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Storm Water Drain

Introduction :

Need for Storm Water Drainage System

The flat terrain of Chennai City needs effective Storm Water Drainage System to prevent water stagnation in roads. The terrain of Chennai city is flat and average level of the land in the city is only 2.5m above the Mean Sea Level (MSL). Because of this flat terrain and partial coverage of roads with storm water drains, flooding and water stagnation happens in the city during the monsoons.

Statutory Provision

Section 176 of the Chennai City Municipal Corporation Act, 1919 entails the Corporation of Chennai to provide and maintain a Sufficient System of public drains throughout the city.

Storm Water Drain Department

In accordance with the Statutory rule, the Storm Water Drain Department of Corporation of Chennai Constructs and maintains a network of Storm Water Drains and Canals.
Corporation of Chennai developed and maintains a Storm Water Drain network of 1660.31 km in the city.
Corporation of Chennai also maintains 31 canals criss crossing across the Chennai City. Rain Water runoff gets drained through Storm Water Drain network & canals and reaches the Sea Via five Waterways-Otteri Nullah, Buckingham Canal, Adyar River, Cooum River       a and  XXand Kosathalaiyar River -running across the city

Construction of Storm Water Drain and Canals

Usually Storm Water Drain will be Provided in 12 m road and above. The minimum size of the drain will be 600X750 mm; the size will be designed depending upon the catchments area, land pattern and discharge. Under JnNURM Scheme, Storm Water drains are designed to relieve Water Stagnation in the Water logging areas irrespective of the width of the road. In Bus Route Roads Storm Water drains are provided usually in the footpath. The height of the drain top will be 6 inch above the road level. The Slab level should be lowered at all the entrance gates. The top Level of the Slab and man hole doors should be flush with the footpath Slab level. In all roads crossing the Slab Should be flush with road level. The drain should be in straight alignment. SFRC (Steel Fibre Reinforced Concrete) / FRP (Fibre Reinforcement Polymer) Man hole door with chute pipes to be provided at every 5 m interval with chute pipe.  In addition to that Inlet Chambers with Rain Water Harvesting is also provided at every 30m intervals to collect the rain water and to increase the ground water level. Pre-cast RCC drains are proposed according to the site condition with inlets at 10m interval.  PVC Pipes should be provided to accommodate the electrical and other utilities in Storm Water Drain crossings. The Canals are constructed with retaining wall which retains the earthen banks and gives an aesthetic appearance to the canal. The flooring facilities is such that men and machineries to carry out desilting works easily. In addition to that Inlet Chambers with Rain Water Harvesting is also provided to collect the rain water and to increase the ground water level.

Improvement of Micro and Macro Storm Water Drainage network in Chennai under JnNURM

In order to alleviate a flooding comprehensive Proposal was prepared by the Corporation of Chennai in association with the Public Works Department (PWD). This proposal was approved by the State Level Sanctioning Committee, and subsequently appraised and Sanctioned by the Central Sanctioning and Monitoring Committee, Ministry of Urban Development, Government of India if four packages.

The details the four basins are tabulated below:

Sl.No	Name of Basin	Chennai Corporation Component
1	Northern Basin	277.17
2	Central Basin	261.11
3	Eastern Basin	140.40
4	Southern Basin	136.20
	Total	814.88



• On the basis of a topographical survey and its detailed analysis, the   city was divided into 4 drainage basins and these basins further sub divided into 12 watersheds.

• Four Basins namely

• North Basin
• Kolathur Water Shed
• Captain Cotton Canal Water Shed
• Otteri Nullah Water Shed

• Central Basin
• Mambalam & Nandanam Water Shed
• Cooum Water Shed
• Virugambakkam & Arumbakkam Water Shed

• East Basin
• Royapuram Water Shed
• North B Canal Water Shed
• Central B Canal Water Shed
• South Canal Water Shed
• South Basin
• Adyar Water Shed
• Velachery Water Shed

The Government of India grant component under the JNNURM scheme is Rs.285.25 crores being 35% share, Government of Tamil Nadu contribution is Rs.122.25 crores being 15% share of expenditure and the balance of Rs.407.44 crores being 50% share has to the borne by the local body i.e., Corporation of Chennai. The Administrative Sanction has been accorded for the project in G.O.(Ms).No.116, Municipal Administration and Water Supply Department dated 06.07.2009  by the Government. The Corporation of Chennai proposes to meet its share of Rs.407.44 crore by availing a loan of Rs.203.72 crores from Tamil Nadu Urban finance and Infrastructure Development Corporation Ltd. (TUFIDCO), Rs.150 crores from Tamilnadu Urban Infrastructure Financial Services Ltd., (TNUIFSL) and balance Rs.53.72 crores from Corporation of Chennai’s own funds.

