Sleepyhead Estate: Creating good outcomes with a multi-disciplinary approach

Pranil Wadan
Pranil Wadan
Principal Engineer - 3 Waters Manager
Sleepyhead Estate

Sleepyhead's $1.2 billion mixed development at Ohinewai is backed by the Directors of The Comfort Group, Craig & Graeme Turner’s vision of creating affordable and quality homes alongside stable jobs in a genuine, thriving community that the future residents and workers can be a part of. 

The Woods team is involved across a number of key areas, including Civil & Infrastructure Engineering, Surveying, Stormwater and Flood Management. Our multi-disciplinary approach and collaboration with stakeholders has enabled us to create good outcomes and support our client in getting the go-ahead for their vision.

Getting the green-light for rezoning at Ohinewai

The Sleepyhead master-planned mixed-use community development required a private plan change as part of the resource consent process.

The 178 hectares of land for the proposed development required rezoning from rural as noted in the proposed Waikato District Plan to a mix of industrial, residential, commercial zonings along with communal recreation and open space.

This plan change was approved at the end of May 2021 and appeals period was settled in December 2021. 

The challenge: Getting the plan change approved

To get the plan change approved, there were a number of challenges to overcome. We provided evidence that the infrastructure, wastewater, and environmental risks can be managed appropriately. Flooding and stormwater management were key areas that required Woods expertise in in order to resolve these for the client.

Flooding

Approximately two-thirds of the development site is in a significant 100-year floodplains with some areas that may flood up to two meters deep. Trying to develop in a flood plain was always going to be difficult.

Flood Plain Storage

Mercury Energy has a significant stake in the area and was concerned that development within the floodplain would affect flood storage capacity and subsequently impact the power generation capacity of hydro dams.

The 178ha development site contributes to about 2% of the catchment area so we needed to demonstrate that the site is a small proportion of the contributing catchment and how the downstream impacts can be managed.

Environmental

Downstream from the proposed development is Lake Rotakawau and the Whangamarino Wetlands. We needed to understand and provide evidence of how we would manage stormwater to ensure there are no impacts on the receiving environment downstream.

Existing drainage scheme

There is an existing drainage scheme of drainage networks in the area that enables land owners to use water for irrigation and discharge water back into River Waikato. These drainage networks traversed through the site and require a certain level of servicing. We were required to work out how we best manage this whilst the site is getting developed to make sure there's no long-term impact on the serviceability of existing drains.

How Woods overcame these challenges to get the plan change approved

Complex flood model and robust flood assessment

Before we started, the area wasn't well understood. Waikato Regional Council (WRC) had commissioned modelling works for this area, but it still underway and draft. Woods worked closely with all the stakeholders and collaborated quite closely with WRC to establish a flood model that would allow us to assess flood risk for the existing site as well as neighbouring sites for various possible scenarios.

Getting WRC acceptance of flood model was also really critical. We ensured that WRC were involved in the process by working with their technical representatives on a regular fortnightly basis. After we completed the model, WRC reviewed and accepted all the work undertaken. The model was used to support the plan change submission and respond to submissions from other parties such as Mercury Energy.

A multi-disciplinary approach to create better outcomes

Woods’ ability to integrate different disciplines has been key for the collaboration required for this project. It was led by a multi-disciplinary approach rather than each team or consultant working in silos.

The Woods surveyors, civil designers, and stormwater engineers worked closely together to complete work related to flood modelling and stormwater management. We were able to sit down with them and work quite closely around what was happening in the water team and get inputs from the different disciplines on the best approach to tackle different issues faced during the project.

This approach saved us from rework as we were able to look at the earthworks model design as we were working on the flood modelling to try and inform it to minimize rework or minimize iterations. It is always an iterative process, but we were able to capitalize on each other’s perspectives to understand things differently and more efficiently to create a good outcome.

Collaboration, collaboration, collaboration

There was a lot of collaboration required to get this to happen; there were Mana Whenua inputs, expectations from the client, local council, Waikato Regional Council as well as open days with the local community, Waikato District Council, and Waikato Regional Council. The quality and detailing provided by Woods made it easier for us to collaborate as we were able to gain confidence and trust of the other parties.

The right strategy from the start

Having a strategy from the start  was the best decision we made, and it is the strategy that eventually helped the project team succeed. There were multiple other ways it could have been done, but these may have come unstuck during the hearings. The fact that we chose to do robust and excessive modelling meant we were able to get Mercury Energy and all of the other submitters onboard and across the line with confidence.

Having the plan change approved and receiving rezoning approval was a great outcome for the Comfort Group and the future of the Sleepyhead Estate development.

If you would like to find out more about how Woods’ collaborative, multi-disciplinary approach can help you create good outcomes, get in touch.

Pranil Wadan - Principal Engineer, 3 Waters Manager