The Brihanmumbai Stormwater Disposal System is a project planned to overhaul Mumbai's water drainage system. The estimated budget for implementing the project is Rs. 1,200 crore (approx. 300 million US dollars) as of August 2005. Such a high-budget project would require funds from the Central Government.
The estimated time required to implement the project once funds are made available is 12 years. The project was originally meant to have completed in 2002.
The current drainage system in Mumbai, which was put in place at the beginning of the 20th century, is only capable of handling rain intensity of 25 mm per hour which is inadequate to meet present requirements. The system is also clogged at several places.
The project aims at enhancing the drainage system through larger diameter storm water drains and pipes, using pumps wherever necessary and removing encroachments. The intended increase in storm water carrying capacity is to 50 mm per hour.
The proposal was drawn by UK based consultants for the BMC in 1990 after the city had faced waterlogging at several places. At that time, the estimated cost of implementing the project was Rs. 616 crore but the BMC committee had rejected it on the grounds that it was "too costly".
Storm water drains shouldn't be deeper than the Water Table, else at places near to sea like chedda nagar, water will accumulate in drains during high tide and be a source for breeding of mosquitos and other water born insects. When the mud is removed for drains, if the water table is near to top soil , water will accumulate in this ditch. Presently labourers use this water from the ditch to construct drains nearby! (cleaning the stones are OK). If water table is just below top soil, during high tide, water will wet top soil, this water comes from below soil and is not water backing up from sea.