What are the important engineering considerations when going underground?

A new underground distribution system must cater to existing loads as well as to the projected future demand. As a baseline, records pertaining to the configuration of the existing overhead system in terms of loads, demand patterns, and infrastructure (transformers, substations, conductors etc.) should be compiled and supplemented through site surveys as needed.

In order to determine the most appropriate construction method and cable layout, the site should be surveyed physically for the density and sizes of buildings, street and sidewalk dimensions, infrastructure locations etc. The underground structure should be analyzed in a non-invasive way using a Ground Penetration Radar. Data pertaining to the routes of existing underground waterworks, gas pipes, and telecom / power cables should be collected as well. Other information relevant to designing the new system and for scheduling the construction e.g. daily traffic patterns, annual precipitation patterns and maximum flooding levels should be collected too. Cable sizes and types should be standardized with a view to require minimum underground space.

Based on these considerations, the most appropriate construction method e.g. open-cut or no-dig needs to be selected with a view to minimize road repairs and traffic disruption. If the space available under sidewalks is inadequate, cables would need to be placed under the road surface.

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