Dr Andy Hughes
On Hampstead Heath in Central London, just 3 kilometres from the centre of the city, there are more than 20 dams and reservoirs set within the landscape setting of Hampstead Heath. A number of dams were built in the 16th century and formed the original water supply to the City of London. They are set in a landscape laid out by the world renowned Humphrey Repton.Three of the embankments which are laid out in two chains of reservoirs across the Heath are subject to safety legislation in the UK. As such they were identified as being deficient in spillway capacity and thus fairly significant works were required to be carried out in this sensitive setting.The Heath is protected by the Hampstead Heath Act of 1870 which seeks to prevent significant changes to the Heath and thus it was quite clear that there would be opposition to any works on the Heath, even though they were required by law to protect persons and property downstream. In fact a significant lobby group formed which challenged the need for the works and also the legislation of the UK via a judicial review. This paper will describe the process by which significant stakeholder consultation was undertaken (costing more than £2M), the judicial review that took place in the Royal Courts of Justice, the option study and the major engineered elements carried out on the Heath.
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Lisa J Neumann, Rod Westmore
In Australia construction of a new dam on a greenfield site is relatively uncommon and construction of a new dam on a brownfield site is even more unusual.This paper presents an innovative design solution to address the challenges associated with such a project.Ridge Park Dam is a new flood retarding dam located in a suburban recreation park, less than 10km south east of Adelaide, South Australia.The dam was constructed in 2014/15 and was designed to limit the peak flows in the creek downstream of the park under the 1 in 100 ARI event and to impound water as a component of the infrastructure required for the Managed Aquifer Recharge (MAR) scheme located in Ridge Park.The expectations of both the client and community and the technical issues encountered in the early stages of the project resulted in some unique design criteria. At the outset the client and community expectation was that the dam would improve the overall amenity of the park without impacting the existing vegetation or functionality of the park, including public access and safety.Identifying a dam type to suit the client and community expectations and address the technical issues was not straightforward.Typical dams types such as embankment dams, mass concrete gravity or concrete buttress structures, were found to be not suitable.A less typical, innovative solution was sought.The outcome was to construct a dam comprising a concrete core wall supported by rock filled gabion baskets.
Andrew Balme, Dan Forster, Tim Logan
The MW7.8 Kaikōura earthquake on 14 November 2016, ruptured over 20 faults during the initial shaking,which lasted nearly two minutes. A complex series of fault ruptures propagated northeast for nearly 180 km from the initial rupture location. Instrumentation from dams across New Zealand shows that whilst most dams did not suffer physical damage, piezometric responses were measured in dams and their foundations. Earthquake related changes in seepage regimes are not unusual and depend on the characteristics of the ground motions,and site specific characteristics that influence how a dam and its foundation respond to ground motions. The ability to measure a piezometric response in a dam or foundation is heavily influenced by the instrumentation network and method of monitoring. Data collected during events such as the Kaikōura earthquake provides valuable information for both characterising performance of a dam during the event, and assisting future analysis such as failure mode assessments. Careful consideration must be given to the scope of installed instrumentation and the frequency of monitoring in order to provide these benefits,and the robustness of the system to ensure it adequately survives the event.
Peyman Andaroodi, Barton Maher
Seqwater is a statutory authority of the Government of Queensland that provides bulk water storage, transport and treatment, water grid management and planning, catchment management and flood mitigation services to the South East Queensland region of Australia. Seqwater also provides irrigation services to about 1,200 rural customers in the region that are not connected to the grid and provides recreation facilities. Seqwater owns and operates 26 referable dams regulated under Queensland dam safety legislation.
Leslie Harrison Dam is an Extreme Hazard category dam located in the Redland Bay area of Brisbane.A significant portion of Population at Risk is located within a short distance downstream of the dam, reducing the available warning time in the event of a dam safety issue and impacting on the estimated loss of life used to assess risk. Following the Portfolio Risk Assessment undertaken by Seqwater in 2013, a series of detailed investigations were undertaken to confirm the assessed risk and the scope and urgency of the upgrade works.
Before a final decision on the scope and timing of the dam upgrade is made, Seqwater has completed a detailed review of the downstream consequences. This review was intended to update the Population at Risk(PAR) and Potential Loss of Life(PLL) estimates using the latest estimation methods for a range of scenarios. Three life loss estimation methods were used including empirical and dynamic simulation models and the results were compared.
This paper discusses the updated consequences assessment and the impact on the assessed risks, for Leslie Harrison Dam for both the current dam and the proposed upgrade scenarios using the revised Potential Loss of Life estimates.
Stefan Hoppe, Vicent J. Espert-Canet
Monitoring data has to be transformed into useful knowledge to provide owners and operators with valuable information about the safety status of their dams. This information should be up-to-date and easily accessible for all technicians and engineers involved inthe safety program,and directly linked to operation and emergency preparedness procedures.This article describes the main functions of a web-based software for the acquisition, processing,and evaluation of monitoring data. It runs on conventional internet browsers,and does not require the installation of any additional software. It provides appropriate tools for monitoring the safety status of dams and analysing dam behaviour.This article uses a case study to outline the experience gained from implementing and operating the software for 8 years to control more than 50 Spanish public dams owned by a river basin authority. The implementation involved completely revisingthe installed monitoring systems and recompiling all available information. This was used as a basis for an updated,goal-oriented definition of necessary variables, configuration of charts, SCADA views and threshold values. A key aspect of the software ́s successful implementation was the theoretical and practical training of all stakeholders.As a result of the software ́s implementation, the dam owner was able to use the data from their monitoring system more efficiently. The development of safety reviews and dam safety status evaluations were also considerably improved.
Alberto Scuero, Giovanna Lilliu, Marco Scarella, Gabriella Vaschetti
Hardfill dams present technical and cost advantages. Placement is like in embankment dams, thus construction is fast. The typical trapezoidal shape makes possible use of local aggregates and low cement content. Despite the low strength material, these dams can be built on weak foundation, and resist earthquake and overtopping. However, being the material semi-pervious, they require an impervious facing. Until 2014 this was typically made with conventional concrete slabs with waterstops, or grout enriched hardfill. Concrete facings require heavy and costly equipment, long construction time, are expensive, frequently require maintenance.Construction of the facing can have a big impact on the overall construction costs of the dam. Replacing the concrete facing with a geomembrane lining is a cost-effective solution. This paper describes two hardfill dams’ projects with an exposed geomembrane as upstream liner: Filiatrinos (Greece, 2015), 55.6 m high,and Ambarau(Democratic Republic of the Congo, 2017), 19.30 m high.