Civil works | Taking a civil approach
An increasing number of dam removal projects across the globe is creating the need for greater study into various aspects, such as cost estimations, and even local opposition to removal projects
COST ESTIMATING DATA AND tools are needed for dam removal prioritisation, planning, and execution, according to new research in Frontiers in Ecology and Evolution.
Reliable estimates are important for effective decision-making, especially when a portfolio of dams is being evaluated. However, as estimating the costs of decommissioning and removal is a challenge, Duda et al say in their study, it makes it difficult to determine when removal may be a viable alternative to maintaining ageing or problematic dams. Unrealistic estimates, the authors go on to add, can lead to elimination of dam removal as a feasible alternative, create distrust among the public and affected parties, and delay or derail projects. One of the key difficulties is that a wide range of
Above: Glines Canyon Dam removal on the Elwha River in the US
factors can affect price, along with limited publicly available data to understand their impact on total cost. Factors which can affect price estimates include: Size of the dam and its impoundment. Geographic setting - rural versus urban. Volume of stored sediment and its degree of contamination.
Presence of sensitive species or infrastructure. Requirements for post-removal site restoration, such as stabilisation and revegetation. Regional differences in permitting requirements and history of dam removal. Need to replace the function of the dam. Socio-economic dimensions. As with dam construction, dam removals can also be swamped by substantial uncertainties, ranging from discovery of unknown structures, contaminated materials, unexpected high flows, or exceeding water quality limits. And then in addition, dam removal can also involve mitigation requirements which influence cost estimation, the scope of which is often hard to predict in the early planning stages. Whereas cost estimation for civil infrastructure is commonly based on design-bid-build contracts, where the client hires the engineer and contractor under separate contracts, with bids based on unit prices, more complex dam removals may be contracted as design-build projects. Here, the authors explain, the construction contractor maintains ownership of the process from start to finish, and typically bills for the
30 | October 2024 |
www.waterpowermagazine.com
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