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Vapor Intrusion and Sub-Slab Depressurization Systems

vapor intrusion & migration diagramVapor intrusion (VI) of radon gas has been recognized as a potential cancer risk for more than 30 years. Radium, a breakdown product of uranium, produces the short-lived daughter product Radon, which presents itself as a gas that can migrate into living space of overlying buildings. More recently, volatile organic compounds (VOC’s), such as trichloroethylene (TCE), Tetrachloroethylene (PCE), and constituents associated with gasoline, such as benzene has been identified as compounds likely to migrate into indoor air as well.

It’s generally thought that vapor intrusion occurs from the subsurface to the basements, crawl spaces and first floor slabs on grade, but also through adjoined attics and walls in commercial\retail spaces. Some buildings are better insulated and sealed than others and heating, ventilation & air conditioning (HVAC) systems vary in vacuum and flow. Hence, the HVAC system running in ‘building A’ can draw odors in from adjoined ‘building B’. I have personally experienced cigarette smoke and bathroom odors (something which isn’t so funny if you are on the receiving end) being drawn into my commercial space from the industrial condo next door.

So What’s Being Done about Vapor Intrusion?

The ASTM vapor encroachment screening standard (E 2600-10) was published in 2010 to provide guidance to environmental professionals performing Phase 1 assessments on determining when a vapor encroachment condition (VEC) exists. Two VI guidance documents were issue for external review by EPA in April, 2013. Closer to home, the NCDENR-DWM released a VI guidance document in April 2014 on the DWM home page which was intended to emphasize the potential impact of VI on due diligence in property transactions and allocation of responsibility among the parties for VI issues.

Since early 2013, a number of State agencies and professional associations have developed guidance documents and short courses to educate professionals and the public on issues associated with vapor intrusion.

In the past six months we have had a huge increase in orders for custom sub-slab depressurization systems with control panels for vapor mitigation. These systems typically are designed to capture and remove migrating vapors before they enter indoor air. Most of these systems have been designed to remedy problems with existing commercial and residential structures. Recently, we have noticed more designs for systems being installed with new structures, which is typically much easier than retrofitting an existing structure. The amount of controls and sensors associated with the system is typically a reflection of the danger associated with the migrating vapors. Some larger systems incorporate remote telemetry to monitor the operation of the vapor mitigation system and to make sure any malfunctions are repaired quickly.

I look forward to building more of these custom systems in the near future!

Brian E Chew Sr. P.G.
Principal Hydrogeologist

For more information please email: remediation@enviroequipment.com.


Planting the Seeds of Environmental Stewardship

loblolly-pine-tree-farmBack in the late 1970’s, when I was still a student at Indiana University in Bloomington, I was notified that my Great Aunt Lillian Graves had passed away. This was a sad time for me as I was very fond of her. She had lived in New York City during the summer and in Greenwood SC during the winter. She had a very young soul for an elderly person, and was great fun to be around and talk to. I remember when my father told me about her death, and I was very surprised when he also informed me that she had left me something in her will. That something was a loblolly pine tree farm in Georgia that had been in our family for generations. Aunt Lil had leased the land to Georgia Kraft, a timber company, and the land had a healthy tract of trees growing at the time the land became mine. What I didn’t know was that Georgia Kraft was going to clear cut the property and leave 118.75 acres of stumps and brush piles, but that was exactly what happened.

About a year after graduating from IU with a geology degree I married my college sweetheart. It was 1980, the country was in a deep economic recession, and interest rates were in double digits. We began our marriage with one old car, some used furniture donated by my family, and little else. We had no money in the bank, few job offers that paid more than minimum wage, but we did have our 118.75 acres of stumps and brush piles (wind rows).

It wasn’t long before a forester called and inquired on whether we were going to sell the property or plant trees. Selling it did cross our minds. Most 23 year olds would have sold the property and bought a nice car. We considered everything and decided to carry on the family tradition of being tree farmers and investing for the future. We called the forester back and he told us of several programs through the US Department of Agriculture that would provide some monetary assistance for planting. The rest of the cost of planting would be up to us. Somehow over the next 5 years, with loans and the assistance of the USDA, we managed to become tree farmers by planting parcels of the land in stages.

Thirty plus years later we still have the farm and the trees have grown tall. They are now saw timber size. We managed to dodge forest fires, droughts, and pine beetles attacks, but not poor economies and lousy governments. In the last several decades Canada has allowed timber companies to cut timber on their federal lands basically for free and dump the timber on the US market. This has resulted in many timber companies and mills closing their doors in the south. It is still not a good time to sell timber. While we wait, we do take some comfort in knowing that we are doing our share to help clean the air in Georgia. No one knew anything about carbon footprints back in the early 1980’s when we planted our tree farm, but it is a real concern now.

