Controlling Dust Levels In a Hospital Zone
The Medical University of South Carolina (MUSC) in Charleston has begun construction of the MUSC Shawn Jenkins Children’s Hospital and Pearl Tourville Women’s Pavilion.
The team of Robins & Morton/Cumming/Brownstone started the demolition of a series of concrete buildings on the MUSC grounds, which are to be replaced by a new $385 million state-of-the-art concrete, glass and steel facility scheduled to open in 2019. The project involved demolishing four buildings from a 185,000 ft2 (17,187 m2) area in 6 months. Being surrounded by fully operational hospital facilities, the goal of the project was to conduct a compliant and environmentally-responsible demolition, with the lowest amount of fugitive dust emissions possible.
To begin the takedown, boom excavators with hydraulic attachments cut thick rebar-reinforced concrete supports into measured chunks. Approximately 94% of the 7,000 tons of metal, concrete, brick, wood, lighting, and piping were separated and transported to recyclers throughout the process.
One of the challenges the team faced was a significant amount of dust produced by demolition activities, debris separation and the loading process. In addition, adverse weather conditions and debris storage piles – as much as 6 ft (2m) tall -- had the potential to contribute to air quality issues. Sitting directly on the site line is the Charleston Center, a rehabilitation clinic, and the MUSC Hospital Ashley River Tower, the newest cancer care center built in 2008. Surrounding the location is the entire pediatric, patient care and cancer research infrastructure of MUSC, spanning several blocks. These sensitive environments caused hospital administrators concern over the effect of atmospheric particulate levels on patient treatment and recovery, so board members required extra monitoring and data collection.
In addition, a densely populated community surrounds the facility, where high airborne particulate levels could yield complaints from neighbors. The area’s weather plays a large role in the management of fugitive dust as well, since the site is near the tip of Charleston’s South Channel leading into the Atlantic Ocean. High winds off the ocean can intensify as breezes move up the channel and into the river basin, contributing further to the challenges of effective dust control.
Creating a Dust Plan
With the local community and weather issues in mind, the air quality plan for the project was written in accordance with federal and state requirements, which restrict fugitive particulate matter (PM) measuring 2.5 microns in diameter or larger caused by industrial activity from affecting the air quality in the surrounding area. Tiny particulates less than 10 microns in size are considered “respirable,” which means that they can bypass the body’s natural defenses and enter deep into the lungs, potentially contributing to health issues -- especially for people with current respiratory conditions.
To ensure dust levels were compliant with MUSC expectations and air quality regulations, Robins & Morton required the use of a DustBoss® suppression system from BossTek in the air quality plan. Project managers rented two DustBoss DB-60 Fusion™ atomized misting cannons and used them at various points on the site throughout the project.
Mounted on a roadworthy trailer with a standard pintle hitch, the DB-60 Fusion system uses a specialized barrel design with a powerful 25-hp (18.6kW) industrial fan on the back end and a misting ring on the front. A 10-hp (7.5kW) booster pump draws water from a 1.5-in (38.1mm) fire hose and increases pressure to as much as 250 psi (17.2 bar), 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) cone, covering up to 62,800 ft2 (5,834 m2) when using the 0-180º oscillator.
The unit was powered by a 45-hp (33.5kW) Genset with a John Deere diesel Tier III Flex engine and fed by a 100-gal (378 liter) fuel tank. Delivering approximately 24 hours of runtime, the gen set and fuel tank are located on the trailer and housed in a protective metal cabinet. The machine’s functions can be controlled via digital touch screen display mounted on the unit in a NEMA 3R enclosure. The entire system can be shut down, hitched to a pickup truck, moved easily around the site and positioned by a single worker within minutes.
Unlike large sprinklers and hoses, which are usually maneuvered by workers standing near large machinery and in proximity to dangerous impact or loading zones, the DustBoss is fully programmable, requiring no manual labor for ongoing operation. This allowed workers to concentrate on other important tasks further away from the most dangerous areas, creating a safer and more efficient worksite.
At MUSC, the most effective method during upper level operations in windy conditions was to place one DustBoss at the point of the sheer, and the other on the opposite side of the building. Smaller, lighter droplets offer air suppression high up, and larger droplets provide surface suppression in the impact zone, confining the dust to a limited area.
In demolition projects like the one at MUSC, loading material in windy conditions at debris storage areas can create large amounts of dust. By keeping the debris contained in one zone, a single atomization unit was able to cover the whole storage area. When the wind was calm, the atomized mist machines worked in tandem to offer dust suppression over the entire site.
Proof of the effectiveness of atomized mist is in the project’s daily data log, with consistently low dust levels. Regular checks of the air intake filters for the hospital revealed no significant increase in particulate capture.