That was said by director of the HCMC Steering Center of Urban Flood Control Program Nguyen Ngoc Cong last night.
During the heavy rain on September 30, investor Quang Trung Industry Joint Stock Company deliberately functioned the system at 7:17 p.m. when the rain had started for an hour and the street had been submerged under 30-50 centimeters.
Therefore, floodwater did not recede as fast as expected. At 8 p.m, many spots in the street were still submerged under 20 centimeters.
The company said the delay aimed to examine the efficiency of the system.
During the first testing previously, the precipitation was insufficient for the system to operate so tidal water was released into the street to increase floodwater to 0.5 meter. It was pumped out within 15 minutes.
Hence, that has not been able to estimate the efficiency of the system as it just pumped a fixed volume of water without heavy rain.
During the second testing on September 30, the investor did not correctly anticipate the rainfall so it took longer than the first time to pump out floodwater. The rainfall measured 93mm within 40 minutes, equivalent to 150mm during three hours. Rainwater drenched the street too fast causing heavy flooding.
In addition, garbage still slogged manholes in the street despite a sewer cleanup project has been done this year.
After nearly an hour of running, pumps reduced flooding time in the street faster than before when there was no the pumping. However, sluice gates were blocked with lot of garbage so floodwater drained off more slowly, especially in positions far from the system such as areas near Nguyen Huu Canh and Saigon bridges.
Mr. Nguyen Van Trai whose house at 57 Nguyen Huu Canh street said that formerly rainwater flowed into his house and just receded after 2-3 or even 5-6 hours after rains ended. On September 30, it took nearly one hour to flow out. Street flooding also reduced faster than before.
Despite big capacity pumps, floodwater will not drain off quickly if there are no workers picking up garbage from sluice gates, according to Mr. Trai