Whether the coffer dam built to facilitate the construction of the Malavoor vented dam across the Phalguni (Gurupura) on its downstream has created a pond-like formation thereby aggravating the contamination?
While officials of Karnataka State Pollution Control Board (KSPCB) and experts from College of Fisheries believe so, engineers with Dakshina Kannada Zilla Panchayat dispute the suggestion.
Nevertheless, continuation of the existence of the coffer dam even after four years of the construction of the vented dam remains an undisputed fact as against the practice of removing the same from river beds immediately after completion of any construction.
In his report on the cause of recent fish kill, Gangadhara Gowda, Head, Department of Aquatic Environment Management, College of Fisheries, Mangaluru, said that the accumulated organic waste downstream the dam was not flushed out during high tide due to more depth.
The coffer dam, built about 200 m downstream the vented dam to prevent flow of saline water during high tides, becomes visible when the water level recedes during low tides. Added to this is the water gushing out of the vented dam during floods deepening the riverbed downstream thereby creating a pond-like structure.
KSPCB officials believe that the structure reduces the force of high tide water, as a result of which the accumulated organic waste, particularly that on the riverbed, remains intact.
Zilla Panchayat engineers, however, sought to differ with the suggestion claiming that the coffer dam is broken in the middle thereby providing sufficient space for movement of water during high and low tides. “The dam is in place since about four years and the problem has occurred only this year. The contamination must be due to industrial effluent,” said an engineer.
Another engineer said that there is no reason to believe that accumulation of organic waste resulting in water contamination downstream the vented dam as everything gets flushed out during the monsoon. If necessary, the panchayat would get the coffer dam removed, the engineer said.
