Construction Method: Identification of Existing Underground Utilities

One of the early activities taking place in any construction project in the UAE is the identification of existing underground utilities (or services). A contractor operating in Dubai will need to expect to find one or more utility lines operated by the following government authorities within the confinement of his project limits:

• DEWA 
• Dubai Municipality
• du
• Etisalat
• RTA 

Quite often, some contractors don't invest much diligence in the process of identifying what utilities existing underground which, as a consequence, results in the damage of those utility lines and ultimately, the imposition of hefty fines borne by the contractor. It is worth noting that some of those fine may reach up to hundreds of thousands in value, if not more!

To identify underground utilities, the contractor is required to carry out two steps. The first is to obtain the as-built drawings that reflect the existing services. The contractor then is to set out the location of those utilities as determined by the coordinates extracted from the drawing. 

The second step that follows is for the contractor to carry out a visual inspection of the site to determine if there are any utility markers or manholes found on the project site that may not be reflected on the as-built drawing. If those are found, the contractor will then need to survey all those markers and manholes and include them in the as-built drawing and submit them for the Engineer's records.

The contractor will then need to prepare a shop drawing that indicates the location of the proposed trial pits (sometimes referred as trial trenches) and submit this for the approval of the Engineer. The locations of the trial pit is to coincide with the utilities route identified on the as-built.

Once approved, and after obtaining all the necessary permits (NOCs), the contractor will need to cordon off the trial pits areas with the use of a barricade system that is determined by the depth of the proposed pit. The barricade system will need to allow for sufficient work space that takes into consideration a number of factors including the area required to store the excavated material from the pit. To avoid any damages to the utility lines, it is highly recommended that the excavation is carried out by hand shovels. Most (if not all) live underground utility lines in Dubai are placed under a buried tape marker (or cover tile) that identifies the type of service placed beneath it. Remember: before relocating any utility line, make sure to disconnect the live service lines by applying for the relevant permits in advance, and involving the authorities during the shut-down phase.

Detectable warning tape

Polyethylene Warning Tapes 

Polyethylene Cable Cover Tile

HDPE Cable Cover

Once all trial pits have been excavated, and the utility lines have been revealed, the contractor will need to submit for the Engineer's records a cross-section of each trial pit excavated. To avoid confusion, it is advisable that the contractor numbers the proposed trial pits on the layout drawing, then use the same numbering system to identify the pits on the site, as well as when submitting the cross-section drawings of the excavated pits. If the contractor reveals a utility line that has not been identified by either the as-built drawing or the on-site visual inspection, it is good practice (and a contractual requirement) that the contractor marks this line on the as-built drawings, and if necessary, conducts further trial pits to determine the direction of the line's route in order to assess if relocation works will be required. 

Once all existing underground utilities have been identified, the contractor may then proceed with major excavation works in areas clear of any services and also in developing a utilities relocation plan for all identified services.

To recap, in order for the contractor to identify underground utilities, the following steps will need to be carried out:

• Marking existing routes as per as-built drawings
• Visual inspection to identify any services not reflected on the as-built drawings
• Submitting a Trial Pits Layout drawing for the approval of the Engineer
• Application of all necessary permits
• Cordoning off the area using a barricade system for safety purposes
• Excavating trial pits using hand shovels
• Survey findings, and submit cross-sections of trial pits excavated for the Engineer's records
• Conduct further trial pits if deemed necessary due to discovery of unforeseen underground utilities

What other measures do you think are considered best practice to identify existing underground services?

Images credit: 

Trial Pit - Gulf News

Tape Markers and Cover Tiles - Alinshira.com