Contact your local SCS Office to ask our professionals for guidance in your jurisdiction.
Vapor intrusion is a regulatory hot button gaining traction on states’ radar nationwide. This is driven by a growing understanding of how vapors travel through the soil into structures, posing health risks to occupants, coupled with research showing volatile vapors can be problematic even at very low concentrations.
As in California, conservative assumptions by regulatory agencies call for careful due diligence during the assessment process. These salient concerns recently brought a real estate developer in Monrovia to seek a professional engineer.
The client plans to convert a commercial property to residential use. But before moving forward, it needs to assess potential environmental issues associated with the property. That’s where SCS comes in, drawing on its concrete knowledge base in geology and chemistry—and leveraging its grasp of regulatory requirements.
The work in Monrovia entails a detailed soil vapor assessment, looking for volatile organic compounds (VOCs); the discovery at this site came as little surprise to Julio Nuno, Senior Vice President, and Project Director, as these constituents are often found during evaluations of this kind.
Assessing for VOCs
In this case, the soil contained eight VOCs, some at non-compliant levels. The good news is, after an extensive, multi-step vetting process, Nuno and his team came up with a relatively inexpensive solution to tackle a potentially daunting problem.
“As part of the soil vapor assessment, we compare concentrations we find on-site to screening levels established by the Department of Toxic Substances Control. We often see levels in exceedance of regulatory thresholds, particularly in industrial areas with releases that can travel from groundwater to soil into the building through the slab,” Nuno says.
Most prominent at the Monrovia site were two chlorinated compounds that have been used as solvents in industrial applications: tetrachloroethylene, also called PCE, and trichloroethene, or TCE. PCE is commonly present in industrial settings and communities as drycleaners widely and routinely used the chemical for decades.
Nevertheless, the work begins even before confirming VOC levels and other specifics around these compounds. The first step is a Phase I Environmental Assessment looking to see if past use of the property or surrounding property may have left a significant environmental impact. The SCS team discovered the adjacent property had a release of VOCs they identified as a ‘recognized environmental condition,’ meaning it needs further evaluation using a Phase II to determine if vapors could migrate onto the client’s property.
During the Phase II Environmental Assessment –the collection of soil and soil vapor samples –the SCS team gets even more specific, determining what’s present, specific locations, what degree of contamination, and what these findings mean for redeveloping the property and its final use.
“We confirm subsurface concentrations and if they exceed state screening levels, and if the site represents a potential risk for future residential use. The information informs our possible solutions to mitigate any migration of certain VOCs into the building and the indoor air,” Nuno explains.
Redevelopment Goals – safety and cost containment
Safety comes first, but containing project costs is a priority, which comes down to knowing design options, how to piece components together with both function and economics in mind. At this site, achieving safety and controlling costs centered largely around looking at the mandatory infrastructure– a ventilation system for a planned underground parking garage to prevent accumulation of carbon monoxide and other vehicle exhaust emissions.
“We knew the underground parking would require a ventilation system. It makes sense to look at the parameters associated with that design to verify if it serves dual purposes to ventilate the garage and mitigate the potential for VOCs to enter the building,” Nuno says.
By studying air exchanges that would occur, the number of times replacing air-containing pollutants with cleaner air per hour, Nuno gets his answer. “We determined that a second, separate system would not be necessary for sufficient ventilation; the assessment enabled us to confirm vapors would not travel into the residential portion of the building.”
The client can save $50,000 to $75,000 in capital expenses upfront while achieving their safety goals and avoids ongoing operations and maintenance costs for added infrastructure.
An added layer of protection
Identifying the issues for site developers and their tenants, then plotting the best course of action to ensure safety and regulatory compliance takes experience and knowledge. SCS devises a soil monitoring plan, alerting developers of indications of potential contamination to the soil, of odor, or anything unusual that could suggest an environmentally adverse condition. The plan advises on how to respond should there be an unexpected condition adding a further protection layer.
“It’s essential that an engineer understand the applicable federal, state, and local standards for completing assessments, as well as understand regulatory stipulations. You must also know the variations in those stipulations to effectively design a sustainable plan,” Nuno says. “In Monrovia, we comply with the Department of Toxic Substances Control requirements, the requirements of the Los Angeles Regional Quality Control Board, and others. Each has specific stipulations for evaluating each contaminant. So, we stay on top of which rules apply to which location,” he says.
