The risk of vapor migration through the subsurface from contaminated soils and groundwater has always been a part of risk assessment completed by environmental professionals. However, during the past few years the risk of vapor intrusion has become a significant concern for many who are evaluating the environmental risk associated with a property. Point to Point Environmental understands the differences between the terms and can assist with performing the risk assessment associated with quantifying the risk for vapor migration, and if a risk is present we can perform soil gas investigations and evaluate the risk for vapor intrusion into a structure.
When soil and groundwater contaminants have been identified as a result of environmental impact, there may be a risk for soil gasses to migrate from the impacted areas through the subsurface. The potential for soil gasses to migrate are a function of the contaminants of concern and the soil types. Soil and groundwater contaminated by volatile organic compounds (VOCs) pose the greatest risk for vapor migration. VOCs, semi-volatile organic compounds, gases generated as a by-product of organic matter decomposition (methane), and other contaminants of concern may all produce vapors that have the potential to migrate from the impacted soil and groundwater through the subsurface strata. Migration of these soil gasses is not by itself a risk. However, when these vapors migrate towards the surface where they may enter into a subsurface structure (basement, parking deck, utility trench) or even through a building foundation or slab and into an overlying building, this occurrence can result in vapor intrusion.
Vapor intrusion is the documented phenomena where a source of environmental contaminants in the subsurface soil and/or groundwater release gasses that migrate through a subsurface pathway and enter into a man-man structure where they become an exposure risk to human health and the environment. Environmental consultants have been evaluating these risks for some time as the risk for vapor migration has always been a part of the Phase I Environmental Site Assessment (ESA) standard. However, a full vapor migration assessment is more than what is required for the majority of properties, and a Phase I ESA should not include more than a discussion of the potential for vapor migration within a subsection of the report. When an environmental scientist completes a vapor migration assessment and concludes that there is a risk, a soil vapor investigation should be completed to insure that there is no risk for vapor intrusion.
There are currently many states that have adopted new vapor migration and vapor intrusion investigation regulations or are in the process of examining the risks to citizens in their state. However, there are states that have decided not to adopt any sweeping new regulations, and have chosen to address these vapor intrusion occurrences on a case by cases basis. Even where there is not an environmental regulation governing vapor intrusion investigations, this has become a significant issue for lending institutions, attorneys, and concerned residents.
An experienced environmental professional can evaluate the potential threat of vapor migration and vapor intrusion at a specified property. The characteristics of the underlying soil, the contaminants of concern, and the depth to the impacted soil/groundwater are the most important factors when assessing the potential for a vapor migration pathway to be present. In a variety of circumstances, the presence of soil and groundwater contamination beneath a site does not necessarily pose a risk for vapor migration. If an environmental scientist determines that there is a risk for hazardous vapors to migrate within the subsurface soils and may pose a risk for vapor intrusion, a soil-gas investigation can be completed to characterize and delineate the extents of the soil vapors that are present. This is completed by installing soil test borings in areas where soil vapors may be suspected and collecting samples of the subsurface gasses. Installation and sampling of these soil test borings must be completed based on site specific characteristics and in accordance with the applicable state regulatory framework or industry best practices. Point to Point Environmental has experience collecting samples of soil soil gases for laboratory analysis, and also employs the latest in-situ quantitative screening technologies including membrane interface probe (MIP) and light-induced fluoresce (LIF).
If a soil gas evaluation reveals the presence of soil vapor contamination, the extents of the soil gases should be delineated and an evaluation should be completed directly adjacent to man-made subsurface structures and/or above ground buildings. If there is indeed a risk of vapor intrusion into a structure, additional (and more intrusive) investigation may be completed including the collection of soil and vapor samples beneath a building slab or foundation, or even from inside the structure itself.
Contaminants in vapor phase that enter into an underground structure such as a utility trench may be an explosion risk. The risk of environmental contaminants entering into a structure can be a risk to indoor air quality and exposure to human health. An actual risk to either a subsurface structure or indoor air quality will require immediate corrective action to be completed. It is therefore key to have an experienced environmental scientist from Point to Point Environmental advising you on the risks associated with environmental contaminants. Our experience conducting soil gas investigations can identify the potential risks and design an investigative plan customized for your situation. Please contact Point to Point Environmental at 678-565-4435 to discuss any questions or concerns you may have regarding soil vapor migration and intrusion.