Five culverts w/ weir control inlet

Year proposed

  1981

Status

  Not implemented

Location description

  Taumutu

Description of option

  A set of five culvert pipes of 2.4 m internal diameter (ID) was proposed as an option to maintain the lake at a level of 0.5 m via an inlet weir. The intake structure consisted of a canal 90 m long, flowing over a gravel trap before the water entered the culvert proper. The canal was to be constructed with a concrete liner to minimise erosion and enable easy removal of sediments that will build up. The culvert structure extended approximately 85 m from the exit of the canal (located along the centreline of the Kaitorete Barrier). This large structure would require support saddles connected to piles at estimated 9.76 m centres, and would extend 40 m from the high water mark out to sea.

Opening, closing, and lake level control description

  Maintaining the level of the lake at 0.5m means that during high tides, the sea level is greater than the lake level - possibility that water could flow from the ocean into the lake, etc.

Maximum discharge

  below 50 cumecs

Maintenance/Management description

 

Cost description

  The large swells common at Taumutu represent a significant threat to a large, inflexible structure in a surf zone.  Maintenance costs likely to be high.  1969 cost estimate for 5 pipes = $2,250,000 (comparable to Marsden PS installation)

Fish passage benefit rating

  Low

Potential running impacts or benefits

  Maintaining a lower lake level is likely to allow greater saltwater intrusion to lake.