Technical FAQs

ERH Operations

What is in situ steam generation and why is it so important?

ERH makes steam in situ, in all soil types regardless of permeability. This steam acts as a carrier gas to sweep evaporated VOCs toward the vapor recovery wells. In situ steam generation allows ERH to be equally effective in low permeability and heterogeneous soils, and within the vadose zone, perched water, capillary fringe and saturated zones.

How does TRS mitigate the downward migration of DNAPLs?

The net effect of our ERH remediation systems is the movement of contaminants, vapors, steam, water and air moving into the system - not away from it. This is due in part to steam/vapor buoyancy, applied subsurface vacuum, and net groundwater extraction. This net effect has been observed consistently on our projects. Contaminant migration outside of the remediation area has never been observed at our sites. There are additional engineering design features that we provide including thermal barriers below and outside the focused treatment region that will intercept any contaminant in the unlikely event migration occurs.

How effective is ERH at uniformly heating the subsurface treatment volume?

ERH is highly effective at uniformly heating the subsurface treatment volume. The professional staff at TRS has demonstrated this uniformity in subsurface heating at over 60 sites nationwide since 1997. Subsurface temperature is monitored at every 5-foot subsurface interval at all of our project sites using thermocouples. Temperature data is automatically logged in our control computer and subsurface temperature profiles are generated routinely. Please see our project examples by selecting this link TRS Projects for direct project evidence of uniform heating in the subsurface treatment volume.

Does ERH cause soil settlement and can it cause building subsidence?

Settlement or subsidence has never been demonstrated on a TRS ERH project with the exception of some (expected) settlement in an unconsolidated municipal landfill. ERH does not dewater the site and therefore does not create void spaces in the subsurface that can cause settling or subsidence. All of our projects involving remediation underneath above ground structures require building surveys pre- and post-ERH to prove there is no impact to building structures from ERH remediation.

Does rebound occur following ERH remediation?

Overall contaminant rebound has not been observed at any of our sites. Although a few wells have shown increased concentrations (relatively to shutdown) in the years following ERH, the average groundwater concentrations have always continued to decrease with time. Continued reductive dechlorination has been observed at sites during the subsurface cool down period following source area cleanup using ERH.

For more information about specific projects please see TRS Projects.

How long does ERH typically require to complete site remediation?

It depends on the specific site characteristics but generally ERH remediations are completed within 6 to 12 months.

What employment opportunities are available at TRS?

TRS is always looking for the best engineers, remediation project and field managers and sales people. Please select this link to learn more about employment opportunities at TRS - TRS Employment.

When you say "TRS will reduce your VOC mass by 95%...", how is that measured?

We mean that the average soil concentration after ERH will be 5% of the average initial soil concentration (comparing samples from similar locations and depth intervals). We mean that the average groundwater concentration after ERH will be 5% of the average initial groundwater concentration. Or both - ERH is equally effective in soil and groundwater.

How does one sample hot soil? Hot groundwater?

If practical, we recommend using direct push technology (DPT) to collect soil samples. A brass or Teflon(TM) sleeve is required due to the soil temperatures. The soil sample is immediately capped, a meat thermometer is pushed through the cap, and the capped sample is placed on ice. When the soil has cooled to below ambient temperatures, the sleeve is cut open and an analysis sub sample is collected from near the center of the core barrel.

Groundwater monitoring wells must be constructed of stainless steel to withstand the applied subsurface temperatures. A Teflon(TM) tube is inserted through the well cap into the well to the appropriate sample depth. The upper end of the sample tube is connected to a stainless steel cooling coil at the surface. The cooling coil is immersed in ice water during sampling. Groundwater is pulled up through the tube and cooling coil and the cool groundwater is used to fill the sample containers.

TRS developed the above procedures. They have become the industry standard and have been validated and uniformly accepted by regulators.

What is an electrode? What makes it hot?

In most cases, a TRS electrode is a well with a casing and screen and it can be used for whatever purposes one would want to use a well - extract water or vapor, inject bioamendments or oxidants (TRS has patents pending on this). However, an electrode also has the special capability of directing electrical current into the subsurface depth interval that you want to heat. Occasionally, TRS will specify pile-driven electrodes if they provide a cost advantage over drilling.

