News Vapor intrusion mitigation brings contaminated properties back to life safely

When vapor intrusion mitigation services are necessary

As North Carolina continues to grow and thrive, property development plays a major role. Sometimes a property’s previous use can create stumbling blocks to development, particularly if a site has been contaminated. At many sites, this contamination may be near or under an existing or planned building. It may also cause vapor intrusion concerns. Vapor intrusion can require remediation or mitigation to enable property development.

Learn about Vapor Intrusion Risks

Vapor intrusion mitigation services often come into play on industrial or commercial properties that previously used or stored chlorinated solvents or petroleum products.

For example, dry cleaning businesses often cause contamination because they have used many chlorinated solvents over time. These substances can break down in the environment and form new chemical compounds. These new compounds can be more harmful than the original substance. As a result, contamination from chlorinated solvents usually requires vapor intrusion mitigation.

Properties where petroleum was used or stored, such as gas stations or bulk fuel terminals, typically pose less of a contamination risk. However, they may still require vapor intrusion mitigation. In fact, sites next to these properties can also become contaminated and should be investigated. This helps rule out vapor intrusion and other risks.

In these cases, licensed environmental professionals can collect soil, groundwater, and sub-slab gas samples. They can then assess whether vapor intrusion is a concern at the property. If there is a concern, those same environmental professionals can offer consulting and design services for vapor intrusion mitigation.

Developing a vapor intrusion mitigation system

The process at a contaminated site begins with research. Interviews with site owners and operators about usage history, records research, and visual investigations can provide clues about the possible presence of contamination.

For sites unused or abandoned for years or decades, institutional knowledge may be gone. Legal records may also not exist. In those cases, subsurface utility engineering (SUE) can help. Ground Penetrating Radar (GPR) can reveal tanks, pipes, and other appurtenances that may have held chlorinated solvents or petroleum products.

If a source of contamination is found, then the next step is to remove it if possible so that it does not continue to make the environmental situation worse.

The investigation then determines how widespread the contamination is and who it is affecting. Once the nature of the contamination and its risks are understood, the next step is designing a vapor intrusion mitigation system so that people are not exposed.

A vapor intrusion mitigation system is site-specific. A good design is customized to work with the existing structures if there are any or with proposed structures if the site will involve new construction.

When designing a system and implementing it, some challenges are obvious: you can’t see vapor and you don’t always smell it. Some of the concerns are very long-term in nature: an occupant could be in a building for years and not see the effects of vapor intrusion.

Additionally, while the Environmental Protection Agency (EPA) has been around since 1979, it has mostly focused on surface water contamination and groundwater contamination. Vapor intrusion services have really only been formalized in North Carolina for a little more than 10 years. NCDEQ continues to update guidance and those regulations.

The role of state government in vapor intrusion mitigation

In North Carolina, contaminated properties can often be enrolled into the North Carolina Department of Environmental Quality (NCDEQ) Brownfields program. NCDEQ defines a Brownfields site as “an abandoned, idled or underused property where the threat of environmental contamination has hindered its redevelopment.”

NCDEQ’s Brownfields program is driving a greater focus on vapor intrusion, assessment, and mitigation as a safeguard not only for the people who use a redeveloped brownfields site, but also for the site owners and for companies like WithersRavenel who work on the property’s vapor intrusion project.

Remediation vs. mitigation

Sometimes the best decision—and NCDEQ agrees—is not to remediate a contaminated site at all. Cleaning up contamination often costs a lot, and it can be hard to remove all contaminants from a site. Sometimes it is cheaper and just as safe to leave the contamination in place, then install a vapor intrusion mitigation system as a barrier to protect building occupants. NCDEQ is using a more risk-based approach for the Brownfields program. It focuses on finding and reducing environmental and health risks. It does not require a full cleanup in every case.

The bottom line

NCDEQ’s Brownfields program, environmental cleanup, and vapor intrusion mitigation systems help reuse properties once left unused due to contamination liability.