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Site Based Sotrmwater Management Plan
In reply please refer to:
Our: Troy Paulsen
At: Sunshine Coast
Our Ref: SC-8839
24th February 2021
Noosa Shire Council
PO Box 141
Tewantin QLD 4565
RE: SITE BASED STORM WATER MANAGEMENT PLAN FOR PROPOSED
APPARTMENTS AT 31 BOTTLEBRUSH AVE, NOOSAVILLE
1. INTRODUCTION
The proposed development consists of a multi-apartment development and associated car
parking. The site is fronting Bottlebrush Ave to the South West and existing residential
allotments to the remaining boundaries. The site is currently occupied by a single two story
residential dwelling with its associated access driveway. The total site area is 506m 2 and has an
approximate fraction impervious of 46% (Fi = 0.46).
2. STORMWATER CONNECTION
Under existing conditions, stormwater runoff discharges to the kerb and channel fronting the
subject site, before falling to the North West before flowing into the existing 300mm diameter
underground stormwater network. The proposed stormwater will continue to discharge into the
Bottlebrush Ave kerb and channel in accordance with local council’s discharge flow rates of
maximum 25L/s.
3. STORMWATER QUANTITY
The proposed development will increase the impervious nature of the site compared to pre-
development to a fraction impervious of 80% (Fi = 0.80). Therefore, peak flow mitigation is
proposed to limit minor and major flows (50%, 20%, 10%, 5%, 2% & 1% AEP), to that of the
pre-development scenario to ensure the downstream pipe capacity is not worsened.
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Detention will be incorporated in the post-development scenario for the minor events that will
discharge into the existing kerb and channel. XP-STORM V2017.2 was used to determine the
detention volume required and the results are illustrated in Table 1.1. Table 1.1 illustrates that
10kL of detention with two 100mm diameter outlet mitigates the minor event discharge to less
than the required 25L/s flow rate and less than the pre-development scenario.
A concept stormwater management plan has been provided in Attachment 1, and hydrographs
have been attached in Attachment 2.
AEP (ARI) Pre-Development Post-Development Peak
Peak Flows Flows (Mitigated)
50% (2yr) 0.024 0.015
20% (5yr) 0.033 0.018
10% (10yr) 0.043 0.020
5% (20yr) 0.049 0.021
2% (50yr) 0.046 0.023
1% (100yr) 0.051 0.025
Table 1.1 – Pre vs Post Development Discharge
Page 3
Subject Site:
31 Bottlebrush Ave,
Noosaville
N
Figure 1.1 Site Location
Should you have any further requirements in relation to the above matters, please contact the
undersigned.
Yours Faithfully,
Troy Paulsen
RPEQ No. 6990
For and on behalf of
Empire Engineering Pty Ltd
Page 4
ATTACHMENT 1: Concept Stormwater Management Plan [OCR of page images] ATTACHMENT 1: Concept Stormwater Management Plan td te bbb beg ed OPLETETTELELTTELL EDIE by OCELELLEEELELELEELELELEA EEL EDEL ‘Fi COLELELELEELELELELEELETEDELLTLELELEEE PAGE OLEULLLELEELELELELEELELELELLELELEED tt tt Fi AOLELELEELELELELEELELELELEE ED CL IELELEELELELEELELEE LGD ELEE tes CbEttE ELS tH: Clipe ch ti tests et ttt tt ér be A ‘C4 COCEELELEEE LET: AOL EDELLTLELEELEL ELLE EES ‘t OLE AIEEE EE: tht eg ‘onee, ee eee tts tilt tt tt tt LETHE ELE sthtirlbistttttbheg OCPEEE, bP IEEE DRL ETE tts SPbEt tty 2 > ‘te Post Outlet >
Page 5
ATTACHMENT 2: Hydrographs
Pre-Development
Post-Development
[OCR of page images]
ATTACHMENT 2: Hydrographs
Node - Pre-Development
= = =
ECN_50Opct_15min_2[Max 0.024] ECN_20pct_15min_2[Max 0.033] ECN_10pct_30min_3[Max 0.043]
ss = =
ECN_5pct_30min_3[Max 0.049] ECN_2pct_30min_6[Max 0.046] ECN_1pct_30min_6[Max 0.051]
0.050
0.045
0.040
0.035
> 0.030
So
it 0.025
0.020
0.015
0.010
0.005
0.000
Fri 0:30 1:00
Jan 2016 Time
Pre-Development
Conduit 2/100mm Dia from 10kL Tank to Post Outlet
= = =
ECN_SOpct_15min_10[Max 0.015] ECN_20pct_15min_10[Max 0.018] ECN_10pct_30min_3[Max 0.020]
= — —
ECN_5pct_30min_3[Max 0.021] ECN_2pct_30min_6[Max 0.023] ECN_1pct_30min_6[Max 0.025]
0.025
0.020
0.015
&
we
0.010
0.005
0.000
Fri 0:30 1:00
Jan 2016 Time
Post-Development