24647 Seaview Tce Enviro Mgmt Plan

The P factor represents the combined effect of management practices and structural methods to control
erosion. Further, the P factor is reduced by practices that reduce both the velocity of runoff and the
tendency of runoff to flow down slopes. An industry default P factor value of 1.3 has been applied to the
risk assessment, which is considered conservative, and is recommended for the construction phase
condition (per table E11 of IECA, 2008).

4.5.          Estimated Soil Loss
Results of the erosion risk assessment are presented in Table 1. Estimated soil loss is expected to be in the
order of 159 t/ha/year while the initial piling works are undertaken. The soil loss increases as the exposed
area of the site and sloe lengths increase, with an estimated soil loss of approximately 1,700 t/ha/year
during the bulk earthworks phases when the majority of the work area is exposed.
Based on soil loss only, Type 1 sediment controls are triggered (per Table 4.5.1 of IECA). However, due to
the area of disturbance (i.e. < 2,500m²), Type 2 controls are triggered for the proposed works. However,
due to the sensitive nature of the site, Type 1 controls will be implemented, representing Best Practice
Management across the site in terms of erosion and sediment control.
It should be noted that the soil loss estimate is not considered representative of actual annual soil loss at
the site, and should be used rather as indicator of potential erosion risk. If at any time circumstances
affecting the above factors should change, a reassessment should be conducted immediately.
Table 1 – Soil Loss Estimation


  Construction              Area (Ha)              Slope (%)         Length (m)                 LS           Estimated Soil
     Area                                                                                                    Loss (t/ha/yr)

  Stage 1 Piling                 0.05                 36                    7                1.45                   159

  Stage 2 Piling                 0.08                 31                 21                  3.86                   426

     Earthworks                  0.23                 27                 60                  9.23                   1,698


5.            Erosion Control
Erosion management techniques for various erosion risk ratings in accordance with IECA (2008) guidelines
are presented in Table 2.
Table 2 - Erosion Risk Rating Based on Soil Loss and Required Management (adapted from Table 4.4.7 of IECA, 2008)


                                         Advance Land                             Staged Construction
 Erosion Risk      Soil Loss Rate                              Max days to                                     Stockpiles
                                        Clearing Allowed                           and Stabilisation of
    Rating          (t/ha/year)                                Stabilisation                                   stabilised
                                           (wks work)                             Earth Batters >6H:1V

  Very Low            0 to 150                 8                 30 (60%)

      Low            150 to 225                8                 30 (70%)

  Moderate           225 to 500                6                 20 (70%)                   

      High          500 to 1500                4                 10 (75%)                                           
71 Seaview Terrace, Sunshine Beach - Erosion and Sediment Control Plan                                                    Page 4

Hutchinson Builders
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