Project background

NHS Property Services Ltd commissioned RSK to carry out a PAS128 ground-penetrating radar (GPR) utility survey at Edgware Community Hospital, a working community hospital in London. The survey area covered approximately 6.7 ha. Given the large scale and sensitive nature of the site, it was imperative the work was carried out efficiently and safely while minimising the impact on the operations of the hospital itself. The survey aims were to identify underground services and potential unknown buried features, reducing the risk for future developments on the site.

PAS128 GPR utility survey

For the utility survey, state-of-the-art electromagnetic locating (EML) instruments were used in conjunction with a fully documented inspection cover lifting exercise and a GPR survey utilising a 400 MHz radar system. The GPR survey was undertaken to PAS128 Type B specifications on an orthogonal grid of 1 m lines across the entire area to ensure that all detectable buried obstructions and services were imaged to a depth of approximately 2 m. All the utility tracing, visual inspection and GPR information was combined with a topographic base plan of the site and existing utility record drawings to produce a comprehensive PAS128-compliant plan of the services within the survey area.

By utilising GPR across the entire site and by completing post-processing of all GPR data, as well as non-metallic services, the team was able to identify and map the extent of reinforced concrete slabs, buried obstructions and potential areas of made ground. The provision of a more complete and accurate service drawing enabled the early identification of problematic features and reduced the likelihood of encountering unexpected ground conditions later in development.

Programme efficiency

Works were undertaken at night to minimise disruption to the hospital, its staff and patients. RSK liaised directly with the hospital estates manager to coordinate access to internal courtyards and locked enclosures at times suiting hospital routines and to close off sections of car parks, thereby reducing the impact on sensitive areas and enabling complete survey of the area. RSK’s project manager provided a single point of contact for the client, allowing a smooth working relationship and maximising programme efficiency. For road sections on the external areas of the hospital, RSK utilised its in-house traffic management suppliers, reducing reliance on external contractors and enabling the completion of the works on time and to budget.