7 Things You Need to Know About Safety on a Thermal Remediation Project

Thermal technology is powerful and rapid. The heat applied to the subsurface has the power to remove many types of contaminants from the subsurface, including VOCs, SVOCs, petroleum hydrocarbons, MGP waste, PAHs, PCBs, pesticides and PFAS.  Main removal mechanisms are governed by increases in volatility, increases in saturation, higher NAPL mobility and for some chemicals in-situ degradation due to the applied heat energy, all of which occurs over just a few short months. While thermal’s might is impressive, it also requires caution since that same energy can result in personal injury or harm to the environment if the proper steps aren’t taken.

In this blog post, I’ll share some of the specific safety issues associated with thermal conduction heating (TCH), electrical resistance heating (ERH), and steam enhanced extraction (SEE) thermal sites. I’ll also cover what your contractor should do to keep your site and stakeholders safe.

Site Security

Just like an active manufacturing facility, a thermal remediation site could be dangerous if unauthorized people enter it. A variety of energized systems are used to heat and remediate the subsurface, so no one should be wandering around in the area without a high degree of awareness and care. While you and your contractor understand this, the public may not.

To prevent this, your thermal contractor should install a robust and clearly signed perimeter fence, and for some site a series of redundant security sensors may have to be added as well. This provides multiple layers of assurance that if someone gained unauthorized entry to the site, the site operator will be alarmed and energized systems would be suspended and prevent an electrical hazard and injury. The downside to these sensors is they can go off often. Fortunately, most of the time, they pick up spiders, squirrels, cats, raccoons, etc., and not people.

Vapor and Liquid Extraction Redundancy

When your site is at temperature (typically 100°C), an extraction blower or groundwater pumping failure could result in vapor releases to the environment or groundwater migration of contaminants outside the treatment zone. It is crucial to ensure that steam and hot water being produced during heating and remediation is actively being recovered so there are no uncontrolled releases and to keep your project on schedule.

To ensure this, all critical equipment are backed up with installed spares, including critical equipment like blowers, pumps and/or power supplies for essential surface equipment. These spares are fully wired up and ready to go, should they be needed due to equipment failure or scheduled maintenance. Additionally, an interlocked vacuum switch can be placed on the vacuum header located furthest away to rapidly alert the operator if a blower belt breaks or if there are blockages somewhere in the manifold system limiting vacuum of the header network.

Carbon Requirements

On a typical soil vapor extraction (SVE) site, you may be used to collecting air samples in the first hour, day and week for air permit compliance, with concentrations decreasing to a relatively constant minimum. But with a thermal site, we typically see peak concentrations two to three months into heating as the site approaches temperature.

Once at temperature, a thermal site has the potential to remove significantly more mass than anticipated due to unavoidable uncertainties in starting mass estimates. For this reason, it is prudent for your thermal contractor to have backup carbon on standby since a carbon change out can take several days to schedule and complete. This pre-planning allows for flexibility during operations and ensures no stack exceedances will occur.

Constant Monitoring

More extensive and complicated thermal treatment systems require continuous monitoring, so at least one technician should always be located within 20-30 minutes of an operating site. If system alarms are received, operators will therefore be available to respond and get the system back online. Although thermal project sites have many remote monitoring features, response time is critical on larger sites due to the elevated temperatures and potential for vapor releases.

Voltage Potential

If you have chosen ERH as your thermal remediation technology, multiple voltage checks at the surface are required during startup and immediately following any operational changes. These voltage checks ensure a voltage potential at the surface won’t be discovered by anyone other than the site operator using the proper equipment.

This is not a box to check off a list – it’s essential that your thermal contractor takes it very seriously and considers the unique aspects of your site that could hide voltage potential. In my experience, one of the most overlooked areas of a site is swinging gates on a fence. In the closed position, the gate would have no voltage potential, but when opened, the contact is broken, and voltage potential is present. The solution is to properly asses, monitor and ground all critical infrastructure within the thermal treatment footprint, that have the potential for picking up stray voltage from the ERH system. We routinely do voltage surveys, to document a safe environment at our ERH sites.

Equipment Temperatures

You and your thermal contractor’s crew should assume every piece of surface treatment equipment at the site is too hot to handle and use proper personal protective equipment (PPE) at all times. Steam production causes pressures, so also assume everything is under pressure. For the same reason only authorized and trained personnel are typically allowed in the wellfield and near operating thermal equipment.

Confirmation Sampling

Confirmation sampling of hot soil and groundwater requires specific training, supervision and oversight, and it’s not something you want an inexperienced person handling. Since TerraTherm has been doing this work for many years, we have developed written standard operating procedures for hot soil and hot groundwater sampling that ensures everyone’s safety.

In situ thermal remediation (ISTR) is a robust technology that is most often technically viable for the remediation of CVOCs, SVOCs, pesticides, PCBs, petroleum hydrocarbons, PAHs, NAPL, energetic compounds and PFAS. If your client is interested and needs to remediate an environmental liability quickly and reliably, it is a tremendous force for good. But with great power comes great responsibility. Thermal remediation should only be implemented by experienced contractors with a proven track record of site safety.

If you have a question about the safety of thermal remedies or on thermal project sites, feel free to send a message to our team.


Jeff Brink

Client Services Manager

Jeff Brink has more than three decades of environmental consulting and contracting experience, and he’s dedicated over half his career to helping clients solve their toughest remediation challenges with thermal remediation solutions. He has successfully managed some of the largest TCH and ERH projects in North America to date. In his current role, Jeff works…

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