• The Chennai Corporation component of the project involves

Remodeling of 337 nos for a length of 182.95 kilometers of micro drains at a cost of Rs.277.24 crore. Presently 87 nos. of works are in progress.

      Construction of new drains of 701 nos for a length of 320.90 kilometers
      in  un-served  areas of the city at a cost of Rs.380.12 Crore

      Improvements of 16 Canals to a length of 28.64 kilometers at a cost of Rs.159.57 crore.

Revised Detailed Project Report

• Revised DPR has been prepared and send for approval after dropping some works and adding new works according to demand.
• So far 442 nos of works of 139.62 km length of Storm Water Drain and Canal at a cost of Rs.149.57 crore have been completed.
• Presently at 193 locations 130.49 km length of Storm Water Drain at an estimated cost of Rs.149.28 Crores, 28.64 km length of Canal works at the estimated cost of Rs.159.57 Crores are in progress. 
• All these works will be completed in phased manner.

Construction of Storm Water Drain in extended areas  

Under the gird system providing infrastructure in extended areas, Pre-cast Storm Water Drains are provided along with other works such as roads, duct, street lights etc., A consultant has been appointed and DPR is being prepared for construction of Storm Water Drain and improvements for canals by TNUIFSL.

Desilting of Storm Water Drains and Canals

De-silting operations of Storm Water Drains are done by the respective zones. The de-silting of Storm Water Drain is done in a cyclic manner and us carried out twice in a year. This activity is being carried out in a weekly programmed manner throughout the year either with the use of departmental de-silting gang or through contract labors. De-silting gangs of Corporation of Chennai enter the drain through the inspection chambers of the drain and remove the silt. The removed silt is cleared immediately and transported to the designated place through departmental vehicles. Some of the Storm Water Drains passing through the dense populated areas, commercial areas and areas devoid of sewers always carry sewage. De-silting of such kind of drains is very difficult. To overcome this kind of problems, presently COC is providing silt trap arrangements inside the Storm Water Drains and remove the collected silt of sludge from the trap either by pumping or with the use of hand tool. The drain which requires replacement of inspection chamber covers structural repairs are also carried out as and when required. The in-let chambers and entry(chute) pipes are cleaned periodically.
To carry out these activities other than permanent gang, separate budgetary provision is made and is operated by zones.
Canals maintained by Corporation of Chennai
Chennai Corporation maintains 16 canals in the old city and 15 canals in the expanded areas. De-silting of canals maintained by COC is done every year using men and machineries. The silt removed is taken away and dumped in Kodungaiyur and Perungudi dumping grounds or at designated places. To ease movement of de-silting machineries others with sound retaining wall and service roads, Floating machineries in deep water will be deployed.

Canals maintained by Corporation of Chennai

Rain Water Harvesting :

Rain Water Harvesting prevents wastage of the rain water runoff into the sea and also raises the ground water level, apart from improving the quality. Rain Water Harvesting has been done by providing percolation pits, percolation wells and by roof top harvesting method. All the house- Owners are insisted to provide Rain Water Harvesting Structures in their houses. Building Plans are sanctioned only if Provision is made for Rain Water Harvesting in the plans. Building Assessments for Tax Computations are done only if Rain Water Harvesting Structures are Corporation of Chennai Owned buildings like Schools, hospitals, office buildings, community centres, parks and playfields etc.   Inlets are provided in ongoing Storm Water Drains at 30m intervals with Rain Water Harvesting structures. In all zones 5000 inlets with Rain Water Harvesting are proposed and in progress.