2. Mangatawa catchment consents for earthworks, storm water ...

NZ Transport Agency and Tauranga City Council
Mangatawa Drain Flood Bypass and TEM Stormwater AEE
c) Herpetofauna
The availability of native reptile habitat was visually assessed within the Special Ecological Site 13 (SES,
Tauranga District Plan) on 28 November 2008. The SES consisted of saltmarsh and mangrove, and was
considered unsuitable for native lizards.
d) Water Quality
The water quality being discharged from the stormwater treatment wetland through the special ecological site
was generally characterised by elevated levels of some nutrients and bacteria. Elevated concentrations of the
total nitrogen, nitrate and total phosphorus were recorded downstream of the stormwater treatment wetland,
within the special ecological site (Site W1a), and were in excess of the ANZECC (2000) upper guideline limits.
As the inorganic nitrogen and phosphorus species tested were below the relevant guidelines levels, with the
exception of nitrate, it is likely that the majority of nutrients present in the system are in an organic form, and
are therefore less readily assimilated by macrophytes.
High bacterial counts recorded at the outlet from the stormwater treatment wetland (Site W1a) were in excess
of the guideline levels for contact recreation in freshwaters (MfE, 2002). No specific guidelines have been
established for bacteria in relation to the protection of aquatic life and it is accepted that this waterway is
unlikely to be used for contact recreation.
The number of Escherichia coli at the outlet from the stormwater treatment wetland (Site W1a) exceeded the
lower MfE (2002) guideline, which indicates faecal contamination. Farm runoff is one possible source of
contamination within these waterways, given the historical farming landuse of the area surrounding Maranui.
Table 7: Sampling Site Locations
Status: Final Page 57 April 2009
Project Number: 3932036
NZ1-1552092-Mangatawa Drain Flood Bypass and TEM Stormwater AEE