Nuno has submitted a draft report for review by his client and its legal counsel; he’ll meet with them to discuss findings and explain their meaning. SCS includes an executive summary, explaining in plain language what is salient; often, a backup report includes thousands of pages. “It’s a lot of complex information, so we work on the language,” Nuno says.
“It’s important to paint an accurate picture and use terms that all parties, whether the client, investors, or other stakeholders understand. These redevelopments are major projects with many due diligence considerations. We want to provide accurate findings and recommendations that the client and their advisors can digest to help them with their decision making.”
SCS Engineers Vice President Ashley Hutchens is now the Environmental Services Director for its Long Beach and Las Vegas operations. Besides managing her current projects and clients, Hutchens will manage the environmental professionals and technicians in each city. She is responsible for allocating resources for business development, project management, and coordinating activities with other SCS offices nationwide.
“Ashley’s proven capabilities solving environmental challenges for industries will serve our Long Beach and Las Vegas clients well,” said Julio Nuno, SCS Senior Vice President.
Hutchens has 18 years of experience in property evaluation and due diligence, site assessment, characterization, remediation; vapor intrusion assessment and mitigation; and hazardous waste management. She has led hundreds of projects, including all phases, from the development of cost estimates for site assessment, mitigation, and remediation, to groundwater monitoring and sampling, preparation and review of final reports, interfacing with regulatory agencies, and management of all aspects of projects, staff, and various subcontractors.
SCS Engineers’ environmental solutions directly result from our experience and dedication to solid waste management and other industries responsible for safeguarding the environment. For more information about SCS, please visit us at www.scsengineers.com, or contact .
The Remediation Technology (RemTEC) Virtual summit will take place March 9-11, 2021.
RemTEC will be much more than your typical video-based virtual conference. Their robust virtual platform will provide a seamless experience of educational sessions, networking opportunities, custom-built exhibitor booths, and much more.
The Conference Keynote will feature a panel discussion on “Lessons Learned and What’s Next for Site Remediation from Industry Titans.”
The conference will feature several Tracks:
The Los Angeles County Board of Supervisors designated Alpine Village in Torrance, a Historic Landmark. The parking lot is a former landfill, and in the early ’70s, SCS Engineers designed building protection/sub-floor ventilation systems for several on-site structures. Once completed, SCS entered into contracts to monitor, maintain, prepare, and submit regulatory reports that the firm still performs well to this day.
“As we celebrate our 50th Anniversary, Alpine Village is an example of one of SCS’s oldest and longest continuously running projects,” said President and CEO Jim Walsh. We’re proud that we provide valuable environmental services to businesses and communities.”
Dave Ross, Senior VP (retired), said, “This certainly underscores SCS’s longevity and sustained superior client service. I can recall the elation when we won the first LFG [landfill gas] monitoring job there…I completed one of the earliest rounds of [air] sampling on the roof of the main building.”
Learn more about SCS Engineers and the award-winning environmental services this employee-owned firm provides.
The Department of Toxic Substances Control (DTSC), State Water Resources Control Board, and San Francisco Bay Regional Water Quality Control Board have developed supplemental vapor intrusion guidance for conducting vapor intrusion evaluations in California. The Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion is available for review and public comment until 12:00 noon, April 30, 2020. Click here for available public meetings and comments.
According to the published Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion Executive Summary
Toxic vapors can move from contaminated groundwater and soil to indoor air. This process is called vapor intrusion. Vapors inside buildings can threaten human health. The science behind vapor intrusion has been evolving quickly. To protect the health of Californians, the DTSC and the California Water Boards drafted a supplement to the existing vapor intrusion guidance. This is important information to collect for environmental protection. This document is called the “Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion” (Draft Guidance). This Draft Guidance contains recommended improvements for vapor intrusion investigations and promotes consistency throughout the state. It also offers suggestions on the following topics:
The Draft Guidance is intended to be used with existing State guidance – DTSC 2011 Vapor Intrusion Guidance and San Francisco Bay Regional Water Board 2014 Interim Framework 1 – when there is a spill or disposal of vapor-forming chemicals. This guidance does not apply to any leaking petroleum underground storage tanks (USTs) since they are governed under the State Water Resources Control Board’s Low-Threat UST Case Closure Policy.
