Articles & Case Studies


Posted: Tuesday 24th May 2011

With over 50 years experience in the water industry, structural repair and refurbishment contractor, CONCRETE REPAIRS LIMITED (CRL), was recently called in to carry out specialist repairs to BAA’s Heathrow water tanks. The underground water reservoirs supply potable water to Heathrow’s various terminals and, during routine maintenance of the tanks, BAA was faced with unexpected issues that required CRL’s specialist expertise and ability to mobilise at short notice.

After the tanks had been drained down and further more detailed inspections carried out, it was discovered that the waterproof banding strips over the joints on the walls and floors had failed in a number of places, potentially allowing water to leak out from the tanks. BAA takes water wastage and the effect this wastage has on the environment, as well as the surrounding soil, very seriously and, so with time of the essence, CRL were called in immediately to rectify the situation.

Charles Severn, CRL Project Manager for the work comments, “The previous installation proved to have very poor surface preparation which did not allow the proper adhesion of the resin; this is crucial because it bonds the waterproof banding to the concrete structure. In these wet or damp conditions it is imperative to have a properly prepared surface to provide a good mechanical key and to keep it as dry as possible before the application of the resin.”

Following the inspection survey, CRL devised a solution using its vast knowledge and expertise in leaksealing and waterproofing. A price was submitted and through BAA’s supply chain partners, Inviron and Specialised Diving Services, CRL were awarded the works.

It soon became apparent though, that the repair work was not as straightforward as first envisaged. To undertake the task properly and prevent another failure of the system, it was paramount that all freestanding water was first removed. However, with the water out of the tanks and no positive pressure on the joints, the water began leaking back into the tanks through the joints from the outside. In order to continue with the application of the overbanding, the leaks had to be stopped. CRL’s quick reaction ensured that detailed proposals on how to stop the leaks and the associated costs were soon put forward to the client, and once these had been agreed the leak sealing was able to commence.

With the areas requiring repair now dry, CRL were able to continue with the remainder of the works by first removing the existing bandage and preparing the surfaces for the application of the new material. Once the preparation was complete, the new overbanding was applied and, following the specified curing period, the tanks were thoroughly cleaned and sanitised.

Charles continues, “This project ended up presenting quite a challenge for CRL. The works needed to be undertaken at extremely short notice, with minimum mobilisation time and within a tight programme. By pulling out all the stops, CRL was able to start on site within a week after the initial enquiry and site visit. By anyone’s standards, this is a particularly short period to arrange all the health and safety requirements in addition to organising the labour and material. Originally we were given between six to seven weeks to complete the work, but once we were on site, BAA requested that we provided additional labour to enable the works to be completed in four to five weeks. CRL was able to meet this challenge by providing the additional resources and all the overbanding, including the additional instructed leak sealing work, was finally completed in just six weeks.”

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