Taking on the dust

Architects likely aren’t thinking about demolition as they design new buildings. But as the recycling of construction and demolition (C&D) materials has become an increasingly important part of the demolition process, creativity in architectural design at the time of construction can have a profound impact on demolition—especially when it comes to dust control. Structures built with a variety of materials can be challenging to demolish, as it’s not only the demolition process that releases dust but also the separation of materials for recycling.

Adamo Group is well-versed in the issues associated with the demolition of a wide variety of construction materials. Operating since 1964 and headquartered in Detroit, the demolition firm has demolished and cleared projects across the region.

“Our business model is to employ the best practices for any project, which includes diligent recycling and effective dust control,” says Al Penrod, Adamo Group equipment manager. “The basics of what it takes to complete a job successfully [are] talented people, high-tech facilities and a fleet of top-of-the-line equipment, and DustBoss misting cannons [from Peoria, Illinois-based BossTek] are an integral part of that portfolio.”

Consistently updating operations using the latest methods and equipment is at the core of Adamo’s operations.

With a $25 million fleet of modern machinery, the company provides a wide range of services. Some large projects involve highway and bridge demolition, excavation and grading, utility installation and hazardous waste removal. Smaller projects require just as much expertise, including site decontamination, facility decommissioning, asset management and recovery, selective demolition for facility renovation, asbestos abatement, recycling and industrial processing. Most of these projects involve some sort of dust control.

The Eastland project

One recent example is the demolition of the Eastland Shopping Center in Harper Woods, Michigan, just northeast of Detroit.

Opened in 1957, the Eastland Shopping Center was considered one of J.L. Hudson Co.’s most ambitious department store expansion projects. With waning occupancy over the past decade, the facility was purchased by a development company and retained roughly 10 percent occupancy by late 2021. The development company closed the mall in early 2022 with the intention to build a $94 million industrial distribution center.

The approved plan, part of a collaboration with the Michigan Strategic Fund, involves three commercial light industrial buildings totaling 1.3 million square feet. In addition to the three buildings, the project will include 35,711 square feet of infrastructure improvements, such as sidewalk, curb and gutter improvements and road repair.

From start to finish, the demolition project took eight months. After environmental testing and a meticulous hazard assessment, asbestos abatement was performed. The building also was cleared of “universal waste,” including batteries, mercury-containing equipment, lamps and aerosol/pressurized containers.

Once the toxic substances were removed, the taller structures were demolished first. The Adamo Group dismantled the structures using several pieces of equipment, including a midsized high-reach crane, front loader and magnetizing machine. An integral part of this process, the company says, was the DustBoss DB-60 misting cannon. Directed toward the demolition activity, a fine engineered mist raised the humidity of the area, preventing dust from becoming airborne and traveling into the surrounding community as well as protecting workers on-site from hazardous dust.

Recovered materials, including structural steel, shredded material, brick block and concrete, were separated for potential recycling. A second DB-60 unit was used to reduce dust emissions created by separating, piling and storing material as well as filling transport canisters.

“Materials were separated on-site by mechanically picking or magnetized picking,” Penrod says. “These structures collected over 60 years’ worth of dust, so the separated materials can release a lot of emissions. The DustBoss really helped us control air quality so we could stay compliant.”

Controlling dust emissions

Different materials can produce and attract different particulates. Some are more regulated than others. When regulators measure particulate matter (PM), they’re primarily looking for particles 10 microns (µm) in mass or smaller. For perspective, dust is light enough to remain airborne on ambient air currents at 200 µm and becomes barely visible to the naked eye at 100 µm—approximately the size of a cross-section of human hair.

The reason PM10 is regulated is because it can penetrate past the body’s defenses and enter deep into the lungs. Long-term exposure could irritate existing breathing problems and could lead to chronic lung diseases.

Crushed or broken concrete, for example, can release silica particulates, which are generally smaller than PM10. Silica is also present in brick and mortar as small as PM2.5. Structural steel can have static or magnetic qualities that attract heavy metals and other hazardous dust particles, capturing them within recycling piles and shedding them in large quantities on windy days or when disrupted.

To capture small airborne particles, the droplets need to match the general size of the particles. This allows them to collide, and the combined mass causes them to drop to the ground. Droplets greater than 200 µm are large enough to sail through the air and create a slipstream current that moves around them, which repels smaller particles and leaves them to remain airborne.

