Remediation Techniques: Then and Now
Looking 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 paid for by 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 seems to be 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) will. 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.