Tekapo Canal Condition Assessment and Mitigation Concepts Project

The 26km long Tekapo Hydropower Canal was constructed to link Lakes Tekapo and Pukaki between 1971 and 1977. In 2008 a dive inspection unexpectedly identified major sinkholes in of the earthen canal lining above a culvert beneath the Canal. This led to urgent mitigation measures to stabilise the canal lining over the short term. Extended buttresses were built and an innovative lining repair carried out underwater. Comprehensive studies followed to see if there were further deficiencies along the Canal. Damwatch developed Mitigation in the three areas found as deficient, all with different characteristics.

For more information on this project, download the case study sheet here.

 

Rangitata South Irrigation Project

Irrigation is important to the development of New Zealand’s primary production. Damwatch contracted with Rooney Earthmoving Ltd to design and construct a sustainable and commercially viable irrigation scheme, on land adjacent to the Rangitata River. The scheme will divert water during high flow periods to the biggest irrigation storage facility in New Zealand, with a capacity of 16.5 million cubic meters enabling irrigation of 12,000 hectares.

For more information on this project, download the case study sheet here.

 

Vietnamese Small Hydro Project Dam Safety Plans

As part of the World Bank’s Renewable Energy Development Program (REDP), the Vietnamese Ministry of Industry and Trade require adoption of Dam Safety Framework (DSF) for all small hydropower projects financed under the REDP. The World Bank’s policy on safety of dams (OP.4.37) required four dam safety plans within the DSF.

Sung Vui HEP is one of six small hydropower stations (SHP) in the Ngoi Xan Hydropower Scheme in Bat Xat and Sa Pa Districts of Lao Cai Province of Vietnam. The Sung Vui project is located at elevation 800m in very steep and deeply incised terrain. It will have a 24m high intake dam providing limited pondage, 4km of buried concrete power pipe and 1km above the ground steel penstock.

Damwatch prepared a pilot set of Dam Safety Plans and Guidelines for Small Hydro Projects in Vietnam. Sung Vui was chosen as a suitable project for the pilot. The guidelines reviewed and upgraded management plans covering dam safety aspects of design, construction and commissioning. The guidelines are to be used for workshops with potential developers, commercial banks and design consultants.

The desired outcomes are that dams are built and operated safely and improved quality control and that this pilot project can be repeated on other SHP’s in Vietnam and other countries.

For more information on this project, download the case study sheet here.

 

Revelstoke Dam Safety Review

Revelstoke dam is a major power station on the Columbia River in Canada, owned by BC Hydro, with internationally recognized reservoir landslides. It is the second in a cascade of dams on the Columbia River and is located below the 240m high Mica Dam. The Revelstoke power station consists of a 175m high Concrete Dam incorporating the outlet facilities and the power station, and an adjoining 79m high Earth Dam.

There are a number of large potential landslide areas along the reservoir and one of these, the Downie Slide was stabilized as part of the dam project. The Checkerboard Creek Rock Slope is another active feature, which has been extensively investigated and is subject to ongoing monitoring.

This Dam Safety Review was more demanding than usual, due to the characteristics of the structure and the presence of major reservoir landslides. This DSR included review of the dam and reservoir’s physical condition, operation, maintenance, surveillance, performance and dam safety management processes as these relate to the safety of the dam.

Damwatch was able to bring its expert knowledge of concrete and earth dams, and reservoir landslide and dam foundations in schist rock terrain.

For more information on this project, download the case study sheet here.

 

Pukaki Intake Canal Repair

Pukaki Canal is a key 350 million cubic meter water conveyance asset in Meridian Energy's hydropower network. In late 2009, a risk assessment identified that gravel erosion damage to the concrete stilling basin could lead to structural collapse if not remediated. Meridian was able to take advantage of a transmission network outage, scheduled six days after the risk was identified. The unique aspect of this project is that all repairs were successfully completed during ’62 hours on the slab’. A 13 km long earth lined canal required dewatering for the first time in 20 years. An upgrade design was developed in collaboration with the contractor and engineers worked closely with contractors workforce to effect the works. Excellent pre-planning and cooperation was essential, involving competing electricity generating companies, a number of contractors, client staff and consultants. From identifying the problem to completing repairs it took 13 days, which included a Damwatch manage d 24/7 on site surveillance team from before dewatering to one week after.

For more information on this project, download the case study sheet here.

 

Arapuni Dam Foundation Remediation Project

In 2005, an Alliance comprising MRP (Mighty River Power), Trevi, and Brian Perry Civil (Fletcher Construction) installed 95m deep secant pile cutoff panels at Arapuni Dam on the Waikato River, while maintaining a full reservoir. Damwatch was technical advisor to the owner and maintained 24/7 on-site instrument monitoring and surveillance.

For more information on this project, download the case study sheet here.

 

Mokihinui Feasibility Studies

Damwatch carried out feasibility studies for a 100MW hydro station on the Mokihinui River on the South Island of New Zealand. The 80 - 85 meter high RCC (Roller Compacted Concrete) dam with free overflow spillway is located in a high seismic zone and special assessments were made to understand the major natural hazards at the site. Hazards addressed included: high seismicity with possible proximal active faulting; potential rock slides into the reservoir; potential for landslide dams forming upstream of the reservoir; depth of alluvium at the dam site and large floods.

Senior Damwatch specialists presented evidence at resource consent hearings.

Click here for more information on the Mokihinui Hydro Proposal.

 

Cosseys Dam Design and Construction Peer Review

Cosseys Dam is a zoned earth fill embankment of 1950s vintage, which initially had no filter materials protecting its core. This water supply dam (south of Auckland, NZ) experienced a number of seepage incidents associated with piping of core material into the underdrain, which necessitated a significant upgrade programme.

Damwatch carried out an independent peer review of the upgrade. This involved attendance at workshops and progress meetings during the investigation and design, and a detailed independent peer review of the final upgrade design.

To read more about the review process and project outcomes, download the case study sheet here.