WoldWide Drilling Resource

A One-Two Punch in Cleaning Contamination Adapted from Information by the U.S. Environmental Protection Agency Removing contaminants belowground is challenging. However, when you combine soil vapor extraction (SVE) and air sparging, you have a safe and effective way to help clean contamination. So, how does it work? Let’s start by taking a look at the processes and how they work together. SVE works by extracting vapors from the soil above the water table using a vacuum to suck the vapors out. Air sparging involves pumping air underground to help extract vapors from groundwater and the wet soil beneath the water table. When used together, the addition of air makes the chemicals evaporate quicker, which makes the SVE process work even better. These methods are typically used in areas contaminated with chem- icals that evaporate easily, such as those in solvents and gasoline; chem- icals known as volatile organic compounds, or VOCs. Let ’s dive a l i t t le bi t deeper into the process beginning wi th extract ion. SVE involves drilling extraction wells into the con- taminated soil to a depth above the water table, which must be deeper than three feet below the surface. Blowers or vacuum pumps, which are used to pull out the air and vapors, is then attached to the wells. To prevent vapors from escaping into the air aboveground, the treatment area may be cov- ered with a tarp, or even paved. This also prevents the vacuum from pulling in the air from above- ground, which would reduce the efficiency of the cleanup. Air sparging tackles the problem by drilling injection wells into the groundwater-soaked soil below the water table. Using an air compressor at the surface, air is pumped underground through the wells. As air bubbles through the groundwater, it carries contaminant vapors into the soil above the water table. The mixture of air and vapors is then pulled out of the ground using SVE. The next step is treating the extracted air and vapors, more commonly called off-gasses, and there are a few different methods. First, the off-gases are piped from the extraction wells to an air-water separator to remove moisture. Then, the vapors are separated from the air, usually by pumping them through containers of activated carbon. The chemicals are captured by the carbon while clean air exits to the atmosphere. Another method, cal led biofi ltration, adds tiny microbes (bacteria) to break the vapors down into gases, like carbon dioxide and water vapor. The final way to treat the off-gasses is to use high heat to destroy the vapors. When properly designed and oper- ated, SVE and air sparging is safe for workers and the community. The vapors are completely contained from extrac- tion to treatment so they can’t be acci- dentally inhaled by anyone. Only clean air meeting air qual ity standards is released into the atmosphere. SVE and air sparging are efficient ways to remove VOCs above and below the water table. The methods can help clean contamination under buildings while causing little disruption to nearby activities when in full operation. It is being used, or has been selected for use, at Superfund sites around the country. 46 JULY 2019 WorldWide Drilling Resource ® Open the Doorway to all the Event Photos during Shallow Exploration Drillers Clinic 2019. To see all the photos from this event, go to www.worldwidedrillingresource.com Feel free to download at will and print the photo(s) of your choice. Compliments of WorldWide Drilling Resource ® . Photos are copyrighted and released for personal use only - no commercial use permitted. Pipes carry vapors from the underground SVE extraction well to treatment. ENV