IntroductionThis design was born from a need to treat storm-water run off from the Poplar Lake Business Park Design. The system was designed to treat the storm-water at the source where possible, however at the lowest point of the design a lake was planned, primarily as an aesthetic feature and a water storage with some filtration on the edges. It was this lake that became the focus of the next design.

The original lake design was intersected by a road. The first decision made was to turn this road into a cause way and use it to divide the lake up into 4 separate water bodies. Two would become storm water wetlands (1,2 below), treating run off from the surrounding areas and roads, and being fed primarily by road Swales. These two lakes then feed into a third lake (3), a storm-water retention lake that is effectively a large forebay for the final and largest lake (4). It was intended that the water be clean enough for recreational use (paddling, swimming and boating) by the time it entered these final lakes. Similarities were drawn to the muddy banks of rivers, estuaries and natural occurring wetlands, which my design attempts to reflect.

This area is also the visual focus of the development, and as such these final two devices needed to draw in workers from the surrounding business park on their breaks, as well as visitors from further afield. As such this design’s focus is more about integrate more public amenity into a func-tional storm-water treatment device than the device itself. However there were some functional and safety constraints.

In particular for safety the edges of the pond must be shallow (0.3 m deep) . Where the design meets the pond this was ensured. These shelves may also be plant-ed to bar access and provide a degree of filtration. Where water flows in and out of the lake, devices that slow water (eg: Rip Rap) prevent erosion.

In the design the spillway from the upper wetland was protected with rocks and boulders. The shallow shelf was seen as a safe access point to the water and vegeta-tion was used to guide people to this.

Poplar LakesIntegrating people with stormwater treatmentAlex Smith 1347248

The Design1. Four 0.3 m terraces lead the visitor down to the water, the lowest (consisting mostly of soils retained behind a wall) will be mostly submerged and acts as a shallow shelf along this edge, providing a degree of safety and a platform on which wetland plants may grow. The next terrace is intended to be occasionally flooded. It would be formed from light grey con-crete into which a herring bone pattern would be etched to expose the aggregate, as a reference to the rafts of kauri logs floated down the rivers of the region.

The third terrace would also feature the herringbone pattern, which is used to divide it into a series of concrete paths and lawns. These lawns will house shade trees such as Pohutukawa, making this area more attractive to the nearby employees at lunch in summer. The fourth and highest terrace features a multipurpose lawn.

2. A Shallow “harbour” brings the water up tho the edge of the second terrace and is intended to encourage people to use this lake for recreation, providing a safe, flat and shallow place for them access the water. The water in this area is a maximum 0.3m deep and this part of the lowest terrace would be paved permeable blocks to allow safe movement when in the water.

3. Shallow wetlands provide visual amenity and restrict access points to the water. They also provide a degree of water filtration. Species planted here and along the banks of the wetlands and lakes will consist mainly of sedges (Oioi) and rush-es in the wettest areas, with cabbage trees, and flax (Harekeke) usually higher up.

4. A boardwalk brings visitors through the wetland planting out to the lake edge, and forms the edges of the “harbour”. Construction would be of Hardwood timber, which would be allowed to weather.

5. Bringing colour to the design, multi- coloured fibreglass seats are scattered around the lower terraces, in the shape of dinghies pulled out from the water. These are intended to provide a novel form of seating and infer the lakes recreational purpose. They also reference a common sight beside rivers, estuaries and lakes for years.

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Above: the plan of the Poplar Lake business park showing the lake at it’s northern edge.Below: The stormwater study and concept diagram

Left: An overview of the site from the spill way. Note the fibre-glass boat seatsBelow: The site from the road. Seen here are the terraces leading down from the carpark to the water.

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