124-002 Technical Memorandum Revision B

The total minimum required head above the discharge point is 0.477m. With 2.600m of potential head
available this is easily achieved and demonstrates that the charged line would be functional.



                               FIRST FLUSH DEVICE

The first flush diverter will operate typical to the below Figure 3. When the 147 litres 300mm PVC pipe is full,
the ball float blocks the first flush and diverts water to the discharge point at the driveway. The first flush
volume and the water held in the pipework below the discharge point will be approximately 853 litres and
will drain to the rear via a 20mm drain pipe. The flow rate of this 20mm pipe will be approximately 0.5L/s




Figure 3 – Proposed First Flush Device



                                BUTTERFLY VALVE TANK DIVERSION

All roof water will drain directly to the rainwater storage tank with an electronic butterfly valve to
automatically switch-over and discharge to the kerb and channel on Enterprise Street when the rainwater
tank is full. This will ensure that the proposed stormwater design will not alter the site’s stormwater
discharge characteristics in a manner that may substantially damage or cause nuisance to a third-party
property.




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   2261 david low way, peregian beach, qld 4573      acn: 626 671 092              [email protected]