Southampton Central Station Quarter
No delays at this station!
…But there may have been serious delays to the design and construction process if it wasn’t for a SUMO geophysical survey.
£3M of improvement works faced delays after last minute concerns of attenuation tanks in the construction area.
No records were available to confirm their existence.
Their accurate location was urgently needed.
Digging trial holes became costly, risky and time consuming.
SUMO consulted to devise a non-invasive solution to locate all buried anomalies.
SUMO carried out an initial reconnaissance of the site.
No surface responses were visible and so multi-geophysical survey techniques were required.
The entire 1,000 square metre site was surveyed on a 1.0 metre transect grid. Low frequency ground penetrating radar (GPR) backed-up with an electromagnetic ground conductivity survey.
The survey data revealed eight well-defined parallel linear anomalies crossing the site, characteristic of the responses expected from attenuation tanks.
The crowns of the GPR images indicated eight tanks approximately 0.9 metres beneath the ground level.
Unknown areas of reinforced concrete buried under asphalt were also detected.
Typical configuration of attenuation tanks
Two examples of actual survey data indicating parallel anomalies confirming the existence of the tanks
Costs and benefits
The survey cost was only £2,500. But, the accurate detection of all buried obstructions in the construction area avoided the need for trial holes costing several times more without the added risk of damage. Furthermore, the prompt delivery of the survey report allowed the project to continue on time.
“The results were very accurate. The design process minimised additional costs from excavating trial holes and also minimised disruption to the public by carrying out the work overnight.”
Balfour Beatty Senior Engineer
Survey techniques used in this case study...
Ground Probing Radar (GPR)