2022-09-06 P&E Agenda - Item 5 - Attachment 1 - Six Mile Creek Bridge Replacement Offset Report - TMR

Whilst assessment of the proposed action’s impact upon the Giant barred frog and Rufous fantail indicated
that these species are not likely to be subject to significant impacts (refer Section 2.3.3 and 2.3.4), the
provision of a direct offset for the Lowland Rainforest of Subtropical Australia TEC would ensure that these
species are subject to a positive conservation outcome as a result of the proposed action.
It is noted methodologies to calculate offset obligations within Appendix A (Section 8.1) utilised values which
incorporated a 50 m buffer (in addition to a 10 m construction buffer). As it is identified that the action will
involve the direct removal of part of this community, offset obligations are to be calculated on the area of
direct removal (incorporating the 10 m construction buffer). Therefore, this section provides a recalculation of
the quantum of proposed offset to achieve a net ecological benefit. Calculations related to the quality of
quantum of impacts is provided in Table 3.1, and assumptions used to calculate the quantum of offset
required (as required by the Commonwealth Offset Assessment Guide (DSEWPaC 2012)), are provided in
Table 3.2. Refer Appendix B for a copy of the completed Offset Assessment Guide.
Table 3.1.       Impact site calculations used to determine offset obligations

    MNES feature requiring offset            Comments
    Threatened Ecological Community          Lowland Rainforest of Subtropical Australia
    EPBC Act listing                         Critically endangered (annual probability of extinction 6.8%)
    Impact site quality                      Site condition (structure and condition of site, diversity of relevant endemic and
                                             non-endemic species)
                                             The assessed patch:
                                              contains 33 diagnostic endemic species listed in Appendix A of the listing
                                                 advice
                                              contains 118 endemic species and 26 non-endemic species
                                              contains multiple strata, including emergent, canopy, sub-canopy, shrub and
                                                 ground layers
                                              meets criteria for condition threshold B of the listing advice
                                              obtained a site-based score of 44/80 within a 100 m by 50 m BioCondition
                                                 assessment plot at the impact site (refer Appendix 4).
                                             Sub-component score = 7
                                             Site context (connectivity, importance in relation to overall TEC occurrence,
                                             threats)
                                             The impact site is currently connected to a band of mapped rainforest (RE
                                             12.3.1) along Six Mile Creek and some other watercourses in the region.
                                             Connectivity is occasionally broken by existing roads. A BioCondition
                                             assessment at the impact site (refer Appendix 4) gave the following results:
                                              the site lies within a patch containing 23 ha of remnant and 14 ha of regrowth
                                                 mapped vegetation
                                              <10% of the perimeter of the mapped rainforest area is connected to mapped
                                                 remnant vegetation and >25% is connected to mapped regrowth vegetation
                                              59.2 ha (19%) of remnant vegetation and 68.95 ha (22.3%) of regrowth
                                                 vegetation is mapped within 1 km of the site
                                              landscape-scale attribute score of 9/20.

                                             Sub-component score = 6
                                             Overall site quality = 7
    Area impacted                            0.173 ha
    Total quantum of impact (in              0.12 ha
    consideration of community
    quality)

As an offset site has not been identified for the proposed action at this stage, the following assumptions have
been used to estimate an indicative offset requirement:
     The total quantum of impact = 0.12 ha (refer Table 3.1)
     The offset site will have a starting quality of 5
     The proposed offset works will raise the offset site quality to 7 after 20 years

                                  Project number 511784 File Six Mile Creek - Matters of National Environmental Significance Report 2021-12-03 Revision 1   35