Conducting Underground Utility Surveys

Failing to locate all utilities before site works begin can have major implications on a project’s cost and schedule.

Aside from the financial implications of standing labour down after unexpected finds (and during the subsequent re-planning required), a shift in a project’s timescales can cause havoc with scheduling the many trades required on site.

Above all else, inadvertently uncovering cables and pipes can have major Health & Safety implications for the workforce. These risks are easily mitigated by undertaking a non-intrusive utility survey at the design stage, accurately identifying and mapping all services present.

Rock Surveying is a team of experienced surveyors, who specialise in accurate GPR Geophysical and Topographical surveys to guide safe and accurate construction decisions. The approach taken is always

bespoke to each project, so to provide you with greater insight, we asked the team to describe the key factors which impact the survey brief:


By capturing the main drivers for the survey, we can tailor the approach taken.

  • For example, when surveying a utility connection point, tracing the route of one electrical cable can be a simple survey. Compare this to trying to trace and map all the utilities in a plot of land; the whole surface area needs to be scanned, requiring a comprehensive survey strategy.

  • Survey depths also impact the time taken. A shallow survey can be much quicker than surveying at depth.


Very simply, whether a location is rural or urban can impact the amount of hours it takes to complete a survey and also the hours during which the team can work.

  • Rural sites are often easier to access, whereas urban sites may have restricted access if the works are within public highways or on private land.

Section 50s may be required (which can have application lead times) or there may be access restrictions (such as gated developments or needing to obtain permission from multiple landowners).

  • Urban environments tend to have more infrastructure and more people by their very nature. More utilities mean a longer survey time. More human activity often means restrictions in the hours during which the survey can be completed.

For example, on a recent site for Transport For London, access was restricted to between 2am and 4am due to active tramlines on the site. This meant that the survey was conducted over three nightly sessions instead of a single day session.


Having local knowledge and information available makes a survey quicker and easier to undertake.

  • This can include obtaining local knowledge from estate owners, local residents or site workers (such as caretakers) who have invaluable, historical knowledge of the site.

  • It is critical that the client has copies of current statutory utility plans (also called ‘dig plans’). A survey cannot be conducted without these and it also helps the client to see in advance the kind of obstructions that exist before we provide more detail.


According to the BSI PAS 128 guidelines ('a new specification for underground utility detection, verification and location'), a client can pick what level of survey they require. As a survey becomes increasingly complex in depth, accurancy and the level of information provided, this can take longer to conduct.


Certain high risk sites have additional complications or require specific accreditations. A prime example is substation sites.

  • Rock Surveying The team have been working for National Grid, Scottish and Southern Energy Power Distribution and Western Power Distribution for the past 8 years.

  • These sites require greater skill in the interpretation of survey readings because the electrical switchgear present (such as busbars) can cause interference.

  • Safety is also a big consideration. Our team has undertaken additional training to ensure the highest levels of health and safety on these sites.


Rock Surveying boasts a specialist and experienced team who excel in tailoring utility mapping surveys, including both GPR and Topographic surveys, to meet individual demands, creating a detailed final product that saves time, cost and resource when compared to conventional trial hole excavations.

We’d be delighted to offer you a free, no obligation, competitive quote for your surveying requirements. Please email Emma on or call 01905 456384.

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