Drain
To investigate the probable cause of a poorly running drain, several drill holes can be made. In these drill holes, water must not flow over the surface of these boreholes. Even more accurate is the installation of several vertical groundwater level pipes, with a length of approximately 1.20 meters. If this is perforated over its deepest length over which a sleeve has been pulled, an excellent filter is obtained. The water level can be read regularly in this tube. By placing them right next to the drains and between the drain, the influence of the drain can be measured. By placing one or more at several distances from the power tube, an impression of the hydraulic gradient is also obtained and the presence of airlocks or a negative gradient can also be demonstrated. The water level can be checked approximately 24 hours after the monitoring wells have been placed or drill holes have been made. With good drainage, the results should be as shown in figure 1 A. In this case the groundwater level may be above the drain, but no more than 10 to 15 cm. If the results are as indicated in figure 2 B, then either;
- the ditch level is temporarily too high, which results in drains being underwater
- the drainpipe is too small in relation to the surface
- the tube is clogged, soiled, or disturbed
If the pipe dischargers to little or no water, the casing material or perforations in the drain may be blocked (figure 1C). This can be seen through puddles forming on the plot while the groundwater level is low and the drains do not or hardly drain. In this case, the drainage works well, but the cause is compacted or congested soil. This can occur on a plot that has been cultivated under unfavorable conditions. Grassland is sensitive to this, for example, when it has just been sown. The cutting (clay) or compacting (sand) can then easily occur during an intensive rain shower. Even after heavy leveling, there is a risk of disturbance in the profile. Even after heavy leveling, there is a risk of disturbance in the profile. In these cases, the solution must be found in a profile operation. A poorly permeable layer can easily occur deeper in the profile. This can be caused naturally, but it can also occur after processing. This can be solved through profiling. There is various equipment for this. The entire profile can also be poorly permeable. This cannot always be improved through profiling. Figure 2 F, shows excellent draining, but the drain distance is too great. In this case, interim drainage will often be necessary. When checking the drain trench, one more borehole must be made, or one monitoring well must be placed in the drain trench. One hole or monitoring well approximately one meter from the drain and one hole or monitoring well must be placed in the middle between the drains. In figure 2 F it can be established that the drain trench is poorly permeable. The cause may be that the side of the drain trench is smeared while digging the trench.
[figure 2]
Remaining control methods
In addition to monitoring the construction of drainage and the operation via monitoring wells and measuring the discharge, there are other monitoring methods. Such as the method in which a transmitter is placed in the drain using a hose. The transmitter emits radio waves which are received above-ground. This way, a possible malfunction can be accurately traced to less than half a meter. This can prevent unnecessary digging. The pierce ability can be checked with a piercing device. The back pressure which the head of the piercing device experiences in the drain is thereby measured. If the resistance is too high, the pipe may be dirty or there may also be obstacles in the drain. Sometimes deformation of the pipe has already occurred during construction. The drain can also be compressed if the location of the drain is too shallow or damaged during deep tillage. Another device is the drain scope. A recording device and a light source are placed in the drain through a puncture in the drain. This way you can look into the drain and, if desired, record the degree of pollution or malfunction on a photo.