Attachment 1_20-000713 - Line 5 Tech Memo.docx

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4    PROPOSED INTERIM SOLUTION
At the time of this Memo, there is a significant delay in pipe supply. Currently lead times currently sit at between 20 to 32
weeks, primarily due to COVID 19 constraints as well as the recent closure of a major pipe supplier in Qld.
In the short term it is proposed to adopt an interim solution to enable the balance of the project to be completed. An interim
solution utilising HDPE pipes (which are readily available but not accepted by Noosa Council) was investigated but discounted
to avoid sacrificial works and multiple excavations with Hofmann Drive.
The interim design consists of utilising the currently constructed stormwater network – i.e. the original Barlow Shelley design –
and submit an uncompleted works bond to Noosa Council to the value of 150% of the proposed ultimate design configuration.
This approach has the following benefits:

    1.   It retains the use of the existing network constructed as part of the development works.
    2.   Avoids the need to excavate the road to install additional redundant pipework.
    3.   Provides certainty to Noosa Council that the ultimate configuration will be constructed.

It is acknowledged that this approach will result in the drainage network being partially submerged until such time as the
ultimate configuration is construction. This is not considered problematic as the ultimate configuration is expected to be
completed within the maintenance period and the uncompleted works bond shall have sufficient value to clean out the line on
completion.



5    CONCLUSION
The proposed design solution discussed above is considered the most efficient given the site and construction constraints. The
proposed final design mentioned above includes the relocation of the Line 5 outlet headwall structure to a more suitable location
with a lower surface level, thus reducing the area of clearing and earthworks within the drainage reserve. The stormwater line
from structure 2/1 (Lot 3 outlet) to outlet headwall structure 7/1 to be constructed using 1200 x 600 box culverts. This design
solves both stormwater drainage problems in the most effective and efficient manner.


Yours sincerely
Calibre Professional Services Pty Ltd




Shaun Pilcher
Principal Engineer - Urban Development




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