United Utilities operate nearly 150 reservoirs across their operational area in North West England. Each one, as specified in the Reservoirs Act of 1975, requires regular inspections and Atlantic Geomatics have carried out the routine levelling to monitor the reservoir embankments for movement since 2013.
Before the levelling could commence Atlantic Geomatics had to ensure the condition of the primary control markers and monitoring pins met an acceptable standard. A survey team visited each reservoir and where markers were not in an acceptable condition replacements were installed. Berntsen markers were used for primary control and were constructed on virgin ground away from the reservoir embankments.
For the monitoring pins at each site a tag with a unique ID was attached to each one from which a a monitoring information sheet produced for each reservoir. This would enable the second team who were to carry out the levelling, to quickly position each pin and carry out the task as efficiently as possible.
A second team then carried out the routine 2D levelling using a Trimble DiNi Level. All monitoring pins were surveyed as change points within a double run levelling circuit. Verification and performance checks were carried out on the level, data recording and outputs each day throughout.
3D deformation surveys were also carried out on 4 reservoirs. Reservoir monitoring pins were observed from a minimum of 2 survey control points based on the existing co-ordinate system. A one second total station was used to obtain the greatest level of accuracy.
Levelling information collected was processed using Trimble Software. The data was transferred into the existing Excel Spreadsheet updating the main data table and creating a number of graphs for each pin.
The spreadsheet was accompanied by a monitoring information document for each site which included:
-Survey History information
-Site location and access information
-Monitoring Monuments information including a location plan and coordinate schedule
-Benchmark description and location sheet
The result is United Utilities not only meet their legal requirement of the Reservoirs Act but more importantly can assess the condition and movement of their reservoir embankments.