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Copyright of RSK
PAS 128:2014 Specification for underground
utility detection, verification and location
What it requires ...
Copyright of RSK
PAS128 – launched on 30th
June, 2014
9 July 2014 2
Copyright of RSK
What is a PAS?
•A Publicly Available Specification (PAS) is a
sponsored fast-track standard
•Written by a...
Copyright of RSK
Aims of this PAS
PAS128 aims to provide:
•Clarity in the service provided and
methods employed
•Consisten...
Copyright of RSK
Specification of minimum requirements
vs best practice guidance
Specification:
The normative text set out...
Copyright of RSK
Survey types
9 July 2014 6
ABCD
Type D
Desktop
utility
records
search
Type C
Site reconn-
aissance
Type B...
Copyright of RSK
Survey output - Quality Levels
Each segment of utility in the deliverables will be identified with a ‘Qua...
Copyright of RSK
QLD – Desk study
9 July 2014 8
a) Identify known utility owners within
the specified survey area
b) Reque...
Copyright of RSK
QLC – Site reconnaissance
9 July 2014 9
On-site checks shall document
a) The presence, type and markings ...
Copyright of RSK
QLB – Detection surveys
9 July 2014 10
•Use geophysical techniques to detect and identify
utilities withi...
Copyright of RSK
Detection accuracy
9 July 2014 11
The positional
accuracies for QL-B1,
QL-B1P... etc. and how
these vary ...
Copyright of RSK
QLA – exposure and verification
9 July 2014 12
Data shall be obtained through visual
inspection of the ut...
Copyright of RSK
Detection – levels of effort and return
9 July 2014 13
PAS 128 sets out guidance on the minimum effort re...
Copyright of RSK
Detection – levels of effort and return
9 July 2014 14
Copyright of RSK
Post-processing of data – when and why?
9 July 2014 15
Copyright of RSK
Some subsurface environments are too complex
to detangle using real time signals on site
Copyright of RSK
Recording data and post-processing provides
more accurate interpretation
Survey grid baseline
Directionof...
Copyright of RSK
Post processed data can deliver detail not
possible from site mark out
Copyright of RSK
Comparing apples with apples at tender stage
It is required for the practitioner to submit:
a)The survey ...
Copyright of RSK
Transparency of work done - Deliverables
A detailed report including:
detailed survey outcomes including ...
Copyright of RSK
Transparency of work done - Deliverables
Retention of survey data/records:
All recorded and processed dat...
Copyright of RSK 22
Why were these missed?
Copyright of RSK
Accountability of results
In the deliverables the practitioner must state:
the quality level (level of ac...
Copyright of RSK 9 July 2014 24
Survey quality/accuracy and accountability
Copyright of RSK
Accountability of results
The client gets further protection if they specify:
all geophysical data to be ...
Copyright of RSK 9 July 2014 26
Evidence of detection work done
Survey company A
claims that GPR
didn’t work
GPR data acqu...
Copyright of RSK
Protection for the client
•The practitioner needs to set out:
• What they did and where
• What the outcom...
Copyright of RSK
Take up
9 July 2014 28
If adopted by the industry the PAS
could enable:
•Clear definition for a minimum
s...
Copyright of RSK 9 July 2014 29
George Tuckwell is the director responsible for geophysics within RSK, providing site
inve...
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PAS 128; Specification for underground utility detection, verification and location: What it requires and how to use it

