BMC digs deep for new water lines

At total cost of Rs 1,179 cr, civic body plans 5 tunnels - 70 metres underground
Dhaval Kulkarni

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 tunnel
for water pipes - 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 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) P.K. Charankar. "They are more durable
and need much less maintenance. They cannot be breached during work on
utility lines and don't 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.

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.

dhaval.kulkarni@ hindustantimes.com The 5 planned tunnels 1 MALABAR
HILL-CROSS MAIDAN Length: 4.5 km Cost: Rs 102 crore Areas covered: Girgaum,
Kalbadevi, Thakurdwar, Charni Road, Bhuleshwar, Cross Maidan, Fort, Nariman
Point, Cuffe Parade, Churchgate, Navy Nagar areas 2 MAROSHI-RUPAREL COLLEGE
Length: 10 km Cost: Rs 315 crore Areas covered: Bandra (West), Mahim, Dadar
and Parel 3 VERAWALI-ADARSH NAGAR-YARI ROAD Length: 6.5 km Cost: Rs 187
crore Areas covered: Andheri (West), Versova, Yari Road and Adarsh Nagar
Work on this tunnel has begun, likely to be completed by 2011 4 GUNDAWALI-
BHANDUP FILTRATION COMPLEX (Part plan to replace ageing Tansa (East)
pipeline supplying water to Mumbai) Cost: Rs 450 crore 5 MODAK SAGAR-BEL
NAGAR, IGATPURI (As part of Middle Vaitarna project) Length: 7.5 km Cost: Rs
125 crore These projects will start by end of this year or in 2007;

Gundawali-Bhandup complex tunnel may be started later Rs 1,179 crore is
total cost of project HOW PIPE TUNNELS ARE LAID ? Tunnels are not laid by
digging entire road, but by digging only at entry points ? They are built by
drilling 70 metres into the ground via a shaft and boring through the earth
using machines ? Tunnels will be large enough for men to work in and repair
in case of breakages and leaks ADVANTAGES No need to dig entire road, only
entry points ? ? No disruption of underground utilities ? No danger of
encroachments along the pipeline ? Lesser risk of breaches and leakages ?

Longer longevity, scope for capacity additions ? Less risk of corrosion by
seawater ? Can be laid below already constructed structures DISADVANTAGES ?
More expensive to construct ? Longer time to build ? Instability of rock
surfaces can cause problems


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