DETECT, LOCATE & MAP SUBSURFACE PIPES & CABLES WITH GPR
Our chartered status, proven geophysical expertise and underground utility surveying experience makes us unique. We provide the highest quality PAS 128:2014 and ASTM D6432-11 compliant underground utility surveys.
- Specialist underground utility surveyors since 1994.
- The only dedicated GPR surveyors in Ireland and the UK.
- The only chartered geophysicists in Ireland and the UK providing underground utility detection surveys.
PAS 128 COMPLIANT UNDERGROUND UTILITY SURVEYING
EXISTING DATA REVIEW
PAS 128 Survey type D: Desktop utility records search | Quality level QL-D +
We source, review, compile and merge all existing utility maps, records and information for the survey area. Survey type D is a prerequisite for survey types C, B and A. This existing utility information is assigned quality level QL-D. 
SITE VISIT/TOPOGRAPHIC SURVEY
PAS 128 Survey type C: Site Reconnaissance | Quality level QL-C +
We inspect and survey all visible utility-related surface features on-site. When compared and merged with utility information from the existing records search (survey type D) this step conforms to a survey type C.|
EM LOCATION SCAN
Part of PAS 128 Survey type B: Detection | Quality level QL-B3 +
We scan and trace all utilities both within and intersecting the boundaries of the survey area using passive and active electromagnetic radio frequency (EM) cable and pipe locators. These methods can detect metallic/conducting utilities only and the horizontal locations obtained for detected utilities are acceptable for QL-B3.
MANHOLE SURVEY
Part of PAS 128 Survey type A: Verification | Quality level QL-A +
For each access point (manhole or inspection chamber) relevant to the survey area exposed utilities are visually inspected, photographed and surveyed. We record location and attribute information for each utility as specified in PAS 128. The exposed utility is assigned quality level QL-A at the point of direct measurement. Our surveyors have the necessary training and certification for site work, traffic management and working in confined spaces. We can also provide manhole condition and CCTV surveys if requested.
GEOPHYSICAL SURVEY WITH GPR
Part of PAS 128 Survey type B: Detection | Quality levels QL-B2/B1 +
We carry out detailed GPR reflection profiling, using site-specific frequencies and acquisition settings, on a suitable grid basis over the survey area. The survey grid/ search resolutions are chosen to conform to PAS 128 detection methods (M1-M4).We are chartered geophysicists and acquire our GPR surveys in accordance with the standards set out in ASTM D6432-11. We own and operate a wide range of GPR antenna configurations to guarantee optimum data acquisition over different site conditions. The GPR experience of the GPR operator is crucial to ensure high quality data is acquired.
SITE MARK-UP +
We mark out utilities on the ground to indicate the utility location based on the detected signal return in the field.
OFF-SITE ANALYSIS
Part of PAS 128 Survey type B: Detection | Quality levels QL-B2/B1 +
Off-site signal correlation and processing is strongly recommended especially in congested urban areas as errors can occur where utilities are closely spaced and cross at different depths and also where signal penetration is poor. Post-processing is necessary to achieve the highest quality level QL-B1P for a PAS 128 survey Type B. Additional GPR signal processing (filtering and amplitude analysis) and interpretation of the data in the office is recommended to ensure that the acquired GPR data is thoroughly checked and utilised fully. This minimises the risk of undetected utilities. As part of a PAS 128 survey all GPR anomalies, not just those caused by utilities, must be noted and recorded. Our geophysicists have the proven qualifications and experience in advanced GPR data processing and interpretation to provide this information. GPR wave velocities are converted to depths using direct calibration from service access points to achieve quality level QL-B vertical location accuracies.
GROUND TRUTHING
Part of PAS 128 Survey type A: Verification | Quality levels QL-A +
Quality level QL-A utility data is obtained by directly surveying the true position (horizontal and vertical) of a buried utility at a given location. This can be achieved in a manhole or inspection chamber or by exposing the utility in a trial hole using safe digging practices. We provide a vacuum excavation service to achieve QL-A. The trial hole data can be used to confirm the quality level QL-B location of a mapped utility obtained from the type B detection survey and to provide further information on the ground and utility condition. Location and attribute information is recorded as specified in PAS 128. The exposed utility is assigned quality level QL-A at the point of direct measurement.
DATA MERGE/QUALITY CONTROL +
Information from all sources is correlated and merged. Any discrepancies are noted and resolved if possible, sometimes through a site revisit. This step is necessary before the appropriate PAS 128 quality levels can be assigned to each run of utilities through the survey area.
