It’s more than efficiency, it’s good stewardship.
Groundwater is no friend to construction sites. The groundwater table level must be lowered before any type of construction excavation begins. The question isn’t if you should use a dewatering technique. There’s hardly ever a time when it isn’t necessary.
The type of dewatering system you use depends on the situation you uncover on the construction site. An engineering study will uncover it beforehand. Or, you’ll make a dewatering system selection based on what you discover as you begin excavation. In all situations, there are general guidelines to follow for safety and for effectiveness. Here’s a collection of best practices.
The water has to go somewhere
Regardless of the pump systems used to dewater a construction site, it’s crucial to decide where the water gets moved. A poor decision will cause erosion or other types of damage. A storm sewer conveniently located nearby isn’t necessarily the solution. If the water is pumped to adjacent lakes or wetlands, you still have important concerns.
You’re removing water or lowering the groundwater level. The extraction of water alters the characteristics of the surrounding soil. You must be aware of how this change impacts your excavation. You also must be aware of and take responsibility for the safe relocation of the water.
If you fail in this process, you’ll erode the soil on and around your construction site. The resulting instability will cause problems for you and the owners of the surrounding property. You may be liable for the damage and consequences. Use these general precautions:
- Be aware of local and federal environmental protection regulations before you begin. They may require you to remove sediment from the water you extract. Apply for permits well in advance. Not having them in hand will delay your start date.
- Avoid discharging the water onto slopes. Nothing causes erosion faster.
- If you are able to discharge water nearby, choose wooded buffer areas. They have the best ability to absorb and disperse it.
- Monitor both the area you are dewatering and the area where you are discharging the water. Stop and investigate if either site shows signs of erosion. You don’t want instability in either area.
- If you’re moving water along a dewatering channel, you can stabilize it and reduce erosion by protecting the channel with grass or other ground vegetation.
- Groundwater should be tested for contaminates and overall quality. Large areas of standing water in open pits should be tested to make sure they don’t contain oil or chemicals. This may add a further treatment step to the dewatering process. The untreated water can never be discharged without first being treated. Additional permits and requirements might be needed from state, local, or federal agencies.
Pumps and dewatering
You need the groundwater out of the way during your construction project. Dewatering pumps are brought in to lower the groundwater table level only in the area of your excavation.
If the groundwater level is below your excavation level, you may only need trash pumps to evacuate standing water. These pumps also can be used to remove groundwater from the construction excavation site.
You’ll have to use more aggressive dewatering techniques if there’s excessive groundwater, or your excavation level is below the groundwater table level. These pre-drainage dewatering techniques use specialized pump systems.
Submersible pumps and wellpoint systems are installed to drain the excavation area. These systems lower the groundwater level. Often, they must stay in place and running until construction is complete.
The right pump system keeps you on schedule and ensures the safety of your crew. Following best practices demonstrates that you’re a proud environmental steward and an informed builder.