Lake Conjola Submarine Cable

UEA was awarded a significant HDD project to replace the existing submarine cable running under Lake Conjola. The project was crucial due to the identified risk of service disruption during the peak tourist season in the area. HDD technology was employed for the seamless installation of the new cable.

Construction Technique

Before commencing HDD works, UEA needed to identify and avoid a treated effluent main located beneath the lake, which could have interfered with the new alignment. A 180mm conduit was installed over a length of 880 metres through sand and sandstone. This installation represented one of the longest HDD boring projects ever undertaken by the authority. Additionally, a 350mm steel casing was used for the first 80-100 metres to prevent “frac-out” during the drilling process. Frac-outs can occur when pressures build up due to obstructions in the borehole, causing drilling fluid to escape to the surface.

Challenges

One of the key challenges involved identifying and managing the location of the effluent main under the lake. Another challenge was the prevention of frac-out, which was addressed through the use of a steel casing to protect the borehole during drilling through the softer formation before reaching the harder sandstone.

Completion

The replacement of the submarine cable successfully reduced the risk of service disruption in the area, particularly during the peak tourist season, thereby enhancing the reliability of the power supply.