UTILITY QUALITY LEVEL CLASSIFICATION +
We classify each utility by type and quality level from D to A in accordance with PAS 128.
SURVEY DELIVERABLES +
- Every Scantech survey is planned, overseen, reviewed and signed off by a chartered professional geophysicist (PGeo) who is also a registered member of the European Federation of Geologists (EFG).
- Utility drawings are delivered in 2D or 3D CAD/GIS formats to client specifications.
- We can provide a full topographic survey or use the client's base map if required.
- We always provide a separate survey report detailing the equipment used, the survey methodology, GPR survey locations, GPR processing and interpretation, the merged results and the final data quality levels. Provision of this information is now part of a PAS 128 compliant utility survey.
- A copy of the located raw and processed GPR survey data, manhole logs and a photographic record of the survey are available to the client as required by PAS 128.
References
PAS 128:2014 Specification for underground utility detection, verification and location (British Standards Institution (BSI), 2014)
ASTM D6432-11 Standard Guide for Using the Surface Ground Penetrating Radar Method for Subsurface Investigation. (American Society for Testing and Materials, 2011).
ASCE 38-02 Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. (American Society of Civil Engineers, 2002)
ABOUT PAS 128
PAS 128:2014 Specification for underground utility detection, verification and location.
BSI PAS 128:2014 is the UK publically available specification (PAS) for underground utility detection, verification and location. This specification sets out the standard requirements and recommendations for underground utility surveying, from project documentation through to data capture and the format of deliverables.
PAS 128 provides clients with a consistent approach to specifying a utility survey by defining survey types and methods and also provides a classification system using quality levels (QL) to indicate the degree of confidence and accuracy associated with located utilities.
GPR surveying is a principal component of a PAS 128 detection survey (type B) and is needed to obtain accurate utility depths. PAS 128 includes the requirements for GPR data acquisition, processing interpretation and documentation. Geophysical knowledge and expertise are crucial to correctly acquire GPR data, to identify GPR anomalies caused by utilities and to interpret utility depths from the GPR survey results. This specification will provide useful guidance for clients but also more importantly for practitioners from other disciplines with limited geophysical knowledge or experience.
PAS 128 applies to utility detection down to a depth of 3 m below ground level. It defines four survey types A, B, C and D which are outlined below. Each survey type has associated quality levels (QL-A, QL-B, QL-C, QL-D) and each level has an associated horizontal and vertical location accuracy requirement. PAS 128 also defines detection methods M1 to M4P. Each method has an associated survey grid/search resolution and range of achievable quality levels.
- SURVEY TYPE D is a desktop utility records search where underground utilities are identified from existing utility records. Utility quality level QL-D is achievable. Survey type D is a prerequisite for survey types C, B and A.
- SURVEY TYPE C is a site reconnaissance survey. The site is visited and inspected to validate existing records obtained from survey type D. Utility quality level QL-C is assigned where an existing utility record matches visual evidence that the utility is present on-site.
- SURVEY TYPE B is a detection survey where geophysical surveying is used to find and locate underground utilities. Both GPR surveying and EM scanning are the minimum requirement for survey type B. EM scanning is used to find metallic/conducting utilities and GPR surveying is required to detect non-metallic utilities and to obtain depths to the detected utilities. Utility quality levels QL-B4 to QL-B1P are achievable.
Note: Both the detection methods M1-M4 and the detection survey quality levels QL-B can be suffixed with a "P" to indicate that the geophysical data (GPR) was post-processed off-site. Processing off-site can help resolve ambiguities in GPR anomalies especially in congested urban areas with high utility densities and also where subsurface conditions impact signal transmission. Scantech geophysicists have the experience and qualifications in GPR data processing and interpretation to provide all levels of post-processing, from basic to advanced, as part of a PAS 128 survey. ABOUT GPR PROCESSING + - SURVEY TYPE A involves the verification of utility presence and location by direct observation and measurement of the exposed utilities. The utility is exposed by excavation or at access points. The utility is assigned the quality level QL-A at the point of direct measurement.
Different survey types, detection methods and quality levels can be requested for different parts of the same survey area. As experienced geophysicists Scantech can advise on the most suitable combination of survey methodologies and quality levels to best achieve the survey objectives. Typically we carry out Type B detection surveys and aim to achieve quality level QL-B1P wherever possible. We can achieve a higher quality level QL-A at manholes where exposed utilities are directly surveyed.
Radargram with GPR anomalies from telecoms, drainage, power and two water mains.
Utility survey in AutoCad Civil 3D.