How to set up line and grade in sewer sanitary system construction
n order to place grade and line for developing the sanitary sewer system, four methods are mostly applied. One of these methods or combination thereby may be utilized in the construction. Given below, the detail information on these methods.
Methods of Setting Line and Grade in Construction of Sewer Sanitary System:
1. Stakes or crosses are set up on the surface on an offset from the centerline of sewer sanitary
2. Stakes are set in the bottom of the trench on the sanitary sewer line since the rough grade for the sanitary sewer is finished.
3. Elevations provided for the finished trench grade and sanitary sewer invert whereas sanitary sewer construction proceeds.
4. A laser beam of light set in the manhole or a particular height over sanitary sewer flow line.
1. Stakes or crosses set up on the surface on an offset from the centerline of sewer sanitary: In general, this method is very effective for small diameter sewer sanitary system. Substantially, crosses, stakes, or spikes are arranged at a consistent offset from sewer sanitary centerline.
The excavated soil material should remain at one side of the sewer sanitary trench and the stakes should be arranged at the other side.
If it is required to accomplish an accurate and reasonable job, there should be perfect sheet on which reference points of sanitary sewer stations, offset, and vertical distance from each reference point from projected sanitary sewer invert will have to be recorded.
Finally, the line and grade of sewer sanitary is transmitted to the bottom of the trench with tape and plumb bob unit or tape and level.
2. Stakes are set up in the bottom of the trench on the sanitary sewer line because the rough grade for the sanitary sewer is finished: This method is ideal for large diameter sanitary sewer as well as the sloped trench wall.
For the sloped trench wall, the top width of the trench should have been significantly wide, and the deployment of short offset would not be recommended.
Under this method, surface references are transmitted to the stakes which are arranged at the bottom of trench along sanitary sewer system.
When stakes are set up at the trench bottom, string line should have been drawn among at least three points. The string line should be examined by applying the same process for batter boards.