The 8no manhole chambers were allowing water ingress, meaning that additional water was entering the waste water treatment process. We were tasked with giving a solution to this problem.
The solution was to “tank out” / waterproof the chambers using a specific tanking system prior to a final coat of waterproofing but highly chemical resistant mortar. This resists the hydrogen sulphide and biogenic sulphuric acid that is typically found within these chambers.
The leaking chambers were washed down using a high pressure spinning jet to remove contamination and give a clean surface for the start of the waterproofing process. The first coat applied was Remmers Kiesol, a liquid combination product made of water repelling silicic acid compounds, applied with a low pressure sprayer. Once this had penetrated into the concrete substrate, a coat of Remmers rapid curing grout was applied with trowels and slurry brushes. This was then left to cure.
Once satisfied the grout was cured sufficiently, a second coat of Remmers Kiesol liquid was spray applied, and allowed to cure.
Another coat of Remmers rapid cure grout was then applied, but this time using a “spatter dash” method to provide a key for the chemical resistant mortar to bond to. Once cured, a coat of Remmers SD1, a two component, highly chemical resistant mortar was applied with trowels and slurry brushes. This gives the impermeable barrier to ensure chemical attack does not occur, leading to failure of the waterproofing mortar. This was left to cure before Remmers SD1 curing compound was applied to assist in the complete curing of the mortar.
Whilst we work in the safest manner possible on all projects, this was of added importance due to the majority of the manholes being located on public highways and the confined space element of the works. Our specialist applicators are all confined space rescue trained, and so know how to safely and effectively retrieve an injured party from the manhole chambers utilising the tripod and winch located over the entry. Gas detectors were used prior to entry to ascertain whether the atmosphere is safe or not and was continually monitored throughout. All works were correctly segregated, to keep members of the public safe as well as our operatives. Traffic management was put in place and managed at all times by a specialist traffic management contractor.