The procedure quickly identifies soil type, which is used to determine topsoil stripping depth during clear-and-grade operations.
The “˜Back of the Ute’ soil test procedure was created by Mike Bugler and implemented by Matt McDermott (both of CNC Project Management), whilst working for Spiecapag Lucas during the construction of a Queensland gas pipeline.
The challenge
Spiecapag Lucas was required by the project’s soil management plan to show that soil type had been identified in advance of topsoil stripping, and that the stripping depth corresponded with the prescribed depth for the identified soil type.
The clear-and-grade crews needed advice on topsoil stripping depth quickly, and a process of taking samples, sending for analysis and then responding to the results was at best a 24-hour time delay; not suitable to clear-and-grade operations that were otherwise ready to proceed through properties as soon as access was obtained.
Not enough verified information of soil type was available in advance, and preliminary testing indicated that soil type varied greatly with topography in the rolling country of the alignment.
Technical basis
The procedure uses the same principles as the Emerson Aggregate Test, which is based on particle size characteristics of the soil and a combination of sieving and settlement time in water.
This is to distinguish between the three basic topsoil types commonly encountered – sandy, loamy and clayey – which generally have different prescribed stripping depths.
Improving environmental outcomes
Prior to the creation of the procedure, the construction contractor was faced with two scenarios.
The first was to estimate the topsoil type on a qualitative basis i.e. past experience, a scenario that would have been considered a non-conformance with the environmental conditions and could have led to poor environmental outcomes such as: mixing topsoil and subsoil; insufficient stripping in some situations – leading to insufficient topsoil for rehabilitation requirements; and, excess stripping in other situations – leading to increased rehabilitation issues through the presence of subsoil.
The second was to use a quantitative methodology, taking regular soil samples and sending them to a laboratory which would then undertake analyses and provide results.
This process would take 24 hours (at best) to complete and would add significant effort and expense, not to mention potential delays to construction caused by the length of time needed to submit samples and obtain return results in a fast-paced environment.
Creation and application of the procedure allowed real-time soil identification in the field, which enabled topsoil stripping to be undertaken accurately and to the correct depths.
The “˜back of the ute’ soil test procedure achieved compliance with the environmental conditions, facilitated construction and allowed for accurate stripping depths to be achieved, leading to improved rehabilitation outcomes through effective management across the variable terrain of a pipeline construction corridor.
Raising industry knowledge
Carrying out tests in the presence of the clear-and-grade crew, combined with the ability to provide results in a quick, easily understood and directly-applicable fashion, led to better understanding of the process and encouraged ownership of the results by the clear-and-grade plant operators.
During the period following implementation of the procedure, operators became increasingly interested in soil issues, to the extent that in a situation where a soil change had not been identified, they would seek confirmation that they had not moved into a different soil type as they progressed through the alignment.
The successful implementation of the procedure reinforces that adoption of a proactive mindset can lead to a low-cost innovation that can be used to create efficiency and savings whilst maintaining compliance with environmental conditions.
Applicable across Australia
A version of the “˜back-of-the-ute’ soil test can be applied to most situations involving a mix of sandy/loamy/clay soils – and can be modified to account for any encountered soil type.
In any given situation, field environmental management should work with the project proponent or an independent soil scientist to identify the sieve size and settling times applicable to the situation in question, and should then obtain approval from the project proponent to apply the procedure in the field.
The process does not claim to be a precise soil analysis of all trace elements however it is an easily shared and understood, fit-for-purpose and cost-effective test for use in a clear-and-grade.
Cost-effective
The procedure is extremely cost-effective from three basic standpoints.
Firstly, by using the test, the construction contractor can remove topsoil accurately, leading to an increased likelihood that the optimum amount of unmixed topsoil has been conserved, which in turn improves the likelihood of rehabilitation success at the first attempt.
Secondly, demonstrating that soil has been correctly identified and that the correct amount of topsoil has been stripped is a key compliance measure and one that would be much harder to achieve in the absence of the test; non-compliances likely lead to costly restitution and re-working requirements.
Finally, the test requires very little time, no special equipment and can be conducted by non-technical staff – all aspects which lead to cost savings.
For further information on the implementation of the “˜Back of the Ute’ soil test procedure, please contact CNC Project Management by visiting www.cncprojects.com.au