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The new Publicly Available Standard from the British Standards Institute specifies the minimum that should be done in respect to underground utility detection, verification and location, and also provides guidance and pointers to best practice.
It sets out 4 types of survey: Desktop Study (Type D), site reconnaissance (Type C), detection (Type B), and verification (Type A).
The PAS supports both the practitioner and the client throughout the project cycle. At tender stage It is required for the practitioner to submit:
a) The survey type(s) to be deployed, including the extent for each type
b) For survey type B, detection methods to be deployed as specified in Table 2, including estimated extent for each method
c) Comment on these survey type(s) and, for survey type B, detection methods, with regard for satisfying the client’s requirements
d) Comments on the expected achievable quality level
e) Names and experience of the project team
f) How the survey area is to be managed to maximise the area available for survey and ensure the safe execution of the works
The client should then be able to compare apples with apples when seeking multiple quotes.
Following the work, the practitioner should submit a detailed report including:
• detailed survey outcomes including how successful each detection methodology proved to be and a plan showing any areas where these detection methodologies were not successful
• Utility segments identified with the quality level achieved
• Recommendation for any further survey work required to meet the client’s requirements
All recorded and processed data, site notes, metadata, and intermediate stage processing files shall be retained, and shall be available to the client on request
It is recommended as best practice for all data to be recorded as evidence of detections and of work undertaken. This is required where post processing has been specified. This is optional for other detection surveys – unless the client chooses to make it a requirement.
The practitioner needs to set out what they did and where, what the outcome was, i.e. what accuracy and confidence was achieved and what areas of uncertainty and risk remain. The practitioner should then stand by their deliverables.
If used properly by the client, the practitioner can no longer hide behind the ‘black box’ of complex geophysical equipment to explain away why something was missed or inaccurate in their survey output.
If adopted by the industry the PAS could enable:
• Clear definition for a minimum standard of utility verification and location
• More control to the client
• More comeback for the client when issues arise
• Fewer incidents related to service strikes
• Fewer delays caused by unknown buried services

Dr George Tuckwell
www.safe-ground.co.uk

Published in: Engineering, Technology
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PAS 128; Specification for underground utility detection, verification and location: What it requires and how to use it

