Heavy rainfall brings down several retaining walls

The methods currently being used in the construction of retaining walls throughout the country continue to be a cause for concern to officials here.{{more}}

Over the past week, the National Emergency Management Organization (NEMO) received reports of ten retaining walls which collapsed as a result of the heavy rainfall which affected the country earlier this week.

This need not happen, as according to Chief Engineer Brent Bailey, a properly constructed retaining wall is capable of withstanding the forces of nature.

Bailey said it is commonly observed at construction sites around the country that the foundation for retaining walls is about three feet.

However, the width of the foundation should be about half the intended height of the wall, Bailey said.

“So you will see persons building 8, 10 or 15-foot walls where the base is inadequate,” he explained.

He added that in the case of an 8-foot high retaining wall, a three-foot base may be adequate, but for anything in excess of this, it becomes inadequate.

“But that is the construction practice going on, and that is wrong,” the Chief Engineer stated.

The situation is made worse when the soil behind the retaining wall gets wet, Bailey said.

“…When you have situations whereby the soil gets over saturated, it actually exerts more pressure than the earth would normally apply.”

While the laws of the country spell out certain penalties for not building according to code, the problem is with the enforcement of the Law.

Bailey explained that for example, permission must be sought from the Chief Engineer before construction of a wall structure within 11 feet from the edge of the roadway begins.

“The biggest problem is in the enforcement, however, and the jurisdiction. We typically try to go through the Planning Board as that is the easiest mechanism because the Planning Board’s legislation is clearer,” he explained.

The Planning Board also has the capacity to move around and ensure people have the necessary approvals and they can serve the appropriate notices to halt work for work going on without the required approvals, Bailey said.

Bailey also pointed out another flaw in local construction.

Too often, the Chief Engineer said, plans are submitted for approval without the inclusion of a proper drainage system.

“Once you have built a structure, the water that would have percolated down into the soil no longer occurs. It’s now all running surface water, and when it gets to an embankment, it then becomes susceptible, and this is widespread in our construction.”

Bailey contended that too often, a sketch of the proposed draining system is lacking from the plan, or if included is not carried out during the construction phase.

“This leads to problems not only to the government, who has to deal with the associated drainage, but to the residents who usually come back to government to resolve these issues,” he said.

He urged persons when making an investment in the construction of a house to put some emphasis on ensuring a proper design is put in place.

Bailey is of the view that the responsibility is on the owner to ensure that the simplest issues are dealt with.

“We have to question our design professionals to ensure that these things are managed and not leave it for 10 years down the line when we are sitting in the house and we are comfortable and the banks slip away and the foundations are exposed and all that we have invested is lost,” he said.

Vincentians are only too aware of the hazard posed by poorly constructed retaining walls.

In September 2008, after days of sustained, heavy rainfall, a large retaining wall in the Ratho Mill area collapsed on a vehicle killing the lone occupant Patsy Jack-Bowman.