2016-09-06 - Planning & Environment Committee Agenda

PLANNING & ENVIRONMENT COMMITTEE MEETING AGENDA                           6 SEPTEMBER 2016



Code          Discussion

Water         Master planning for the Noosa Springs estate included the constructed lake
Sensitive     system to treat water to the standard acceptable at the time of that approval.
Design Code   That standard was for stormwater runoff to not worsen the water quality in Lake
              Weyba. Provided the development is consistent with the master plan approval,
              this proposed development will not affect the quality of Lake Weyba.
              The approved masterplan design assumed waters from Precinct E2 would flow
              to that lake system for treatment. Since the time of the master planning,
              constructed lake systems are now known to have high risk of algal and
              cyanobacterial outbreaks if not managed correctly.              Management of
              cyanobacterial outbreaks can be costly to the asset owner (for example Elysium
              estate spent over $20,000 to remove a cyanobacteria outbreak from its lake
              system). Given the constructed lakes are now in separate ownership to Precinct
              E2, it is important that this development can demonstrate that it is unlikely to be
              responsible for increasing the risk of any algal or cyanobacterial outbreak in the
              receiving constructed lake. Factors that affect cyanobacterial or algal blooms in
              constructed lakes are nutrient concentrations as well as appropriate
              management of hydraulic residence times (flow through of water).
              The applicant has provided an RPEQ certified Stormwater Management Plan
              for Precinct E2, which also addresses Precinct F.             The Stormwater
              Management Plan proposes for runoff from Precinct E2 to enter the Noosa
              Springs constructed lake untreated. Despite absence of treatment, the
              Stormwater Management Plan suggests that stormwater runoff from Precinct
              E2 is unlikely to increase algal and cyanobacterial risks in the receiving lake
              system for the following reasons:
               the modelled 90th %ile nutrient concentrations in stormwater runoff from
                 precinct E2 and Precinct F combined as well as E2 in isolation are less than
                 the measured 90th %ile nutrient concentrations measured over the previous
                 8 years.
               the proposed development is unlikely to have a significant negative impact
                 on the hydraulic residence times of the lake.
              Assessment against The Noosa Plan’s Water Sensitive Design Code and the
              State Planning Policy is applicable.
              By proposing no onsite treatment of stormwater quality, Precinct E2 would not
              meet the following Specific Outcomes of the Water Sensitive Design Code of
              the Noosa Plan:
              O1 Development uses a combination of detention and retention systems to
              capture run-off from areas on the site
              O9 Natural treatment strategies, including grass swales and bio-retention
              systems, vegetated filtration strips and gross pollutant traps, are used wherever
              practicable
              Additionally, the State Planning Policy requires stormwater polishing on
              developments greater than 2500m2 with >25% impervious surface. The
              polishing targets are 80% reduction in Total Suspended Solids, 60% reduction
              in Total Phosphorous and 45% reduction in Total Nitrogen. The development
              application for Precinct E2 has not demonstrated this outcome can be achieved.
              In addition MUSIC modelling for the development assumes filtration of
              stormwater to groundwater (instead of the constructed lake) will not contribute
              any pollutants to the system.


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