A report by the Comptroller and Auditor General tabled in the Maharashtra Assembly on Tuesday said that drains in Mumbai are enough to handle only 25 mm rainfall per hour, PTI reported. The report also pointed out that a master plan for the storm water disposal system has not been updated in six years. The Brihanmumbai Stormwater Disposal System was planned to overhaul Mumbai’s water drainage system.

The report was tabled in both Houses of the legislature on a day when Mumbai received near-record rainfall, forcing authorities to curtail train services and disrupting traffic on roads. The rainfall in 24 hours from Monday night was the highest since the deluge of 2005 and the second-highest since 1974.

Chief Minister Devendra Fadnavis told the Assembly that Mumbai received around 375 to 400 mm rainfall in three to four hours, which was unprecedented.

The CAG report said that in larger drains, siphons and utility services create numerous obstructions. Flat gradients are leading to drains being affected by tides, the report said. It pointed out poor structural conditions, poor workmanship and lack of attention to repairs when the drains got damaged by utility service providers.

“Due to flat gradients, drains are affected by tides,” the CAG report said, according to the Hindustan Times. “The system is heavily silted and major outfalls discharge much below mean sea level [between high and low tide mark]. Stormwater drains discharge directly by gravity through outfalls, as floodgates have been provided in only three of the 45 outfalls. As the outfalls discharge below mean sea level, tidal control is possible only at these three places.”