At Geospatial World Forum 2014 in Geneva this year Andy Rhoades, Head of Service Protection Knowledge & Information Management Technical Standards and Assurance at Heathrow Airports, gave a fascinating presentation on the accuracy of geolocation information about underground utilities.
Heathrow is like a small city. It has 13 different types of services (utilities), some of which are unique to the airport environment, with over 50 different owners. For example, Heathrow's infrastructure includes more than 45 000 man holes, 72 miles of high pressure fire mains, power cables ranging from 9v up to 400 Kva, 81 miles of aviation fuel pipes ranging between 1.5 inches to 20 inches in diameter and between 3 and 115 bar in pressure.
At Heathrow safety is the most important objective. It is essential for passenger, staff and contractor safety that everyone knows precisely where all of the underground infrastructure is. At Heathrow Information Modelling refers to a co-ordinated set of processes and information requirements that add value by creating, managing and sharing the properties of an asset throughout its lifecycle. The same principles apply whether it is a building, a gas main or an AGL light fitting on a runway. Information Modelling provides a platform for asset management across the entire lifecycle - acquisition, operate, operate, maintain and disposal - so that everyone involved works collaboratively sharing information in a common way. This makes it possible for the transitions from architect to designer to constructor to client within the acquisition phase to happen seamlessly.
A key dimension of the information maintained by Heathrow about underground facilities are "confidence codes", which are a measure of how confident a surveyor is that he/she has pinpointed the service he/she is surveying. There are a number of technologies for detecting underground facilities including electromagnetic, ground penetrating radar, acoustic, seismic and others, and they all require interpretation. Heathrow's confidence codes are a way of classifying the results of underground utility detection, verification and location undertaken by different survey methods:
- D – Desk top survey followed up with site reconnaissance.
- C – Use of underground scanning tools to locate services with a reasonable degree of confidence of what has been located.
- B – Detection - Use of two techniques to verify the location of the utility, for example, using Ground Penetrating Radar (GPR) to confirm the location found with an electromagnetic scanner.
- A –Verification - Digging a trial hole using a vacuum excavation/air pick or hand tools to expose the service, then surveying the location and extents to 25mm accuracy.
Validation life cycle
Heathrow has developed a business process for continuous improvement of the location accuracy of underground infrastructure called the "Validation Life Cycle". It relies on a process that progressively updates confidence codes for underground facilities impacted by a construction project so that the information captured during a project is not lost but is integrated into Heathrow's asset database.
- Project manager sets scope and requests latest information
- Designer receives existing information
- Designer carries out site reconnaissance, applies confidence codes
- Designer/client/project manager agree on scope for survey
- Survey carried out increasing confidence codes
- Design completed, survey and design passed to constructor(contractor)
- Constructor surveys as they go increasing confidence codes
- Progressive handover to client for integration
- Information fully integrated into existing information
Heathrow Map Live is a web-based application that provides business visibility into model information. It is based on the Common Language (CL), which defines the structure of all asset information at Heathrow. Deliverables are progressive throughout projects. All information resides in two databases, Document Management and Asset Management System. These contain infrastructure and building models (BIM), design drawings, health & safety files, operation and maintenance manuals and asset maintenance information. This information provides the basis for operating the airport safely, and also helps management make informed decisions. In addition it helps Heathrow fullfil its legal obligations under the CDM (Construction Design Management) regulations and the Corporate Manslaughter Act.
As a result of these measures service strikes (accidentally hitting a utility cable or pipe) due to inaccurate information about underground infrastructure have declined at Heathrow by a factor of 6 since 2002.
Going forward Heathrow is planning to implement a "Base Station", an application which will be mandatory for all contractors. In the future Heathrow will only accept “as-built” information that is created using the Base Station application. Heathrow plans to review each company and user’s competence on a project by project basis.
Heathrow has been supporting the development of the PAS128 standard for underground infrastructure which I have blogged about previously. PAS 128 is aimed at the practitioner, surveyors who make their living detecting and reporting the location of underground utilties.
Heathrow has also supported the HSG47 guide Avoiding danger from underground services which is aimed at all those involved in commissioning, planning, managing and carrying out work on or near underground services. It outlines the potential dangers of working near underground services and gives advice on how to reduce any direct risks to people's health and safety, as well as the indirect risks arising through damage to services.
Heathrow has helped to develop National Vocational Qualifications (NVQs) relevant to underground asset management. National Vocational Qualifications (NVQs) are work based awards in England, Wales and Northern Ireland that are achieved through assessment and training. To achieve an NVQ, candidates must prove that they have the competence to carry out their job to the required standard. NVQs are based on National Occupational Standards that describe the 'competencies' expected in any given job.