The traditional method of dust control is a worker holding a hose and spraying water toward the area. This practice has several drawbacks. One is that it puts workers in proximity to the activity area and fall zone, which can be highly unpredictable.

Hoses connect to hydrants, so they use between 100 and 500 gallons per minute (GPM) of water, causing a tremendous amount of wastewater runoff, mud and hazardous standing water. Reaching high up or across rubble toward active demolition requires high water pressure. So, along with the water volume, the droplets produced by these hoses need to be large, approximately 200-1,000 µm, which is sufficient for surface suppression of dust but ineffective against airborne particulates.

In addition to the safety issues associated with hoses, factors such as the cost of labor, higher water bills, the greater risk of complaints and air quality violations can contribute to a rising overall operating costs.

For those reasons, methods that rely on water pressure are being replaced with atomized mist cannons as the preferred method of dust control. Automated mist cannons such as the DustBoss DB-60 produce droplets approximately 50-200 µm from a misting ring in the front, that are propelled long distances by a powerful fan that pushes air through the rugged barrel. They can be more effective, cheaper to run over the long term and require no workers to operate.

Dust control

The permit for the Eastland project did not specify the method of dust control beyond the fact that it must be water-based. Adamo Group purchased its first DustBoss unit more than 15 years ago to provide better service to customers, retain high air quality and exceed compliance standards. The company has since bought another unit, and both have become an integral part of the operations.

The DB-60 cannon is one of BossTek’s midsized fan-driven designs. The cannons are 81 inches wide, 117 inches long, 86 inches tall and weigh 1,800 pounds. Mounted on road-worthy wheeled carriages, the cannons easily can be moved to where they are needed by a pickup or vehicle equipped with a hitch.

Units have an adjustable elevation angle ranging from zero to 50 degrees, with a throw distance of 200 feet of fine mist propelled in a wide cone by a 25-horsepower fan running at 30,000 cubic feet per minute. When running with the optional 359-degree oscillation, each one can cover more than 125,000 square feet.

The cannons are equipped with a 1-inch to half-inch cam-and-groove quick disconnect female hose coupling. Connected to municipal hydrants with variable pressure, the DB-60s require only 10 pounds per square inch of constant pressure. Water passes through an in-line 30 mesh 595-micron filtration system that captures any impurities in the water that might foul the lines. The water then enters a booster pump, where the pressure is increased to the adequate level needed for the 30 specially designed nucleating nozzles attached to a brass mandrel to fracture the water into millions of minuscule droplets. The use of a booster pump allows the DustBoss to use a fraction of the water of hoses, only up to 26.7 GPM.

Positioning the cannons

Understanding where the wind is blowing is the first step in properly positioning the cannons. As with any water-based application, adjusting for wind is a part of the dust control process. Prior to activity on the site, workers place the cannon upwind and allow the cone of mist to fill the area. The droplets will travel with the wind into the activity area where the crane attachment is operating, float with the particulates as they are produced and pull them to the ground.

Units designed for high-wind operations are available, but Adamo Group finds the standard misting units suffice for its current project needs. This is where the wheeled trailer offers a large benefit. It allows the cannons to be wheeled around easily by a medium-duty vehicle and positioned for precision dust control.

The water source is a consideration for any water-based solution, but most dust cannons also require a power source. Adamo chose standalone units for their smaller space requirement and easier maneuverability.

Signs of success

The general rule for demolition dust is to avoid any situation that yields complaints regarding air quality from the public, as complaints submitted to the Environmental Protection Agency can trigger an inspection. Like most of Adamo Group’s projects, no complaints were lodged about the Eastland Shopping Mall demolition.

“Since we bought our first unit, we rarely receive complaints,” Penrod says. “With the addition of the second machine, the recycling piles are treated, so there’s little chance that dust leaves the site line.”

The addition of more robust dust suppression means the company can have two units on large projects or split them between smaller projects as needed. This ensures that projects can keep operating in adverse conditions where dust could have been a problem in the past.

“Low maintenance is a standout trait for us. We position the unit, it turns on every time, and we walk away,” Penrod says.

The author is president of BossTek, a dust and odor control solutions provider based in Peoria, Illinois. For more information on the company, visit https://bosstek.com.