A proper water management system is one of the keys to success of any construction projects. That is why it is a big challenge for any projects to be designed with a sustainable stormwater management solution.
Indeed, runoff water created by stormwater (or melting water) can create erosion on a land due to flooding and/or increase pollutant discharges in a natural stream. All types of surfaces from natural permeable soil to impermeable surface are affected differently by runoff water. The best way to attack this problem is to be aware of it at the design stage of your project in order to be able to implement sustainable and affordable solutions.
Common Storm Water Management Problems and Solutions
A natural permeable soil is able to drain water by infiltration, provide groundwater recharge and naturally treat the water. Indeed, most water treatment systems for potable water or sewage water are using sand as an essential part of the treatment process.
The problem is that any soil has its own water infiltration limit. After that point, the soil cannot accept any more water and the water begins to flow on top of the soil. This runoff water can create flooding, transport pollutant particles in natural streams and even create erosion either to the land or to the nearby natural stream.
In a residential site, a possible solution to improve the overall water infiltration limit of the land would be to install a “rain garden”. This “rain garden” has to be lower that the lawn around it and made of mulch, soil, and deep-rooted native plants. This garden would capture, absorb, and infiltrate stormwater and could improve the overall water infiltration limit without adding an unnatural water retention system. The “Homeowner’s guide to stormwater” offers a variety of residential solutions for stormwater management.
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Impermeable or Semi-Permeable Surfaces
A impermeable surface cannot infiltrate water. This is why engineers often use water retention systems to manage stormwater runoff.
The best example to demonstrate this is a grocery store’s parking, which is made of a large area of impermeable surface. If a rain with a high return period occurs on this parking, the sewers might not be able to take all this water and the runoff water might cause flooding that could be a hazard for the population and also transport pollutants to a natural stream. The retention system would retain a certain amount of water excess before the water goes back in the municipal water system.
Furthermore, the water retention system is often made of clean stone that will allow a certain filtration of pollutant brought by the runoff water. Finally, the water retention system’s size (volume) has to be designed according to the area of the impermeable surface that is draining in it (watershed) and to the return period of rain the engineer is judging safe. A mix of melting snow and high return period rain could also be the critical factor for designing the system.
Stricter EPA Requirements
EPA requirements are getting stricter on every aspect of construction projects. In the case of stormwater management, the main criterion is the amount of pollutant particles discharged in natural streams and the monitoring of those particles.
Depending on the size of the project, a developer can face different EPA requirements. It is very important to confirm with a specialist which EPA requirements are relevant to the project at the design stage. Those requirements change often so it is important to check it before every project even they are similar to a former project. The article “The challenges of stormwater management” explains this situation and other problems related to this topic.
Runoff water management of any project is a challenge because it affects all types of surface differently and is too often underestimated by developers and contractors.
Good engineering firms like Godfrey Hoffman Hodge constantly improve their stormwater management systems in order to meet the stricter EPA requirements and remain competitive in the market. You can check their Stormwater System Design page entirely dedicated to this topic and applicable to residential, municipal and commercial projects.