Vapor Intrusion Assessments
What is Vapor Intrusion?
Vapor intrusion is a way that contamination in soil or groundwater can get into the indoor air. Contaminants that are spilled onto the ground or leak from underground storage tanks can seep down through the soil and dissolve into the groundwater. Certain contaminants can evaporate from the groundwater into air pockets in the soil and travel upwards. In undeveloped areas, the contaminants disperse into the air. However, in developed areas, vapors can enter buildings and impact indoor air quality. This movement of contaminants into a building is called vapor intrusion.How do vapors get into buildings?
When contaminated vapors are present directly next to or underneath the foundation of a building, vapor intrusion is possible. Warm air rising in the building can draw vapors through cracks, holes for utilities, or other openings in the foundation. This is often more likely to occur in the winter months when the frost layer, operation of furnaces, and closed windows increase the potential for vapor intrusion. Vapors can also travel through the permeable gravel used to backfill utility line installations, and be drawn into nearby buildings.
Source: MassDEP Policy #WSC-16-435
What contaminants might be entering my home?
Only certain contaminants are a concern. Metals like lead or chromium do not cause indoor air vapor problems because they do not evaporate or volatilize. Volatile organic compounds (VOCs) are a group of contaminants that can easily become vapors. VOCs are found in petroleum products such as gasoline or fuel oil and solvents used for dry cleaning and industrial uses.Are there other sources of indoor air contamination?
Yes. VOCs are found in many household products including paints, paint strippers, thinners, glues, cigarette smoke, aerosol sprays, mothballs, air fresheners, new carpeting or furniture, fuels, and recently dry cleaned clothes. These products can be a source of VOCs found in indoor air. MassDEP does not regulate VOCs in indoor air from household products.Why is vapor intrusion a concern?
Exposure to VOCs can cause an increased risk of adverse health effects. Whether or not a person experiences any health effects depends on several factors, including the amount and length of exposure, the toxicity of the chemical and the individual’s sensitivity to the chemical. When the vapor intrusion is the result of environmental contamination, MassDEP requires that steps be taken to eliminate the exposure as much as possible.What should I do?
Property owners, developers, and investors should take vapor intrusion very seriously. They should include Vapor Encroachment Screenings and/or Vapor Intrusion Testing in their due diligence activities. If tests indicate that chemicals are intruding into your home or commercial structure, there are several actions you could take. You might seal any cracks in your walls or foundation. Or you could have a mitigation and/or remediation system installed. CSE has certified environmental consultants who conduct Vapor Encroachment Studies according to the guidance of the ASTM E2600-10 ‘Standard Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions‘. A Vapor Encroachments Study is a method for evaluating the potential for a vapor intrusion condition. If the Vapor Encroachment Study determines that a Vapor Intrusion Condition is likely, a Vapor Intrusion Study may be performed. The preferred method for performing a Vapor Intrusion Study involves the collection of soil vapor samples directly adjacent to or beneath the existing structure or the area of a proposed structure. Soil vapor samples collected are compared to prevailing soil vapor screening levels established by the MassDEP, when available. If soil vapor concentrations exceed established screening levels, then a Human Health Risk Assessment may be necessary to determine site specific risks based on many factors including building characteristics. If the Human Health Risk Assessment finds an elevated risk to human health exists, indoor air sampling, mitigation, or remediation may be necessary.CSE Services
CSE provides full scale vapor intrusion assessments (VIA) to address vapor encroachment conditions (VECs) identified during Phase I ESAs or during response actions at nearby contaminated sites. Initially, CSE will collect sub-slab soil gas samples to determine if vapor intrusion is likely occurring at your property, and confirm with indoor air quality tests. The following sections describe a typical scope of work.Installing Vapor Pins
CSE will utilize a hammer drill and a 5/8-inch diameter masonry drill bit to advance several sub-slab soil gas probes through the concrete slab of the Property building and install a Vapor Pin® (VP) system in each. The preliminary screening event will consist of connecting each VP to a portable photoionization detector (PID) and recording the Total Organic Vapors (TOVs) to obtain more information about the sub-slab vapors and the extent of potential impacts to the Property building.
Sub-slab Soil Gas Testing
The VP locations with the most elevated TOVs will be selected for further analysis of air toxins in soil gas by a Massachusetts-certified analytical testing laboratory using USEPA Method TO-15 (VOCs in Air) or similar such as MassDEP Air Petroleum Hydrocarbons (APH). The sub-slab soil gas samples will be collected using a six-liter passivated SUMMA canister and a 15-minute regulator. The approach and methodology used to collect the samples will be consistent with the Massachusetts Department of Environmental Protection (MassDEP) Vapor Intrusion Guidance (WSC#-16-435, dated October 14, 2016).
Indoor Air Quality Testing
CSE will deploy air canisters in areas of concern as determined by the sub-slab soil gas testing to evaluate the vapor intrusion migration pathway. Air canisters are collected over 8 hours for commercial businesses or 24 hours for residential occupants.