Appendix B - Stormwater Management Plan

4.0        WATER QUALITY MANAGEMENT PLAN
4.1        Proposed Stormwater Treatment System and Catchment

The developed site will be treated by the Bio-retention basin at 14 Eagle Drive.

Due to the existing topography, proposed lots 1-5 and 7-9 fall away from the road. Rather than install rain-gardens
and detention in these lots the proposal is to treat these areas in one location to make maintenance easier. This
involves treatment of adjacent existing catchment instead. This is considered reasonable to make the end results of
flow detention and treatment possible in the same catchment.

The developed site area for stormwater quality treatment is as per Table 3.1, and Plan 1702-01B:

TABLE 4.1            CATCHMENT AREAS FOR STORMWATER TREATMENT AND DETENTION (DEVELOPED)

                    Catchment                       Land Use         Original Area (ha)      Treatment Area (ha)

                      A+B                         Urban + Road              1.585                    1.585
20 Eagle Drive Tewantin plus proposed lot 7
 (part of 35A Tait Street Tewantin). Existing
  house on 0.06Ha to remain so this area is
           excluded from catchment

 14 Eagle Drive Tewantin (demolish house)             Urban                 0.845                      0

             TOTAL                                                                                 1.585Ha



Based on a percentage of site area, the requirement stormwater quality treatment area will be:

1.5% of 1.585Ha = 0.024Ha or 240sqm (area subject to detail design at Operational Works)

Discharge points will include the:
     Detention basin overland overflow into the adjacent park at 15 Tait Street (Lot 42 RP149497)
     Piped connection from detention basin to stormwater system at 15 Tait Street (Lot 42 RP149497)

The detention/bio-retention component of these treatment systems will remove the nutrients, heavy metals, and
retard flow.

Water Quality Management

The use of a bioretention basin is required for the site to treat pollutant loads generated from the proposed increase
in impervious area. As this is at a Reconfiguration stage the extent of information is based on estimation of required
bio-retention basin treatment area. Detailed calculations will be provided at Operational Works phase.

4.1.1 Bioretention Area
The Bioretention basin (see Plan 1702-02A, 1702-03A) has the following features:
      Filter Area = 240m2 (subject to detail design)
      Filter depth = 0.5m
      Transition layers depth = 0.1m



Eagle Rise Estate                                                                                             pg. 6