Lighthouse sinkhole, debris flood culprit

“The current drainage channels are undersized. Larger and better standardised drains will be built that will be easier to maintain and will alleviate flooding in the city,” Shamshad Mohamed, Director of Drainage in the Ministry of the Environment and Water Resources told Sunday Newsday on Wednesday at the ministry’s head office at Tower D, Wrightson Road, Port-of-Spain.

“No one can stop the flooding, but it could be alleviated to a minimum to ensure no loss of property,” Mohamed said.

“Two to three and four feet of water in South Quay is too much,” he said, referring to recent floods in the area twice in August and in recent years. The designs for the IDB-funded drainage project in the city are currently being drawn up by the architectural firm WSP Designs — a subsidiary of Genivar.

The loan has three components of which US$90 million is earmarked for the development of the drainage channels in Port-of-Spain. US$15 million is earmarked for the development and restructuring of the Drainage Division itself into a Drainage Authority in the second component. In the third, US$20 million is for the development of a “linear park” in the East Dry River for recreational purposes. WSP is due to submit the designs for approval next month, Mohamed said. Once approved the drainage project will go out to tender. Construction works are scheduled to start after the 2015 Carnival season.

There will be interruptions and inconveniences to vehicular and pedestrian traffic, Mohamed said, “but we will try to minimise them by working the evenings, on weekends and doing less work during normal working hours.”

On previous major works, Mohamed said the enlarging of some drains was done incrementally in different areas including sections of Wrightson Road. However, there was no complete overhaul, he said. The City Engineer’s Department made an effort in 1981. Recommendations were made in the 1981 Millette Report which the city commissioned to develop the drainage channels in Port-of-Spain. However, funding was an issue. Due to constant flooding in the city, prior to 2011, Mohamed said even though the Drainage Division is not responsible for maintenance of drains in the city, for the past three to four years, it has assisted the City Engineers Department with the maintenance where they have challenges.

The mandate of the Drainage Division is the maintenance and the development of natural water courses and not dry rivers and paved drains.

The Dry River Act gives the Port-of-Spain City Corporation the responsibility to maintain the East Dry River and over 50 paved underground drains. Each street has two drains on either side from north to south as well as cross drains. The East Dry River is the major water course that drains the city on the east, and the Maraval River, another dry river, drains it on the western side.

The Drainage Division has done all year round cleaning by contract of the city’s drains, depending on the availability of funds, Mohamed said.

“The drains were last cleaned at the beginning of this fiscal year in time for last Christmas... We are cleaning them again,” he said.

For 2014, he said the division and City Engineer have done monthly inspections of all the drainage channels in Port-of-Spain.

Speaking about the August 6 floods in Port-of-Spain, he said the drainage channels could not accommodate the additional rain water to drain the city because they came at high tide.

At high tide the sea water enters the city drains as far as Broadway at the roundabout on Independence Square. “Once there is high tide, there will be no immediate relief,” he said, but within 15 minutes to 20 minutes flood waters should subside.

The floods that followed on August 15, he said were during low tide. “It is not normal to flood at low tide,” he noted.

No check of the drainage channel was done after the August 6 floods, but checks done after August 15 revealed that over 90 percent of the refuse found in the drains were styrotex cups and food boxes, plastic cups/bottles and plastic bags. No silt was found in the drains.

Apart from South Quay, two other streets — Richmond and Duncan Streets — were affected by the floods.

On Richmond Street, the Drainage Division discovered that lumber decking that had been used while paving the drainage channel in the area had rotted and fallen into the drain. This has been causing massive flooding the area.

Along South Quay and Duncan streets, where once there were inlets, they are now few due to constant repaving.

“We have to rebuild cow mouths there,” he said.

The August 15 heavy rainfall over 22 minutes, he said, exceeded a one in a 20-year storm.

“Port-of-Spain was designed for a one in a ten-year storm,” he said “and it would have flooded anyway, but it would not have been so high because the channels would have been free hadn’t there been so much garbage in the drains.”

The massive flooding at South Quay, he said, are compounded by several drains that were blocked when the Public Transportation Services Corporation (PTSC) was built.

“Previously, every street in that area had a drain that emptied into the sea. We now have only three going out,” he said.

After the August 15 floods, on inspection at low tide in the vicinity of the Cove, he said the Drainage Division found a pile of lumber in one of the three blocking the exit to the sea. “We believe that the lumber came from repair works undertaken by the Ministry of Works on a sinkhole that occurred in the area last year.

