Posted: Wednesday, August 28th, 2019

AQS Environmental Solutions has led a project working with specialist partners to clean, disinfect, and repair a major supply reservoir using advanced technologies that enhance safety and quality assurance.

The twin-cell reservoir, with a combined capacity of 65,000 cubic metres, had been actioned to be cleaned and disinfected under the Service Reservoir Programme (Southern Region) 2018.

It was known, also, that one of the cells had been leaking. To minimise downtime, AQS arranged for a remotely-operated underwater vehicle (ROV) to be used to investigate the sources of the leaks before the drain-down began.

Powerful suction technology removes sludge

Acting as contractor under the SHW at Work (Construction Regulations) 2013, PSCS and PSDP, AQS development a risk assessment and method statement (RAMS) for all activities before work began.

Following drain-down, an AQS tank cleaning crew entered the reservoir which was more over 10 metres deep, through a top-mounted access cover.

Personnel trained in confined space entry removed a heavy deposit of sediment from the base of the tank using two methods – via a scour, and through suction.

AQS deployed one of its most advanced and powerful jetting and suction tankers, a JHL SuperFlex, which is specifically designed to carry out deep suction jobs, lifting thick sludge at high volumes over long distances.

Chemical cleaning delivers impressive results

Due to the tank’s height, a chemical cleaning process, provided by project partners Panton McLeod, was employed to clean and disinfect all walls, soffits, and internal surface areas.

The low-pressure and non-aggressive process could remove bio-fouling quickly and safely without any risk of damaging the tank.

AQS also facilitated an internal visual inspection of the tank to confirm the ROV survey reports. As a result, a decision was made to repair multiple floor defects and overband perimeter joints.

Within four working days, project partner Adrian Queally Ltd had mobilised a repair crew, which carried out all works within 48 hours.

After a three-day curing period, the tank floor was chlorinated, then wash-water dechlorinated and scoured, ready for the reservoir to be handed back for service.

Multiple benefits – quality, speed, and safety

Key benefits delivered in the cleaning and repair of a critical asset focussed on the quality of the cleaning process combined with the minimising of service down-time.

Inspection of the reservoir by our client prior to it being recommissioned showed that 100% of internal service areas had been cleaned to the required high standard.

Downtime for the reservoir had been minimised by meticulous forward planning, good collaboration and use of remote access inspection equipment.

Also central to the speed and safely of service delivery was the use of industry-leading suction equipment, and a chemical cleaning system, which eliminated the need for internal scaffolding.