An underground utility survey is a crucial step in any construction or excavation project.
Utility
survey or underground services survey allows for the identification and mapping
of underground utilities. These utilities can include electrical cables,
drainage, water pipes, gas lines, telecommunications infrastructure, and
more.
By
accurately detecting and mapping utilities, potential conflicts and hazards can
be avoided, ensuring the smooth progress of your project.
At KB
Surveys we specialize in providing comprehensive underground utility survey utilizing
advanced technologies such as Ground Penetrating Radar (GPR) and
Electromagnetic Locator (EML). Our priority is to ensure accurate detection and
mapping of underground utilities for a wide range of projects, adhering to
industry standards like PAS 128.
Use of Electromagnetic Locator (EML) in PAS 128 utility survey
Another powerful technology we employ when performing utility
detection survey is EML (Electromagnetic Locator). It is one of the primary
tools used if conducing utilities survey. It operates by detecting and tracing
the electromagnetic signals emitted by underground utilities. Our surveyors use
advanced EML equipment to precisely locate buried utility lines, enabling us to
provide you with accurate information about their depth, alignment, and type.
Please note that not all utility surveys must meet level A of
PAS 128 industry standards (the most precise survey involving trial pits) if
you choose to keep the cost of utility survey down.
What is a utility survey?
A
utility survey is a crucial step in any construction or excavation project, as
it allows for the identification and mapping of underground utilities. These
utilities can include electrical cables, drainage, water pipes, gas lines,
telecommunications infrastructure, and more. By accurately detecting and
mapping these utilities, potential conflicts and hazards can be avoided,
ensuring the smooth progress of your project.
Having
utility survey completed in an early stage of the development might allow your
company to extend the boundary of the project. That is especially important
nowadays with the ongoing shortages of developable land.
Another
important aspect of utility survey is increased site safety. Utility strikes
during construction or excavation projects are serious risk. Damaging existing
underground infrastructure can have substantial financial repercussions on your
business, not to mention injuries to the workers and public or in the
worst-case scenario on site fatalities.
According
to UK DIRT Report, in 2023 there were 4 million holes and excavation dug across
United Kingdom every single day with 60,000 utility strikes which costed UK
economy £2.4 billion. The report observed that utility strike numbers over the
recent years show increasing tendency.
Utility
survey performed by trusted surveying company will greatly mitigate that risk
and should be considered in your utility damage prevention plan.
Using Ground Penetrating Radar (GPR) in PAS128 utility survey
Ground Penetrating Radar (GPR) is one of the primary tools used
if conducing utilities survey. By sending high-frequency electromagnetic waves
into the ground and analysing their reflections, GPR allows us to create
detailed subsurface images. This helps us identify not only the location of
utilities but also detect additional features such as voids, rebar, and
geological anomalies. By combining EML and GPR data, we deliver comprehensive
utility survey that leaves no room for uncertainty.
Utilities located with geophysical methods, such as Ground
Penetrating Radar (GPR) meet category B at PAS 128 accuracy levels. That means
you will know horizontal and vertical position (depth) of any detected object.
Ground Penetrating Radar (GPR) vs. Electromagnetic Locator
As already mentioned, Ground Penetrating Radar (GPR) and
Electromagnetic Location (EML) are totally different technologies:
GPR works by sending a signal into the ground and listening
for reflections from that signal and contains its own transmitter and receiver
within the unit.
EML works by detecting the electromagnetic signal that may
be emitted by power cables, or the energy from low frequency communications
signals which has ‘coupled’ onto metal services. Alternatively, in the case of
a metal service which is not a power cable, it can be induced to emit a signal
by accessing the service and clamping a separate transmitter onto it.
Let us explore the main differences between those two
techniques as when conducting a survey, they need to be approached in a logical
way and require training and experience to produce the best results.
Based on our experience and controlled experiments, Ground
Penetrating Radar will recover the locations of more underground features
compared to Electromagnetic Location methods (within the penetration and
resolution limitations of a GPR) in a like for like test with no manhole
access.
The missing information from a GPR survey is the information which is recovered by the site reconnaissance phase of a survey (by lifting manholes and identifying services) which is usually performed alongside an EML survey as part
of the process of clamping onto services to induce a signal. The other
difference is that EML works by inducing a known signal onto a specific utility
which is then traced, therefor EML enables services to be positively identified
and tracked compared to just located by GPR.
A summary of the advantages and limitations of each method:
-GPR provides its own transmitter and is able to detect
underground features without a power source
-GPR is able to detect most types of utilities including
plastic and other non-metallic services, as well as metal
-GPR will also detect other below surface features (rebar,
voids, structural information)
-GPR does not require manhole access
-GPR cannot identify services
-EML can detect smaller diameter cables
-EML can detect metallic services which have had a signal
induced onto them
-EML can track a specific, induced signal and therefor
identify individual services
-EML requires manhole access
-EML cannot recover any other below surface information.
These differences mean that the final drawing from a GPR
only survey will differ from the final drawing of an EML (and site
reconnaissance) only survey with the GPR detecting underground features and
recovering more below surface information but unable to identify the different
utilities. Whilst in the EM survey results (combined with the crucial
information from site reconnaissance) services will be identified, but the
drawing will lack the additional details recovered by the GPR and would not be
able to detect any non-metallic services or services for which there is no
manhole access.
The best utility survey is one which combine the strengths
of both methods as detailed both in PAS128 and the TSA utility survey
guidelines.
What is PAS 128?
PAS 128 refers to the Publicly Available Specification 128,
which is a widely recognized standard developed by the British Standards
Institution (BSI) for all utilities survey providers. PAS 128 provides
guidelines and recommendations for conducting utility surveys and determining
the accuracy level of utility information. It aims to improve the quality and
consistency of utility data collection and mapping processes.