“We think that the others would be blocked, and we are checking them out,” he said.

To alleviate flooding following a similar flood about a year ago, Mohamed said the Drainage Division in consultation with the City’s Engineers Department took the initiative to place gratings across the “cow-mouths” (inlets into the underground drains) having seen the same types of garbage that had blocked the drainage channels after the August 15 rains.

Within one month of putting the gratings, they were removed by the City Engineer Department because of complaints that garbage was blocking up the inlet and the water could not get into the drains. “What were they blocking? We did some investigations and found that a number of plastic bags would end up on the cow mouths and if they were long enough they would block the smaller inlets. They flow with the water to the inlet,” Mohamed said.

Speaking with the City Engineers Department’s staff, Mohamed said he was told that the covers were removed because they were “blocking the cups and boxes from going into the drain, and out to the sea.”

Mohamed said he indicated that was what his division was trying to prevent.

“The garbage is clogging up the manholes. We agree that the drains are too small to take the discharge into the sea. We realise that if cleaning is not done on a regular basis, we will have clogging of the drains and flooding every time rains falls.”

“Somebody has to investigate how the City Engineers Department cleans the city,” he said.

Because the cow mouths are of different sizes, Mohamed said the division has recommended standardized sizes for all cow mouths/manholes. “It allows for easier maintenance and repairs with standard items,” he said.

Another problem, he said, is that concrete trucks and construction workers add the remains of concrete into the drains when they wash the pumps through which concrete is poured into them. “That is not our business. The City Engineer has to manage that,” he said.Apart from South Quay, two other streets — Richmond and Duncan Streets — were affected by the floods.

On Richmond Street, the Drainage Division discovered that lumber decking that had been used while paving the drainage channel in the area had rotted and fallen into the drain. This has been causing massive flooding the area.

Along South Quay and Duncan streets, where once there were inlets, they are now few due to constant repaving.

“We have to rebuild cow mouths there,” he said.

The August 15 heavy rainfall over 22 minutes, he said, exceeded a one in a 20-year storm.

“Port-of-Spain was designed for a one in a ten-year storm,” he said “and it would have flooded anyway, but it would not have been so high because the channels would have been free hadn’t there been so much garbage in the drains.”

The massive flooding at South Quay, he said, are compounded by several drains that were blocked when the Public Transportation Services Corporation (PTSC) was built.

“Previously, every street in that area had a drain that emptied into the sea. We now have only three going out,” he said.

After the August 15 floods, on inspection at low tide in the vicinity of the Cove, he said the Drainage Division found a pile of lumber in one of the three blocking the exit to the sea. “We believe that the lumber came from repair works undertaken by the Ministry of Works on a sinkhole that occurred in the area last year.

“We think that the others would be blocked, and we are checking them out,” he said.

To alleviate flooding following a similar flood about a year ago, Mohamed said the Drainage Division in consultation with the City’s Engineers Department took the initiative to place gratings across the “cow-mouths” (inlets into the underground drains) having seen the same types of garbage that had blocked the drainage channels after the August 15 rains.

Within one month of putting the gratings, they were removed by the City Engineer Department because of complaints that garbage was blocking up the inlet and the water could not get into the drains. “What were they blocking? We did some investigations and found that a number of plastic bags would end up on the cow mouths and if they were long enough they would block the smaller inlets. They flow with the water to the inlet,” Mohamed said.

Speaking with the City Engineers Department’s staff, Mohamed said he was told that the covers were removed because they were “blocking the cups and boxes from going into the drain, and out to the sea.”

Mohamed said he indicated that was what his division was trying to prevent.

“The garbage is clogging up the manholes. We agree that the drains are too small to take the discharge into the sea. We realise that if cleaning is not done on a regular basis, we will have clogging of the drains and flooding every time rains falls.”

“Somebody has to investigate how the City Engineers Department cleans the city,” he said.

Because the cow mouths are of different sizes, Mohamed said the division has recommended standardized sizes for all cow mouths/manholes. “It allows for easier maintenance and repairs with standard items,” he said.

Another problem, he said, is that concrete trucks and construction workers add the remains of concrete into the drains when they wash the pumps through which concrete is poured into them. “That is not our business. The City Engineer has to manage that,” he said.