An electrode does not get hotter than the rest of the subsurface - it does not heat the soil or groundwater. Rather, it is the flow of electricity between the electrodes that creates the heat in situ.

What happens if there is a power outage?

When the ERH "off" button is pressed or site power is lost, in situ steam generation stops instantly - like flipping off a light switch. The transition is like lifting a whistling tea kettle off the burner - steam pressure stops and only steam diffusion remains (like watching vapor rise from a hot cup of coffee on a cold day). This steam diffusion will slowly expand the heated zone at the site; it grows by about one foot per day if the vapor recovery system is not operating. When power is restored and vapor recovery resumes, the action of pulling cool air through the newly heated zone pulls the temperature front back with its previous boundaries.

No VOC vapor emissions have been detected from a TRS site either during operations or following a power outage.

What happens to the steam that is extracted from the heated subsurface during ERH operations?

TRS extracts steam and vapor from the subsurface, condenses the steam, and cools the vapor for treatment. The rate of condensate production is typically 2-10 gpm. Henry's Law applies to the conditions within the condenser and for common VOCs, over 99% of the VOC mass remains in vapor form and less than 1% of the VOC mass dissolves in the condensate. The condensate is high quality water (no mineral content) and therefore TRS recycles the condensate as make-up water for the condenser cooling tower. Due to the energy balance, the condensation of one gallon of water in the condenser leads to the evaporation of about one gallon of water from the cooling tower - the production and use of water balance and therefore very little net water discharge is required. Thus, condensate handling, treatment, and disposal rarely leads to more than 1% of the total remediation cost.

How does TRS mitigate the loss of control of contaminant vapor in the vadose zone?

Establishing and maintaining complete vacuum influence and subsequent vapor and steam recovery in the subsurface.

What is the impact of ERH on soil microbes?

ERH provides a strong overall benefit to bioremediation processes. Increasing temperatures to 30-40°C seem to be very beneficial to almost all dehalogenating microbes. Temperatures above 60°C do not kill microbes; however, most microbes will transform into inactive spores and wait for temperatures to cool. Some microbes use a combination biotic/abiotic process (probably coupled with iron) to eliminate chlorinated VOCs - this process is not yet well-understood.

After ERH is complete and the site begins to cool, anaerobic dechlorination rates increase markedly. Thermal enhancement (compost pile effect) is part of the reason. However, ERH and boiling convert some of the naturally occurring total organic carbon into water-soluble (and bioavailable) forms. This in situ bioamendment avoids the distribution problems inherent with trying to inject a carbon substrate from the surface.

Does ERH dewater the site?

ERH does not dewater the site. Subsurface moisture is required for ERH to work. ERH raises subsurface temperatures to the boiling point of water (100°C or 212°F). Subsurface moisture conducts the electricity between the ERH electrodes. Within the saturated zone, TRS's net water extraction results in a slight water table drawdown - inches in sandy soils and a foot or two in low permeability clay soils.

Utilities

Why doesn't electricity travel off-site via subsurface piping?

TRS's Power Control Units (PCUs) are highly adaptable to treat soils of varying electrical conductivity. Our custom built PCUs include isolation transformers that make it impossible for the electrode current to leave the remediation region and interfere with adjacent facilities.

Are buried utilities affected?

Generally no. If the utility is a plastic pipe and located in the heated depth interval it will need to be relocated or replaced with a temperature-resistant material such as steel. Most of the sites where ERH has been applied have buried utilities near or in the heated region. It is the rare occasion when relocation of buried utilities is required. Otherwise, there is no effect from ERH on buried utilities. By far the most common temperature-sensitive component found in our treatment regions is PVC monitoring wells.

Geology

Does ERH cause soil settlement and can it cause building subsidence?

Settlement or subsidence has never been demonstrated on a TRS ERH project with the exception of some (expected) settlement in an unconsolidated municipal landfill. ERH does not dewater the site and therefore does not create void spaces in the subsurface that can cause settling or subsidence. All of our projects involving remediation underneath above ground structures require building surveys pre- and post-ERH to prove there is no impact to building structures from ERH remediation.

Is ERH effective in low or high permeability soil?

