Mohammed Suleman Chandio, special secretary (technical) proposed in his report urgent revival and upgradation of the system, which could work for next 50 years.
The city's battered roads were being carpeted in haste without completing work on drainage system's overhaul, which might give rise to problems in near future, sources in the Public Health Department said.
The Public Health Department prepared a project that for restoration of old drainage system with minimum damage to roads and permanent solution to disposal of sewage and the Rs200 million project was almost ready with minor linkages, storm water drain, said Irshad Abbasi, executive engineer.
The expert said that in certain areas there were no disposal drains and in others there were two sided drains and single side drains. In some new drains electric poles were standing right in their middle, he said.
He suggested connecting drains with 'catch pits' on both sides of the roads.
The Natioinal Highway Authority, which was working on inter-city road network, had already dismantled defective drains, which had doubled the expenses, said the sources.
The expert pointed out use of inferior quality of concrete and proposed that three pumping stations located near Akil road, Phull road and Baharpur road, which release sewage into Dadu Canal should be switched over to the SCARP drain to make Dadu Canal pollution free.
The planners would encounter problems in restoring damaged portions of the old drainage system because somewhere work on roads had been finished and somewhere it continued, he said.
The planners should have completed the underground drainage system well ahead of start of work on the roads, said the expert.
The sources said that MNA Faryal Talupr had emphasised the need for completing the drainage system simultaneously with inter-city roads.
Overflowing gutters at many places in the city pose serious threats to health while 39 pumping stations are releasing this poisonous water into Rice and Dadu canals, making them highly contaminated and injurious for health.
The expert said that practice of releasing untreated sewage into canals should be stopped and arrangements should be made to release it into SCARP drain.
It required both long term and short term planning based on scientific methodology to minimise if not wipe out completely, future health risks, said Dr Shafqat Soomro, chairman of Sindh People's Development Committee (SPDC).
Three big pumping stations are releasing half of sewage into perennial Dadu Canal in addition to innumerable pipes of various sizes carry sewage from the different localities.