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Modern day remediation techniques for tainted soil under gas stationLooking back over the last three decades of remediation projects, I’ve noticed a very interesting trend.  Despite advances in technology and equipment, a good majority of the techniques we were using in the early 1980s are still in use today, only with less disruption to the property.

One big difference between then and now is that in many cases the cost to remediate a contaminated site was much higher in the 1980s than it is today.  Obviously, some of the cost differential has to do with competition and funding sources as back in the early ’80s, I remember both North Carolina and South Carolina having only a partial page listing under ‘Environmental Consultants’ in the Yellow Pages.  What are the Yellow Pages you ask?  Well, let’s not go into that right now.

Differences in Remediation Funding
These days, most US states have Trust Funds which are funded by underground storage tank (UST) fees and taxes paid at the  gas pump. In addition, some states even have special Trust Funds for dry cleaners.  While most industrial sites are still funded by either the responsible party (RP) – if one can be found – or by insurance, in the ’80s most of this work was paid for entirely by RP’s or insurance.  Interestingly, the few States that still operate without Trust Funds have the fewest sites left to be remediated. In my experience, Trust Funds collected for a specific purpose and “managed” by government agencies are a recipe for disaster. But enough about that.

Below, are listed the technologies I am referring to and what they have morphed into in the last three decades. Although I am using a typical UST site as an example, the same holds true for industrial and Superfund sites as well.  The example site has free product present and soil\groundwater impact.

  • Remediation Techniques: 1980s
    The tanks and lines were excavated along with source soils.  The soils were either land-filled, land-farmed, aerated in soil piles (if space was available), or made into bricks.  After the assessment, recovery wells were installed along with a pump & treat system.  The fuel and impacted water was pumped from the wells to a system that included bag filters, an oil water separator, a product storage tank, an air stripper and granular activated carbon (GAC).  In some States, the exhaust from the air stripper had to be treated by activated carbon or thermal\catalytic oxidation.  The activated carbon was land-filled or regenerated.  On larger sites the water may have been treated by ultraviolet light or a GAC fluidized bed reactor (FBR) or a combination of all of the above. 
  • Remediation Techniques: 2015
    Due to the fact that most UST systems have been replaced by upgraded double wall tanks and feed lines made of coated steel or fiberglass, the systems are typically repaired and very little soil is removed (unless it is a business closure).  The product removal is performed by dual phase extraction (DPE) or product eating injectates.  The above ground soil aeration or biological treatment has been replaced by in-place soil vapor extraction\bioremediation. The above ground air stripping has been replaced by in-place air sparging or injection of compounds that release oxygen or ozone.  And last but not least, the above ground GAC or GAC FBR has been replaced (very recently) by the injection of carbon based injectate (CBI).  Typically, combinations of remediation technologies are used to clean the site more quickly.

As you can see from the examples above, the trend has been to take the technologies used above ground in the 1980s and use them in-situ today.  Another fact I found disturbing, is that some of the sites put out for bid recently were initially reported in the mid 1990’s.  Technology has allowed us to remediate sites faster, but the Government has not changed a bit.

Brian E Chew Sr. P.G.
Principal Hydrogeologist



EPA's 2015 Vapor Intrusion Draft RevisionsAfter a very long wait, it’s finally here. Thirteen years in the making and spanning multiple Presidential administrations, it’s finally being released to the public.

I bet you think I’m talking about the new Star Wars movie, right? Wrong, as it’s only been 10 years since the last Star Wars movie was released. Rather, I’m talking about the Oswer Technical Guide For Assessing And Mitigating The Vapor Intrusion Pathway From Subsurface Vapor Sources To Indoor Air  and Technical Guide For Addressing Petroleum Vapor Intrusion At Leaking Underground Storage Tank Sites.

Since our Federal government was so prompt in getting us a final document after releasing the Draft in 2002, many State agencies developed and adopted their own rules.  Over the next several years the State and Federal agencies will (maybe) get on the same page on Vapor Intrusion (VI).

So what is the big deal?  From what I can tell, one of the biggest differences between the 2002 and 2015 documents is the guidance document specific to the UST releases.  UST releases are responsible for the bulk of the VI issues found in the USA as the 2002 Draft document was geared more toward Superfund sites.  The 123 page 2015 Draft document is filled with useful flow charts and diagrams, but is mostly a page of text followed by two pages of references.

Lucky for those of us in the environmental remediation business, technology has not been standing still for the last 13 years.  If you are interested in finding out about the latest monitoring, assessment, and mitigation devices for VI, please contact us at info@enviroequipment.com.