ERH effectively remediates both low and high permeability soil. For example, we have successfully applied ERH for the rapid remediation of chlorinated solvents in very low permeability soil with hydraulic conductivities as low as 10-8 cm/sec. We have also successfully applied ERH for the remediation of DNAPL and LNAPL in very high permeability soil with groundwater flow velocities of 10 to 20 feet per day.

Can I use ERH in rock?

Yes. ERH is effective in fractured rock and porous sedimentary rock. Competent igneous bedrock with no fractures is another matter. In a fractured rock media the electricity will follow the same fractures or pathways that the water and contamination have followed. Please refer to the following two case studies for examples: Dry Cleaners in Fair Lawn, NJ and U.S. Naval Station Annapolis, MD. However, there are fewer case studies of bedrock remediation than are available for unconsolidated soils.

Safety

Why is there no fear of being shocked from an ERH system?

TRS pioneered the safe application of ERH in public areas. We have applied ERH underneath operating roads, shopping malls, and operating manufacturing facilities leaving areas open to pedestrians and vehicles during installation and operations. We use standard electrical grounding techniques to ensure our ERH systems are well below the OSHA standard for safe working voltages.

When the ERH system is not in a public access area we install security fencing around the remediation area making it inaccessible to the public.

Why doesn't electricity travel off-site via subsurface piping?

TRS's Power Control Units (PCUs) are highly adaptable to treat soils of varying electrical conductivity. Our custom built PCUs include isolation transformers that make it impossible for the electrode current to leave the remediation region and interfere with adjacent facilities.

Is ERH unsafe and will it cause electrical shock?

ERH is a very safe in situ thermal remediation technology. In fact, our engineering and operations staff pioneered the safe application of ERH in public areas. TRS uses standard grounding techniques that have been used by the electrical utility industry for decades. We have applied ERH under operating industrial manufacturing facilities, operating retail shopping malls, and other public access areas including roads and public right-of-ways.

How does one sample hot soil? Hot groundwater?

If practical, we recommend using direct push technology (DPT) to collect soil samples. A brass or Teflon(TM) sleeve is required due to the soil temperatures. The soil sample is immediately capped, a meat thermometer is pushed through the cap, and the capped sample is placed on ice. When the soil has cooled to below ambient temperatures, the sleeve is cut open and an analysis sub sample is collected from near the center of the core barrel.

Groundwater monitoring wells must be constructed of stainless steel to withstand the applied subsurface temperatures. A Teflon(TM) tube is inserted through the well cap into the well to the appropriate sample depth. The upper end of the sample tube is connected to a stainless steel cooling coil at the surface. The cooling coil is immersed in ice water during sampling. Groundwater is pulled up through the tube and cooling coil and the cool groundwater is used to fill the sample containers.

TRS developed the above procedures. They have become the industry standard and have been validated and uniformly accepted by regulators.

Does vapor intrusion occur?

Vapor intrusion has not been observed on any of the ERH remediations TRS has performed. As a result of our strong background with subsurface air movement technologies including vapor recovery we are highly experienced with vapor, steam and fluid recovery systems. It is critical to maintain a complete vacuum influence in the subsurface during ERH remediation to ensure complete steam and vapor capture. We have demonstrated this on all of our projects. We have also shown through continuous online air/vapor sampling and helium gas tracer tests that our systems maintain complete vacuums eliminating vapor intrusion or migration.

Contracting/Pricing

What does TRS pricing include? What are the component costs

TRS pricing is all inclusive; we include all elements that we are responsible for as well as the elements that our customer manages. The following tables describe a typical breakdown of project tasks performed by TRS and Others.

TRS Tasks
Percent of Project Total (est)
Design, Work Plans, Permits
5%
Subsurface Installation
10%
Surface Install and Startup
21%
Remediation System Operations
24%
Demobilization and Final Report
5%
Total TRS Price
65%
 
Tasks Performed by Others
Percent of Project Total (est)
Drilling and Soil Sampling
14%
Drill Cuttings and Waste Disposal
2%
Electrical Utility Connection to PCU
2%
Electrical Energy Usage
10%
Carbon Usage, Transportation & Regeneration
2%
Water/Condensate Disposal
1%
Other Operational Costs
3%
Biological Amendments (heat enhanced bio)
1%
Total Costs by Others
35%

How much does a performance guarantee cost?

