ft2 (9,290m2) structure. Thanks to a DustBoss® DB-60 Fusion™ atomized misting cannon, DTSS mitigated harmful particulates and keep demolition dust under control throughout the project.
DTSS General Superintendent Seth Herber says that while the building was constructed of a steel skeleton, wrapped in precast concrete and brick, implosion wasn’t a viable option, as airborne particles could migrate to the air intakes of the other buildings.
“Because there was asbestos fireproofing material used in the original construction, the floors were encapsulated one at a time with plastic wrap, so negative air pressure could be created,” Herber says.
For much of the exterior demo work, DTSS used a Volvo EC380 mid-level excavator with a bucket and thumb, as well as a Volvo EC480 high-reach excavator to access the upper floors. The company also used a third excavator with a shear attachment and a concrete processor that crushed the brick and concrete and readied it for loadout.
The DB-60 Fusion made sense for the hospital site in several ways. Hoses and large sprayers common to demolition projects typically produce droplets as large as 10,000 microns in size, large enough to create a phenomenon known as “slipstream effect.” Instead, the DB-60 Fusion creates millions of tiny droplets in the 50-200 microns size range – roughly the size of most dust particles generated by demolition projects.
Due to their small mass, atomized mist droplets produce virtually no slipstream and are light enough to travel with dust particles on air currents, increasing the chance of a collision and allowing the droplets to quickly drive dust to the ground. [Fig. 1]
Mounted on a roadworthy trailer, the DB-60 Fusion system uses a specialized barrel design with a powerful 25-hp (18.4kW) industrial fan on the back end and a misting ring on the front. On this project, the 10-hp (7.5kW) booster pump drew water from a metered city hydrant and increased pressure to as much as 250 psi, supplying the circular manifold fitted with atomizing nozzles. The nozzles fracture the water into an engineered mist, and the fan throws millions of tiny droplets in a 200-ft (60m) long cone, covering up to 62,800 ft2 (5,834 m2) when using the 180º oscillator. Another key feature for DTSS on the project was the ability to quickly reposition the DB-60 to accommodate the changing worksite and prevailing winds.
“Wherever we need dust control as the job progresses, we can get the unit there quickly and have it running in minutes,” Herber says.
A further advantage to precision dust control is the effect on equipment. In the past, workers have had to clean excessive dust buildup out of equipment air intakes and radiators to prevent engine breakdowns. When dust is addressed right at the point of emission, this activity is reduced considerably, saving maintenance time and protecting valuable equipment. By having a versatile hands-free dust control unit, sites are safer and more compliant, while reducing the overall cost of operation.
“This was a delicate project, strictly controlled, in a highly urban environment, yet we received no dust-related complaints on the job,” Heber says.
Once the nine-month demolition was complete, Herber’s crew brought in 5,000 yd3 (3,823m3) of dirt to fill and decommission the basement. Hospital officials report that a beautiful greenspace is planned in the location to serve as the front vista for the new facility.