Polyurea Storm Tank Lining Kent

THE PROBLEM

The waste water treatment works required extra storm capacity and site constraints meant that a new tank could not be constructed. Therefore it was necessary to refurbish the extremely dilapidated primary settlement tanks and convert them to storm tanks.

The tanks were in an extremely poor condition, with numerous areas of cracking and evidence of previous


SOLUTION

Given the extremely poor condition of the tanks we proposed an extremely flexible but also high tensile polyurea lining in the form of SPI Corrolastic HT.

Initially all of the failing render was removed using lightweight vibration damped breakers. This was contained and removed from within the tank to on site skips.

During these works it became evident that in areas of the tank significant water ingress was occurring – particularly through the tank base. These areas were investigated and broken out to expose the point of water ingress.

Initially the active points of water ingress were resolved using Remmers Rapid Hardener water stopping compound. Given the flows occurring this required quite an effort to resolve completely.

Once the active leaks had been resolved, the storm tanks were waterproofed throughout using Remmers WP Sulfatex applied by slurry brush and trowel. This cementitious tanking system is highly proven and one that we have used successfully for many years.

Once the tanking system had set and cured sufficiently heating and air movers were installed to ensure that the moisture content was sufficiently reduced to ensure adhesion of the new polyurea tank lining.

A highly damp tolerant epoxy primer was applied in two coats to fully seal the surface if preparation for the application of the polyurea tank lining. The first coat of primer was reduced in viscosity to aid penetration into the cementitious matrix.

The second coat of damp tolerant epoxy primer was applied without reducing the viscosity to better seal the surface and prevent outgassing. To provide additional adhesion for the polyurea tank lining quartz aggregate was broadcast into the wet primer in order to provide a mechanical anchor for the polyurea tank lining as well as a chemical bond.

Because polyurea materials are applied at typically 70 – 80 degrees centigrade and experience an aggressive exothermic reaction once mixed and applied, this will heat any air trapped in the substrate and cause it to expand and force its way to the surface if not properly sealed by priming. This creates pin holing in your new tank lining. By double priming you are ensuring that the surface is sealed as best as possible and minimising the chance of pin holing.

SPI Corrolastic HT Pure Polyurea was then spray applied to a thickness of 2mm, with additional material applied in corners for greater strength. SPI Corrolastic HT contain SPI’s patented Ultra Bond molecule which allows this material to adhere to itself even once the conventional overcoating window has been exceeded. Typical overcoating windows for polyurea materials are less than 12 hours.

What this enables the applicator to do is properly and thoroughly spark test the lining, which is essential in ensuring a seamless tank lining. Any pin holes were identified using a DC Holiday spark tester, marked and then made good.

Finally termination points were sealed and detailed using a polyurethane jointing compound. This termination points had previously been cut using a chaser to ensure that the polyurea lining did not finish with an exposed edge which could be liable for moisture ingress.

Properly applied polyurea tank linings such as this typically has a service life in excess of 25 years, providing an extremely durable and long lasting lining solution.

Polyurea Storm Tank Lining 15
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