  1. 1. Copyright of RSK PAS 128:2014 Specification for underground utility detection, verification and location What it requires and how to use it 9 July 2014 1 Dr George Tuckwell PhD FGS CGeol CSci Director
  2. 2. Copyright of RSK PAS128 – launched on 30th June, 2014 9 July 2014 2
  3. 3. Copyright of RSK What is a PAS? •A Publicly Available Specification (PAS) is a sponsored fast-track standard •Written by a drafting panel, supported by a steering committee. •After two years the PAS is reviewed and a decision is made as to whether it should be taken forward to become a formal British Standard 9 July 2014 3
  4. 4. Copyright of RSK Aims of this PAS PAS128 aims to provide: •Clarity in the service provided and methods employed •Consistency in the approach to data capture •Classification of the results and the confidence that can be associated with them •Standardisation of the format of deliverables •Accountability for the work undertaken 9 July 2014 4
  5. 5. Copyright of RSK Specification of minimum requirements vs best practice guidance Specification: The normative text set out the minimum that must be done. Best practice: The informative text provides guidance and also points to best practice. This allows a range of responses to any request from the client, who needs to decide what specification they want, and what contractual conditions they want to put in place 9 July 2014 5
  6. 6. Copyright of RSK Survey types 9 July 2014 6 ABCD Type D Desktop utility records search Type C Site reconn- aissance Type B Detection survey Type A Verification
  7. 7. Copyright of RSK Survey output - Quality Levels Each segment of utility in the deliverables will be identified with a ‘Quality Level’ 9 July 2014 7
  8. 8. Copyright of RSK QLD – Desk study 9 July 2014 8 a) Identify known utility owners within the specified survey area b) Request asset information from identified utility owners c) Collate all data on utility owners and their assets
  9. 9. Copyright of RSK QLC – Site reconnaissance 9 July 2014 9 On-site checks shall document a) The presence, type and markings of utility- related surface features b) Measurements between known surface features on the ground compared with those depicted on the plan c) Differences between the map/drawing or digital features supplied and those extant on the ground
  10. 10. Copyright of RSK QLB – Detection surveys 9 July 2014 10 •Use geophysical techniques to detect and identify utilities within the survey area •The quality level (accuracy) achieved shall be documented as QL-B1, QL-B2, QLB3 or QL-B4 •If post-processing has been used to improve the confidence of the data, the quality level shall be suffixed with the letter ‘P’
  11. 11. Copyright of RSK Detection accuracy 9 July 2014 11 The positional accuracies for QL-B1, QL-B1P... etc. and how these vary with depth
  12. 12. Copyright of RSK QLA – exposure and verification 9 July 2014 12 Data shall be obtained through visual inspection of the utility a)at access points such as in a manhole or inspection chamber; and/or b)by its excavation and exposure
  13. 13. Copyright of RSK Detection – levels of effort and return 9 July 2014 13 PAS 128 sets out guidance on the minimum effort required for different situations. For example, an urban area expected to be congested with multiple surveys would be expected to require a more dense detection grid in order to detect utility segments accurately. It also makes clear that additional confidence and accuracy can be obtained by post-processing the data; that is taking the recorded geophysical data off site, processing it in 3D volumes to enhance and isolate signals from buried utilities, and transferring the results of that analysis onto detailed CAD drawings.
  14. 14. Copyright of RSK Detection – levels of effort and return 9 July 2014 14
  15. 15. Copyright of RSK Post-processing of data – when and why? 9 July 2014 15
  16. 16. Copyright of RSK Some subsurface environments are too complex to detangle using real time signals on site
  17. 17. Copyright of RSK Recording data and post-processing provides more accurate interpretation Survey grid baseline DirectionofGPRsurveylines
  18. 18. Copyright of RSK Post processed data can deliver detail not possible from site mark out
  19. 19. Copyright of RSK Comparing apples with apples at tender stage It is required for the practitioner to submit: a)The survey type(s) to be deployed, including the extent for each type b)For survey type B, detection methods to be deployed as specified in Table 2, including estimated extent for each method c)Comment on these survey type(s) and, for survey type B, detection methods, with regard for satisfying the client’s requirements d)Comments on the expected achievable quality level e) Names and experience of the project team f)How the survey area is to be managed to maximise the area available for survey and ensure the safe execution of the works 9 July 2014 19
  20. 20. Copyright of RSK Transparency of work done - Deliverables A detailed report including: detailed survey outcomes including how successful each detection methodology proved to be and a plan showing any areas where these detection methodologies were not successful Utility segments identified with the quality level achieved Recommendation for any further survey work required to meet the client’s requirements 9 July 2014 20
  21. 21. Copyright of RSK Transparency of work done - Deliverables Retention of survey data/records: All recorded and processed data, site notes, metadata, and intermediate stage processing files shall be retained, and shall be available to the client on request It is recommended as best practice for all data to be recorded as evidence of detections and of work undertaken •This is required where post processing has been specified •This is optional for other detection surveys – unless the client chooses to make it a requirement 9 July 2014 21
  22. 22. Copyright of RSK 22 Why were these missed?
  23. 23. Copyright of RSK Accountability of results In the deliverables the practitioner must state: the quality level (level of accuracy) achieved for each segment of utility identified; and which detection techniques were used in all surveyed areas of the site, including areas where no utilities have been detected. 9 July 2014 23
  24. 24. Copyright of RSK 9 July 2014 24 Survey quality/accuracy and accountability
  25. 25. Copyright of RSK Accountability of results The client gets further protection if they specify: all geophysical data to be recorded and retained evidence provided of the detections achieved and areas where detections were not possible as part of the deliverables Benefits: Evidence is retained of the work done Data can be reviewed at a later date in light of subsequent findings or as part of a routine audit, either by the practitioner, the client, or a third party 9 July 2014 25
  26. 26. Copyright of RSK 9 July 2014 26 Evidence of detection work done Survey company A claims that GPR didn’t work GPR data acquired by survey company B
  27. 27. Copyright of RSK Protection for the client •The practitioner needs to set out: • What they did and where • What the outcome was, i.e. • What accuracy and confidence was achieved • What areas of uncertainty and risk remain • What further could be done to reduce risk •The practitioner should then stand by their product •If used properly by the client, the practitioner can no longer hide behind the ‘black box’ of complex geophysical equipment to explain away why something was missed or inaccurate in their survey output. 9 July 2014 27
  28. 28. Copyright of RSK Take up 9 July 2014 28 If adopted by the industry the PAS could enable: •Clear definition for a minimum standard of utility verification and location •More control to the client •More comeback for the client when issues arise •Fewer incidents related to service strikes •Fewer delays caused by unknown buried services
  29. 29. Copyright of RSK 9 July 2014 29 George Tuckwell is the director responsible for geophysics within RSK, providing site investigation, consulting and expert witness services. Amongst others, he has advised National Grid, the Environment Agency and the United Nations on the deployment of geophysical technologies. George is a past Vice President of the Geological Society of London, is a Chartered Geologist and a Chartered Scientist and is a member of the Editorial Board of the Journal of Engineering Geology and Hydrogeology. He provides expert witness services in cases relating to the use of geophysical technologies, the interpretation of, and reliance placed on, the data acquired. This includes cases of buried service detection, mapping and avoidance.

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