Stormwater Management Plan -OPW (A) · OPW25/0042

Infiltration Rate (mm/s) = 13mm/sec + 33 x head (m)

Refer to Appendix D for 2024 prototype test results.

Video of prototype testing being carried out are included at Appendix K.




6.2.3 PROTOTYPE            RIP    TEST     RESULT       COMPARISON           AND
APPLICATION

It is not entirely clear as to the factors contributing to differing infiltration
rates observed in 2003 and 2024.

2003 testing was carried out at a relatively elevated northern area of the site
compared to 2024 rates observed at a lower southern area of the site.

Both locations saw the prototype founded on clean white sands although
possibly insitu sand density may have differed between the two locations.

Inclusion of a rock base may have contributed to higher infiltration rates
observed in 2024 although the arrangement better replicates actual RIP/RIC
construction.

Regardless of contributing factors both 2003 and 2024 prototype test results
returned very high infiltration rates.


7.0 RIP/RIC DESIGN AND MODELLING

In order to ensure a conservative approach is adopted for infiltration of
stormwater and to minimise risk of RIP/RIC surcharge the following
approach has been adopted: -

   •    Size proposed RIPs/RICs to infiltrate associated catchment flows based
        on the Excel model mentioned in Section 5.1

   •    Conservatively adopt the lower 2003 algorithm for all RIP and RIC
        infiltration rates modelled in eXcel.

   •    Apply a Factor of Safety of 2.0 to infiltration rates modelled.



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A6769/25/SWMP/Rev OpW(A) – Feb 2025
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SH/PL
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