The “Heritage Mews” urban development is an integrated water cycle management project that applies a regime-in-balance stormwater management strategy which requires runoff volume from a developed site to be equal to the discharge from the site prior to development in the adopted critical design storm. Retention and infiltration technology, the first option of choice, was impractical at “Heritage Mews” because of the impermeable nature of its surface geology. Instead, the objectives of ‘before-and-after’ runoff volume equality and peak discharge less than permissible site discharge (PSD) were achieved using rainwater tanks, gravel trenches and ‘slow-drainage’.
Continuous simulation using the PURRS model and distributed modelling using the WUFS model was used to prove that the configuration of retention components planned for the development delivered the flow quantity objectives set by Council and, also, that the 3.0 kL rainwater tanks would provide 22% of domestic water use. The development incorporated four “UniSAtanks” which provide a high standard of quality control to 95% of average annual flow. The water sensitive urban design (WSUD) approach resulted in infrastructure savings of $2,500 per allotment and land savings of $51,000 per allotment.