Key features of PAS 128 specification
PAS128 defines four survey levels (D, C, B, and A), each
representing different levels of accuracy and data quality. These levels guide
utility survey practitioners in selecting the appropriate survey method based
on project requirements.
Level D: Desk-based utility records and historical information
are used for preliminary identification of utilities.
Level C: Site reconnaissance and visual inspection are conducted
to verify the existence of utilities.
Level B: Detection technologies, such as Ground Penetrating
Radar (GPR), are used to locate and map utilities.
Level A: Precise, high-accuracy methods, such as trial pits or
vacuum excavation, are employed to expose and verify the location and
attributes of utilities.
How is utility survey performed?
Our
utility survey processes are strict and follow the steps below:
Desk-based research
The
first step in a utility survey is to conduct a desk-based study to gather
information about an area. This can include obtaining utility records and
plans, site history, photographs, and any previous survey data.
If
you cannot provide records information (STATS) we can obtain them ourselves.
STATS records offer us valuable insight into which utilities and services are
supposed to be present in the ground and roughly where they may be. The STATS
information is also very helpful for ruling out what is not expected within a
given area. Finally, having access to STATS records can help to identify
services which would otherwise be classified as unknown.
Site reconnaissance
We
begin by understanding your project requirements and objectives. Our team
assesses the site and reviews available plans and records to gather essential
information about existing utilities.
If STATS are available surveyor will attend site, with a copy of the records confirming the presence of underground utilities where possible from manholes, buildings, and street furniture. Identifying where buried services are supposed to be located.
Field Data Collection
The
surveyor will systematically lift every manhole cover, identify the service
located within and trace it where possible.
Using
advanced GPR and EML equipment, our skilled surveyors conduct on-site data
collection. We scan the area, mark utility locations, measure depths, and
capture important information for accurate utility mapping. Electrically
conductive services will be traced using EML (Electromagnetic Location)
techniques, where the service is clamped, and a signal is induced into it from
a signal generator. The surveyor will then follow along the service using his
Electromagnetic Locator to trace the signal. The location of the service will
be marked on the ground in real time.
All
accessible street furniture will also be accessed – for example lamp posts,
road signs, telephone poles, bus stops, exterior fittings of buildings. Where
possible these will also be clamped and traced.
Services
that cannot be traced electromagnetically (for example, drainage or
non-metallic pipes) are traced using Ground Penetrating Radar (GPR) or using a
sonde – which is a signal transmitting device which can be attached to a rod
and pushed down a pipe, for example a drain. Where spurious signals are
received, these are traced inductively using the generator box to induce a
signal along its length.
After all the above is complete, the majority of the
services will have been located, identified and traced. We then sweep the
entire area using passive detection methods including EML in power and radio
modes, and GPR, to detect any unreported lines. Where anything is located it is
also traced and added to the drawing.
After all the above is complete, the utility survey should
have located, identified and traced most of the detectable services within an
area. The location of every pipe and utility is recorded using topographic
survey methods, such as GPS or Total Station and sent back to the office for
drawing.
Data Analysis and Mapping
To ensure that our results are as accurate as possible our
team processes and analyses the collected data using specialized software. We
interpret the GPR and EML results, identify utility locations, and create
detailed utility maps and reports.
Deliverables
We provide comprehensive deliverables that meet your
specific needs. This includes utility maps, CAD drawings, geospatial datasets,
and detailed reports outlining the location and characteristics of detected
utilities.
How much does utility survey cost?
Utility
survey cost is estimated on the project-to-project basis.
When
requesting a quotation, it would be helpful if you could include a clear survey
boundary (something like a google maps image or a topographic survey, with a clear
line showing the extents of the area), in addition it would be helpful if you
can specify what kind of survey you would like (if you know).
If you
are unsure exactly what you need, contact us and we can discuss your
requirements in more detail.
For
more information about utility surveys, or to request a quote. Please contact
us at info@kbgprsurveys.co.uk or
fill in the contact form below.
Benefits of utility survey
Increased land space
Utility detection and mapping survey will maximise land space for your project where you can safely dig
Cost saving
Fixing damaged pipeline will be costly and time consuming. Prevent it by commissioning utility survey
PAS 128 compliant
Depending on your needs our underground utility survey will meet all the requirements of PAS 128 standard
Site safety
Gas pipe strike during construction works is not only costly but can be dangerous to you or your contractor
Why choose us?
Our utility surveyors have extensive expertise and experience
Our utility surveyors were involved in major airport and highways infrastructure projects
We are trusted by large construction companies and local councils
We are honest and reliable in dealing with all our clients
With our experience in GPR and geophysical surveys, coupled with our utility survey experience, we are able to get the most out of every survey. No utility survey is 100%, but you can have 100% confidence that our surveyors have used industry leading equipment and followed the correct processes, to locate and map all of the underground utilities that can be found, within a given survey area. Each of these steps plays a critical role in ensuring that the utility survey is carried out safely, accurately and effectively, and helps to minimize the risk of damage to existing underground utilities during construction or excavation work.
A utility survey is performed using an Electromagnetic Locator (EML) and Signal Generator to allow metallic services to be accessed, clamped and traced. For drainage, a Sonde (transmitter) is pushed along the drain and traced using the EML. Finally, non-metallic services such as Gas and Water mains are traced using Ground Penetrating Radar (GPR). In addition to the detection equipment, GPS and Total Station are used to record the locations of detected utilities for the CAD drawing.
Locations of underground services are sprayed directly onto the ground using marker paint, these marks are colour coded to represent different services. In addition to spray marks, service locations are recorded by GPS or Total Station and compiled onto a CAD drawing which will detail both the locations of services and their depths from the surface, services can be identified both by line type and colour.
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