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Date

September – December 2017

Client

Water Authority

Project objective

To replace the membrane over a concrete roof of a reservoir drinking water tank with a new
impermeable waterproof membrane.

Project description

As the roof expansion joints were getting old, the reservoir tank roof and wall joints had failed to remain watertight, which resulted in untreated water coming into contact with treated potable water. The leakage of water through the roof and wall joints caused bacterial failures which meant the tank needed emptying and inspecting, as well as having to be cleaned again.

Initially, the structure was assessed and remedial work was carried out to enable the reservoir tank to return to normal operation. However, the issue arose again and a full plan of action to resolve these problems was needed to get the tank back to a full working condition and to improve its longevity.

The principal collaborator initially removed the overburden from the concrete tank roof, as well as the perimeter trench and drainage, which passes below the roof/wall joints. We then installed a newly designed ‘intelligent’ membrane system which provided a new watertight structure.

This included a system within the membrane where faults can be detected. This new system is made up of several layers which were installed to the manufacturer’s instructions (see video below for further information on this new system).

This system required the welding of 2 layers of a 1mm thick membrane and the positioning of sensors and cables which help detect faults. This new impermeable waterproof membrane passes by the roof/wall joints and is connected to the concrete wall with stainless bar/fixings and silicone seals to prevent water ingress. The roof also has several inspection hatches which require sealing and protecting from rain fall.

Outcome

We completed the work over 12 weeks from September – December 2017.

This system design required no adhesives or coatings which lead to a quicker installation.

The works were all carried out to the Water Authority’s brief, which required a thorough approach to waterproofing as well as backfilling, which we delivered in a timely process and managed the different trades needed for this job effectively.

The reservoir waterproofing was completed over 10 weeks with a further 2 weeks of testing and
monitoring. The reservoir was returned to service in the planned period.

Statistics

500+

working days/ working 7 days a week over 12 weeks.

250,000

Circa sq.m of membrane installed and tested.

over 2km

Stainless bar installed.

Benefits

The reservoir has been waterproofed effectivity with a hi-tech system to ensure that future faults will be easily detected and bacterial failures or leaks will be minimal.