Today’s changes in the weather conditions as a result of global warming, more especially with the incessant rains coupled with flooding need for the implementation of more secure and robust drainage systems. Since the infrastructure being constructed is disruptive to the natural water flow where natural soil that used to allow water to permeate and flow is now being changed into a hard surface that when water hits, it does no longer allow it to infiltrate but rather to gather on the surface and run down the most suitable channel. This is how stormwater is created and needs to be controlled to protect the public from flooding.
Besides other things, the impact of rain directly affects the project schedule through increased non-working days as no construction work can occur during heavy rain or where the ground has become too saturated that the results would be detrimental to the quality of the final structure. High moisture content in the ground will as result affect the compaction, permeability, and shear strength of the material.
Before construction is implemented, it is very crucial to gather information around the location of where the construction is to take place and work around an idea on how to implement certain measures to manage the work. This will help you to understand how your schedule will run. The following factors need to be taken into consideration:
The “It has happened this way in the past, so it will happen this way this time too!” Factor
Assessing the pattern and risk of rainfall takes into consideration statistical analysis. This step needs you to pay careful attention to current, future, and past rainfall data with the specific area where the construction is to take place. You will be surprised at how much data is at disposal but not being used to its maximum value in effectively planning the execution of construction. The current data is obtained by direct measurements where current rainfall is recorded using rain measuring instruments to assess any sudden changes taking place to help make quick and informed decisions. Future data is helpful for short-term planning on weekly activities and is obtainable from weather forecast services. Historical data plays a major role as it refers to experiences on rainfall at specific locations and is helpful in the long-term planning over months and years. South Africa’s historical rainfall data can be obtained online from weathersa.co.za and dates back to the 1850s.
South Africa’s annual average rainfall is 464mm and is considered low as compared to the global annual average. There are, however, still large and unpredictable variations that can make working during a rainy season to be a hassle. The probability of rainfall for most of South Africa during the summer is very high as convective rains develop due to all the areas having enough heat to warm most air causing it to rise and then cooling down to condensation and precipitation.
Unlocking strategic measures that can be implemented to ensure fast-paced construction
Once you have estimated the number of days in which you might experience rainfall and are now entering or in a rainy season, you must put up a plan of action around working through the rains to get everything completed in the best possible time. If you are in South Africa then you know that the weather can change quickly so it is essential to have a plan in place for everyone involved in the project so that they are prepared on exactly what they need to do to mitigate damage. Post the plan in an easily visible location for everyone to see and stay up to date.
Your plan needs to take account of construction equipment and material that is damageable by rain as well certain construction areas that are susceptible to accumulating rainwater or getting washed off by the runoff. Using tarps and plastic sheets to cover out material and equipment can be a highly effective solution to implement to keep the moisture out. Rain will delay the project further not only by causing damage to construction material and equipment that you might need to replace but also by an extended waiting period for surfaces to dry out. Although you can always drain out the water flooding sections such as trenches by using a pump, it can be very beneficial to place covers, install permanent or temporary drainage, or divert the runoff away from the construction.
It is wise to start constructing drainage services that go underground first to leverage out of using them even during the construction phase as once these services are in place they can be used to direct the water away. These services are designed taking into account the low points around the site and can be easily noticed, as they are likely to be water paths or areas experiencing puddling. Directing the water away after or when it accumulates on these sections can be quite effective.
Another method that is effective in preventing surface runoff from works and can be used especially on road layer works is the creation of temporary berms to separate small catchment areas that collect raindrops and slopes to one side to allow the flow of water to be diverted off the road works. They can be formally constructed and built up with two or three compacted layers or as hips along the cut-off area as desired.
The top of one mountain is always the bottom of another
Surface runoff is controllable through the visible drainage systems that allow for runoff entry and then effectively directing the water to suitable outlets. Runoff that penetrates the ground around the surrounding areas results in a rise in the water table. Effective control on the underground water level is a crucial part of drainage systems to ensure that no further flooding can occur as the surrounding areas become waterlogged. Though the water table is susceptible to seasonal change, in some areas it is naturally high to depths that if not controlled, construction cannot take place.
In such situations, it is extremely important to implement subsoil drainage systems that help minimize the amount of underground water at desired areas so that damage does not occur from underneath. Many constructed roads for example have crumbled at the sight of underground water. The damage is only accounted for at a later stage when communities have already suffered from deteriorating roads to the severity that the road needs to be entirely reconstructed. Such locations can also be characterized by excessive flooding during rainy seasons.
Layer works are stronger when the material is dry and become weak when wet. To ensure that no moisture can come into contact with the elements of your structure that are in contact with the ground or are underground, the following measures of effectively constructing subsoil drainage can be considered:
It comes underneath all the construction work and covers all the areas where the construction will be affected by underground water. This will thus include excavating further deep into the soaked ground to reach a certain depth where there is some resistance.
Components of this layer can include dump rock, geotextile layer, subsoil pipes, and some crushed stone. A geotextile fabric such as a bedim is used to wrap the intermediate thickness of dump rock to prevent any silt or fine material from getting in between the gaps between the rocks.
Wrapping the dump rock with bedim to ensure that it stays free of fines that may clog up the spaces in between the rocks that allow water to flow as it does underground is crucial. This will cause the water not to rise to a level where it meets any layer works or foundation works. The subsoil pipes are installed on the sides to take in any excess water. They are placed on top of crusher stones to give them elevation from water flowing with many fines and then wrapped with bedim to prevent any other fines from getting into the pipes
This post would not be complete if it did not address health & safety issues
While the quality of the constructed work and the project duration remain a serious concern when it comes to rainy seasons nothing is of greater importance than the safety of workers as well as everyone else affected by the construction. It is extremely important to ensure that all workers are in their reflective gear at all times even more when you know you are expecting rain as visibility is minimized during these conditions. Further measures to be taken are obtained from the OH&S Construction Safety guidelines obtainable at safetyrisk.net and will require that both workers and employers cooperate on following these guidelines however, worker safety must be prioritized at all times.