News and views

Subscan Completes Vacuum Excavation Verification Survey in City of London

20 April 2012

Vacuum%20excavation

Subscan has a reputation for successfully completing complicated utility mapping surveys in a variety of congested urban environments. Using our knowledge, expertise and specialised survey equipment we are able to survey the position and depth of underground utility assets to assist with future design and build projects.
Often when a client receives our survey data they realise that the position of underground utilities conflicts with their proposed design causing potential costly redesigns or utility diversions. One such example of this is a complex project that we have just completed in the City of London. Sandwiched in between Moorgate Tube Station and the Barbican, the former Fore Street Telephone Exchange building is surrounded by a variety of telecoms, fibre optics, and every other major utility service imaginable. Our utility mapping survey provided the client with a clear, but complex survey drawing. In order to establish the precise depth and position of the utilities our client asked us to provide the safest, cleanest and least obtrusive method of exposing underground utilities at strategic locations.
Our solution was to undertake a vacuum excavation verification survey. By using vacuum excavation, high pressure air was used to break up the soil and cut a series of trenches exposing the underground assets at strategic locations. The soil from the trenches was removed by vacuum into a holding tank and then returned into the trench after each excavation was complete. This enabled precise utility positions to be surveyed and compared to our utility mapping survey. This allowed our client to see that our original survey data was very accurate and allowed their project to proceed without any element of risk or extra cost due to unknown utility conflicts.
The benefits of using vacuum excavation over traditional hand digging methods are:
• Much safer as only high pressure air or water is used to expose utilities, meaning no infrastructure damage.
• Less Intrusive. It is possible to excavate much smaller test holes to expose utilities. Sometimes a one metre deep hole only needs to be 300×300mm in size.
• Cleaner. All spoil is removed via a vacuum hose into a holding tank.
• Quicker. Vacuum excavation is vastly quicker than traditional methods.
This system of utility mapping followed by vacuum excavation is called Subsurface Utility Engineering (SUE) and is a method of survey verification that is proven worldwide to save overall design and build costs.
Please contact us to discuss if this method can assist you with your project.