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

Field testing was carried out consisting of filling the pipe with water from a
nearby fire hydrant and timing the rate of fall as water infiltrated sands
below.

Results were consistent indicating a linear relationship between driving head
and infiltration rate such that:

Infiltration Rate (mm/s) = 4mm/sec + 13.6 x head (m)

Refer to Appendix D for 2003 prototype test results.




6.2.2 PROTOTYPE RIP TESTING 2024

On 4th December 2024 further on-site prototype testing was carried out in
similar fashion to that completed in 2003 at a location approximating the
proposed RIC/Bioretention basin location on site (refer RIP/RIC site layout
drawing at Appendix A).

The 2024 prototype differed from the 2003 version in that a shorter 2.2m long
pipe was utilised with a rock spalls wrapped in geofabric as a base rather than
a simple geofabric filter over the end of the pipe.

Levels taken on site indicated a prototype base level of approximately RL8.8m
AHD.

Once again field testing was carried out consisting of filling the pipe with
water from a nearby fire hydrant and timing the rate of fall as water
infiltrated sands below.

Notably, at the commencement of testing, the 50mm diameter fire hose being
used to fill the pipe with water could not keep up and water levels remained
at or near the base.

After approximately 20 minutes with the fire hose on maximum flow the pipe
began to fill to the top allowing timing of the rate of water level fall to be
taken.

Results once again were consistent but this time indicating a significantly
higher liner relationship between driving head and infiltration rate such that:


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