Raingardens to improve lake’s water quality
Waipā District Council’s quest to filter stormwater from the streets of Cambridge to make improvements in the water quality of Lake Te Koo Utu is starting to flow.
Construction on the first of a three-step process to build several raingardens to treat stormwater runoff before it enters the lake is programmed to start this month and is expected to finish in June.
Water services manager Martin Mould said the town’s busy intersections such as Victoria Roundabout, were the focal areas in the early stages.
“This is the first step in improving the water quality of Lake Te Koo Utu,” he said.
“At this stage we have targeted the busiest roads and intersections for maximum effect in treating contaminants from stormwater runoff before they enter into the lake.”
A raingarden looks like any other traditional garden on the surface, but under the soil there are layers of various media and plant roots that act as natural filters for surface runoff.
Mould said the gardens help provide a place for rainwater to soak into the ground allowing a natural filtration process to remove contaminants such as oil, petrol, zinc and rubber from cars which are collected in rainwater and eventually made their way into the lake.
Raingardens can play an important role in protecting habitat and helps with climate resiliency, Mould said.
“The specifically designed garden is set into the ground to remove sediment and contaminants, such as hydrocarbons, from the road’s surface at first flush, which prevents those from entering Lake Te Koo Utu and will help improve the water quality.
“Lake Te Koo Utu is home to many fauna and flora, improving the water quality here will improve the ecosystem for our eels and native invertebrates to thrive.”
Installing raingardens was one of Council’s approaches to improving water quality through the Lake Te Koo Utu concept plan, adopted in 2021. The [cost] to fund design and installation was allocated through the 2021-31 Long Term Plan.
Design and construction of stages two and three, aimed at targeting high use and other collector roads will proceed as funding allows, Mould said.