Brian E Chew Sr P.G.
Principal Hydrogeologist


What VOCs Are and How They Affect You

wwhere do VOCs come fromThe next time you’re out shopping, you may notice that some products have the words “low VOCs” on their label. An increasing amount of manufacturers are using this label because of the growing awareness of the harm that VOCs (i.e. volatile organic compounds) pose to human health.

VOCs Defined
Unfortunately, few people have ever heard of VOCs let alone know what they are. So, the first step in understanding what VOCs are and how they affect us is to break down the term itself. If you string each definition of the term together it becomes a “…substance that can easily evaporate and spread through the air, contains carbon in its molecular formula, and consists of two or more separate elements.” It should also be noted here that there are many different ways of classifying and categorizing VOCs, but that discussion is outside the scope of this article.

Now that you have a brief idea of what a VOC is, the next step is to understand how widespread VOCs are.  Many different consumer products contribute to indoor VOCs that people are exposed to, such as personal care products (nail polish, perfumes, hair spray), paints, fuels, cleaning products, and much more.  An example of a specific VOC would be Acetone (Chemical Formula: C3H6O) found in nail polish remover.  If you’ve used or been around nail polish remover before, you know how quickly the smell travels throughout a room.

VOC emissions from motor vehicles, factories, and manufacturing facilities are a large source of VOC emissions outdoors in the environment.  VOCs are also produced from naturally occurring sources, such as vegetation, bacteria, and fossil fuel deposits.

Why We Should Care About VOCs
At this point, you’re probably wondering why we care about VOCs?  The main concern for VOCs indoors are the adverse health effects that some of them have on people and animals.  VOCs from car emissions and other processes contribute to outdoor pollutants such as smog.  Outdoor VOC pollution is an important topic, however, this article focuses mainly on indoor air quality.

VOCs can have health effects such as irritation of the nose, throat, and eyes, headaches, nausea, dizziness, allergic skin reactions, damage to internal organs such as the liver and kidneys, cancer, and more.  One important thing to know is that the health effects vary greatly depending on the VOCs that you are exposed to, the length of exposure time, and the concentration of the VOCs.  Some VOCs are highly toxic and do not take long to have adverse health effects, some VOCs have no known adverse health effects at all.  OSHA and other safety administrations have developed occupational exposure limits for toxic VOCs that workers are not to exceed for safety reasons.  The exposure limits can vary from one organization to another.  Below are some examples of these types of exposure limits:

  • Time Weighted Average (TWA): The concentration in air of a substance that shall not be exceeded in an 8-hour work shift or a 40-hour work week. 
  • Short Term Exposure Limit (STEL): The time-weighted average exposure that should not be exceeded for any 15-minute period. 
  • Ceiling Limit (C): The exposure limit that shall at no time be exceeded.

This is why products containing potentially toxic VOCs recommend that you use them in a well ventilated area.  In an enclosed room, the more fresh air you add the less concentrated the VOCs become.

Measuring VOCs
So how do you measure VOCs?  Unfortunately, that is a complicated question.  This quote from the EPA website on VOCs provides useful information:

“All available measurement methods are selective in what they can measure and quantify accurately, and none are capable of measuring all VOCs that are present… The range of measurement methods and analytical instruments is large and will determine the sensitivity of the measurements as well as their selectivity or biases.”

For identifying the presence of VOCs, organic vapor analyzers such as photoionization detectors (PIDs), including the MiniRAE 3000 or ppbRAE 3000, can be used to measure Total Volatile Organic Compounds.  An important note about these meters is that they do not tell you the exact VOCs that you are measuring, just that VOCs are present.  Some VOCs require stronger lamps to be installed for detection, and others cannot be detected by PIDs (see our article on PID Lamp Selection).  If you know that only one VOC is present or if you know the exact mixture percentages of compounds where you are monitoring, then you can multiply the reading you get by a correction factor to get a more accurate reading for the compound(s). See RAE Systems Tech Note 106 for more details.

Other methods include colorimetric gas tubes that offer quick on-the-spot measurements of many different gases and vapors.  These tubes react with the compound in question and change color based on the concentration present.  The color can be compared to a color scale to get a value.

The most accurate method of testing VOCs involves collecting a sample using a SUMMA canister or air sampling pump with a tedlar bag and having it analyzed in a laboratory.  This method is best left to consultants who are trained professionals and know the correct sampling methodology.

Questions or Comments?
I hope this article answers some common questions that it may have about VOCs.  If you have any questions or comments, we would love to hear from you!  If you like to know more about VOCs, I recommend reading the following sources: