An ambitious masterplan to tackle Bombay's perennial water-logging problem during its ferocious monsoons will use an innovative, sub-surface "no dig" technology. The new system, part of a Rs 616-crore project drawn up by the Bombay Municipal Corporation, which is up to its neck in public grievances, repairs pipes and stormwater drains without blocking and annually devastating roads and rail tracks.

The plan is based on two and a half years of studies conducted by the BMC. A study by its stormwater department and an "internal condition survey" of the city's stormwater drains, concluded that the entire old and clog-prone drainage systems must be replaced or renovated. New drainage systems are imperative, and in some places the drains have to be re-routed.

The new technology uses a mechanical tunnelling process that leaves the surface unruffled. "The earth is tunnelled from the side of the road at the level where the pipe or drain is to be laid," says V K Arora, chief engineer in the Central ministry of surface transport. "The structural life of the drains is enhanced by 20 to 30 years because this ensures that the pipes are always properly covered." The 12-year project is expected to reduce the estimated Rs 46-crore the monsoon extracts annually in terms of lost production, person-hours and property.