For more information about the various contracting options we commonly provide including Guaranteed Fixed Price Remediation (GFPR) please see TRS ERH Contracting Options.

TRS professional staff has been providing fixed price performance guarantees for in situ remediation since the early 1990's. We have been providing specific ERH remediation guarantees since 1997. We have provided more guaranteed, fixed price and performance-based contracts than any other ERH provider, and have stood behind each and every one of them to successful conclusion.

Performance guarantees come in many shapes and sizes. Before we can determine the pricing of a performance guarantee, it is important to understand the exact nature of the guarantee. We need to understand how the performance will be measured and the risk, reward, and possible penalties. However, in most cases a performance guarantee will add 10-20% to the total project cost.

TRS has provided guaranteed fixed price performance contracts for several projects for the U.S. Department of Defense and the private sector. Our past performance guarantees have included a percent reduction in contaminant mass or specific soil and/or groundwater cleanup goals, and operating time periods. As with any commonly available financial surety such as insurance or bonding the more risk the more the premium for the insurance. TRS has structured its guaranteed contracting to provide the level of risk management you require at very competitive pricing.

When you say "TRS will reduce your VOC mass by 95%...", how is that measured?

We mean that the average soil concentration after ERH will be 5% of the average initial soil concentration (comparing samples from similar locations and depth intervals). We mean that the average groundwater concentration after ERH will be 5% of the average initial groundwater concentration. Or both - ERH is equally effective in soil and groundwater.

How do I get started evaluating ERH for remediation at my site?

Please select this link to begin an evaluation of your site - Begin a Site Evaluation.

TRS ERH and Heat Enhanced Technologies

What is the "TRS ERH Process"?

We have developed a unique and highly effective methodology for in situ thermal remediation using Electrical Resistance Heating (ERH) that we call the "TRS ERH Process". Fundamentally, the TRS ERH process is simple and highly flexible.

The roots of our ERH process originate from the work of the Pacific Northwest National Laboratory, managed by Battelle for the Department of Energy. We are licensed by Battelle to apply all of the ERH and Six-Phase Heating patents that Battelle developed.

A major component of the TRS ERH Process is properly combining ERH with vapor, steam, and multi-phase recovery systems. We also possess vast experience with the unique challenges of using vapor treatment systems in conjunction with ERH. The majority (~90%) of our projects have involved the remediation of chlorinated solvents (TCE, PCE, and breakdown products), often at DNAPL concentrations under very challenging site conditions.

The TRS ERH Process can deliver varying amounts of energy into discrete subsurface unsaturated and saturated intervals, resulting in increased temperatures for rapid and aggressive contaminant source zone remediation and for gentle heating for enhanced biotic and abiotic in situ degradation. No other in situ thermal technology is nearly as adaptable.

Since 1997, we have built on the knowledge base that came from the DOE's investment of tens of millions of dollars into ERH research and development. We continue to promote a culture of R&D focused on improving the application of ERH based on our experience at each new site. Having now performed ERH on a multitude of sites with varying degrees of complexity, the technical, schedule and budget requirements on our projects are always met and are often exceeded.

TRS is the leader in combining heating with bioremediation, oxidation, and reductive dechlorination. We have patents pending on the synergies of these combinations.

How many sites have been treated using the TRS ERH Process?

We have implemented the TRS ERH Process on more than 80 remediation projects since 1997. Please see TRS Projects to read about many of our ERH project examples.

When is it appropriate to consider the TRS ERH Process for remediation?

The TRS ERH Process is unfazed by low permeability or heterogeneous soil, unsaturated or saturated conditions, or by concentrations indicative of DNAPL. Thus, ERH is especially applicable for sites that would be difficult to remediate by other means. The TRS ERH Process is commonly deployed on sites where other in situ technologies were not able to complete the contaminant remediation usually due to high concentrations of contaminants and/or low permeability lithologies.

