The Wai-iti Valley is located in the northern region of New Zealand’s South Island. Water demand during summer in the Wai-iti Valley is greater than the available supply, resulting in water allocation restrictions and pressure on in-stream habitat and uses. Further, the summer water resource in the Wai-iti Catchment is currently over-allocated. Thus, since the mid 1980s, Tasman District Council (TDC) has been unable to grant new water permits to take water from either rivers or
groundwater in the Wai-iti Catchment. Existing water permit quotas have been reduced where they were not being used, but despite this agricultural, horticultural and domestic use is frequently restricted during dry years.
Recently, the need for a community solution was identified for the Wai-iti Valley area. The Wai-iti Water Augmentation Committee (comprising representatives from the local community and TDC) was set up in 1995 to find the best option for the northernmost extent of the Wai-iti valley. A feasibility study for a community dam was completed in 2001 identifying small off-river storage dams as options. The proposed scheme is located in a tributary of the Wai-iti River and is essentially a water harvesting project where winter flows in the stream would be impounded and stored, and gradually released on a regular basis back into the stream and Wai-iti River system during dry summer periods.
The paper will cover the project’s economic objectives as well as community and environmental impacts and the consenting process under the Resource Management Act. Dam construction is planned to start in October 2004.
The PT Kelian Equatorial Mining (KEM) Gold Mine is located in the foothills of Central Kalimantan in Indonesia, only 3km south of the equator. Namuk Dam was completed in September 1991, to receive tailings from the gold mine that commenced commercial production in January 1992. Mining operations ceased in mid-2003. Progressive closure of the mine has been underway since 2003, but processing of ore stockpiles will continue to the end of 2004.
KEM and the local Government formed a Mine Closure Steering Committee, supported by four Working Groups to provide assistance and guidance to KEM in achieving responsible closure of the mine.
Engineering aspects of the Namuk Dam closure included flattening of the downstream slope to withstand overtopping in the event that the spillways should fail or be blocked for whatever reason. The design also required large rock to be placed as an apron over the tailings upstream of the dam as a security precaution against potential sabotage. This is intended to deter illegal mining of tailings, which could potentially initiate breach of the dam, and to protect the dam from malicious damage.
Ross River Dam is dam of extreme hazard located immediately upstream of a population in excess of 100,000. A comprehensive review undertaken by a team of international experts (ref 1) identified a number of unacceptable risks that required immediate attention.
The State Government designed and oversaw the construction of the dam that was completed in 1976. NQ Water is of the belief that the problems identified by the team of international experts were a result of poor design by the State and inadequate attention by them during the construction process.
NQ Water developed a comprehensive communications plan (ref 2) with the objective of keeping the community adequately informed, gaining positive media exposure, obtaining the support and confidence of the business community and key stakeholders, and securing State Government funding towards the upgrades.
The climate at the time was characterised by adverse media history in relation to the dam, reluctance by the State Government to take responsibility, and poor brand awareness of NQ Water and its activities.
This paper focuses on the process undertaken by NQ Water in engaging the community, various levels of Government, key stakeholders, and business community, which resulted in securing the necessary funding for the dam upgrades. It will discuss the key elements and components of the communications plan, their objectives, the results achieved, and lessons learnt.
J Walker, M Gillon and L Mejia
The Aviemore Dam was built in the late 1960’s and is located on the Waitaki River in the South Island of New Zealand. It is comprised of a 56m high earth dam and a concrete dam housing the power plant and spillway. The dam is located across the Waitangi Fault. This fault was considered to be an ‘inactive’, normal fault at the time the dam was built. The dam is owned and operated by Meridian Energy Ltd.
This paper is in two parts. The first is to introduce the owners Dam Safety management processes. The second discusses the application of these processes to a State of the Art investigation of the faults near the dam, the derivation of seismic loads and the assessment of the dam for seismic loads including potential movement on the Waitangi Fault affecting both the earth dam and the reservoir.
Notable features of the work will be described including:
Mount Morgan dams Nos. 4, 5 and 6 were originally built on the Dee River in central Queensland in the 1880s and 1890s to provide water to the Mount Morgan mine. The largest of the dams, Dam 6 is a mass concrete structure 9.7 metres high storing 63.6 ML.
Today the dams are no longer used for water supply and the stored water is highly acidic and heavily contaminated by the runoff and tailings from the mine site. They are also in a seriously degraded state with major undermining and significant structural decay. Failure of these dams either individually or in cascade would put lives at risk and severely contaminate downstream areas. The decision was therefore made to decommission the dams and remove that risk.
As well as the substantial removal of the dams, the decommissioning process involves dredging or
excavation of approximately 500,000 tonnes of tailings from the dam storages and the storing of this material in the mine pit.
The challenge was to decommission the dams in a safe, economical and environmentally friendly
manner while retaining as much of the heritage value of the three dams as possible. To avoid carrying the risk over another wet season, the work needs to be substantially completed prior to the end of September 2004.
The paper discusses the investigations and the planning that has gone into the project including:
the real time flood warning system to provide early warning of conditions likely to cause dam
the decontamination of the storages;
the contingency provisions to minimise the risk of further contamination;
the removal of the dams; and
the measures to improve the long term quality of water in the Dee River.
Historically dams have been built across our river systems with little regard for the impacts on fish passage both upstream and downstream of the structure. Today’s increased environmental awareness and standards means that the impacts of a dam on the fish community are key issues that must be addressed by the operators of existing dams and in the design of new infrastructure.
Although fish transfer systems are currently being retrofitted to existing structures, there is a limited Australian knowledge bank on the performance of these systems and their impact on the fish communities. This lack of knowledge coupled with the potential for more strict environmental requirements in the future requires fish transfer systems to be designed with maximum flexibility and to rely on overseas practices where a greater knowledge bank exists but which may or may not be relevant to Australian conditions. For example, high lift fish transfer systems such as fish lifts and sluicing have been commonly used in North America for the last 20 years but are only now being considered for use in Australia.
This paper presents an overview of North American experience with the management of fish passage at dam structures and considers some of the following key issues relating to Australian conditions.
1. Upstream passage.
2. Downstream Passage
3. Sluicing as a method for conveying fish.