Beard Stream - Te Marua Water Plant
Beard Stream runs of the Mackaskill Lakes, the twin water storage bodies at Te Marua, and meanders its way down to the Hutt River. This stream is situated inside the beautiful Kaitoke Regional Park and is an important part of the local native ecosystem.
Ongoing scour and instability of its stream banks was a growing concern, and Wellington Water’s proposed improvements involved structural and non-structural measures designed to eliminate erosion and provide protection to this ecologically sensitive area. Limiting the impact on the existing vegetation and ensuring minimal disturbance of native fauna and flora was a critical objective for this project all the while upholding the areas ecological values.
This project was challenging due to several constraints on-site; access to the stream was difficult in some areas because of the overgrown native canopy and some low lying areas were very soft underfoot which prevented truck access. Consequently, the project commencement date of June was postponed out of precaution due to wet weather and was scheduled for a later date the following March. Consent conditions required a non-construction period for fish life protection 1 August to 31 December.
Wellington Water selected a contractor early to assist with site consultation and enable the design process to scope, along with construction methods. Advance Landscape Systems were also engaged at a similar time and organised a collaborative site inspection with all parties. Flex MSE was the chosen solution for this habitat as being a soft-armour segmental system allowed for the construction of a permanent structure while creating full vegetation of the face – essentially bringing the area ‘back to nature.’ No concrete, forming or levelling was required, which further confirmed Flex MSE was the ideal choice for an ecologically sensitive waterway. An ecologist was appointed to manage the fish which involved setting traps and the reach electric fished. Afterwards, contractors dewatered the stream and ensured all fish were removed before works started. Installation was completed very quickly due to its fast install time – 45m2 per day with a 4-person crew. The ability to have the units at such close proximity to the stream allowed a smooth construction process. The vegetation, being such a vital part of the Flex MSE’s long-term resilience, was specified by an ecologist. A volunteer planting day was scheduled for May, and members of Wellington Water, Greater Wellington Regional Council, and Advance Landscape Systems spent an afternoon live-planting the newly constructed streambanks. The native species included rata, coprosma and a variety of carex grasses, Eco sourced and grown by the Rimutaka Prison Nursery.
The Flex MSE Vegetated Wall System was not only the logical choice for this application, but also the most ideal because of the sites ecological significance. Flex MSE provided the streambank a structure with great resilience to stand up to high stream flows, and guaranteed it would only get greener and stronger as the vegetation established bringing the area back to its natural state. Additionally, the 120-year design life ensured it met all longevity expectations.