Thank you for your question regarding “chemical earth pits” and there associated environmental impact, it is our pleasure to help.
Most often when someone refers to a “chemical earth pit”, they are actually talking about an Electrolytic Electrode. The term chemical denotes a very negative reaction for most people and really is not very accurate for what is actually occurring in most cases.
A good-quality electrolytic electrode is a copper pipe filled with common salt and a desiccant (common road deicer) and is back-filled with natural-earth bentonite clay. These electrodes have been certified by the National Sanitary Foundation (NSF) as being environmentally safe and to our knowledge they are indeed low-impact. The worst that can be said about them is that they leak a few table-spoons of salt every year into the surrounding earth. You should freely use these types of electrodes, except when in high-voltage environments where human safety is a concern. You should never make changes too or re-design a human-safety grounding system without consulting a Grounding Engineer.
Other types of electrolytic electrodes are instead filled with Epsom salt. In these cases, large quantities of the salt are released in to the earth every year, and there is a potential for the formation of hazardous chemicals, should the electrode be struck by lightning and heated to 200F. There are both good and bad reasons to use these types of electrodes, however a Grounding Engineer should be consulted prior to their use.
Back-fill materials range from carbon-based (typically coke breeze) fills, to concrete, to salt, to cow manure. Generally, the Grounding Engineer is more concerned with corrosion of the electrode than they are with environmental concerns. Of course, each of these certainly has a potential for an environmental impact, save the manure. However, none of these should be used as the carbon-based back-fills will corrode the copper, the concrete will crack when heated by lightning or serious electrical faults, and both the salt and manure have very short life spans and only provide temporary reductions in resistance-to-ground.
Currently, E&S Grounding Solutions only recommends bentonite clay as a back fill material for any grounding system. Carbon-based back-fills and concrete in particular should never be used.
That said, if your vendor refuses to disclose the content of the back fill material they use, find another vendor. Good quality electrolytic electrodes are very ease to purchase. You can even order them online as most of the major electrical supply companies have these systems available in their catalogs.
But, why are you installing these systems? Do you have a specific specification, such as 5-ohms or less, that you need to meet? Has a Grounding Engineer analyzed your earthing requirements and your specific soil conditions and told you that you must have these expensive earthing pits? If you haven’t had a professional analysis conducted, you may want to consider doing so. It could in fact save you a lot of money.
We hope you find this information useful, please do not hesitate to call us at 310-318-7151 California time and someone will happily speak with you about your project.
The Engineering Team at E&S Grounding Solutions
Photo credit: E&S Grounding Solutions