We have all witnessed the destruction that was caused to Chennai and its surroundings in November/December 2015. The heavy deluge may have caused large quantities of water to be dumped. However, what is being overlooked is the large scale violation of Environmental Clearance (EC) by Airports Authority of India, that has contributed in a very big way for the destruction and loss of lives.
In November 2005, when there was a deluge and Chennai experienced 24cm of rain and water was released from Chembarambakkam lake, it flooded the Chennai airport, leaving only the main runway unaffected.
Low lying areas near the river banks were the worst affected.
I had earlier written, “The Chembarambakkam lake overflow is through the Adyar river. If the flow area is restricted by the secondary runway or blocked to a large extent, the flooding on the west, south and south-east areas is going to be extensive.”
The PWD department had declared the Flood Level as 11m.
Secondary Runway bridge
AAI obtained EC for the expansion of the secondary runway bridge which states: “The Ministry reserves the right to revoke this clearance, if any of the conditions subsequently, deemed necessary for environmental protection, are not complied with.”
The EC also says that it was indicated by AAI that the bridge will be built 1.4m above the high flood line on the Adyar River, with a span of 200m x 415m.
PWD had indicated that the high flood line in 2005 was 11m above mean sea level. Hence, the top of the column (marked with red arrows in the following photos) should have been 11 + 1.4 = 12.4m.
The undulating levels of the top of the column, as visible from the last image, indicates that AAI has not followed a uniform height for the top of the columns, or the columns have sunk to varying depths.
The proposal from Airports Authority and what is covered by the EC, does not indicate any clearance for the high concrete walls built on either side of the runway bridge, along the Adyar river front.
In September 2010, the Airport director, Mr. E P Hareendranath gave a press conference, in which he said that according to media reports, “Held by 477 pillars, the bridge will be positioned on a grid of 20m by 10m. These pillars will shoulder 2,440 prestressed concrete girders. The latter will be one metre high and 19.1m long and will weigh 30 tonnes each,” and added, “The extension of secondary runway has been awarded to KGL Constructions and Consolidated Construct-ion Consortium Ltd (CCCL).”
CCCL did not have any experience in bridge building. They had not even constructed a road bridge, yet the contract was awarded to them and not Larsen & Toubro who had vast experience.
The AAI also states that the design was approved by IIT Madras, but the reply from the Head of the Department of Structural Engineering is very clear: “May I clarify that the role of IIT Madras in this project (which we had carried out some years ago), as assigned by AAI, was limited to proof-checking the structural design of the bridge, which was designed by a structural design consultant, in accordance with the loading standards and specifications stipulated by the clients, AAI. We did not design the structure. If you have misgivings regarding the loading standards, you may seek clarifications from AAI.
We had recommended and witnessed the load testing to failure of two typical pretensioned girders used in large numbers in this bridge construction. The test results established that these girders had the desired characteristics and margins of safety against collapse, as assumed in the structural design.”
IIT Madras only witnessed the load testing to failure of pretensioned girders and nothing else. They did not approve the bridge construction as claimed by AAI.
There is a slide from the presentation made by AAI to Airports Economic Regulatory Authority of India:
The same AAI gives a different set of figures here. The width given is 447.5m and the R.L. at the bridge is 11m.
With these official statements, AAI has admitted that the bridge was only 11m high and the width for which the EC was obtained is 415m but AAI has built the bridge for 447.5 (or 462m?) without obtaining clearance. Thus a clear violation in a big way by a Government agency.
Another official document (extract shown here)
They admit that the top of the column is only 9m and the diameter is 0.85m instead of 1.2m that they had submitted to Environment Ministry for clearance, and possibly to IIT-M for the structural design test data approval.
Note the following:
Pier height: 9m
Pier cap depth: 1.65m
Girder: 1m
Runway thickness: 1m
Total 12.65m (41.5 ft)
This is confirmed by the original chart they issued.
The bridge, as per the EC, should have had columns to the height of 1.4m above the 2005 flood level.
Pier height: 12.4m
Pier cap depth: 1.65m
Girder: 1m
Runway thickness: 1m
Total: 16.05m (53 ft )
The entire secondary runway bridge is built 11ft below the mandatory EC order. Not only is the structure built in violation, the embankments on either side are also in clear violation as no wall can be built within 100m of a water body.
