Firstly, we would never advocate undertaking excavation works without fully understanding as much as possible about the area in which you are about to dig. However, just because a utility survey is available, it is not necessarily the best or only option available to you.
Many companies now, particularly the larger ones have a procedure where the utility survey is a pre-requisite prior to any works being undertaken. This is a huge step forward for safety whilst excavating, but picking up the phone and booking in the survey is not necessarily the best course of action without the proper consultation being undertaken.
Firstly, under PAS128:2014 a survey comes in four different levels:
Type D – A desktop study where the available utility records are procured from asset owners and presented in a report or even CAD format.
Type C – This is a reconnaissance survey where the records and taken to site and the utilities are marked using above ground markers and features.
Type B – This is the location survey often referred to as a GPR survey. Geophysical techniques are used to locate services across the site.
Type A – Verification survey where trial holes excavation is undertaken to prove the results of a Type B survey.
Each of the above would be classed as a utility survey and to some extent each of the requirements of the previous level are included within the next, just the levels of detail and accuracy increase with the survey level. The automatic choice is generally the Type B as this is how it has always been done.
There are many factors which come into play when planning and undertaking a survey and these include the location, environment and specific site conditions.
For instance, if your site is in a rural location and the records indicate the area has no assets, the Type D survey may well be sufficient. Likewise, if you are working in critical areas of a city like London, you may well feel the need to go all the way to Type A to ensure the greatest level of detail.
Also, specific site conditions may come into play, particularly on larger sites where different types and levels of survey may be used for certain areas like where there are areas inaccessible for GPR due to site conditions.
Discussing these requirements with us prior to starting is always the best option then each party know the expected results from across the site at the start. Without the communication in advance, when the deliverables are received with areas missing due to specific restrictions or a large fee to survey an empty field, the relationship and trust between the surveyor and client suffers. This is not through either party being at fault, this is purely a communication issue which if resolved and the survey planning is collaborative, ensures all parties are happy with the final survey results.