Drainage For Construction Improvement

By Steleanor Bella


All open drains will be cut to natural surface and will not contain fill material unless otherwise directed by the Supervisor. The height of concrete stabilised backfill above the top of the culvert will be as shown on the drawings. Compaction of the backfill material will be by hand operated mechanical vibratory compaction equipment. The mortar mix and method to be used will be approved by the Supervisor. Rock pitching will be placed in the mortar whilst still wet, each rock being hand placed and firmly bedded into the mortar and against adjoining rocks. Rock pitching will proceed in a similar upward progression up the angle being covered, following the mortar bedding.

Rock pitching shall be placed in the mortar whilst still wet, each rock being hand placed and firmly bedded into the mortar and against adjoining rocks. Rock pitching shall proceed in a similar upward progression up the slope being covered, following the mortar bedding. On the day after the placement of the rocks, a stiff cement mortar mix shall be carefully worked in to the joints between adjacent rocks to provide an even, solid, tight surface. The mortar mix and method to be used shall be approved by the Superintendent.

Height of the bedding will be as indicated on the drawings. Protection works will consist of rock pitching adjacent to outlets and headwalls of drainage conduits and at intersections of open drains. Protection works will be carried out to the details indicated on the drawings. Open drains will include table rains, catch drains and dispersal drains. This material will be as detailed on the drawings. Backfill will be placed equally each side of the pope to avoid disturbing the approved installed pipe conduit. Backfill will be placed equally each side of the culvert to avoid disturbing the approved installed box culvert.

Embedded metalwork included in the concrete structures such as open grating, support channels, manhole cover and the like will be constructed to the details shown on the drawings and in compliance with the specification. Before placing rock pitching, the bank on which it is to be placed will be trimmed to a uniform angle as detailed on the drawings. Mortar bedding will first be placed commencing at the lowest point of the angle and placing will then progress upward.

All dirt must be compacted to 90% of maximum dry density as measured by AS 1289 Part 3, aside from under roadways and access areas where the dirt must be compacted to 95% of maximum dry density. Compaction of the dirt material must be by hand operated mechanical vibratory compaction equipment. Compaction must not be used within 150 mm of the pipe. Suitable dirt material must be placed around the pipe to a depth of 300 mm above the top of the pipe or as detailed on the drawings. The remainder of the trench must be smoothed to finished ground level with material previously excavated from the trench.




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