Progress Report: Demolition of Athlone Cooling Towers

The City will be releasing regular progress reports to keep the public informed, via the media, on the progress of the planned implosion of the Athlone cooling towers. The implosion date will be announced as soon as the information becomes available.

Jet Demolition, the appointed firm to demolish the Athlone cooling towers, and Knight Piésold Consulting, who have been appointed to investigate engineering solutions to the structural instability of the two (2) cooling towers, are working closely together with the City to properly cover all aspects, be it safety or environmental, of demolishing the towers at the Athlone Power Station as soon as possible.

Two (2) consulting firms recommended that the towers be demolished after reinforced concrete stiffening rings on one of the towers collapsed on 14 February this year. Jet Demolition was appointed last week and has sixty (60) days from the date of their appointment to demolish the towers. The Environmental Team at Knight Piésold has been tasked with addressing the environmental issues associated with the demolition process.

"The high safety risks associated with a project of this nature requires that adequate attention be given to the technical preparation for demolition; therefore we could not implode the towers by the end of May 2010 as we had hoped. The Project Team will, however, work as quickly as possible to ensure a safe and accurate implosion in a controlled manner. The Project Team is obviously concerned about the safety risks during the preparation of the towers for implosion and will therefore have safety specialists involved in this planning. Further to this, the City has an emergency plan in place that will be activated should the need arise," said Alderman Clive Justus, Mayoral Committee Member for Utility Services.

What are of particular concern to the Project Team are the environmental issues and impacts associated with the demolition of the cooling towers. Knight Piésold contacted the National Department of Environmental Affairs (DEA) to advise on the environmental process to be followed, as well as on the responsible authority. The DEA have concluded that the implosion does not require a Basic Assessment Process or an Environmental Impact Assessment Process, but any future decommissioning proposals for the Athlone Power Station site will still be subject to the mandatory environmental and heritage authorisation process, as well as any associated public participation processes that may be required.

A detailed Environmental Management Plan is currently being prepared for the implosion and clean-up phases of the project. Specialist teams in the fields of dust, noise, vibrations, heritage, local climate and avifauna are being appointed to assist in providing management and mitigation options for the Environmental Management Plan.

Furthermore, a heritage application in terms of a Section thirty eight (38) of the National Heritage Resources Act was both presented and submitted to the Council at Heritage Western Cape. A Record of Decision in terms of the National Heritage Resources Act has since been received, approving the demolition of the towers.

Background to the decision to implode the towers:

The two cooling towers at the Athlone Power Station were designed in 1958 and completed in the early 1960's. Three towers at Ferrybridge C Power Station in the United Kingdom that were of similar design parameters to the Athlone cooling towers suffered catastrophic failure in 1965. This was followed by cooling tower collapses in 1973 and again in 1984. The collapse at Ferrybridge was attributed to insufficient vertical reinforcement to resist uplift forces and wind induced vibrations and the international standards for tower design were rapidly re-evaluated and amended as a result.

The Athlone cooling towers were constructed before the design revision and are therefore only able to withstand thirty six percent (36%) of the wind load which modern structures are required to tolerate. Attempts were made in the 1990's to reinforce the Athlone cooling towers with external stiffening rings when routine checks revealed signs of wind-related structural stress. With the closure of the coal-fired power station in 2003, the towers were deemed benign and the internal infrastructure was removed, leaving only the hollow 125 mm thick concrete shells and the reinforcement rings in place.

On 14 February 2010, the top ring on cooling tower one collapsed and destroyed the structural integrity of the remaining rings as it fell. Cooling tower one may therefore now be vulnerable to even lower wind loads than its design intended, and the collapse of the stiffening rings on cooling tower two seems imminent given the identical age, design, material, and element exposure of this structure to cooling tower one.

Following recent investigations and expert opinion on alternatives, it has been determined that the only safe solution to the structural instability of the cooling towers is demolition. Given the probability of cooling tower two experiencing a similar collapse of the stiffening rings at any time, and the forthcoming windy season threatening the stability of the unsupported shell of cooling tower one, an expedient demolition is necessary.

Issued by:
Communication Department
City of Cape Town