When the following project and site metrics exist the TRS ERH Process usually becomes the most attractive in situ remedial technology:

  • You want to remediate soil and groundwater impacted by volatile organic compounds, especially chlorinated solvents, gasoline and BTEX constituents, and other fuel oils, lubricants and heavier hydrocarbons as LNAPL including diesel, kerosene, jet fuel, solid grease and naphthalene
  • You have a high concentration contaminant source area in soil or groundwater,
  • You have low or heterogeneous permeability soil,
  • Remediation is required under a building or public right-of-way where excavation and disposal would be difficult and expensive,
  • You want completion within 6-12 months,
  • You are interested in a Guaranteed Fixed Price Remediation (GFPR),
  • You are interested in a total plume solution (source area and downgradient dissolved phase plume) using heat enhanced biotic and abiotic degradation, and
  • You are prepared to complete the remediation and eliminate the liability once and for all.

What are the main differences between the TRS ERH Process and ETDSP?

First Major Difference - the method of electrode hydration

Unlike ETDSP, the TRS ERH Process does not rely on pumping large volumes of water into the subsurface. The TRS ERH Process relies in part on the addition of a small amount of water that is slowly dripped (e.g. a gallon or two per hour) into the electrode to maintain moisture and conductivity at the soil-electrode interface. The TRS method of water hydration eliminates the potential for developing an artificial hydraulic gradient that could cause lateral or vertical contaminant migration. The net effect of the TRS ERH Process is that water in the form of steam is removed from the subsurface where it is managed in accordance with regulations. TRS removes net water from the site and thus applies a measure of hydraulic control.

ETDSP also has higher electrical costs because it must continually heat cool water that is injected into the electrodes.

Second Major Difference - the proper combination of ERH with vapor, steam, and multi-phase recovery systems

A second major difference about the TRS ERH Process is the proper combination of ERH with vapor, steam, and multi-phase recovery systems. TRS has vast experience and expertise with the unique challenges of using vapor, steam, and liquid recovery and treatment using Flameless Thermal Oxidation (FTO), Granular Activated Carbon (GAC), Catalytic Oxidation (CATOX) and Thermal Oxidation. Our professional team has over 100 years of combined in situ remediation experience that gives us a substantial knowledge base and expertise in the implementation of these technologies for the treatment of a multitude of chlorinated solvents, semi-volatiles, and petroleum hydrocarbons.

Third Major Difference - highest quality, and largest state-of-the-art specialty equipment fleet manufactured in the U.S.

The specialty ERH equipment used by TRS is of the highest quality available in the industry today. We also have the largest fleet of specialty ERH equipment in the world. We can presently perform 17 separate ERH remediation projects at one time. We are expanding our equipment fleet to provide even greater capability to perform projects.

Our ERH specialty equipment is not manufactured by our employees or in other uncontrolled environments. Our state-of-the art Power Control Units (PCUs), vacuum blower packages, and steam condensers are built only by the best internationally recognized U.S. equipment manufacturers using the highest quality components under the strictest manufacturing standards.

The U.S. company that manufacturers our PCUs is ISO 9002 certified and has 27 years of experience providing custom and off-the-shelf electrical power supplies to Fortune 100 companies. They are internationally recognized leaders in the design and manufacturing of customized industrial power conversion systems, power centers, and transformers.

Our PCUs are designed to apply and control energy input to individual electrodes allowing us to provide variable rates of energy into different subsurface intervals and different parts of the treatment area simultaneously. This provides greater flexibility and higher efficiencies resulting in reduced electrical cost and surgical treatment of discrete zones of contamination.

Our vacuum blower packages and steam condensers are constructed by a nationally recognized U.S. equipment manufacturer that has over 75 years of combined experience building blowers and vacuum systems specifically for the environmental industry. They are known for producing high quality products that provide trouble free operations, and for their 24-hour support system that helps TRS ensure lost production time is minimized.

TRS is a U.S. firm.

What are the main differences between ERH and thermal conduction heating or ISTD?

Both technologies use electricity and heat the subsurface; however, they really don't have much in common and are rarely considered to be competing technologies.

