Is concrete slurry a hazardous waste and does it require special handling? In some cases yes, in many cases no. The subject can be confusing and is governed by federal, state and/or local municipalities. In this article we will look at what could make concrete slurry hazardous and ways to properly handle it.
Laws and regulations
Under the Code of Federal Regulation the Environmental Protection Agency (EPA) is responsible for enforcing Title 40, Protection of the Environment. Within this title there are 33 volumes and over 1,000 parts. Part 261 is the Identification and Listing of Hazardous Waste. If you are inclined to read any part of this section I found Subpart C Characteristics of Hazardous Waste which includes 261.20 – 261.24 the most informative. Subpart D is interesting, but if you decide to take on Subpart D drink a lot of coffee first.
There are four factors that determine if a material is considered hazardous — ignitability, corrosivity, reactivity and toxicity. If you want to know the details of how each is determined, read Subpart C. Research commissioned by the Concrete Sawing and Drilling Association (CSDA), the International Grooving and Grinding Association (IGGA) and California Department of Transportation concluded that concrete slurry is only hazardous when its pH is at or above 12.5, making it corrosive. It should be noted that the settled particulate layer may have a pH over 12.5 and considered corrosive whereas the overlaying water may in fact be below 12.5 categorizing it as non-corrosive.
You might think the simple solution would be to treat the slurry with an acid based solution to convert it to a non-corrosive material — case closed. If it were only that easy!
There is also a set of federal laws called the United States Code (U.S.C.). In this set of laws is the Clean Water Act (CWA) passed by the U.S. Congress who gave the EPA the responsibility to enforce. Regulations relating to implementation of the CWA can be found in the U.S.C., Title 33, Chapter 26 and throughout parts 40 CFR. The goal of the CWA is to protect and maintain the physical and biological integrity of the nation’s waterways. If anything you discharge could find its ways into any waterway you must obtain a permit from The National Pollutant Discharge Elimination System (NPDES) program. Details can be found in the CWA Section 402.
If the slurry pH falls within the EPA’s safe limits and it has been determined in past studies as nonhazardous, what’s the big deal? Under the CWA sediment is considered a pollutant, total suspended solids (TSS). Sediment is considered the most common pollutant in rivers, streams and reservoirs and causes $16 billion in damage a year. Sediment clouds water preventing aquatic plants adequate sunlight to grow, clogs the gills of fish and reduces the depth of waterways.
Not to be the bearer of bad news, but there is one last issue to address. So far we have discussed no- polluted concrete. Not in all situations are we grinding, honing and polishing virgin concrete. Floors being processed may at one time been subjected to hazardous materials such as oils, glues, mastic, fertilizers, solvents, and the list goes on.
Management and disposal plan
Now that we have identified the potential hazards of slurry, let’s look at how we can properly manage and dispose of it.
- Have a best management practice plan in writing.
- In addition to EPA regulations, understand your state and local laws that may apply to disposal.
- Conduct an initial assessment to help determine whether the concrete contains potential pollutants and perform testing if you suspect pollutants.
- Determine how you will collect the slurry and store it. (For example, vacuums, auto scrubbers, 55-gallon drums, totes, lined dumpster, a pit in the ground, etc.).
- Conduct pH testing at scheduled intervals.
- Have a plan for accidental spills or leaks. (For example, the use of jute mesh, floc logs, absorbents such as socks, pads and solidifiers.)
- Dispose of within EPA, state and/or local regulations.