At Purasawalkam, under the bustling shopping hub of the city, when Chennai Metro Rail commenced work to build an underground station for the phase II project a few years ago, it ran into a maze of utility lines, the kind it had not encountered elsewhere.

In the 118.9-km Phase II network, shifting of utility lines such as power cables, sewer and metro water pipelines have been a routine process despite some setbacks.

According to officials of Chennai Metro Rail Limited (CMRL), the upcoming Purasawalkam High Road Metro Station is being constructed under the busy Purasawalkam Junction.

“Moving the utility lines at Purasawalkam has been the most difficult task so far in the Phase II network. This is because of multiple reasons. In this busy high-density commercial hub, the road width was far more limited compared to the other locations and all the lines were clustered in the station box area. The lines and cables were not running parallel to the station box alone; they were criss-crossing the box and shaft. We had to seek multiple traffic diversions to carry out the work and gradually relocate the lines and cables which took nearly three years,” an official said.

These issues aside, what made shifting the utilities here tougher was, unlike most of the stations whose length ranges from 135 metres to 150 metres, at Purasawalkam, it exceeded 300 metres.

Along with the station box, they had to build crossover boxes too, a critical technical feature that allows trains to switch tracks.

“In most of the other stations, the utilities were not as bunched up and we had to relocate them for a maximum of 150 metres. Nearly 100 power cables, two water pipelines with 1,000-mm diameter, a 1,000-mm, 900-mm, 600-mm, and 300-mm diameter sewer lines were among the lines we moved. Though we received the map of these utilities in advance before beginning the work, we were surprised to discover the alignment of the lines sometimes didn’t match with the map that the respective agency had shared with us. These unchartered utility lines made the job much more complex. We successfully finished moving these lines nearly nine months back,” a source said.

While the station is built at a depth of 21 metres, these utility lines were located at a depth of 2-3 metres at Purasawalkam. “It required manual excavation until the utilities were moved which doesn’t happen in other locations. Heavy duty equipment called trench cutters will usually be used for station excavation work. After the three metre depth, trench cutters were deployed,” he added. While some of the lines have been permanently moved, the ones which were shifted temporarily will restored to the original position when the station work is completed in two years.