Tasman District Council recently awarded MWH the design and construction monitoring contract for the important new development of a recreational marina at Port Golden Bay (formerly Port Tarakohe). 

The port is 15 minutes from Takaka and is located alongside the beautiful beaches of Golden Bay and the Abel Tasman National Park making it a key tourism destination for domestic and international visitors. 

The port 

Golden Bay Harbour was originally established over 100 years ago to ship bulk cement produced by Golden Bay Cement Company at the local limestone quarry. TDC purchased the port assets after the closure of the cement works in 1994. The port supports coastal trading vessels and is a key resource for local marine farming activities. Today, the port has a 60-berth marina, a 100-year old timber wharf and a concrete wharf dating from 1977.

Aquaculture activities at the port are expected to increase significantly in the near future. To ensure the successful balance of both commercial and recreational use of the port, TDC decided to construct a new marina in the western inner harbour, which will be separated from commercial activities in the wharf area.

The plan

MWH was initially engaged to prepare a comprehensive asset management plan for all of the assets at the port. This included a condition and structural assessments of the breakwaters, wharf and other structures to determine the remaining life. MWH also prepared the asset valuation and maintenance and renewals programme as part of the asset management plan.

TDC’s future vision for the new marina is that it will be a significant catalyst for the developments in the adjoining area. The existing port and adjacent land provides a springboard for significant economic growth and job creation. 

Marina concept design

To ensure the best approach, TDC recognised that the development of a marina needed to be undertaken in a structured manner and asked MWH to prepare an overarching concept design. The work included detailed cost estimates and a financial model to test the viability of the proposal against different usage scenarios. Once this stage is completed the design and consenting phases can commence with confidence.

MWH has developed a number of specific concept plans to help determine the most appropriate layout, maximising the number of berths at the marina. A key constraint to achieve the maximum use of the marina space is the location of the boat ramp. At present the ramp occupies a prime location, which will not allow the marina area to be developed to its full potential.

The most desirable layout for the marina users would be to have the boat ramp completely separate from the marina. However the boat ramp is an integral part of the port and it is currently the most accessible and most protected boat ramp in the area. A number of layouts have been considered with the two goals of trying to maximise the number of berths and also retain a well-protected boat ramp for the local residents and visitors to Golden Bay. 

The preferred arrangement at this stage provides 190 berths with the boat ramp reconstructed adjacent to the middle breakwater.  The other critical constraint in this project is the need to provide a recreational marina within a functioning port; which have in some cases conflicting requirements in terms of manoeuvrability and space constraints. 

As part of the concept design MWH is also considering the full range of servicing requirements for the port and marina. This includes improvements to the access road and the provision of power, water and wastewater services.

Dredging and reclamation

The proposed concept will mean dredging the area of the marina to a minimum depth of 2.5 metres below chart datum. The estimated volume of dredging required from the bed of the marina is approximately 70,000 cubic metres. The majority of this material will be reused at the southern end of the port where a new parking area is to be created for marina traffic. Existing rock protection on the breakwaters will be reused alongside rock from the old cement works quarry. MWH has undertaken a detailed review of previous geotechnical investigations and reports to determine any significant construction issues that may occur during in the dredging and reclamation. Further geotechnical investigation will be undertaken during the design phase of the project.

Penguin habitat

Golden Bay in general and this area in particular, are favoured habitats for the little blue penguin. TDC has trialled a number of nesting boxes for penguins on the inner breakwater, which are now inhabited. The future reclamation and breakwaters will provide penguin habitat and nesting boxes with the aim of encouraging the penguins to avoid crossing the road to access the cliffs. TDC are also considering providing a penguin viewing platform and visitor kiosk within the marina development. 

Diverse team

One of the most exciting aspects of this project is the interaction and innovative ideas generated by having a diverse team of specialists covering a full range of disciplines all working together.  MWH has brought together marine engineers, geotechnical specialists, architects, planners and penguin specialists to support this project.  This diverse team should lead to a successful project outcome that fully meets TDC’s aims of delivering a vibrant and well-used marina facility.

Track record

MWH has extensive experience in coastal engineering ranging from coastal protection works to geotechnical investigations and planning and consenting projects. Another recent project has involved work with Southland District Council to assess and design coastal protection works on Stewart Island. Due to historical erosion and its corresponding impact on road and utility infrastructure, MWH worked on four main areas: Halfmoon Bay, Lonneker’s Bay, Butterfield’s Beach and Horseshoe Bay. MWH undertook site reconnaissance visits, surveying and a review of historical information that impacts on erosion and other coastal processes. Consultation with residents and previous asset engineers provided significant historical perspective for the remedial protection works. SDC adopted the recommendations provided by MWH and commenced works in 2009. The works were paused due to resource consent conditions but are likely to be completed in 2010.

For more information please contact Denis O’Brien, Technical Development Leader, Water and Waste, Ph 03 546 0622 or Email Denis.V.OBrien@mwhglobal.com