Dams and Appurtenant Structures

Hopua te Nihotetea Detention Dam, Whangarei

Kotuku Dam fromNRC 400
The Hopua te Nihotetea Detention Dam has a high Potential Impact Classification (PIC) in terms of the Dam Safety Regulations 2008.  In the event of a dam break, the potential for significant damage is high and loss of life is likely if evacuation does not occur.   The dam is designed to retain flood waters and will provide attenuation of flows during significant flood events.  Attenuation is accommodated by the reservoir volume.  The reservoir is designed to retain water for no more than several days.

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Hopua te Nihotetea Dam Video

Deep Stream, Otago

DeepStream 400
The Trustpower Deep Stream Hydro Project utilises the 310m elevation difference between the existing pipeline diverting water from Deep Stream and Lake Mahinerangi (the principal storage for the Waipori Scheme near Dunedin).  The scheme includes two power stations, a storage lake and conveyance systems involving canals, penstocks, and associated structures.  

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Patea Dam Relief Well Installation

PateaDrillRig 400
At 82m high, Patea dam, the fourth highest hydroelectric dam in New Zealand, is classified as a high potential impact category dam under the 2015 NZ dam safety guidelines.  The dam impounds the longest man-made reservoir in New Zealand at 45km.  An independent dam safety review following up on monitoring of foundation water pressure at the dam toe recommended the installation of new relief wells to alleviate increasing foundation pressures. Trustpower, the dam owner,then  commissioned the design and installation of relief wells and standpipe piezometers at the dam’s toe.  Geotechnical and civil engineering involvement included assessment and comparison of the previous relief well design with current practice; tender evaluation; and on-site supervision and monitoring of well installation progress.  A portable drill rig used to install the wells was lowered to site via a helicopter.  The wells were then drilled to approximately 40m depth, intersecting alternating layers of limestone, siltstone, and sandstone.  During the course of the well installation a notable decrease in foundation pressures was observed. which demonstrated the effectiveness of the new wells.

Patea Dam Spillway Check

PateaSpillway 400
Assessment of capacities for the service, auxiliary and emergency spillways at Patea Dam.  The project included surveys and the development of a hydraulic model in HEC-RAS.  Related studies have assessed further options for upgrading the combined spillway capacities.  Work included client liaison, project management, field supervision and review, and HEC-RAS modelling.

McKays Creek Flume Replacement

McKays 400
Commissioning of a new siphon pipeline supplying Mckays Creek power station.  Work included investigation, detailed design, tendering and construction management.  The completed flume replacement created an additional generation capacity of 25 per cent for the scheme.

Rangitaiki Canal

RangitaikiCanal 400
Design and earthworks supervision for a sediment trap on the Rangitaiki Canal, a key element of the Wheao hydro-electric scheme.  The design included extension of the existing brown ash lining to minimise seepage losses.

Fletcher Road Dam, Waimauku

FletcherRd 400
A low hazard, 3.5m high homogeneous earthfill dam breached during a moderate flood event.  Geotechnical investigations were undertaken prior to preparing the remedial embankment and spillway design.  Drawings and specifications were prepared to obtain resource consent prior to construction commencing. RILEY supervised the construction works and prepared the final completion report.

Tirosh and Weta Estates Reservoirs

TiroshWeta 400
Geotechnical investigations, design, tendering, contract management, and construction observations for two lined reservoirs, 75,000m3 and 150,000m3 at Tirosh and Weta Estates.

Waipori HEPS

Waipori 400
Review of hydrology and PMF associated with the Waipori hydro-electric power station in Otago.  The project included the development and calibration of a hydrological model in HEC-HMS to assess the capacity of the scheme under various design scenarios including the probably maximum flood.  Responsible for technical overview and reporting. 

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