Fundamentally, the TRS ERH process is simple and highly flexible. ERH is an in situ thermal remediation technology that uses the heat generated by the resistance of the soil matrix to the flow of electrical current to raise subsurface temperatures up to the boiling point of water (212°F or 100°C). ERH electrodes do not get any hotter than the rest of the soil - the electrodes direct electrical current into the proper subsurface depth interval that you desire to heat. During ERH volatile compounds transition to the vapor phase and are captured by a vapor recovery system. ERH is equally effective in saturated and unsaturated soils. Subsurface heating may be used for a variety of remedial purposes including contaminant volatilization, in-situ steam stripping, enhancing soil vapor extraction efficiency, and increasing biological degradation and chemical dechlorination reaction rates.

Conductive heating relies on using electricity applied to heater wells to generate very high temperatures (i.e. >1,000°F) at the heater well. Radiation and thermal conduction heat transfer are effective near the heater. As a result, thermal conduction and convection occur in the bulk of the soil volume. Thermal conduction heating can heat the vadose zone or de-watered zones to temperatures far above the boiling temperature of water; this makes it possible for thermal conduction heating to treat compounds like PCBs or pyrenes, though at high energy costs. Thermal conduction heating has great difficulty in treating the saturated zone. Its inherently uneven heating is not conducive to thermally enhanced bioremediation.

It is common for the price of ERH to be about half the cost of thermal conduction heating when considering remediation of the same treatment volume. This is primarily due to ERH requiring about half the number of boreholes. The amount of electricity required during ERH remediation is also less than what is required during conductive heating.

What are the differences in soil thermal conductivity vs. soil electrical conductivity?

While certain claims are made that soil thermal conductivity only varies by a factor of 25 and that soil electrical conductivity varies by over three orders of magnitude, the claim is both completely true and completely misleading. A site that is tidally influenced by the ocean might be 1000 times more electrically conductive than a mountainous site with high rainfall. TRS designs its remediation equipment with the flexibility to treat the entire range of electrical conductivities - neither end of the conductivity range is either more difficult or easier to remediate. However, at any one site the electrical conductivity will typically vary by only a factor of about 2. Most of this variation is caused by the anaerobic decomposition of chlorinated VOCs - a process that increases the local conductivity and attracts current for faster heating.

What is the difference between three phase and six phase heating?

Please see Three Phase and Six Phase Heating to read the paper that describes in detail the differences between the two forms of ERH.

What is the benefit of combining technologies such as ERH with enhanced bioremediation and abiotic degradation?

Fundamentally, the TRS ERH process is simple and highly flexible. TRS can deliver varying amounts of energy into discrete subsurface unsaturated and saturated intervals, resulting in increased temperatures for rapid and aggressive contaminant source zone remediation and for gentle heating for enhanced biotic and abiotic in situ degradation. No other in situ thermal technology is nearly as adaptable.

The benefit of combining ERH with enhanced bioremediation is a total plume remedial solution at lower cost. Heat enhanced biotic and abiotic remediation of the downgradient dissolved phase contaminant plume can be accomplished at reduced cost compared to source area treatment and offers the benefit of reaching lower cleanup goals over time following source area treatment. Once the ERH remediation system is in place for source area remediation, heat enhanced biotic and abiotic remediation in the downgradient dissolved phase plume can be accomplished for an additional $10 to $20 per cubic yard

Is ERH applicable for remediation of soil and groundwater?

ERH is equally effective for the remediation of soil and groundwater.

What does ERH do to metal contamination? Dioxin? PCBs?

ERH makes them warm. After ERH, they cool down again. There is essentially no direct remedial effect. However, ERH can effectively remove co-contaminants that act as carriers for these compounds. These carriers include VOCs and oily NAPLs.

What is hydrolysis and when is it important?

Hydrolysis is a water substitution reaction; the chemical reacts with water itself without regard to redox conditions or available microbes. For some compounds, the hydrolysis rate is insignificant. For halogenated alkanes at temperatures near 100°C, hydrolysis is likely to destroy the compound or render it non-toxic in a matter of days. Hydrolysis is very important for compounds such as:

  • Methylene chloride (MeCL)
  • Trichloroethane (TCA)
  • Tetrachloroethane (PCA)
  • Ethylene dibromide (EDB), dibromoethane
  • Most fumigants and pesticides

For more on Hydrolysis see the following TRS Publication.

How deep can ERH be applied?

