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As indicated above the detailed design phase will ensure that the designed and constructed
SPTP will effectively service the proposed development and minimise the potential
environmental impact on the area.

5.3. MEDLI Modelling — Irrigation Area

The MEDLI model is a computer model for designing and analysing an effluent disposal system
for rural industries and sewage treatment plants using land irrigation. MEDLI (Mode! for Effluent
Disposal using Land irrigation) was developed jointly by CRC WMPL Pty Ltd, the Qid Dept of
Natural Resources & Mines, and the Qid Dept of Primary Industries.

MEDLIi models the waste steam from its production through to the disposal area, and is able to
simulate the behaviour of water and nutrients in the soil column, and the growth of irrigated
pastures or crops in response to climatic and nutrient inputs. The required area to be irrigated,
the buffer storage required, the stresses on the vegetation irrigated, and the concentration of
nitrates in groundwater below the soils, among other things can be determined using this
model. The model requires climate information (temperature, rainfall, evaporation, and solar
radiation), estimates of the quality and quantity of effluent, and soil properties.

A number of assumptions have been made for several site specific input parameters and
conditions required for the modelling. These are as follows.

1) The effluent volume is 350 EP with 180 L/Person/Day equalling 63 m® /day average dry
weather flow.

2) Effluent nitrogen and phosphorous concentrations of 10mg/L and 2mg/L.

3) A low infiltration level of stormwater to the sewerage system during wet weather.

4) No pre-treatment of the effluent prior to irrigation (other than treatment through the on-
site package treatment facility).

5) A single storage tank. :

6) A tank side slope of 90 degrees and a length to breadth ratio of 1:1.

7) Coastal couch grass vegetation on the irrigation area.

8) An irrigation rate of 2 mm per m* per day.

The borehole information described in Section 2 presents details of the types of soils present in
the area. This data was used to compile representative soil strata with the required parameters.

Meteorological data

Average rainfall, pan evaporation, maximum and minimum temperature values and solar
radiation values for a 50-year time period is presented below in Table 5.3.1-

 

PETRAC LAND HOLDINGS P/L Noosa North Shore Eco-Tourism Porta! September 2003
LA7296-O3\Report\FINAL REPORT - 18Sept03.doc Commercial in Confidence Page 13