Pumping Station Tank Repair

Effluent Sump Lining

This pumping station tank repair was a challenging job for the SLS team with many critical components requiring individual attention. The chamber was a final pumping station for a large logistics site. A pumping regime was needed in the adjacent chamber which was the last point before the pumping station. There was a requirement of 2 x 10000 litre tankers daily for taking away foul, which gives you an idea of the water usage on this site. It also made the project even more time critical as costs could easily escalate with the continued usage of the vacuum tanker.

On arrival at the site, the manway lid was removed and the suction tanker was utilised to get the sludge levels down to the base for manned entry. On manned entry, the pumps & pipework were removed to allow the pumping station tank repair to commence. The initial water ingress damage was then checked. There was a fracture at the base and the GRP base was found to be 75% delaminated resulting in the water coming in at a high rate.

SLS operatives washed the internals of the tank using a high-pressure jetter followed by contact cleaning using bleach before rinsing. The suction tanker was stopped and the rise in the water was visualised. Within 20 minutes the water had risen well over 1 metre which showed we were dealing with a large degree of hydrostatic pressure.

Installing a false floor into a Pumping Station Tank Repair

Subsequently. the tank would need a false floor installed which would mean a decrease in the capacity of the chamber. The false floor consisted of 500mm of stones levelled and compacted followed by the installation of 25mm GRP close topped grating with a 250mm diameter hole centrally.

The water would need to be controlled throughout the process so initially the pump was set in a plastic pipe on the original floor and the stones built around this. The floor level would be built up to a total thickness of 32mm. This would be stitched in GRP to the existing tank walls.

Once the floor was stitched in, a 10mm thick GRP stub flange complete with backing ring was installed to the hole and the pump moved centrally. At this point the groundwater was under control and we now had the opportunity to work on strengthening the tank.

As we were dealing with such strong hydrostatic pressure from the water table the tank walls would need some good strengthening too, particularly as the base was now the strongest point meaning the water table would find the next week point. Our 7mm structural GRP Lining was installed with the addition of balsa core strengthening rings.

Once the laminate system was fully installed, we cured the laminate using the indirect fired heater for 4 hours to ensure it was cured.
The final part of the works was to seal the sump lining up. In a very quick 10 minutes of work, we had to get the pump removed, the gasket, stainless blank plate, and stainless bolts tightened and torqued before the water got there first.

The works were successfully completed in a 10-day period saving the client time & money. Installing our effluent sump lining system prevented the slab being broken up. The damaged tank removed, and a new tank installed. The small footprint made by SLS during the work caused minimal disruption to the logistics site around us.