To walk along Yari Road in Andheri (West), it's hard to imagine the kind of furious activity that will soon be going on underneath.
The civic body has just begun work on the city's newest underground water tunnel —70 metres underground — at a cost of a whopping Rs 25 crore to Rs 30 crore per kilometre.
Work began in September, with a 70-metre shaft being dug for the tunnel, which will stretch from Verawali to Yari Road, via Adarsh Nagar.
Next, earth-moving machines will be lowered and started up. The tunnel is expected to be complete by 2011.
This is the first of the five such projects being undertaken by the civic body. A proposal for funds for three — Malabar Hill to Cross Maidan, Maroshi to Ruparel College and Verawali to Yari Road — under the Jawaharlal Nehru National Urban Renewal Mission has been submitted to the Centre.
Work on these tunnels is expected to begin by end-2006 or early next year.
Each tunnel will be wide enough for men to work in and repair. But the really good news: They will bypass utility cables and pipelines, which are laid just under the road.
They will also solve the problem of encroachments at pipelines for good.
And, with work on the tunnel carried out underground, there will be no need to dig up the streets, except for the shafts.
"Underground tunnels are the way of the future," said civic Chief Engineer (Water Supply and Sewerage Projects) PK Charankar. "They are more durable than water pipelines and require much less maintenance. They cannot be breached during work on utility lines and don't disrupt traffic or mess up the streets during the laying work."
Charankar added that tunnels also solved the problem of battling for space for pipelines.
"What with the city's railway lines stretching all across, it was becoming extremely difficult to find space for new pipes," he said. "And digging up concrete roads was also extremely difficult, messy and expensive."
To start with, the civic body has picked areas that needed old and corroding pipes to be replaced. The tunnels planned for these areas can be expanded to suit future water supply need.
Being underground, they can also go straight from point to point, reducing the length. And the reinforced mortar lining will reduce the chances of breaches.
On the flipside, these tunnels are about four times as expensive to construct. For instance, a conventional 3,000-mm water-supply pipeline costs Rs 7 crore to Rs 8 crore per km.
An underground pipeline costs about Rs 25 crore to Rs 30 crore per km — taking the total cost of the five proposed projects to Rs 1,179 crore.
The tunnels are also expected to take marginally longer to construct.
And experts claim uneven terrain could pose problems too. "The BMC will need to be really careful during the tunneling, as there is a chance of rock collapses," cautioned Professor Kapil Gupta of the Indian Institute of Technology-Powai, who specialises in urban water supply and sewerage systems. "Seepages are also possible in low-lying areas, due to the water table," he added.