Civil Engineering Cover Letter

Response
The resulting daily pollutant loads estimated by MUSIC modelling have been reduced
significantly from the previous submission to best meet the water quality objectives for the
surrounding waterways. The levels of reduction and estimated daily pollutants leaving the
site have been provided to Seqwater during discussions. Refer to updated Stormwater
Management Plan SMP for details of proposed treatment details

21. Information Required
Demonstrate the development is consistent with the SeqWater Development Guidelines:
Development Guidelines for Water Quality Management in Drinking Water Catchments 2012.

Response
Response: The third party advice from Seqwater dated 23rd August 2016 (CE:DB F16/3997)
identified that they had reviewed the submitted SWMP against the development guidelines
identified in Item 21 above. The only further information requested was the annual rainfall
data used for modelling and a comparison of the daily pollutants loads leaving the site
against the water quality objectives. The response to the third party advice from Seqwater is
detailed separately within this letter.

22. Information Required
Provide a preliminary drainage plan to demonstrate there is adequate grade between the
underdrainage of the bioretention basin and receiving stormwater network.

Response
A stormwater management has been updated to demonstrate there is adequate grade
between the underdrainage of the bioretention basin and receiving stormwater network.
Refer to Plan SWMP01.

23. Information Required
Demonstrate that the footprint allocated for the bioretention basin includes sufficient area for
inclusion of batters from the surrounding area to the surface of the filter media consistent
with the Water by Design Bioretention Basin Technical Design Guidelines (in particular Table
9).

Response
The inclusion of a rainwater tank to the site has enabled the bioretention basin to be made
smaller and thus a batter can be constructed on the northern side of the basin to prevent a
high drop from the retaining wall/kerb into the basin .The southern side of the basin remains
a retaining wall. This arrangement is generally in accordance with the water by design
guidelines. The set down to the basin surface is controlled by the proposed underground
pipe network.

24. Information Required
Demonstrate how the bioretention basin will be accessed for maintenance purposes.

Response
A maintenance access stairwell was indicated on the plans submitted with the initial
application. This has been amended to include a maintenance access ramp suitable for
access by a skidsteer loader. Refer to Plan SWMP02.