Method Statement for the Construction of Manhole Chambers
This example is for the construction of basic manhole chambers with concrete surrounds.
- The Engineer to set out the manhole position and carry out a CAT scan of area and dig trial holes in areas of any known services and location pegs installed with warning tape.
- Excavate the area to the required depth for the chamber in accordance with the issued construction drawings.
- A manhole box to be used for shoring the excavation. The excavation is to be suitably fenced off at the end of the shift.
- Depending on the depth a gas detector should continuously monitor for atmospheric changes. Ground water to be pumped out.
- Adequate access to be maintained at all times with secure ladders.
- When the correct formation level is achieved and checked by the engineer, the base will be prepared and concrete blinding poured.
- The Manhole base will be constructed as per the design drawings.
- The invert inlet and outlet levels of the manhole will be formed using a proprietary system or by shutters.
- The manhole chamber rings will be lifted into position using a chain and harness and by the lifting pins / points supplied by the manufacturer or by attachment to precast points.
- The chamber rings to be checked and installed in accordance with the design drawings and manufacturers specifications, the manhole could be benched prior to the surround shutters being installed taking care to ensure the design void is adhered to.
- The surround will be concreted to the required level and a vibrating poker to achieve compaction.
- Final brickwork to be completed and the cover and frame installed to the design level and specifications.
- The manhole will be backfilled once the concrete surround has cured, back filling in accordance with all issued specifications.
- As-built invert and cover levels to be recorded.