If the housing industry recovers, and US saw timber prices rise, we may finally realize a return on our investment. In the meantime, we love being tree farmers, helping the environment, and carrying on our family tradition. I know Aunt Lil would be proud.



"After 27 years, I was honored to finally meet Charles R. Livingston face to face on August 28th, 2014."

After 27 years, I was honored to finally meet Charles R. Livingston face-to-face on August 28th, 2014.

I first heard of Charles R. Livingston – a man who at the time had 35+ years experience in geology, geotechnical and environmental projects throughout the U.S. – through the Association of Environmental & Engineering Geologists (AEG) in 1987. I was a 30 year old Project Hydrogeologist and Environmental Department Manager for Law Engineering Inc. (LAW) in Greenville, South Carolina.

I was getting ready to go before the Principal Board within LAW to become a Principal Hydrogeologist, one of only three in the company of about 5000 employees.  To be designated Principal you had to own company stock, have liability\loss prevention training including contract review, 7 plus years of experience in your field, professional registration and pass a grueling (hazing) interrogation by other experts in the field (internal and external) at the corporate office. Many did not make it through the Principal Board review and typically quit or did not try again if they did not pass.

In the summer of that year, my wife Denise received a call on a Sunday afternoon from a fellow AEG member (Charles R. Livingston) whose daughter was headed home from College and had car trouble.  His daughter’s car was at a gas station in a not-so-good part of town near Spartanburg, South Carolina.  It was getting late in the day and he was very worried for his daughters safety.  With repair shops closed because it was Sunday in the Bible Belt, and not knowing anyone in the area, and being four hours away himself, Charles decided to look for AEG members in the area and found my name in the AEG directory as I lived about 30 miles from Spartanburg.

When Charles called my house Denise answered the phone and told him that I was at the store, but would return shortly.  He just wanted to know if we knew of any auto repair shops open on a Sunday evening.  She told him no, but not to worry.  I was a pretty good mechanic and she knew I wouldn’t mind looking at his daughter’s car and\or help her get to a safe area until the repair shops opened on Monday morning.  So when I returned, off I went to Spartanburg with my car loaded with tools.  I found his daughter and was able to repair her car and get her on her way.  She called her Dad and let him know she was on her way home. I was a road warrior in those days, so I left for a job site that Sunday night and didn’t give it any more thought.

About a week later Denise told me that a beautiful flower arrangement arrived at our house with a card from Charles thanking us for our assistance.  I thought that was a nice gesture on his part but little did I know what he was really going to do.

A few weeks later the annual AEG (national) meeting was held in Atlanta, Georgia and it turned out Charles was an officer in the association and addressed the large crowd.  I was not in attendance but several high ranking officers in LAW were there.  Charles proceeded to talk about the “brotherhood of the AEG” and included the above story as an example of this brotherhood.  He also said that I was a great example of the caliber of the professionals at LAW.

I was not aware of what Charles had done until several weeks later when I was at the corporate office for my Principal “hazing”.  I was a nervous wreck!  My testing/review board consisted of internal experts in my field, an attorney, and a Georgia Tech Professor of Engineering Hydrology.  Also on the board was the CEO of LAW who had happened to hear what Charles said at the AEG meeting.  I was very surprised when the CEO introduced me to the board by standing behind my chair with his hands squeezing my shoulders as he told the story of how I had helped Charles Livingston’s daughter.  He went on to enthusiastically retell the positive things Charles had said about the professionals at LAW.

The board went on to grill me for hours over many different topics, but I was much more relaxed and clearheaded following that glowing introduction.

Needless to say, after all that I became a believer in karma and, yes, I passed my Principal Board Review.

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Charles R. Livingston was the first section chair of the Southeastern Section of the AEG in 1972. He has 35+ years experience in performing and managing engineering geology, geotechnical, and environmental projects throughout the United States, Canada and the Bahamas. His work includes geologic/geotechnical investigations for civil projects, material investigations for construction aggregate, investigations for coal and industrial minerals, geologic investigations for nuclear power plants, geologic investigations for hydroelectric facilities (i.e. dams, tunnels, power plants and pipelines), safety evaluation inspections for major dams throughout the western United States, offshore investigations, solid waste studies, contaminant delineation, remediation design, supervising remediation construction projects, and expert witness testimony in court cases involving geologic matters. Charles is retired and lives with his wife in Atlanta, Ga.

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