Noosa Springs SMP_Rev 4 · OPW17/0612

ALTUM CONSTRUCTIONS
PRECINCT F & E2 NOOSA SPRINGS DEVELOPMENT



             The 3 manholes where monitoring is to occur will pond 100mm of water in the base to
              allow the samples to be collected following a rainfall event.

             Trigger rainfall event is 40 mm based on a minimum of 5 samples per annum

             If by the End of November 5 rainfall events have not been collected the trigger will be
              reduced to 20 to ensure that the minimum of 5 rainfall events are likely to be collected.

             Monitoring will commence following completion of construction and all stabilization
              works within the catchment that reports to the monitoring location.

             Monitoring will be undertaken for a minimum of 2 year period. Following the 2 year
              period if it is deemed that the development is meeting water quality requirements
              monitoring will cease.

4.4.3     Flow s Bypassi ng the Noosa Springs Lake Syst em

          All stormwater infiltrating the groundwater table and therefore bypassing the Noosa
          Springs Lake System will be treated via the following means, prior to interaction with the
          water table:

             Contact with vegetation in the infiltration swales prior to infiltration.

             Contact with filter media in the base of the infiltration swales.

             Contact with the sandy subsurface profile between the base of the filter media and the
              surface of underlying bedrock.

          The groundwater table is approximately 5 to 6 m below ground level within the vicinity of
          the proposed development; this provides additional filtration potential for water infiltrating
          the groundwater table. Coupled with the dense planting of the infiltration swales, there is
          significant potential for water quality treatment for flows entering the groundwater system.
          Consideration should also be given to the distance flows will travel within the subsurface
          profile (Approx. 500m), before they will interact with the water quality in Lake Weyba.

          We believe the development of the Noosa Springs site and the proposed stormwater plan
          will not have a material impact on residence times within the existing Noosa Springs Lake
          System. Precinct F and E2 are relatively small catchments when compared to the greater
          catchment for the lakes system, and therefore any changes to these catchments could
          only have marginal impacts to residence times in the full lakes system. Additionally the
          proposed development has endeavoured to maintain the existing hydrology of the site as
          much as possible. As the existing site consists of sandy soil it is reasonable to assume a
          significant proportion of runoff infiltrates across the existing site, therefore bypassing the
          lakes system. The incorporation of infiltration swales will best simulate the existing
          hydrology of the site and offset the increased rate of runoff from impervious surfaces.

          The Noosa Springs Lake system was designed for a developed catchment which includes
          the Site. (Refer to Noosa Springs Master Drainage Plan). The impervious fraction of the


Job No. M7130_001                                                                                   Page 11
                                                                                     Rev 4 : 7 December 2017