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NZ Transport Agency and Tauranga City Council Mangatawa Drain Flood Bypass and TEM Stormwater AEE Concentrations of total nitrogen and total phosphorus were analysed in each of the sediment samples collected from Rangataua Bay. Total nitrogen concentrations were somewhat variable with a slightly elevated concentration recorded from Site 2 in the main channel as the Mangatawa Drain discharged across the intertidal flats. The total phosphorus concentrations in the sediment samples suggest an attenuation effect with a reducing concentration of total phosphorus with an increasing distance from the Mangatawa Drain across the intertidal flats of Rangataua Bay. Together these nutrient results suggest that the Mangatawa Drain may provide slightly elevated concentrations of total nitrogen and phosphorus to Rangataua Bay, however, the variation in concentration is not high and these results are not indicative of serious nutrient input to the upper reaches of Tauranga Harbour. No sediment quality guidelines for total nitrogen or phosphorus are listed in the ANZECC guidelines. A wide range of haloethers, nitrogenous organic compounds, organochlorine pesticides, polycyclic aromatic hydrocarbons, phenols, plasticisers and other halogenated organic compounds were analysed for in the sediment quality samples. In none of the samples were any semi-volatile organic compounds found in concentrations above the minimum detection limit for the analytical methods used. The Mangatawa Drain, the stormwater management area and their respective catchments do not contribute significant quantities of metallic or persistent organic contaminants to the intertidal area of Rangataua Bay and the upper reaches of the Tauranga Harbour. There is some suggestion of slightly increased nutrient input into this part of the harbour, however, any such nutrient inputs are not currently significantly impacting upon the ecological function of either Rangataua Bay or the upper Tauranga Harbour. 5.13.6 Conclusion The stormwater treatment wetland is of moderate significance but only on a local basis, as it contains a relatively large area of flax – cabbage tree – shrubland habitat, a type that does not appear to occur elsewhere in the Te Maunga to Mangatawa area. Nevertheless it only supports species that would also occur in other types of adjacent habitats around the upper part of Rangataua Bay. Calls of spotless crake (Porzana tabuensis plumbea; puweto) were played at four locations adjacent to the existing meanders but no response was elicited. The presence of crakes (sparse; at risk) is unlikely given the lack of any significant riparian rush, Carex or raupo fringe that would provide cover and nesting habitat. Most of the fringing aquatic vegetation consists of Myriophyllum only. In summary, the stormwater treatment wetland provides habitat that is of moderate value but only in a local context and no species of national conservation concern was recorded. The rushmarsh – mangrove habitat of SES No.13 is considered to have high ecological values in a regional context and contains fernbird, a species considered to be at risk nationally, while its use by a second at risk species, banded rail, is also likely. This area should be avoided by any major works associated with modification to the existing stormwater management area. The Mangatawa drain and Maranui waterway (swale, wetland and significant ecological site) are both typically open waterways, with cool to warm water and variable levels of dissolved oxygen, clarity and conductivity. The variable levels of conductivity are considered to reflect the presence of saline waters within the lower reaches of both the Mangatawa drain and the Maranui waterway. Elevated counts of E. coli bacteria were also recorded in both waterways and reflects the agricultural land use. While overall the water quality of the Mangatawa drain was reasonably good, with the water for the most part being cool and well oxygenated, although discoloured on occasions, that of the Maranui swale was poor, with low levels of dissolved oxygen and poor visual clarity (0.1m). Status: Final Page 59 April 2009 Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE
Table 9: Summary of Ecological Characteristics NZ Transport Agency and Tauranga City Council Mangatawa Drain Flood Bypass and TEM Stormwater AEE Mangatawa Maranui Roadside Site 5 (upstream) 1 1a (downstream) 2 (upstream) 2a 2b 2c (downstream) 3 (side swale) 4 Survey date Apr ‘08 Apr ‘08 Oct ‘08 Apr ‘08 Oct ‘08 Oct ‘08 Oct ‘08 Apr ‘08 Apr ‘08 Habitat Average width (m) 1.7 2.4 6.5 3.0 3.5 Pond 4.5 2.5 1.2 Average depth (m) 0.25 0.24 0.2 0.22 0.20 - 0.25 0.23 0.16 Dom. substrate type Sand Mud/Gravel Mud Mud Cobble - Mud/sand Mud Mud Aquatic Vegetation Glyceria Willow weed Curly Pondweed Glyceria Nitella Watercress Willow weed Glyceria Nitella Glyceria Ludwigia Parrots feather Pondweed Willow Weed Curly pondweed Ludwigia Oxygen weed Parrots feather Pond weed Starwort Curly pondweed Parrots feather Starwort Mangroves Ulva Ludwigia Pondweed Willow weed Duckweed Parrots feather Willow weed Water Quality Temperature ( o C) 16.0 14.6 19.1 13.8 20.9 20.8 21.3 15.3 16.7 Oxygen saturation (%) 81 29 91 5 68 70 95 12 17 Dissolved (mg/L) oxygen 8.0 2.8 8.4 0.5 6.0 6.4 8.3 1.2 1.6 Conductivity (μS/cm) 107 130 175 198 190 627 773 - 204 Visual clarity (m) 0.2 0.8 0.5 0.1 0.4 0.5 0.4 0.2 0.1 Status: Final Page 60 April 2009 Project Number: 3932036 NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE
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Mangatawa Drain Flood Bypass and TE
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NZ Transport Agency and Tauranga Ci
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APPENDIX 1 - Drawing 3932036 ck301R
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APPENDIX 3 - Drawing 3932036 ck119
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APPENDIX 5 - Bioresearches Report:
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APPENDIX 7 - Archaeological Assessm
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ARCHAEOLOGY B.O.P. HERITAGE CONSULT
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2 INTRODUCTION Project Background T
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4 ARCHAEOLOGICAL LANDSCAPE Previous
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6 U14/1708 & 1709 Figure 3. Cadastr
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8 Figure 6. Part ML 8133 showing Pt
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10 Hungahunga & Toroa A further ton
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12 APRIL 2008 ARCHAEOLOGICAL SURVEY
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14 Historic Places Act In addition
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APPENDIX 8 - Hydraulic Modelling: M
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Hydraulic Modelling: Mangatawa Drai
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undertake investigations into the d
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Discharge to Papamoa Beach To disch
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• Riparian planting adjacent to t
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2.2 Hydrological Assessment 2.2.1 C
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The Maranui catchment area in the m
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Table 7 - 2% AEP Storm Event Top Sp
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These results include climate chang
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3.3 Maintenance Work in Mangatawa D
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stormwater from the Maranui catchme
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Appendix A Mangatawa Drain Layout P
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Appendix C Runoff Hydrographs
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Appendix E Proposed Lower Mangatawa
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APPENDIX 10 - Drawings 3932036 ck46
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APPENDIX 12 - Drawing 3932036 ck227
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Report Tauranga Eastern Motorway -
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1 Introduction This report describe
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embankment settlement rates, and th
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3.2 Construction Sequence The typic
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concrete contamination as well as s
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Pahse 1 consists of the western sec
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• Installation of Stage 2 decanti
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Appendix A Erosion and Sediment Con
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Activity Status Mangatawa Drain 1.1
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(b) Natural State (River) Water Qua
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6. Reclamation or drainage of the b
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APPENDIX 15 - Legal Descriptions of
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Path: P:\393\3932036\TGI\55_Project
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32 Harington Street PO Box 903, Tau
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32 Harington Street PO Box 903, Tau
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