What Exactly is a Soil Resistivity Desktop Study?

Before installing an electrical earthing system design, there are a couple of other essential tasks to tackle. One of these tasks is the ‘Soil Resistivity Desktop Study.’ This study illustrated in the Soil Resistivity Table below.

Historically installation companies may have offered to drive a single earth rod into the ground and take a range of readings from it at various depths as it is driven deeper. This approach is now considered totally unacceptable for anything other than the most basic of designs, e.g. a generator earth.

The Soil Resistivity Table

The only thorough, scientific and logical method of determining a safe electrical earthing system is to undertake a complete soil resistivity survey. Carried out using an approved methodology.

At GreyMatters we do not endorse anything other than this professional approach when obtaining information that will provide the basis for safety decisions on your electrical earthing system design. Therefore the importance of this variety of life-saving, critical safety system, demands that determinations on requirements are based upon accurate, meaningful and useful data.

Harnessing the wealth of information about the electrical behaviours of soil masses throughout the globe enables GreyMatters to bring that knowledge to contribute to the analysis of each new project. We call upon our database of soil models. Along with the first-hand experience of the geology of an area. Including the influences of seasonal variations in climate, to make intelligent soil profiling decisions about our customers’ projects.

The very first baby step is a Soil Resistivity Desktop Study. Additional this study is followed up with the findings technical note.

A sample Tech Note is included below.

(Free DOWNLOAD the Soil Resistivity Desktop Study Report Template) Download here…

Soil Resistivity Desktop Study Report

Analysis

The bedrock in this area is very high resistivity. However, the depth and resistivity of topsoil and other surface layers is hugely variable. Basically it will only be fully determined by on-site soil resistivity testing.

Therefore, the data provided is purposed to provide indicative guidance on what may be present based on the best available information in the public domain (the UK only).

Deriving an accurate representation of the Soil Resistivity in the form of a Soil Model or table is a critical foundational piece of data for all subsequent safety/design calculations for safe Electrical Earthing and lightning system design.  Because the data contained in this desktop study can only be considered the starting point.

So, what is your next step..?

Soil Resistivity Testing

There is no substitute for the robust physical testing to capture accurate data from the site itself (or as near as is practicable).  But there are many approaches to consider. Namely, the Wenner and Schlumberger methods which are the most widely accepted methods. However, in both cases, the equipment used plays an integral part in making sure the data is error-free.

This approach is why GreyMatters instruments of choice are Soil Resistivity specific equipment that has a signal output voltage of 400-800 V.  Meaning this is over x8 times the penetrating strength of the more conventional general Earth testing equipment. Which typically has 50 to 150 V signal voltages.

What this means is, apart from the apparent accuracy benefits by dominating any in-ground noise. The x8 times stronger signal penetrates every known geology in Europe without question. Hence there’s no need to revisit the site to rework the tests. The equipment self-error checks during the task ensuring measuring are done RIGHT, FIRST TIME, EVERY TIME.

Investing in Top 1% testing equipment is another reason why GreyMatters is a Top 1% Specialist Earthing Consultancy in Europe. Therefore making your life just a little more comfortable in the process.