01 Feb The Phase II Investigation – Confirming the Presence or Absence of Contamination
As we saw in the previous article, the Phase I Site Assessment identified Areas of Concern (AOCs) on the subject property through a review of available historical and environmental information, and a physical inspection of the property. AOCs are areas where Constituents of Concern (COC) were potentially released to the environment. COCs are substances or components, breakdown products, or derivatives of a substance potentially released to the environment. More simply, COCs are chemicals potentially released to the environment. The Phase I also identified potential receptors (human beings, animals, or environments that may be adversely affected by contamination) and potential pathways by which COCs could migrate from the Areas of Concern to the receptors. I have italicized the word “potential” in an effort to drive home the fact that the Phase I only tells us where environmental problems are likely to be found. Confirmation of the presence or absence of COCs requires the appropriate collection and laboratory analysis of soil and water samples. Such sampling and analysis are conducted as part of the Phase II Environmental Site Investigation.
I threw a lot at you in that first paragraph, but the most important thing to understand is that the goal of a Phase II Environmental Site Investigation is to confirm the presence or absence of contamination. In concept, this is simple. We collect soil and groundwater samples and send them to a laboratory for analysis. When we get the laboratory results back, either contaminants are present or they are not. Like I said – simple. Ah, but when was anything ever simple. In reality, the planning and execution of a Phase II Investigation can be tricky. It turns out that proving the absence of contamination (i.e. proving the site is “clean”) is quite difficult. A clean sample may not necessarily mean a clean site. Let’s see why.
The sample may have been analyzed for the wrong contaminants. On TV, lab guys throw sample into a machine and, viola! they get a printout of everything that is in the sample. In real life, it doesn’t work that way. Different types of chemicals require different analytical techniques. For example, Volatile Organic Compounds (stinky chemicals such as the components of gasoline, chemicals used in dry cleaning, etc.) require one type of analysis while metals require a totally different technique. Semi-Volatile Organic Compounds (oils, tar, grease), pesticides, and other types of compounds each also require different analyses. Now we could analyze for everything, but that would be prohibitively expensive (hundreds of dollars per sample or more). If you recall, the Phase I identified “Constituents of Concern” based on the operations conducted at the site. This helps us narrow down the analyses that must be conducted IF the Phase I was conducted properly.
We may have collected our sample in the wrong place (or wrong depth). Let’s start simple. Suppose chemical waste was spilled on the east side of a property, but we collect a soil sample from the west side. Naturally, our sample will come up clean even though contamination is present on-site. Okay, I know – obvious. Let’s look at another example. Suppose we collect a soil sample from under a leaking drum. The most likely place to find contamination is in shallow soils (say, from a depth of 0 to 1 feet). So if we collect a soil sample from a depth of, say, 10 feet, we may miss the contamination completely. But wait; what if the ground surface is paved and sloped? Some contaminants do not penetrate asphalt easily, especially if the ground slopes. These may migrate downhill over the paved surface and end up in soils off the pavement. I should point out that many contaminants, such as VOCs, can pass through asphalt quite readily.
We sampled in the right general area, but we just missed the contamination. Suppose we know that drums were stored somewhere in a 30-foot by 30-foot area. There may be several 3-foot diameter contaminated areas, where individual drums stood. But sometimes there is no visible indication of these contaminated areas, so our sample might fall between them. In this case, since the precise location of the releases is not known, several samples may be needed to improve the chance of hitting one of the small contaminated areas. I should mention that the Connecticut Department of Environmental Protection (CTDEP) generally requires more than one or two samples to demonstrate that an AOC is clean.
There is one last point to be made. Screening methods can sometimes be used to help identify likely contaminated areas. These methods include Photoionization Detectors (PIDs) which measure total VOCs in real time, assay kits (which provide field data but is less sensitive that laboratory analysis), stressed vegetation, Ground Penetrating Radar (which can identify underground tanks and piping), visual evidence of contamination (staining, discoloration), and odor just to name a few.