Pioneering a solution for C&D fines

Finding an end market for construction and demolition (C&D) fines continues to pose a challenge for recyclers as increased scrutiny and questions surrounding the material’s environmental impact arise. Fines, which are generated during the processing of C&D debris, consist primarily of soil, wood, concrete, drywall, rock and other miscellaneous material particles.

According to the Construction and Demolition Recycling Association (CDRA), the most common market for C&D fines is for use as alternative daily cover (ADC) in landfill applications, which helps conserve virgin soil. Fines with a high soil concentration can also be used as clean structural fill, whereas fines consisting of concrete, brick and denser material can be used as structural fill.

While exploring the potential for these materials to be used as fill under Pennsylvania’s Beneficial Use program, the Laflin, Pennsylvania-based aggregate supplier, Pioneer Aggregates, began looking into the possible application of C&D fines.

The Beneficial Use program, which encourages the environmentally sound use of municipal and residual waste, provides guidance on permitting and compliance monitoring for beneficial use facilities. Past permits issued in the state for construction materials have allowed processed construction waste, including gypsum, soil, stone, brick, concrete block and more, to be used as a soil additive and for concrete or asphalt mixtures. With this program in place, Pioneer President Mark Popple saw an opportunity for putting the fines his company was generating to good use while simultaneously avoiding having to landfill the material.

FINDING A USE

In 2016, Popple approached the Pennsylvania Department of Environmental Protection (DEP) to discuss using a mixture of C&D fines with Portland cement, called “re-crete,” as fill material to reclaim a portion of Simpson Stone Quarry, a non-active coal mining quarry in Lackawanna County, Pennsylvania.

“Pioneer held extensive discussions with the DEP over several years to determine the best approach to demonstrate the viability of using this mixture in non-coal mine quarry reclamation,” says Mark McClellan, environmental consultant for Pioneer. “The DEP determined that since the mixture had not been used for this purpose in [Pennsylvania], it would require Pioneer to apply for a Demonstration Project permit under the Solid Waste Management Act, with strict requirements and monitoring for a limited period of time under controlled conditions.”

On Sept. 21, 2017, Pioneer received the Municipal Waste Demonstration Permit from the DEP, which allows the quarry to receive up to 1,000 tons of C&D fines per day. Pioneer’s responsibilities, as detailed in the permit, include creating quarterly reports to the DEP that provide chemical analysis of the fines and re-crete, surface water monitoring data, and other information. To ensure everything is within DEP limits on materials such as copper, lead and mercury, the company is expected to collect and analyze samples of fines every 6,000 tons used or at least once per month.

“Pennsylvania has over 250,000 acres of abandoned coal and non-coal mine sites with no responsible party and limited funds to address the environmental and health risk posed by these sites,” says McClellan. “The successful use of this mixture and other waste materials presents the opportunity to reclaim these sites, eliminate the environmental risks and bring them back to productive use.”

Prior to producing the fine mixture, Pioneer must first source their C&D fines from permitted processing facilities and submit the material to the DEP for chemical testing. Once the fines are accepted, they are transported to the quarry site to be mixed with Portland cement and water through a pugmill system. After the material is placed in the designated portion of the quarry, Pioneer will continually perform on-site testing, stormwater monitoring and leachate testing to ensure the material meets concentration limits and shows no adverse impacts to groundwater or surface water.

MEETING THE REQUIREMENTS

In many locations, C&D fines have not been widely recycled outside of landfill applications due to concerns over trace contaminants. In a 2018 study by the CDRA, researchers addressed these risks by assessing 14 samples from 12 C&D facilities in the U.S. The study analyzed the chemical and physical properties of the fines, as well as direct exposure and leachability when beneficially reused.

One of the main chemicals of potential concern in C&D fines is polycyclic aromatic hydrocarbons (PAHs), which naturally occur in coal, crude oil and gasoline. The study found concentrations among the different samples vary considerably, with half of the samples close to or above Florida’s commercial/industrial risk threshold (0.7 mg/kg) and four samples exceeding New York’s residential risk threshold (1 mg/kg).

In terms of heavy metals, arsenic and lead were two warranting the most concern in the study. Nine samples had concentrations above the EPA’s regional screening levels (RSLs) commercial risk threshold for arsenic. Arsenic concentrations existed at levels above the lowest risk threshold in all samples, with only one sample exhibiting arsenic slightly above Florida’s commercial/industrial risk threshold (12 mg/kg).

The controversy over trace chemicals in C&D fines has led some state regulatory agencies to require routine testing and compliance with risk-based regulatory thresholds. According to a Pennsylvania general permit for construction waste, the processed material cannot exceed the state’s chemical limitations on arsenic, copper, mercury, lead and more, as well as nitrogen, organic nitrogen and ammonium if used for land application.

FUTURE APPLICATIONS

Pioneer’s permit expires on June 12, 2020, when the company must submit a final report to the DEP documenting the results of all testing and monitoring data. Pioneer reports that the data so far indicates the project is successful and these materials can be placed directly into the environment as fill in a manner that is protective of public health and the environment.

“C&D processing facilities will potentially have a long-term alternative to disposal [for fines] and can see their byproducts put to productive use in reclaiming disturbed properties,” McClellan says.

If the DEP deems the project successful, the department can issue a statewide Beneficial Use permit, which would allow the C&D fines mixture to be used for similar fill applications across Pennsylvania. According to Pioneer, the mixture could be used as construction fill to reclaim abandoned mines, restore disturbed properties and remediate other contaminated sites.

“The Pioneer project offers an opportunity to these processing facilities to reuse the C&D fines, avoid disposal costs and, ultimately, provide an environmental benefit,” says McClellan.

The author is the assistant editor of Construction & Demolition Recycling magazine and can be reached at hrischar@gie.net.