Topographical Mapping
- Using the industries latest technology, in this case a Leica 1200 Robotic Total Station alongside a Leica GPS system the g-map surveyor surveyed the substation to produce an accurate topographical map. This map is related to the Ordnance Survey (OS) Grid system in both in horizontal and vertical position, thus enabling any future survey work inside or outside the substation by g-map or third party surveyors to combine or compare surveys seamlessly.
- The Severn Trent drainage system adjacent to the site is also related to the OS, so any design work on drainage connections or storm water run-off can be accurately designed without the need for adjustments in vertical height.
- The surveyor also captures the data marked on the ground by the Utility Location team. These marks are colour coded spray paint marks (chalk is also used in sensitive areas) that physically show to the surveyor the locations found of the underground plant. These underground plant locations were then measured, recorded and added to the topographical survey to produce a combined drawing showing the underground plant and topographical survey in direct relation to each other.
- As the site and surrounding area has been regenerated in recent years the presence of all utilities must be anticipated within the site area. Along with these records historical records of the substation site were also obtained from the site owner Central Networks.
- Once the g-map site surveyors had been issued with a site information pack containing project scope, the existing drawings etc. work could commence, but not until the initial site safety briefings by the Senior Authorised Person (SAP) responsible for the site had been carried out and then all relevant H&S documentation had been approved and accepted (g-map staff are committed to 100% adherence to all H&S policies and procedures of its clients and also their agents.).
- Using the records drawings g-map utility surveyors set about locating the recorded utilities and confirming their accuracy. The g-map technique of producing a final accurate map can be compared to that of putting together a “Jigsaw”; firstly all known and recorded utility plant is located, this is primarily done by Electromagnetic (EM) methods using the Radiodetection range of equipment (considered by many as the industry leader).
- Any recorded utilities that are “untraceable” by EM methods; for example a plastic drainage pipe is then located by Ground Probing Radar (GPR) methods. At the same time as this method is used other unidentified “targets” can also be located. Both EM and GPR methods are used to “sweep” or grid the survey area. The GPR scans will pick out anomalies, the EM unknown linear traces will be also be added and with skilled interpretation the surveyor can gradually piece together the “Jigsaw”.
- Drainage details located by the g-map Utility location teams were also complemented by the addition of a CCTV survey. A g-map CCTV survey team investigated and recorded all the drainage within the substation. Using state of the art CCTV drainage cameras g-map were able to complete a clear picture of the state of the existing drainage and also its functionality be it a storm, foul or combined system.
- Any drainage features not detailed by the Utility location teams could also be added, e.g. the extents of manhole chambers that could only be measured internally by a confined entry trained man-entry drainage teams. A Drainage Condition Report and CCTV DVD were also supplied to Siemens alongside the final Autocad drawing.
Freedom g-map was successfully awarded a contract for Geophysical Mapping, Geotechnical and Geo-environmental surveys, a Topographical Mapping Survey, Underground Utility Survey and CCTV Drainage Survey of the Leicester 132kV Substation upgrade and extension project by Siemens on behalf of Central Networks. These elements form part of a “turnkey” approach offered by the Freedom Group of Companies for pre-design and planning of proposed projects within the Utility Distribution and Supply Sector.
The substation dates back to the 1940’s and plant and apparatus has been abandoned, modified or even in some cases not recorded. It previously once formed part of a Power Station. Although a fairly large substation the plant and apparatus is confined to a compact area with extensive congestion of underground cables within the Grid Transformer locations.
Siemens and Central Networks design proposal on this project involved extensive diversionary routing of existing underground cables. Existing record drawings provided for the site although detailed were inaccurate in position and clarity of the cable identification was also vague.
g-map staff have extensive experience working within the substation environment. All staff have industry accreditation in training and safety competence. Many staff have 20 years plus experience working in electrical substations; be it Midlands Electricity (Now Central Networks), EDF, YEDL, NEDL and National Grid Plc. With this experience and technical training g-map staff were able to accurately record both underground plant and above ground topographical detail, presenting Siemens with a highly detailed and accurate drawing for Siemens design engineers to confidently design the proposed works from.
Underground Utility Mapping & CCTV Survey
- A desktop study was first carried out by Freedom “Safe-Dig” staff to collate existing record drawings of the site. These drawing were collated from several sources: All relevant Statutory Undertakers were contacted and their existing records drawings of the substation site and the immediate surrounding area were requested. Drainage from Severn Trent Water, Gas Pipelines fromNational Grid and Communication cables from British Telecom are amongst other utilities that could be expected on site or passing through the site.
