This case study is focused on a large multi use building in the City of London, incorporating retail outlets, offices and restaurants. A clean and safe water supply is of critical importance to such a building. It is occupied 24 hours a day.
During routine TVC (Total Viable Count) general bacteria sampling, a high count was recorded. The source of the contamination was found to be a leaking sewage pipe that ran above the site cold water storage tanks which provided water to the whole site.
Upon notification of the contamination, Clearwater arranged for 8 environmental services engineers to be on site within 4 hours to undertake an emergency chlorination of the tanks and associated down water services. During this set up period, Clearwater liaised with the building managers, maintenance team and individual tenanted areas in order to facilitate the emergency works.
The work started at 4pm with the pre-chlorination of the 2 cold water storage tanks (approximately 40 cubic metres each). The pre-chlorination was important in providing all personnel with a safe working environment. Once the one hour pre-chlorination was completed, work started on the draining and cleaning of the tanks. The next stage was to pull chlorinated water through to all outlets. After a chlorination period of 1 hour at 50ppm free chlorine reserve, the water in the tanks was neutralised and pulled through to the outlets. The engineers worked through the night to complete the works.
All of the chlorination works were carried out in accordance with the guidelines set out in ACOP L8 (2001), ‘The control of Legionella bacteria in water systems’.
Post chlorination samples for Legionella, E Coli and TVC were all clear, showing that the chlorination works had been successful.
After the emergency works were undertaken, Clearwater worked with the building maintenance company to facilitate remedial works to seal the CWST and add a drain away to the sewage pipe to ensure that this situation could not arise again in the future.
Clearwater has vast experience in building chlorination works, ranging from small mains injections to large multi storey office blocks to ring mains around multi building sites. In each case, the job is evaluated on its own individual merits, site specific method statements and risk assessments are put into place. These working in conjunction with a current Legionella risk assessment provides our clients with peace of mind that Clearwater are capable of handling both routine and emergency chlorinations on their site.
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