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PRECAST CONCRETE STORMWATER PITS AND RISERS
SPECIFICATIONS AND INSTALLATION
CONSTRUCTION
Concrete shall be in accordance with the requirements of AS1480: 1974 and shall exhibit the
following characteristics and features.
(a) Average compressive strength of 40 Mpa
(b) Maximum water/cement ratio of 0.40:1
(c) Minimum cement content of 450 Kg/M3
(d) Reinforcement with Safety Cage conforming to AS1302(d)
Concrete will be consolidated by vibration.
Step irons to be fitted to pits exceeding 1200mm internal depth at 300mm centers or as required
by local authorities
INSTALLATION
1. Pits and risers should only be moved using the appropriate approved lifting equipment and
the lift points provided. When lifted over buildings or personnel loads must be under slung.
2. The pit should be installed on compacted ground at a position and level as shown on the
drainage plan or as directed by the responsible authority.
3. An inverted collar must be cast around the base of the pit to prevent uplift, if aggressive ground water or a high water table is encountered. Consult the responsible authorities before
undertaking these modifications.
4. Using the knockout sections provided, connect drainage pipes as indicated on the plan and make good to the requirements of the responsible authority. Fill the joint between pipe and pit with a 4:1 sand and cement mix sufficient to provide water tight seal.
5. Riser modules can be added to yield a maximum total pit depth of 5000mm. An approved
epoxy mortar must be used between riser joints to provide an effective water tight seal.
Backfill all 4 sides of pit and riser modules with clean backfill material, free of debris and
compact in 300mm layers to ground level.
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