ERH is not depth limited. ERH electrodes can be installed to any depth. If the boring can be drilled to the required depth, ERH can be applied to that depth. We have applied ERH as deep as 130 feet below ground surface. Please select this link TRS Projects and click on the third project description from the top under Completed Projects to read about ERH at 100-ft bgs at the DOE Paducah Gaseous Diffusion Plant.

How does ERH compare to radio frequency (RF) or microwave heating?

RF energy is very strongly adsorbed by soil moisture, which prevents RF energy from propagating more than a few feet from the antenna. In general, this makes RF heating inefficient, expensive, and very rarely used. RF heating may find a niche in treating bedrock with very low water content, which would allow the RF energy to propagate tens of feet from the antenna.

Design Considerations

What does ERH do to metal contamination? Dioxin? PCBs?

ERH makes them warm. After ERH, they cool down again. There is essentially no direct remedial effect. However, ERH can effectively remove co-contaminants that act as carriers for these compounds. These carriers include VOCs and oily NAPLs.

Why doesn't electricity travel off-site via subsurface piping?

TRS's Power Control Units (PCUs) are highly adaptable to treat soils of varying electrical conductivity. Our custom built PCUs include isolation transformers that make it impossible for the electrode current to leave the remediation region and interfere with adjacent facilities.

What is hydrolysis and when is it important?

Hydrolysis is a water substitution reaction; the chemical reacts with water itself without regard to redox conditions or available microbes. For some compounds, the hydrolysis rate is insignificant. For halogenated alkanes at temperatures near 100°C, hydrolysis is likely to destroy the compound or render it non-toxic in a matter of days. Hydrolysis is very important for compounds such as:

  • Methylene chloride (MeCL)
  • Trichloroethane (TCA)
  • Tetrachloroethane (PCA)
  • Ethylene dibromide (EDB), dibromoethane
  • Most fumigants and pesticides

For more on Hydrolysis see the following TRS Publication.

Is ERH effective in low or high permeability soil?

ERH effectively remediates both low and high permeability soil. For example, we have successfully applied ERH for the rapid remediation of chlorinated solvents in very low permeability soil with hydraulic conductivities as low as 10-8 cm/sec. We have also successfully applied ERH for the remediation of DNAPL and LNAPL in very high permeability soil with groundwater flow velocities of 10 to 20 feet per day.

How deep can ERH be applied?

ERH is not depth limited. ERH electrodes can be installed to any depth. If the boring can be drilled to the required depth, ERH can be applied to that depth. We have applied ERH as deep as 130 feet below ground surface. Please select this link TRS Projects and click on the third project description from the top under Completed Projects to read about ERH at 100-ft bgs at the DOE Paducah Gaseous Diffusion Plant.

Are buried utilities affected?

Generally no. If the utility is a plastic pipe and located in the heated depth interval it will need to be relocated or replaced with a temperature-resistant material such as steel. Most of the sites where ERH has been applied have buried utilities near or in the heated region. It is the rare occasion when relocation of buried utilities is required. Otherwise, there is no effect from ERH on buried utilities. By far the most common temperature-sensitive component found in our treatment regions is PVC monitoring wells.

Does vapor intrusion occur?

Vapor intrusion has not been observed on any of the ERH remediations TRS has performed. As a result of our strong background with subsurface air movement technologies including vapor recovery we are highly experienced with vapor, steam and fluid recovery systems. It is critical to maintain a complete vacuum influence in the subsurface during ERH remediation to ensure complete steam and vapor capture. We have demonstrated this on all of our projects. We have also shown through continuous online air/vapor sampling and helium gas tracer tests that our systems maintain complete vacuums eliminating vapor intrusion or migration.

Can I use ERH in rock?

Yes. ERH is effective in fractured rock and porous sedimentary rock. Competent igneous bedrock with no fractures is another matter. In a fractured rock media the electricity will follow the same fractures or pathways that the water and contamination have followed. Please refer to the following two case studies for examples: Dry Cleaners in Fair Lawn, NJ and U.S. Naval Station Annapolis, MD. However, there are fewer case studies of bedrock remediation than are available for unconsolidated soils.

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Please contact David Fleming at 425-396-4266 / email if you have questions or if you need more information.