Lead-Based Paint Picture

Crushing and recycling concrete that contains lead-based paint may pose few real hazards.

A recent study by the U.S. Army Corps of Engineers suggests that the lead content in construction and demolition (C&D) concrete to be crushed and recycled is well below safe limits set by the U.S. Environmental Protection Agency (EPA). These promising results could lead to a better comfort zone for C&D recyclers handling concrete that contains lead-based paint (LBP), preventing such paint-coated concrete from going to a landfill.

The past few years have seen a growing national trend to reduce C&D debris by reusing or recycling wood, concrete and other materials. Currently the U.S. EPA estimates that about 20 percent of the debris and scrap from C&D sites in the U.S. is being reclaimed.

Besides lingering perceptions that recycling is not cost-effective, one of the main deterrents to widespread efforts has been the presence of LBP on many of the materials. And with good reason: Depending on the end use of recycled LBP-containing products and the associated potential for leaching lead, contractors could be held liable under the Resource Conservation and Recovery Act (RCRA).

U.S. ARMY EFFORTS. The Corps’ Engineer Research and Development Center, Construction Engineering Research Laboratory (CERL), is conducting studies seeking to expand deconstruction and reuse of Army buildings slated for removal. The Army is among the world’s largest landlords, owning some 1 billion square feet of real property, much of which has been deemed obsolete. More than 39 million square feet of World War II era buildings are yet to be removed.

Under the Residential Communities Initiative, in which private investors provide quality housing for soldiers, 70,000 old units are being demolished. Hundreds of Korean War era barracks and associated buildings are being replaced with contemporary barracks complexes. In total, 26 million tons of demolition debris will be generated within the next 15 years. Some Army installations report that C&D debris constitutes 80 percent of their solid waste stream. Of this amount, about 63 percent is estimated to be concrete.

On-post landfills are typically available to contractors for "free" disposal. However, installations report their costs in expanding, operating, maintaining, monitoring and eventually closing the landfill to be roughly $50 per ton over its life. The direct cost of hauling and tipping debris at an off-post landfill can be much higher.

CERL’s research is providing guidance for installations to make the best decisions about building disposal options. The effort began with field demonstrations of deconstruction at Fort Campbell, Ky., and Fort Ord, Calif., and has expanded to include removal of LBP from salvaged materials; applications of mechanized equipment to deconstruction; recycling concrete from buildings; identifying environmental performance of recycled concrete materials containing LBP; and modeling the cost, material values, and scheduling impacts of salvaging materials for reuse and recycling.

Concrete Test at Fort Ord. Military installations have a recurring need for aggregate to use as fill, roads, revetments and other projects. Obtaining this material for local use from buildings demolished on site has several advantages, including waste diversion and avoided transportation costs to take it off site. In the past, most contractors who recycled concrete largely ignored the possibility of lead contamination. However, more recently some have started sampling for LBP presence, which has raised concerns about RCRA and discouraged concrete recycling in some minds.

CERL conducted a study at Fort Ord to learn if LBP in crushed concrete actually poses a hazard. The Corps, the Construction Materials Recycling Association and the National Association of Demolition Contractors jointly funded the study. The project involved demolition of 300 old family housing units (Fort Ord was closed under Base Realignment and Closure). These buildings were pre-cast concrete on concrete foundations. Driveways and streets were also demolished.

Prior to demolition, CERL took samples at the site for laboratory tests, including: air-ambient, air-personnel (OSHA), soil, dust, building structure and pavements. Concrete was separated from the C&D materials stream and transported to another site for processing with an Eagle two-stage impact crusher. Researchers took several test samples from the aggregate pile and from under the conveyors.

The buildings, foundations and streets were crushed together to make road base for use in projects on the Fort Ord property and nearby. CERL took samples from the finished recycled aggregate product.

Promising Results. Samples from the intact buildings showed an average of 3,700 mg/kg (milligrams to kilograms) lead concentration in the paint. This number is typical for LBP-coated concrete and is lower than what is normally found for LBP on wood surfaces.

The crushed aggregate from the processed piles at the crusher site had lead concentrations averaging 17 mg/kg. This level is quite low, given the intended application as a road base. The U.S. EPA limit for lead in soil in residential areas is 400 mg/kg (total lead concentration). CERL further tested the two highest concentration samples using the Toxicity Characteristic Leachate Potential (TCLP). For both, the result was less than 0.01 mg/kg—far below the RCRA limit of five.

The area around the crusher had been sampled after a day of processing the concrete. The average total lead concentration in fines under the conveyor belts was 111 mg/kg. This level is well below the limit for lead in soil; however, the fine nature of this residue makes it prudent for workers to wear protective masks when working around this equipment. CERL again performed TCLP for lead on the two samples with highest total concentrations (160 and 130 mg/kg). As with the crushed product, the result was less than 0.01 mg/kg.

Samples from clean concrete pavement showed lead concentration of less than 1.0 mg/kg. For comparison, CERL took samples from the demolished streets and driveways and found 1.5 and 17 mg/kg lead, respectively. The higher concentration in the driveway could be attributed to leaded gasoline exposure over the years.

What’s Next? This study provided an important first step in determining if concrete with LBP is safe to recycle. For the type of buildings tested and the processes used in recycling, the findings show that no hazard exists as defined in the regulations. CERL expects to monitor concrete recycling in future demolition projects for other Army facility types in cooperation with the CMRA and EPA.

With concrete comprising such a high percentage of C&D mass and with a recycling rate that can be improved, there is a huge potential to reduce the amount of C&D-generated material that is landfilled. CERL’s continuing research will result in guidance for the industry to maximize opportunities in the recycling and reuse of these materials.