Four Steps to Evaluate Vapor Intrusion
The Draft Guidance describes four recommended steps to decide if there is vapor intrusion that could pose a risk to the health of people inside buildings. These actions are meant to protect public health and should be carried out under the oversight of the lead regulatory agency.
Step 1 – Decide which buildings should be tested first and how.
When there are several buildings, start with those that are occupied and closest to the contamination. If a building is directly above or very close to the spill, or if it is likely that the sewer could bring toxic vapors inside, skip Step 2 and go directly to Step 3.
Step 2 – Screen buildings from outside.
Measure vapor-forming chemicals underground at these locations:
Step 3 – Test indoor air.
Measure vapor-forming chemicals in indoor air, beneath the building’s foundation, and outdoor air at the same time:
Step 4 – Act to protect public health.
Toxic Vapors Can Travel Through Sewer Pipes
Vapor-forming chemicals can enter sewer pipes that run through contaminated soil or groundwater. Once inside a sewer, vapors can move through the pipes and escape through cracks or openings, under or inside a building. Some of the traditional ways to test for vapor intrusion could potentially miss vapor-forming chemicals moving through sewer pipes. This Draft Guidance recommends evaluating whether the sewer could bring toxic vapors inside.
Vapor Intrusion Attenuation Factors
Attenuation factors are used to estimate how much of the vapors underground or in groundwater end up in the indoor air. This Draft Guidance uses attenuation factors recommended by the U.S. Environmental Protection Agency. These were calculated from a large study of buildings at contaminated sites around the nation, including California.
California Vapor Intrusion Database
Data from sites evaluated using the process described in the Draft Guidance will be entered into a database that will be publicly available. The State Water Resources Control Board (State Water Board) added capabilities to the GeoTracker database including building-specific information for a cleanup case and the ability to differentiate Field Points for collecting samples. The State will analyze the information in the database and learn how to better protect the people of California from vapor intrusion.
Where to Find the Draft Guidance
Vapor intrusion (sometimes known as soil gas intrusion or soil vapor intrusion) is a potential environmental risk that can occur at a wide variety of properties, from former industrial facilities, shopping malls, and even residential properties. Knowing how to assess the risk and mitigate potential harm from soil vapor intrusion is critical to reducing health impacts and mitigating financial and other liability from potential exposures.
What is Vapor Intrusion?
Developers and the public understand that soil and water contamination can pose a health hazard, but vapor intrusion is an environmental health risk that can be overlooked. It is a hazard that can result from both heavy industrial operations and small “mom-and-pop” businesses so that it can be an issue both at industrial properties, suburban strip malls, and even residential developments.
Vapor intrusion is the migration of soil or water contamination from below structures into businesses or homes as a vapor. Common vapor intrusion contaminants from small businesses include benzene from gasoline and perchloroethylene (perc) from dry-cleaners, while large industrial facilities may have a wide range of industrial chemical contaminants. Less common vapor intrusion hazards are mercury, polychlorinated biphenyls, and pesticides.
Determining Whether Vapor Intrusion is an Issue
Environmental due diligence is key to determining whether vapor intrusion is a likely issue. An environmental site assessment (ESA) is critical in assessing the potential for vapor intrusion issues and the current state of vapor intrusion based on past site history. A Phase I ESA will review the current and historical use of the property and surrounding properties to determine where and when potential sources of contamination were present. Leaky underground gasoline storage tanks and poor chemical handling practices at dry cleaners lead to chemical contamination that can create vapor intrusion issues, so the “corner” gas station or the strip mall dry cleaner can be the source of vapor intrusion hazards.
Vapor intrusion can also come from groundwater plumes that originate outside the property boundary, so it is important that any assessment looks for potential contamination issues from nearby properties as well as on-site.
When the potential for a vapor intrusion issue exists, a Phase II ESA should be conducted to determine whether there is contamination, the extent and magnitude of the contamination, and whether the contamination poses a significant health risk. In the Phase II ESA, samples of soil and groundwater are collected from the property and analyzed for evidence of contamination.
