16-001014-02A (Ultimate SCMMP)

Inflow – Nutrient Concentrations Into WQCP

As Council have requested, the WQCP has not been modelled in MUSIC. This is conservative
considering that the pond will provide treatment to suspended solids and some nutrient removal. In
order to avoid outbreaks of algae in the pond, the concentrations of nutrients entering the pond
must be limited (i.e. TN and TP inflow concentrations less than 1.3mg/L and 0.2mg/L respectively).
The proposed stormwater quality management strategy involving a treatment train of primary,
secondary and tertiary treatment devices ensures that runoff into the pond has low nutrient loading.




The TP and TN inflow concentrations are indicated in the table below.
B14158.W_Opworks_Mitigated_Site_Ext_NoPond ‐ (Pond) ‐ Flow‐Based Sub‐Sample Statistics
Inflow                        mean        standard deviation median        maximum      minimum       10 percentile 90 percentile
Flow (cubic metres/sec)          0.00501             0.0469     0.0000154          4.56             0              0     0.00348
TSS Concentration (mg/L)             2.61               7.46          2.21          350             0              0          2.8
Log [TSS] (mg/L)                    0.376               0.18         0.365         2.54        0.193          0.241         0.456
TP Concentration (mg/L)           0.0192             0.0199           0.02        0.666             0              0      0.0221
Log [TP] (mg/L)                     ‐1.67              0.115          ‐1.7       ‐0.177          ‐1.7          ‐1.7         ‐1.64
TN Concentration (mg/L)             0.518              0.261           0.6         3.33             0              0          0.6
Log [TN] (mg/L)                    ‐0.214            0.0553         ‐0.222        0.522       ‐0.222         ‐0.222        ‐0.222
TSS Load (kg/Day)                   0.106               2.38     0.000013           307             0              0     0.00222
TP Load (kg/Day)                0.000276            0.00528 0.000000114           0.557             0              0 0.0000253
TN Load (kg/Day)                 0.00252             0.0364 0.00000332             4.27             0              0    0.000752
Gross Pollutant Load (kg/Day)   0.000218             0.0166              0         6.21             0              0            0

Results indicate that concentration of TP and TN are well below the required limits.