water Infraustructure project( site drainage problem)

The Site Plan Drwg. WD.01 shows the existing residence extending to Pergolas 1 and 2 and a Studio/Toilet. The area north of these structures and the New carport was detained on-site prior to the re-development. Post-development, this area extending to the proposed boundary at the 18.28 m line will be discharging to the council drains. The council has set a 5% AEP (20 years) for all pre- and post-development stormwater discharge. The area north of Pergolas 1 and 2 will be paved with a maximum height RL 50.15 (refer to the Site Drainage Plan for site levels). The paved area will need to have falls to two separate 100 mm x 1 m Everhard Easydrains – Polymer channels and grates. The first Easydrain will need to collect runoff from part of the pavement as well as half of Pergola 1 entering from a downpipe. The Easydrain nearer to the New Store will collect stormwater from the remainder of the new paving. Roof runoff from the eastern half of the New Store and part of the Studio/Toilet enters the piped system from a downpipe north-east of the New Store. Runoff will need to be piped under the New Store with a 75mm uPVC pipe stormwater pipe cast in the concrete raft footing. The stormwater pipe subsequently runs into a proprietary Everhard 450 mm Series Pit (with a grated lid) located west of the New Store prior to discharging through the kerb to the street water table. The open area between the New Store/Store/Toilet and the existing fence will also be paved, falling to a separate pit and may be ignored. The roof runoff from the western half of the New Store will also discharge to a separate piped system from a downpipe and may be ignored. The Everhard Easydrains have 75 mm diameter “Tee” outlets under their base, which will need to be connected to the main 75 mm uPVC stormwater pipe. The 450 mm pit inlet and outlet levels can be customized to obtain the optimum falls and site requirements. The Site and Drainage Plan Dwg No. SP1 shows reduced levels (RLs) to determine the falls to the paving and site drainage. engineer needed from civil and structural engineering who can easily do it.