As Scottish Water starts investigating the cause of one of the biggest incidents ever on its water mains network in the Borders, the utility has outlined the massive scale and almost military nature of its response to the issue.

A fault at Rawburn Water Treatment Works (WTW) near Duns on Tuesday August 26 resulted in drinking water quality for the area falling below its normally high standard.

While was there was at no point a risk to public health through consumption of the water, the publicly-owned utility took the decision to implement restrictions on a precautionary basis to about 300 properties directly fed from the WTW.

The company shut down the treatment works to enable repairs to be carried out, affecting normal supplies to 6000 properties across many parts of Berwickshire, causing loss of water supply, low pressure or intermittent supply and significant disruption and inconvenience.

The areas affected included Duns, Eccles, Coldingham, Chirnside, Paxton, Coldstream, Burnmouth, Lamberton, Drone Hill, Birgham, Whitsome, Swinton and Leitholm.

Rawburn WTW supplies up to about seven million litres of water per day to more than 10,000 properties in Berwickshire and the network has nine water storage tanks and about 370 miles of water mains linking the tanks and supplying water to properties.

Scottish Water said the size of the network brings its challenges when restoring water and this was a complex process that took until Sunday August 31 to resolve.

During the incident, the company protected supplies to 4000 properties by making alterations to the network and brought more than 12 million litres of water to the area by road, preventing a longer outage.

To support the recovery of the network, Scottish Water implemented a large-scale tankering operation across the affected area which saw more than 20 tankers operating 24 hours a day to help refill pipes and tanks in the network.

While, this inevitably caused an increase in road usage and noise levels but the company estimates that it moved over 12 million litres of water and significantly reduced the length of time customers were without their normal supply.

The utility also brought in specialised equipment such as pumps, control systems, pipes and fittings from other parts of the country including Glasgow and Aberdeen and from its supply chain.

Scottish Water deployed more than 100 additional workers to support bottled water provision and the distribution of 210 pallets of water to customers - about 100,800 bottles or 201,600 litres of water – while customers were without their normal supplies.

The utility also supported several farms, where animal welfare was becoming an issue. A farm task team was set up on Thursday 28th August and tanker resources were dedicated to topping up tanks at farms where there was a prolonged outage.

"Undoubtedly one of the biggest and most challenging incidents we’ve ever had in the Borders"

John Griffen, Scottish Water’s Water Operations General Manager, said:

“This was undoubtedly one of the biggest and most challenging incidents we’ve ever had in the Borders and we sincerely apologise for the disruption it caused.

“We responded as quickly and efficiently as we could, deploying all the resources and manpower necessary to resolve the issue and restore supplies to our customers.

“This is a big rural network and when it empties, it takes time to refill. It’s not like a power outage when power is either off or on – we are dealing with a product that has to travel huge distances. That’s why some people were without water longer than anyone would want.”

Acknowledging that the company knew it didn’t get everything right, he continued:

“We have started a full and thorough investigation into the cause of this incident, and will carry out an internal review of our response, to identify improvements for the future and learn from what happened.”