Inverness Search & Rescue
Scope of Works - Sealing of Water Ingress to GRP Chamber
Date - September 2019
At some stage after installation of the 30000ltr GRP Tank below ground, a crack developed in the base resulting in water ingress that filled the tank over a period of less than 10 hours. We were asked if we could resolve the issue to avoid the requirement for full excavation, removal and replacement of the tank.
Over and above the fact that the tank was filling at such an extreme rate, there were a number of other difficulties with the project:
1) Access was limited to a single operative due to the confirmed space nature of the works.
2) The GRP structure was not solid and due to lack of compaction or wash out of surrounding concrete, flexed under pressure of water and movement of operative.
3) The site was a secure unit preventing continued pumping set up through doors. Internal drainage required to be utilised.
4) 24 Hour continuous pumping was necessary to control the ingress of water whilst we sealed the area.
There were a number of stages of process necessary to resolve this issue:
1) Drainage layer and pumps located to control water from below, allowing a dry surface to work from.
2) Steel Frame installed and secured to GRP unit with resin bonded cleats.
3) Fluid Concrete located to provide solid weight over drainage layer.
4) Epoxy bonded flexible bandage bonded to GRP/Concrete Junction.
5) Resin Injection through concrete utilising Fast set and Water Reactive Resin Grouts.
This process required input over a 3 week period with significant management time and operative input to resolve. Elements of the process developed due to the nature of the structure and the flow of water however at completion of the works, we have completely eradicated the water ingress meaning the client has a tank with reduced capacity however no requirement to empty on a daily basis and has had limited disruption to their operations. The Main Contractor has avoided significant costs in having to completely excavate and replace the chamber.