Everything you need to know about PAS 128 Survey

Posted by John MacIntyre

What is a PAS 128 Survey? 

PAS 128:2022 is a publicly available specification established by the British Standards Institution (BSI) for underground utility detection, verification, and location. First published in 2014, PAS 128 was developed in collaboration with industry experts to standardise the process of detecting and mapping underground utilities such as water pipes, gas lines, and electrical cables. With a revision to the specification in April 2022, the aim of PAS 128 is to ensure that utility surveys are conducted using accurate, consistent methods and produce reliable, qualified quality data. The specification is widely used across the UK construction, civil engineering, and utility sectors to reduce the risks associated with working near underground utilities. 

Why is a PAS 128 Survey needed? 

Obtaining precise information about underground utilities before commencing any construction or ground investigation activities is essential to prevent costly and hazardous incidents. PAS 128 offers a standardised method for detecting utilities, minimising the risk of damaging or disrupting utility assets during excavation or construction. This approach reduces the likelihood of injuries to construction workers and damage to underground utilities during work.

Accurate data collection through PAS 128 helps prevent project delays, utility outages, and health and safety risks that can arise when underground utilities are not correctly mapped. It sets a high bar for utility tracing, ensuring measurable quality levels that can assist engineers, designers, and contractors in project planning and execution.

Who might use a PAS 128 Survey? 

PAS 128 is relevant to a wide range of construction and utility work professionals. These include: 

  • Engineers who require accurate underground utility data to design safe infrastructure projects. 
  • Construction and civil contractors who need to manage the risk of damaging utilities during excavation works.
  • Project managers who oversee construction timelines and budgets. 
  • Geospatial and subsurface utility surveyors who responsible for collecting and analysing utility data. 
  • Utility owners who are responsible for managing and maintaining their assets and ensuring they are correctly mapped to prevent disruptions or accidents. 

PAS 128 Surveys can be procured for projects across multiple sectors. Technics has undertaken numerous PAS 128 surveys nationwide, These include residential properties, hospitals, EV infrastructure, district heating schemes, defence sites, aviation and highways.

What are the benefits of PAS 128 Surveys? 

PAS 128 surveys offer numerous benefits, including: 

Increased accuracy – The standard ensures consistent and precise utility detection with quality levels identified, reducing the risk of errors.

Improved safety – PAS 128 surveys enhance safety, efficiency, and project success by providing reliable utility data. This alignment with Health and Safety Executive (HSE) Guidance, HSG 47 reduces utility strike risks, protects workers, and ensures public safety. By mitigating risks, projects avoid costly delays and benefit from informed decision-making.

Cost savings – Avoiding utility damage reduces costly project delays and prevents unplanned work. 

Better project planning – Reliable utility data helps project managers plan construction work more effectively, minimising disruptions. 

Regulatory compliance – Even though PAS 128 is voluntary, it demonstrates adherence to best practices and industry standards, which can enhance a company’s reputation. 

The different types of PAS 128 surveys 

PAS 128 surveys are categorised into four types based on the accuracy and method of information and data collection: 

  • Type D (Desktop Survey) utilities are collated in a report format based on the utility service providers’ statutory plans.  
  • Type C (Site Reconnaissance) data from utility records is corroborated with physical evidence gathered from a site walkover. 
  • Type B (Utility Detection) A qualified and experienced practitioner will select the appropriate technology, such as ground penetrating radar (GPR) and electromagnetic location (EML) to detect the utilities. The accuracy of the utility detection will depend on the methodology used on site, the evaluation of the record information and the competence of the post-processing of the GPR data. Ultimately, these factors determine the practitioner’s confidence in defining the achieved quality level. 
  • Type A (Verification by Excavation)  Identifying and locating underground utilities through a manhole, inspection chamber, or by physical excavation and exposure.

The most accurate survey type, utilities are verified by physically exposing them, usually through hand-dug trial pits or vacuum excavation. 

Why should you use PAS 128? 

PAS 128 ensures that any underground utility survey is consistent, accurate, and reliable. Whether for pre-construction planning or avoiding utility strikes during excavation, PAS 128 helps minimise risks and improve decision-making. The standard is a benchmark for best practices in utility detection and verification and can help organisations demonstrate their commitment to quality and safety. 

For projects in urban environments or sites with complex underground networks, PAS 128 compliance is essential to avoid service disruptions and ensure the project runs smoothly. 

Are PAS 128 surveys accurate? 

PAS 128 surveys are accurate, mainly when higher-level survey types A and B are undertaken. These surveys rely on advanced geophysical techniques such as Ground Penetrating Radar (GPR) and electromagnetic methods, ensuring precise horizontal and vertical location data. The accuracy increases even further with Type A surveys, which verify utilities through excavation. 

While the accuracy of the survey can depend on the equipment used, the utility surveyor’s expertise remains a significant factor. PAS 128 mandates that operators must be trained to a high standard, further enhancing the reliability of the survey results. For specific infrastructure projects, a minimum QCF Level 5 qualification can be required for utility surveyors to work on-site.  

Each survey type (A to D) can achieve a specific quality level. For example, a desktop utility survey can only reach a quality level D (QL-D) based on the accuracy of the plans, and no site visual inspection and detection methods are undertaken. For a survey type A, a quality level A (QL-A) can be achieved with the utility assets exposed following excavation work utilising a vacuum excavator.  

What is the process of undertaking a PAS 128 Survey? 

Firstly, the purpose of the project needs to be determined to ascertain the most effective survey type, the technology to be utilised, and the expected quality levels based on the existing information available, the practitioner’s experience and similar site environments.  

The process of completing a PAS 128 survey follows several key steps: 

  • Project Planning A clear understanding of the project scope and utility detection requirements is established.
  • Desktop Utility Records Search (Type D) Existing utility records are collated and analysed to gather preliminary data regarding the underground utilities located on site. 
  • Site Reconnaissance (Type C): Data from utility records is matched with visible surface indicators on-site, these include inspection covers or utility markers. 
  • Utility Detection (Type B) Specialised geophysical equipment such as Ground Penetrating Radar (GPR) and Electromatic Locators (EML) is used to detect the utilities and plot them geospatially. 
  • Verification (Type A) If required, the detected utilities are exposed to verify their location and condition, often using non-invasive excavation methods, such as vacuum excavation.  
  • Deliverables The survey results are presented in detailed reports and drawings, including all relevant geospatial and verification data. 

Book a PAS 128 Survey with Technics 

If you’re embarking on a construction or development project and need precise mapping of underground utilities, think about scheduling a PAS 128 survey with Technics. With extensive experience in utility detection services, Technics delivers surveys that meet the highest industry standards, providing confidence and ensuring your project remains safe and compliant. 

By choosing PAS 128-compliant services, you invest in your project’s safety, accuracy, and long-term cost savings.  

To discuss your project with us, please do not hesitate to get in touch or email us at enquiries@technicsgroup.com.