Overcoming construction flaws to combat dengue

An Architect's view:

D H Wijewardene, Chartered Architect

Today, the whole nation is combating the mosquito menace that has become a deadly health hazard. Cleaning of buildings, gardens, lands, waterways disposing of waste have become extremely important than never before.

But I have not noticed any attempt being made to pay attention to defects in buildings and their related activities that lead to mosquito breeding. Most of these can not be solved overnight, as authorities expect and others can only be attended to some extent since there are inherit design or construction defects.

Hence it is important to address it during the design stage and also during construction. Poor quality building materials and products also help to retain water in buildings at unnoticeable and inaccessible locations.

Roof is the main item that deals with rainwater in a building and it is important to drain all water that falls without stagnation. Even a very small quantity of fresh water can breed thousands of dengue mosquitoes. Concrete flat roofs which are prone to this defect have to be properly sloped and adequate outlets should be kept to drain water. In concrete sunshades, canopies too can create breeding grounds. Less attention is paid to these aspects especially in smaller scale construction.

Employing unskilled persons

Also keeping smaller outlets is a common defect which leads to collect water. Employing unskilled persons without proper professional advice is the reason behind it. Even these are built to the best quality, the outlets need to be cleaned periodically.

Defective gutters in slopping roofs are common grounds for breeding mosquitoes and other insects. Most UPVC gutters and brackets available in the market do not resist ultraviolet rays and when exposed they get twisted and bent causing disrupting the flow of water. After becoming defective in a shorter lifespan than expected, these tend to retain water longer after rain. The authorities should correct this immediately and ban any product that does not conform to the required standards. While this defect is not present in treated steel gutters, lack of knowledge among the installation persons lead to water drainage problems. Collection of leaves in gutters is a main reason to clog water and in some countries it is compulsory to use pvc coated nets at the time of installation. These become hidden places where insects can breed.

Defective gullies

One of the other defective items that have a bearing on this issue are the gullies in washrooms and in toilets. Most of the time these devices are covered with flaps, some have got in-built traps. Soil water does not facilitate dengue mosquitoes. Employing skilled persons with properly planned out toilets is the answer and also periodical cleaning is also essential for proper functioning of drainage. In other wastelines similar defects may cause breeding mosquitoes.

Rainwater drains/pipes, manholes and soakage pits are defective prone items. Buried pipes get bent at the mid points and if the base is not properly supported freshwater will retain. Manholes without proper slopes will have the same defect.

In some manholes pipes are laid slightly above the floor of the manhole to retain silt and sand but may collect clear water. All these are due to poor construction methods and need to be corrected at the time of building. While these are simple defects, the mosquito hazard such matters too need to be addressed to eradicate.

These also can be easily solved if proper methods are followed. For example by keeping few perforations at the base of the rainwater manholes, the excess water will get absorbed to the ground eventually. What is important is the use of proper material and construction standards.

Blocking of land

Blocking out land into small slots is another cause of environmental problems especially when there are no central waste, storm and sewer disposal systems.

Septic tanks, the most commonly used sewer disposal system in the absence of central system, damage the environment. It is mainly because of incorrect use of this method create problems. Septic tank is a sealed unit that separates solid and liquid and eventually allow solids to decay by means of bacteria which is called the "Septic Action". But to activate this biological action, the size, minute details of water levels, methods to separate solid and liquid and depth of the tank should be according to the required specifications.