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Distribution Stations & What To Be Aware Of

Distribution stations contain high voltage electrical environments that require a well-developed safety regime to address hazards including: 

• Specialized personal protective equipment
• Limits of approach
• Stray and induced current risks 
• Fire protection

While most of these hazard mitigation measures pose no long-term environmental challenges, some do — in particular, the use of herbicides to control vegetation around electrical equipment and insulating oil leaking from transformers.

Arsenic Trioxide: The Challenge & Solution

The Impact of Arsenic Trioxide On Soil:

Prior to 1972, arsenic trioxide was a primary chemical agent used in vegetation control by electrical utilities throughout North America. Over time, it became clear that the risks to environmental and human health outweighed the benefits of arsenic-based herbicides, and their use was discontinued. Unfortunately, the residual arsenic in soil surrounding substations has lasted long past the use of arsenic herbicides. 

Environmental Liabilities Posed By Arsenic Trioxide

According to the US EPA, “Arsenic does not degrade over time; it can only transform into other forms of arsenic — for example, organic arsenic may transform to inorganic arsenic or vice versa — or be redistributed through runoff, leaching, erosion, volatilization, or plant uptake.” 

Arsenic does not degrade and therefore remains residually in the soil near substations, usually at levels that exceed allowable limits. Since the arsenic is redistributed through runoff, this environmental liability often extends beyond the boundaries of the station to neighbouring properties, many of which include more sensitive residential or recreational land use.

How To Manage Arsenic In Soil:

Determining if a risk exists at a site requires the use of specialized on-site testing equipment or analyses in off-site laboratories. 

Specialized On-Site Testing:

An on-site approach is preferred as this allows the rapid characterization of the risk through the use of an iterative testing regime without waiting for off-site analytical results to be received. Advances in on-site testing equipment ensure detection limits are well below most action levels and the use of approaches such as the US EPA Triad Approach that focuses on the area of where the risk is most pronounced.

[Recommended Reading: Reducing Uncertainty in a Phase II ESA with the Triad Approach]

Insulating Oil: The Challenge & Solution

The Impact of Insulating Oil On Soil:

Leaking electrical insulating oil is more visible than arsenic in soil and is generally related to a slow leak from electrical equipment or catastrophic failure. Newer or retrofitted transformer stations often include containment systems to mitigate this risk. 

Quantitative On-Site Testing:

When insulating oil does come in contact with the soil or groundwater at a site they show up as petroleum hydrocarbons in analytical testing and therefore, regulatory action levels are generally tied to these. 

Analytical tests consider the oil to be “heavier end” hydrocarbon which is difficult to assess accurately based on visual or olfactory evidence. Therefore, the use of quantitative on-site testing approaches is of benefit assessing a site. PCBs may also be of concern when testing for residual oil contamination.

Management Strategy: Reducing Risks of Residual Contamination

Once the risk has been characterized, a management strategy can be developed that generally includes remedial work to mitigate the off-site risk and on-going management and containment of residual contamination at the station to eliminate the potential for recontamination off-site and protect workers.

Need assistance mitigating residual contamination on your site? Call us at (800) 267-4797 or contact us here.