Dry Creek Replacement Cleanfill, SH 58, Porirua - Hutt City Council

Recommendations

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5.0 Scope of Works The applicant, Winstone Aggregates, proposes to develop a cleanfill and associated infrastructure, to be staged over a number of years. In summary construction activities will include: Establishment of an access road from SH 58 to the proposed cleanfill site. A docket office and amenity building will be located at the entrance way to the site. Parking for staff and occasional visitors to the site. Vegetation Clearance The filling of the gully system will occur as a continuous development, which has been divided into a series of stages for ease of discussion ; – Shear key and toe establishment including filling to RL 142. This is referred to as Stages One and Two. – Stage Three allows filling up to RL 158 and – Stage Four allows fills to RL 200 with the establishment of a slightly sloping platform. Formation of a new stream channel on the western side of the fill as the fill is progressed. The final fill creating a contoured surface suitable for stock grazing and landscape and visual screening. 6.0 Assessment of Ecological Effects The principal ecological effects of the proposal for this assessment are the removal of indigenous vegetation and the associated loss of habitat for wildlife. 6.1 Vegetation Clearance Overall, we assess the ecological effects of vegetation clearance will be minor. In the context of the wider ecological district the amount of vegetation that will be removed by this proposal is very small. Although a rough tool for such estimates at this scale (noting that the LCDB2 included the entire application site in the category of gorse), a Land Cover Database2 (LDCB2) analysis of the extent of manuka/kanuka forest in the Ecological District is 1,065 ha. The loss of approximately 0.7 ha of manuka/kanuka forest from the application site is therefore in the order of 0.01 percent of the wider Ecological District. The only vegetation communities with moderate ecological value (as described in Section 4.3) are the more advanced areas of manuka-kanuka and manuka-broadleaved gully forest which Dry Creek Replacement Cleanfill, SH 58, Porirua | Assessment of Terrestrial Ecological Effects 16
combined have an area of 0.7 ha. The moderate diversity and connection to large areas of regenerating vegetation of similar and more advanced successional state, lead to the assessment that this vegetation has low to moderate ecological values and good potential for improvement. We therefore recommend some mitigation for the loss of this vegetation. The early successional manuka scrub and shrublands and the rank pasture mosaic with scattered tauhinu, are considered to currently have low ecological value due to low diversity, low stature and poor habitat values. This may change over time if these communities are allowed to continue regenerating, however, they are still of sufficiently low stature that they may be cleared as a permitted activity. The Porirua District Plan provisions recognise that management of the regeneration of these pioneer scrub and shrubland communities within productive pasture is considered a normal and necessary part of farm management. Overall, we assess that the effect of removing these communities on the local ecology will be negligible with no mitigation required for the loss of these communities. While wetlands are much more reduced in extent in the ecological district and ecological region, being originally rare or uncommon (Williams et al 2007), the small seepage wetlands and areas of Juncus in wet pasture within the application site are induced communities with a significant exotic component. The plant species present are a reflection of the prevailing land use, common in similar farm seepages throughout the region. Overall we assess that the effect of removing these communities on the local ecology will be negligible with no mitigation required for the loss of these communities. Two solitary totara and tawa trees are present and will be lost within the footprint. The loss of any mature tree will have some adverse effect on the local ecology, particularly with regard to loss of a seed source for ongoing regeneration of seral communities. Therefore, it is our recommendation that any mitigation package would address this loss. 6.2 Wildlife Given the application site’s location close to the forested Belmont Hills Regional Park and the nearby vegetated fault escarpment, the site is likely to form part of a wider ecological corridor for bird species. However, given the early successional stage of most of the vegetation, and associated lack of diversity, and also given the application site forms a very small portion of regenerating vegetation within this wider area, it is not anticipated that the current proposal will result in a significant or measurable adverse effect on birdlife due to loss of habitat. The only herpetofauna species found was a solitary common skink, another indicator of the early successional stage of the vegetation and of vegetation that has regenerated within pasture. There will be loss of habitat and possibly loss of individuals during vegetation clearance. We have therefore recommended the use of ARs prior to vegetation removal in the upper area of the proposed cleanfill to capture and translocate any lizard species into the main gully system upstream prior to vegetation clearance. 6.3 Summary It is our overall assessment that the proposed clean fill will have minor adverse effects on the local ecology, primarily through the loss of a small amount of advanced manuka and broadleaved gully vegetation, the habitat these areas of vegetation provide and the loss of long term potential for these successions. It is recommended that this vegetation removal be mitigated for through an adequate and well thought out mitigation programme at the site. Dry Creek Replacement Cleanfill, SH 58, Porirua | Assessment of Terrestrial Ecological Effects 17
Page 1 and 2: Dry Creek Replacement Cleanfill, SH
Page 3 and 4: CONTENTS 1.0 Introduction 3 2.0 Met
Page 5 and 6: 1.0 Introduction Boffa Miskell has
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Page 9 and 10: the adjacent Belmont Regional Park,
Page 11 and 12: MAIN HABITATS and FEATURES AREA (ha
Page 13 and 14: These plans and drawings have been
Page 15 and 16: Statement which provides an interim
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Page 21 and 22: terrestrial mitigation sites. Consi
Page 23 and 24: 9.0 References Boffa Miskell. 1998:
Page 25 and 26: Asplenium hookerianum Asplenium pol
Page 27 and 28: Appendix 2 Site Photos Dry Creek Re
Page 29: Photo 7: Looking downstream of main

Dry Creek Replacement Cleanfill, SH 58, Porirua - Hutt City Council

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