We will work safely or not at all


Client requirements

Through a competitive tender process 40Seven were awarded the surveying contract to provide topographical, underground utility mapping and laser scanning surveys as part of the of the East Hyde STW Growth project.


40Seven Solution

The topographical survey involved installing a permanent control network on the site related to the OS network by GPS, in addition to surveying all levels, structures and assets throughout the STW to enable the ground surface to be represented as a 3D Digital Terrain Model (DTM). Witness diagrams and network diagrams were included in the survey report which was issued along with a 3D AutoCAD drawing.

The underground utility survey was carried out to PAS 128 type B specification and involved the survey teams locating and mapping all buried services and features using electromagnetic techniques and ground penetrating radar. All drainage information was collected including invert levels, cover levels and pipe sizes. The ground penetrating radar survey was carried out using Mala Pro Locators and the multi array MIRA system. The survey team endeavoured to locate all services with two techniques (electromagnetic and ground penetrating radar) to produce a B1 quality survey. If any services could only be located with one technique then the relevant quality levels were added to the drawing. All of the ground penetrating radar survey data was post processed in the office once the site works had been completed. During the survey, the client was made aware of a number of buried concrete slabs located in various areas across the site. 40Seven carried out an additional M4b ground penetrating radar survey of these areas using the MIRA multi array equipment to locate and map the slab positions. All of the underground utilities that were located were marked on the ground using temporary spray paint and mapped by Total Station to our topographical survey. The utility data was overlaid on to the topographical survey and issued in 3D AutoCAD along with our survey report and GPR scans.

The 3D modelling of the inlet works and treatment plants was crucial to the client as they were replacing large amounts of plant in this area and needed the 3D modelling for their new designs. The data was captured using a P40 Leica laser scanner to a 3-5mm point density, which created an as-built representation of the specific area for integration into their Building Information Model (BIM).

As the site was a live treatment works it was crucial that the surveys were carried out in the safest manner possible. Before the work commenced the Project Manager attended site for a pre start safety briefing. The site specific risk assessment and method statements were then issued to Thames Water for approval before the works could commence. The survey team all had to complete the Thames Water safety passport and provide training and first aid certificates before they could commence on site.


The results

On the completion of the site works and following QA checks all final information was issued in 3D AutoCAD and Microstation.

Max Dibsdall
Operations Manager (South)
Contact 40Seven
40seven are well known and respected in Cadent Gas to delivery works and services at a high standards every time, this company is dedicated in providing a friendly, open and honest relationship with its customers.
- Cadent Gas, commenting on 40SEVEN Surveys

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