Managing dams and embankments is a big responsibility. You have to take all measures to keep the dam and its environment safe and unharmed. But usually, there is a big confusion among dam owners about whether they should use ROV or divers. Well, in this article, we will talk about different ways to conduct underwater dam inspections.
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Dams: Overview
A dam is a barrier that is constructed across the river to control the flow of the water. The reservoir created around the dam acts as a water reservoir for irrigation, human consumption, and other purposes. It also suppresses floodwater from overflowing around the surrounding area. The power generated by the dam is known as hydropower. It is used to create electricity.
Different sections of the dams:
- Diversion tunnel
- Upstream Dam wall
- Emergency/sluice gate
- Penstock or headrace tunnel
- Tailrace channel/pool
Dam Inspection
Dams undergo stress and pressure due to several factors including weathering, chemical attack, corrosion, and many more. And this poses severe harm to the environment and the surrounding. But this can be altered by regular and thorough inspection.
The main motive of the dam inspection is to ensure the smooth functioning of the dam and omit any threat to life or property.
Issues With Underwater Dam Wall
Over years, there are several ways a dam can be damaged over the time:
- Different types of cavities and cracks on the upstream wall
- Leakages through emergency gate seals
- Grooves for lowering gates damage
- Damage in cement lining of penstock can cause water leakage
- Silt accumulates in the dam
How Often Should You Do Dam Inspection?
There are four different classes of dams:
- Class I (If they fail will cause loss of life)
- Class II (If fails then it will cause substantial downstream property damage)
- Class III (If fails, cause less damage)
- Class IV (Dams with less than 15feet in height and impound less than 15 acres of water to the top of the dam and drain less than 150 acres)
Class I and II dams owners should conduct inspections every two years and a formal inspection every 6-10 years.
For all classes of dams, a periodic inspection twice a year is important. Once in winter when the vegetation is dormant and other in summer after mowing.
Different Techniques of Dam Inspection
With the help of modern-day technology, you can easily conduct underwater dam inspections. Here are some popular methods for dam inspection:
- Sonar Inspection
Sonar stands for sound navigation and ranging. They work on the acoustic pulse. The sonar device consists of a sound transmitter and receiver. The transmitter produces a pulse of sound that strikes the object in front. Similar to echo, the sound comes back and is received by the receiver. The data points collected are then used to produce a 2-D or 3-D model of the target.
- High Definition ROV Inspection
Sonars and other methods are good, but for more detailed and accurate information you should use ROV inspection. ROV stands for remotely operated vehicles. These ROVs are equipped with a high-quality camera that allows them to take high-definition pictures and videos.
- Aerial Inspection and 3D Modeling
An aerial inspection enables dam owners to get a brief look at the dam from all angles. UAVs with high-definition cameras enable them to get clear footage of the dam. Moreover, experts can make 3D models from them.
- Combining Aerial with Sonar
You can even combine aerial with sonar imagery. It helps dam owners to view and underwater data together.
- Ground Penetrating Radar
The radar sends pulses to the ground to derive an image of the subsurface. It is an interesting way to find what is under the surface without destroying anything. It helps to detect any cracks, objects, change in material, or voids under the surface.
- Underwater Manual Inspection Technique
In this technique, packs of divers are used to conduct a manual inspection of the dam. Though other machines can do this much more conveniently and safely. But there are works like repairing and maintaining that divers can do efficiently.
Divers or ROVs? Or Both?
Often people think that they should either use a diver or an ROV for underwater dam inspection. But if they are combined, it works magically. ROVs are more advanced and can be of greater help when the depth is great. Deep Trekker ROVs can operate for up to 8 hours continuously. Moreover, ROVs are more cost-effective than divers.
But when you know how to do repair or inspection, you can use both divers and ROVs. While the divers perform their duty, the ROVs would act as an extra eye for security and guidance.
Conclusion
To sum it up, these were some interesting ways to conduct underwater dam inspections. With the help of technology and labor, one can easily conduct inspections. Remember to conduct dam inspections twice a year. Because if there is a minor carelessness shown towards the dam, it can result in a major disaster.
