Maroshi-Vakola water tunnel on track
Hindustan Construction Company (HCC) has achieved a major breakthrough by day lighting the Maroshi-Vakola tunnel stretch which is the longest section of the Maroshi to Ruparel College water tunnel. It was witnessed by BMC Commissioner Dr Jairaj Phatak. Maroshi-Vakola section will now be concrete lined and tunnel excavation will commence in Vakola-Mahim section. The entire project is scheduled to commission by Aug-2012.
HCC has constructed 21 km of existing 26 km water tunnels that supply drinking water to Mumbai and is currently constructing 12 kms of tunnels of the 23 kms of water tunnels under construction. The Bhandup Complex to Charkop tunnel of 12 km length was the last tunnel completed by HCC. This tunnel was completed 5 months ahead of schedule, despite difficult geological conditions.
HCC was awarded the Contract of Maroshi-Ruparel College Tunnel Project by the Municipal Corporation of Brihan Mumbai in September 2007 with a Contract value of Rs415.10 crore. This is a Water Supply Project executed under Jawaharlal Nehru National Urban Renewal Mission (JNNURM) and is funded by the Government of India, Government of Maharashtra & Municipal Corporation of Greater Mumbai.
The Maroshi-Ruparel tunnel work consists of construction of tunnel having 3.60 m diameter and 12.24 km long using Tunnel Boring Machine from Maroshi connecting to Ruparel College. The tunnel is connected with Shafts at Maroshi, Vakola and Mahim. The shafts are 12 m in diameter and about 80.00 m deep.
The interesting aspect of the Maroshi-Vakola tunnel is that it passes through Mumbai Airport and crosses both the Runways of Mumbai Airport at around 70 meters below the ground level. The tunneling work was carried out without disturbing any operations on the ground level.
The tunnel boring was extremely challenging due to heavy seepages and varying rock strata. During monsoon, the tunnel seepage had increased to about 25,000 m3 per day. Extensive grouting was carried out to control the same. Weak patches of rock necessitated widespread tunnel protection works to ensure safety. The tunnel excavation in this section was completed in schedule.
This project is part of the rehabilitation and improvement of the drinking water conveyance / distribution system from Bhandup Treatment Works to Western Suburbs and Southwest part of the Mumbai city which consists of Vaitarana, Upper Vaitarana, Bhandup, Maroshi, Tansa (East) and Tansa (West) main pipelines. Bhanup-Maroshi main pipeline runs up to Maroshi only and supplies water to the Veravali Group of Reservoirs. Other mains continue to carry water to Dharavi / Mahim and further.
The existing Vaitarana, Tansa (East) and Tansa (West) main pipelines run below runway and pass through airport land and maintenance has become impossible due to security reasons. Moreover, encroachment in other stretches also necessitated rehabilitation of these mains. Under the circumstances, MCBM has decided to construct a tunnel from Maroshi upto Ruparel College, from where a tunnel runs upto Malabar Hill, which is in operation since 2000.