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

1 Introduction
This report describes the key principles of erosion and sediment control to be employed for land
disturbing activities to be undertaken in association with the construction of the Tauranga Eastern
Motorway (TEM). The NZ Transport Agency (NZTA) will engage a Design and Build Contractor to
deliver this project. This Contractor will be responsible for preparing the detailed erosion and
sediment control plans (ESCP) based around their construction methodology. The erosion and
sediment control measures are to be designed and implemented in accordance with Environment
Bay of Plenty Guideline No. 2001/03 “Erosion and Sediment Control Guidelines for Land Disturbing
Activities, September 2001”.
The resource consent applications lodged with Environment Bay of Plenty (EBOP) in 2008 for the
majority of the TEM project (excluding the Mangatawa Drain works) contained an example ESCP.
Under those consents the Contractor will be required to submit an overall ESCP with EBOP at the
time of construction which will be a contractual requirement between NZTA and the Contractor.
A separate resource consent is now being applied for the works associated with the Mangatawa
Drain. This ESCP provides information to demonstrate that appropriate erosion and sediment
control measures can be implemented by providing a plan for the Mangatawa Drain, the stormwater
wetland area, a typical culvert installation, and rail bridge embankment stability works. These areas
are representative of much of the project’s construction activities and working area. It is noted that
the application for the earthworks associated with the main line TEM project was included in the
2008 application.
The ESCPs described in this report are shown on Drawing No.s 3932036-C142, 3932036-CK473,
32932036-CK467A and 3932036-CK461 as included in Appendix A of this document. The ESCPs
detailed in this report give possible erosion and sediment controls that would need to be developed
in more detail by the Contractor for the project.
2 Site Description
The TEM alignment runs generally west to east following the coast near Papamoa, changing
direction inland to bypass Te Puke and link with the SH2 intersection near the Te Puke golf course.
The topography is flat to gently undulating. This plan only relates to the drainage works required
between Te Maunga and Domain Road. The catchments relevant to this ESCP include the
Mangatawa, Wairakei, Arataki and Maranui catchments. In the current situation, most of the
catchments drain to the Rangataua Bay via the Mangatawa drain. The proposed mitigation
measures will provide the same discharge scenario during regular storm events. In major storm
events water will spill over the motorway into the Maranui and Wairakei catchments. The Maranui
catchment will drain to Rangataua Bay bypassing the treatment pond via a floodway corridor.
This section of the TEM covered by this plan begins near the Baypark Stadium in Papamoa and
follows the East Coast Main Trunk railway line (ECMT) parallel to the Papamoa residential suburb
to the Domain Rd intersection with SH2. The total footprint of the site affected by these earthworks
is approximately 10ha, of which excavation and fill are approximately balanced.
2.1 Geology
Geotechnical investigations and subsequent reports undertaken in 2006/07 identify that there are
four geological units found within this length of the TEM alignment. These are summarised below:
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