If contamination is present, results are compared to screening levels established by regulatory agencies or a health risk assessment (HRA) can be prepared. Either of these strategies can potentially be used to demonstrate that health risks are not significant for the property’s current or future use or to determine the level of remediation necessary.
Dealing with Significant Soil Vapor Contamination
If soil vapor intrusion poses a significant health risk, there are ways to mitigate that risk. Mitigation can include removal of the contamination, active mitigation of the contamination source, and protection against indoor air exposure. The approaches are not mutually exclusive, and multiple risk reduction strategies may be used.
The most effective way of reducing soil vapor risk is to remove or treat the soil or water that is the source. This remediation is the most cost-effective for small sources of contamination and when that contamination can be easily accessed. It is often not feasible to remove the source when contamination originates offsite and moves onto the property in a groundwater plume. It may also be more cost-effective to mitigate risk through other means when the source of the vapor intrusion is extensive or difficult to remove.
In active mitigation, soil vapor intrusion is mitigating by reducing contamination at the source. Active systems can include soil vapor extraction, in which vapor is collected and removed; in situ treatment, which uses chemical reagents to transform the contamination into less toxic chemicals; and containment of the contamination source by some form of barrier. Under ideal conditions, these methods have the potential to be highly effective in reducing contamination but monitor treatment for effectiveness and to determine that the resulting contamination levels are acceptable.
It is also possible to mitigate indoor air exposure to soil vapor intrusion. Underground vents, membranes, and seals beneath the foundation and slab depressurization can reduce the flow of soil vapor into a building. This type of passive mitigation leaves the contamination source in place, which may limit future uses for the contaminated property, but it may be more cost-effective than active mitigation, especially in cases where contamination originates off the property. Regulatory agencies typically require that properties mitigating the movement of soil vapor into buildings monitor the ongoing mitigation on a continuous basis with sensors and alarms or periodic resampling.
What You Need to Know
Soil vapor intrusion is a potential environmental liability, but it is manageable. Environmental due diligence can significantly reduce unforeseen costs of vapor intrusion by identifying the issue for proactive management before development, which is always easier and more cost-effective than trying to address a problem after development. It is possible to mitigate health risk from soil vapor intrusion on developed sites. Developers should work with qualified environmental consultants to address vapor intrusion through each stage of the process to adequately minimize risk.
Did you know that vapor intrusion is an environmental issue impacting property development? The U.S. Environmental Protection Agency (USEPA) and related state agencies continue to develop and refine vapor intrusion procedures. How and when you address vapor intrusion can have a significant impact on your bottom line. These tips will help minimize the risk:
Invest in Early, Accurate Detection
Vapor intrusion happens when volatile chemicals from soil or groundwater contamination migrate into nearby buildings. These vapors can come from places like dry cleaners, gas stations, or industrial facilities, and like radon can affect people who live or work in impacted buildings. Prioritize due diligence because waiting can drive up costs. In one recent case in the news, vapor mitigation systems had to be installed in more than 70 homes near a corporation in Wisconsin to mitigate vapor intrusion issues. Even a small error in the sampling technique can dramatically affect the results. So early, accurate detection is key before you buy or build.
Get to Know Your Options
Once assessed, developers have multiple options for saving time and money. For example, it is far more cost effective to incorporate vapor barriers or HVAC controls into building construction rather than to fix the problem after the fact.
Find a Partner Who Knows the Rules
In 2017, some state agencies will update their vapor intrusion guidance documents to include more details on requirements for remediation and redevelopment sites. These regulations are actively evolving, so it’s important to work with someone who knows the changes to regulatory requirements and how they apply to your specific property.
If you are buying or selling a property, it’s time to think about vapor intrusion. Even if a property doesn’t have a history of contamination, it may still be affected if a nearby property has soil or groundwater contamination.
“Vapor Encroachment and Intrusion, What are the real estate risks?”
Journal of Property Management
Is Vapor Intrusion Threatening Your Site?
Public Works Magazine
Contact your local SCS Office to ask our professionals for guidance in your jurisdiction.