EXCAVATION OF CHAMBERS FOR SEWER MANHOLES

Prior to any excavation taking place, the contractor should de-marcate the area where work will take place and the area will then be marked out. Once the area is marked, excavations may begin and digging should only take place up to the correct depth and width as per drawings and specifications. All excavation to be battered to ensure for a safe working area.

The depths of excavations will be determined using a surveyor who will set out bench marks for the determination of invert levels. The invert level is the base interior level of a pipe, trench or tunnel; it can also be considered as the "floor" level.

Take note that the invert is an important datum for determining the functioning or flow line of a piping system. Once this level is established, the contractor should level out the base for compaction as per specification and drawing i.e. 95% MOD AASHTO.

Once this is complete, there should be installation of formwork/shuttering as per drawing designs for the casting of the Manhole Bedding. Concrete cube tests to be taken on every single batch and sent to an independent lab for testing before the construction of the Manhole chamber using brickwork (Clay Bricks) is done.