Appendix A- Stormwater Management Plan

                                                                              Callaghan & Toth

4.     STORMWATER DESIGN AND ASSESSMENT


4.1    Proposed On-Site Stormwater Collection Process

The developed site was divided into Sub-Catchments as shown on Plan 2102-01A and the
stormwater collection system is listed below:

1. The rear of Lot 20 will have its stormwater runoff collection in a new interlot drainage pit
   in the north east corner, refer Plan 2102-01A.
2. The new concrete driveway generally slopes to the rear Lot 21. The driveway will have
   crossfall to the north which will drain via a mountable integral kerb to a new interlot
   drainage pit in the north east corner.
3. The new Lot 21 will have its stormwater runoff collection in a new interlot drainage pit in
   the north east corner, refer Plan 2102-01A.



4.1.1 Rainfall Data
The meteorological data used for the BOM IFD table for Cooroy was used for the runoff
calculations.



4.2    Hydrology

The site has been modelled as part of the previous subdivision to determine the detention
capabilities of the subdivision including this subdivided Lot 18.

The flood study shows that this lot was modelled using the same runoff coefficient and time of
concentration for the pre-development and post-development conditions as the newly created
lots for the previous subdivision. Therefore, runoff alteration improvements were included in
the sizing of the existing subdivision detention basin.

As part of the original adjacent subdivision, interlot drainage pipes were sized as per QUDM
to cater for No.18 being two residential lots.




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