Impact of Secondary Runway bridge during the deluge in November/December 2015
The bridge structure above the columns, 447.5m x 200m x 3.65m is equivalent to 3,26,675 cubic metres. This was the obstruction that caused the huge amount of water to flow over and destroy everything in its path on December 1, 2015.
On November 16, 2015, when water was released from Chembarambakkam lake after the first deluge, the water level was just touching the bottom of the bridge.
On December 1, 2015 with the second deluge and release of water from Chembarambakkam lake, water level rose sharply due to the obstruction of the bridge.
This video gives a clear picture of the flooding of the airport.
Public Works Department mentions that the Highest Flood Level at the airport during the December deluge was 13.39 meters above Mean Sea Level. This means that the runway on the bridge, which AAI claims is at an elevation of 45ft, should not have been under water. It was a known fact that the runway was 10ft under water during the floods. The photograph showing the compound wall of the runway bridge and the barbed wire on top of it fully blown away could not have happened if the elevation of the secondary runway bridge was 45ft. Only the skeleton framework of the bridge wall remained. The main runway with an elevation of 52ft at St. Thomas Mount end was also under water.
The obstruction due to the bridge raised the water level due to the dam effect, resulting in water flowing over the bridge, as well as down the mid portion of the secondary runway bridge. The entire area upstream of the bridge- Pallavaram, Pommal, Airport and the runways were all under water due to the rising level because of the dam effect and lateral spread of water.
Pallavaram end of the runway (Runway 07)
Kolapakkam end of the secondary runway (Runway 12)
Danger to Chennai due to flawed construction of secondary runway bridge
During the inspection of the secondary runway bridge, as part of the Civil Aviation Safety Advisory Council, several portions of the bridge showed damage due to corrosion and cracks in the structure. AAI was carrying out temporary patchwork jobs to cover the flaws.
The AAI document speaks of the design load of 100% for an Airbus A-380 aircraft landing. The all up weight of an A-380 at the time of the bridge design was 3,85,000kg. What the design has not envisaged is that an aircraft is certified to do a 2g landing. This would translate to 2 x 385000kgs for an A 380 = 7,70,000kgs of impact load.
The bridge, by AAI admission is designed for a landing load of 3,85,000kgs. A 2g landing or a harder landing by even an Airbus A330 would exceed 3,85,000kgs.
The other aspect the design engineers have not taken into consideration is the twisting forces when a landing is made in cross wind. A 2g landing of even an A330 in crosswind will result in the bridge collapsing. The design has also not taken into account the twisting forces due to a landing aircraft and the taxiing aircraft in the opposite direction.
Thus, the bridge is practically unusable for a landing by a wide-bodied aircraft and the old runway length, short of the river is more than sufficient for use by narrow body aircraft like a Boeing 737 or an Airbus A 320. Airports Authority of India’s false argument which projects that Chennai will suffer from loss of traffic is a fallacy.
As a former member of the Civil Aviation Safety Advisory Council of Ministry of Civil Aviation, I had already pointed out the dangerous flaws in the structure of the secondary runway bridge. The very fact that the threshold of runway 12 is marked on the bridge and not at the beginning of the runway, is a clear indication that DGCA and AAI do not want an aircraft to touch down on the bridge. The aiming point is beyond the bridge.
What is of serious concern is the diameter of the columns. The design was based on the diameter being 1.2 metres. AAI has built the bridge on columns with are just 0.85 metres. This is definitely dangerous and with the corrosion damage that has been evident, the structure can collapse any time if there is another flooding. If the bridge collapses, a volume of 3,26,675 cubic meters of concrete and iron is going to block the path of the flood waters. The destruction due to the rising and rapid flow downstream would cause unimaginable damage to Chennai.
In the interest of safety of citizens of Chennai as well as several industries that will be destroyed in the event of another flood, MoEF should invoke this clause in the EC: “The Ministry reserves the right to revoke this clearance, if any of the conditions subsequently, if deemed necessary, for environmental protection, shall not be complied with.”
(A letter to this effect has been written to the Prime Minister, Minister of Environment, Forest and Climate Change and Secretary of MoEF)
All Images: Capt. Mohan Ranganathan
Note: The views expressed here are the personal opinions of the author.